Synthesis of Evidence to Support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef

October 2008

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef

Prepared by: Jon Brodie, Jim Binney, Katharina Fabricius, Iain Gordon, Ove Hoegh-Guldberg, Heather Hunter, Peter O’Reagain, Richard Pearson, Mick Quirk, Peter Thorburn, Jane Waterhouse, Ian Webster and Scott Wilkinson This document was prepared by an independent panel of scientists with expertise in Great Barrier Reef Water Quality. This document does not represent government policy.

The Queensland Government supports and encourages the dissemination and exchange of information. However, copyright protects this document. The State of Queensland has no objection to this material being reproduced, made available online or electronically but only if it is recognised as the owner of the copyright and this material remains unaltered. Copyright enquiries about this publication should be directed to the Department of the Premier and Cabinet, by email to [email protected] or in writing to PO Box 15185, City East Qld 4002.

Copies of this publication can be obtained by contacting (07) 3225 8050 or at www.reefplan.qld.gov.au Contents

Background 1

The taskforce 2

Introduction 3

Part A: Review the 2003 statement and update it by reviewing available scientific evidence 4

1 Review scientific evidence for a decline in the quality of water that discharges from the catchments into the GBR 4

2 Review scientific evidence for the presence, nature and extent of land-derived contaminants in GBR waters 9

3 Review scientific evidence for causal relationships between water quality change and ecosystem health 18

4 Review existing scientific evidence for a decline in the quality of water in GBR catchment waterways leading to reduced instream ecosystem health 24

5 Review scientific evidence for the effectiveness of current or proposed management intervention in solving the problem 28

6 Discussing the implications of confounding influences including climate change and major land use change 35

Part B: Evaluate current research and advise on capabilities, gaps and priority research needs 37

1 Assess water quality impacts 38

2 Quantify acceptable levels of pollution 40

3 Locate and quantify the sources of pollution 41

4 Identifying management practices to reduce pollution from key sources 44

5 Assess the effectiveness of actions to reduce pollution 46

References 48

iii

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef

Background

A consensus statement of the current Tasks understanding of Great Barrier Reef Review the 2002 statement and update it by: (GBR) water quality science was prepared to underpin the future direction 1. Reviewing scientific evidence for: of the Reef Water Quality Protection Plan • a decline in the quality of water that (Reef Plan) actions and to guide future discharges from the catchments into investment in Reef Plan activities. the Great Barrier Reef • a decline in the quality of water in Terms of Reference GBR catchment waterways leading to The Terms of Reference for the reduced instream ecosystem health statement, prepared by the Reef Water • the presence, nature and extent of land- Quality Partnership (RWQP) Support derived contaminants in Reef waters Team and Reef Plan Secretariat, and • causal relationships between water quality reviewed by the RWQP Scientific Advisory change and ecosystem health Panel, are provided below. • the effectiveness of current or proposed management intervention in Purpose solving the problem and the social and To review the Summary Statement of economic impediments to uptake. the Reef Science Panel regarding water quality in and adjacent to the Great 2. Evaluating current research, and Barrier Reef, in a contemporary context. advising on capabilities, gaps and This statement, which was produced by priority research needs, to: technical experts in 2002, supported the • assess water quality impacts development of the Reef Plan. Given that • quantify acceptable levels of pollution it was nearing the halfway mark of the • locate and quantify the sources 10-year plan, it was considered timely to of pollution review and, where appropriate, update the statement to support the reinvigoration of • reduce pollution from key sources Reef Plan and guide future investment in • assess the effectiveness of actions to Reef Plan priority activities. reduce pollution. 3. Discussing the implications of confounding influences, including climate change. The wording of the above Terms of Reference has been slightly modified by the Taskforce, in consultation with the Reef Plan Secretariat.

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef The taskforce

A taskforce has been convened to prepare the consensus statement and includes the contributors listed in the table below.

Contributor Title Organisation Expertise

Jon Brodie Principal Research Officer, Australian Centre for Tropical Water quality and agricultural (Lead author) Water Quality Freshwater Research science – catchment to reef

Jim Binney Senior Consultant Marsden Jacob Associates Resource economics

Dr Katharina Principal Research Scientist, Australian Institute of Marine Coral reef ecology Fabricius Coral Reef Ecology Science

Professor Theme Leader, Healthy CSIRO Sustainable Terrestrial ecology and social Iain Gordon Terrestrial Ecosystems Ecosystems interactions

Professor Ove Director, Centre for Marine Coral reef ecology and University of Queensland Hoegh-Guldberg Studies climate change

Principal Scientist, Natural Department of Natural Biogeochemistry of land Dr Heather Hunter Resource Sciences Resource and Water and water systems Department of Primary Dr Peter O’Reagain Principal Scientist Agricultural science – grazing Industries and Fisheries

Professor Director, School James Cook University Tropical ecology Richard Pearson of Tropical Biology

Contracted to Meat and Dr Mick Quirk Senior Consultant Agricultural science – grazing Livestock Australia

Principal Research Scientist, CSIRO Sustainable Agricultural and environmental Dr Peter Thorburn Tropical Production Systems Ecosystems science – cropping

Science Coordinator, Water quality science – Jane Waterhouse CSIRO GBR Projects catchment to reef

Catchment and marine Research Scientist, Catchment Dr Ian Webster CSIRO Land and Water hydrodynamics and and Aquatic Systems biogeochemistry Additional contributors

Research Scientist, Catchment Catchment hydrology and Dr Scott Wilkinson CSIRO Land and Water and Aquatic Systems material fluxes

Apologies have been received from the following individuals Definitions that were approached to participate: The following terms are defined for the purposes of this Tim Wrigley (Canegrowers – cane management practices) discussion paper: Brigid Nelson (DPI&F – grazing management practices) Contaminant – any material that can be detected in water at Miles Furnas (AIMS – marine water quality and oceanography) above ‘natural’ concentrations. Malcolm McCulloch (ANU – marine water quality and climate change). Pollutant – when a contaminant is at concentrations known to cause environmental harm.

2 Introduction

The establishment of the Reef Water This package will constitute Quality Protection Plan (Reef Plan – Commonwealth Government investment Anon, 2003) by the Australian and over the next five years for addressing Queensland governments was supported GBR water quality improvement targets. by a body of evidence showing a There is a need to focus investment decline in water quality on the GBR. in GBR water quality in a way that Efforts to review this evidence included demonstrates a tangible return on Williams (2002), Williams et al. (2002) investment for government agencies, and the Great Barrier Reef Protection regional National Resource Management Interdepartmental Committee Science (NRM) bodies and industry groups over Panel (2003). The latter document was the life of the Reef Rescue policy. a comprehensive review of the evidence Since 2003, there have been significant available at the time, prepared by a advances in the knowledge to support taskforce of experts led by Dr Jo Baker. implementation of the Reef Plan. It is As the Reef Plan approached its five-year timely to synthesise this knowledge (half-way) mark there was recognition of and reach consensus on current the need to improve the effectiveness of understanding of the system to support its delivery, particularly through improved the reinvigoration of Reef Plan and partnership arrangements and a clear guide future investment in Reef Plan focus on land management actions. In priority activities. This discussion paper November 2007, the Labor party released provides a synthesis of current knowledge an election policy document proposing against a set of Terms of Reference funding of $200 million over five years defined by the Reef Water Quality for a Reef Rescue program ‘to tackle Partnership Scientific Advisory Panel climate change and improve water quality and the Reef Plan Secretariat. It reviews in the Great Barrier Reef’. This package the Summary Statement of the Reef includes substantial funding ($146 million) Science Panel regarding water quality in for a Water Quality Grants Scheme, and adjacent to the Great Barrier Reef and supporting monitoring, reporting in a contemporary context and, where and research programs, with additional appropriate, updates the statement. funding to build partnerships.

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef Review the 2003 statement and update Part A it by reviewing available scientific evidence

1. Review scientific evidence for a decline in the quality of water that discharges from the catchments into the GBR

Conclusion: Water discharged from 1.a.ii. Concentrations of nitrate and nitrite with hillslope, streambank and gully rivers to the GBR continues to be of are elevated in groundwater in erosion within individual catchments. poor water quality in many locations. areas under intensive agriculture. • Pesticides – concentrations in The quality of waters entering the GBR A portion of this groundwater is believed waterways are highest in areas of from its river systems and groundwater to enter the coastal waters. intensive agricultural activity including is highly variable both spatially and sugarcane and cotton. 1.a.iii. River loads of nutrients, sediments temporally across the region. Natural and pesticides are higher than in 1.a.v. The priority source areas of catchment characteristics (e.g. geology, pre-European times. contaminants are now relatively climate) and anthropogenic activities well known for GBR catchments. (e.g. land use, land and water management) Inferred from changes in land use and both strongly influence water quality, estimated through monitoring and Analysis of data on fertiliser use, loss including the concentrations and loads modelling, although with significant potential and transport has ranked fertilised of land-derived materials transported uncertainty (in models and monitoring). agricultural areas of the coastal Wet Tropics from the catchment to the GBR lagoon. Long-term datasets in the Tully River and Mackay Whitsunday as the hot-spot Excessive levels of suspended sediment show upward trends in concentrations of areas for nutrients (mainly nitrogen) that and nutrients (nitrogen and phosphorus) particulate nitrogen and nitrate from 1987 pose the greatest risk to GBR reefs. are of concern, as well as the presence to 2001. In the Dry Tropics, high suspended of pesticide residues or other substances 1.a.iv. Concentrations of contaminants in sediment concentrations in streams are that do not occur naturally in the environment. waterways are related to specific associated with rangeland grazing and These pose a risk to the health of aquatic forms of land use. locally specific catchment characteristics, ecosystems both within the catchment whereas sediment fluxes are relatively and in the GBR. Monitoring and modelling identify the low from cropping land uses due to main sources of nutrients, sediments Evidence suggests that concentrations improvements in management practices and pesticides, and show strong regional and loads of suspended sediment and over the last 20 years. differences. Evidence includes: nutrients have increased substantially In the Wet Tropics, sediment fluxes with catchment development, although • Nitrogen – a strong relationship exists are comparatively lower due to high the magnitude of the increases compared between the areas of nitrogen-fertilised vegetation cover maintained throughout with natural conditions is not precisely land use in a catchment and the mean the year from high and year-round rainfall known. Contemporary land uses differ in nitrate concentration during high flow and different land management practices their export rates of these contaminants, conditions, implicating fertiliser from Dry Tropics regions within industries and there are marked cross-regional residues as the source of nitrate. such as beef grazing. differences, particularly between the Wet Elevated stream concentrations of and Dry Tropics. Emerging results from nitrate indicate fertiliser application Urban development sites can be local high long-term monitoring indicates increasing above plant requirements in sugarcane impact sources of suspended sediment. trends in nitrogen concentrations in two and bananas. Of the herbicide residues most commonly river systems. The widespread presence • Phosphorus – elevated concentrations found in surface waters in the GBR region, of certain herbicide residues in both of dissolved inorganic phosphorus diuron, atrazine, ametryn, hexazinone surface waters and groundwater is further are also related to fertiliser application derive largely from areas of sugarcane evidence of a decline in water quality. above plant requirements in intensive cultivation, while tebuthiuron is derived cropping and to locally specific soil from rangeland beef grazing areas. 1.a. Lines of evidence characteristics. 1.a.i. Pesticide residues, particularly • Sediment – most sediment originates herbicides, are present in surface from grazing lands of the dry and and groundwater in many locations sub-tropics. The influence of land use in the catchments. on sediment loads is now well known at a regional scale but more work is These substances do not occur naturally required to identify sources at finer in the environment. scales, due to variability associated

4 1.b. The evidence base groundwater transported contaminants In some cases, estimates have been (especially nitrate) in material transport supported by comparison with monitoring 1.b.i. Pesticide residues, particularly from paddocks to coastal waters. results (Fentie et al., 2005; Armour herbicides, are present in surface et al., 2007a; Mitchell et al., 2007a; 1.b.iii. River loads of nutrients, sediments and groundwater in many Sherman et al., 2007). Results from and pesticides are higher than in locations. such modelling studies indicate that in pre-European times. The presence of pesticide residues, many rivers, suspended sediment loads especially herbicides, is widespread Evidence of changes in river (and hence mean concentrations) may in waterbodies of the GBR region, concentrations of contaminants over have increased by a factor of 5–10 since including streams, wetlands, estuaries, recent decades is only available for a European settlement, and loads of total coastal and reefal waters (e.g. Hunter few rivers. The most complete long- nitrogen and total phosphorus, by factors et al., 2001; Packett et al., 2005; term monitoring data set is from the of 2–5 and 2–10, respectively. These Rohde et al., 2006a, 2008; Faithful et Tully River (Mitchell et al., 2001; models also indicate that nitrate loads in al., 2007; Lewis et al., 2007a; 2007b). 2006) where particulate nitrogen these rivers may have increased twenty- Residues commonly detected include concentrations increased by 100% and fold over the same period (Armour et al., atrazine, diuron, ametryn, hexazinone DIN concentrations by 16% between 2007a). However, it is important to note and tebuthiuron. Although most of the 1987 and 2000. This occurred during a the very high levels of uncertainty that concentrations are very low, these period of increasing fertiliser use in the are unavoidably associated with these substances would not have been present catchment, although a direct cause-effect types of estimates. Consequently, use at all before agricultural development association has not been established. of a different modelling approach may of the catchments. The leaking of these Further, an increase in ammonia and produce a contrasting set of estimates, chemicals from cane paddocks has been phosphorus in the Daintree River over the depending on model assumptions, spatial confirmed by paddock scale studies period 1994–2000 was measured by Cox resolution, and availability of data to throughout the GBR catchment, including et al. (2005). feed into the models. This is highlighted by results for the Johnstone catchment, Bundaberg (Stork et al., 2008) and the It is to difficult to pick up short- or where a catchment model and a purpose- lower Burdekin (Ham, 2006; 2007). medium-term trends in water quality at designed monitoring data set were Atrazine residues have been found in the large scales due to climate variability and used (Hunter and Walton, 2008) which groundwater of many regions including inherent difficulties in logistics associated suggested considerably lower increases the lower Burdekin (Bauld, 1994), Mackay with monitoring at the right spatial and in suspended sediment and nutrient (Baskeran et al., 2002), Bundaberg temporal scales. See also discussion loads since European settlement than (Bauld, 1994) and Bowen (Baskeran et in Section 5. al., 2001). Where this water is used for those reported above (e.g. an increase in drinking water supplies, the detection Changes in loads and concentrations suspended sediment loads by a factor of of atrazine means that the water fails of suspended sediment and the various 1.4 and nitrate loads by a factor of 6). forms of nitrogen and phosphorus to meet Australian and New Zealand Steps in the transport pathway have since European settlement have been Environment Conservation Council now been better quantified; for example, estimated using models such as SedNet (ANZECC) requirements for studies on bedload storage have shown and ANNEX (Brodie et al., 2003; Cogle et drinking water. that sand-sized sediment may take al., 2006) and other models (e.g. Furnas, decades to be transported to the river 1.b.ii. Concentrations of nitrate and nitrite 2003). The models have incorporated (Bartley et al., 2007a). Estimates of are elevated in groundwater in water quality data collected from sites overbank flow in the Tully catchment areas under intensive agriculture. with extensive agricultural and urban land have shown that 43–50% of the sediment uses and compared with data from areas High concentrations of nitrogen have load and 35–46% of the nutrient load is with little or no development (Brodie and been found in groundwaters of many from the river channel of the floodplain Mitchell, 2005). The SedNet and ANNEX regions, and these have been linked to (Wallace et al., in press; Karim et al., model group has been widely used at fertiliser sources (Weier, 1999; Thorburn 2008) and the dynamics of dissolved the catchment and sub-catchment scale et al., 2003a). The final fate of the organic nitrogen are now also being for the entire GBR catchment area and elevated nitrate concentrations found in considered (Wallace et al., in press; has also been repeated and developed groundwater is still uncertain (e.g. in the Wallace et al., 2007) and reported for regional catchments (e.g. Brodie et Burdekin delta refer to Thayalakumaran et (Hunter and Walton, 2008). al., 2008). Drainage of nitrate below the al., 2003; Cogle et al., 2006; Armour root zone in sugarcane in the Johnstone et al., 2007a; Kinsey-Henderson and catchment has been shown to produce Sherman, 2007; Dougall et al., 2006a) to a nitrate ‘bulge’ below the surface predict sediment and nutrient generation, (Rasiah and Armour, 2001; Rasiah et transport and delivery to the GBR lagoon; al., 2003a) and it has also been shown and at small subcatchment scales to that this nitrate is likely to move laterally determine sources and sinks of sediment in subsoil to adjacent streams and rivers at a scale suitable for grazing land (Rasiah et al., 2003b). However, a high management (Kinsey-Henderson et al., degree of uncertainty exists in the role of 2005; Bartley et al., 2007a; 2007b; 2007c).

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef 1.b.iv. Concentrations of contaminants in 1800 waterways are related to specific forms of land use. Farm 0204 1600 2004-2006

The sources of contaminants are now Average nitrate concentration ( relatively well known for the GBR catchments. Current knowledge is 1400 based largely on information derived from modelling (e.g. using SedNet), 1200 Farm 2148 with some of the model results supported 2005-2006 by monitoring data. Large, detailed catchment-specific studies, such as the 1000 Cane sub-catchment monitoring/modelling of the Johnstone 2005-2006 2 = 0.95 catchment (Hunter and Walton, 2008) r overall remain the exception, but results from 800 monitoring programs now underway μ g/L) should enable similar detailed modelling to be carried out in the future for several 600

other catchments. Upper Banyan Ck 1987-1995 400 Nitrogen Tully R, Euramo 1987-1995 Lower Banyan Ck On average, about 50% of the total 1987-1995 nitrogen loads transported annually in 200 Tully R, Euramo catchment waterways is associated Upper T, Jarra, 2004-2005 with the suspended sediment fraction Boulder 1987-1995 (Bramley and Roth, 2002; O’Reagain et 0 al., 2005; Bainbridge et al., 2007; Faithful 0 20 40 60 80 100 et al., 2007; Hunter and Walton, 2008; Rhode et al., 2008), which is associated Proportion (%) of fertilizer-additive land use in each sub-catchment predominantly with soil erosion Figure 1. Relationship between fertiliser-additive land use and average (mean) nitrate processes. The remainder is present in concentration. Sourced from Mitchell et al., 2006. Green symbols are AIMS-BSES data various dissolved forms. Most dissolved from wet-season. Blue symbols represent wet-season data from Faithful et al., 2007 (Cane inorganic nitrogen (DIN, primarily nitrate) sub-catchment) and Faithful et al., 2006 (Farm 2148 – 80% bananas; Farm 0204 – 95% in streams that drain cropping areas sugarcane; Tully River, Euramo). is considered to come from fertiliser land management and concentrations (up to 1000 kg/ha) of nitrogen have also residues (Rohde et al., 2006a; Faithful of other forms of nitrogen are less clear. been found in subsoils in the Bundaberg et al., 2005, 2007; Hunter and Walton, The strong influence of climatic variability (Keating et al., 1996), Innisfail (Rasiah 2008) with 90% of the DIN attributed to on annual loads of nitrogen (and other et al., 2003a) and Babinda (Meier et this source in the Tully/Murray Region constituents) exported, highlights the al. 2006) regions. High concentrations (Mitchell et al., 2006; Armour et al., potential challenges faced in detecting, of nitrogen (N) have been found in 2007a). A strong relationship exists with confidence, any future reduction in groundwaters of many regions, and these between the area of fertilised land use loads associated with the adoption of have been linked to fertiliser sources in a catchment and the mean nitrate improved land management practices. (Thorburn et al., 2003a). Nitrogen fertiliser concentration in high flow conditions management practices in sugarcane proving that the source of nitrate is In the Tully catchment, where sugarcane crops are consistent with these results fertiliser residues (e.g. Mitchell et al., production makes up only 13% of the on the presence of nitrogen in sugarcane 2006; Pearson and Stork, 2007). This is catchment land use, 76% of the dissolved areas. Rates of nitrogen fertiliser shown in Figure 1 (Mitchell et al., 2006). inorganic nitrogen discharged from the applications increased dramatically since However, it is worth noting that results Tully River comes from sugar fertiliser the mid-1970s, and substantially more from monitoring and modelling in the losses, while about 85% is generated from nitrogen fertiliser has been applied to Wet Tropics (Johnstone catchment) have sugar and bananas combined (Armour sugarcane crops than removed from the shown areas of non-sewered residential et al., 2007a). Similarly, in the Johnstone cropped lands in either harvested cane development to have the highest nitrate catchment, sugarcane and bananas or trash that was burnt. The difference export rates of all land uses, on a unit account for 75% of nitrate exported from between the nitrogen fertiliser applied area basis (Hunter and Walton, 2008). the catchment (Hunter and Walton, 2008). and that removed is called the ‘N surplus’, This may be locally important within the Increases in nitrogen concentrations in which is an indicator of potential losses catchment, even if of lesser significance the Tully and South Johnston Rivers have of nitrogen to the environment. Across for the catchment as a whole, due to also been associated with sugarcane the whole sugarcane industry, nitrogen the relatively small proportion of the production (Mitchell et al., 2001; 2006; surpluses have been in the order of total catchment occupied by this land Hunter and Walton, 2008). Large amounts use. Associations between land use or

6 1 kg N/t cane since the early 1980s Sediments (Thorburn et al., 2003b). Thus, for a crop In the Dry Tropics, high suspended yielding 80 t/ha, N surpluses are likely to sediment concentrations in streams be in the order of 80 kg/ha. Expressed derive from rangeland grazing and at a regional scale, in a region producing urban development sites (Bainbridge et 7 Mt of sugarcane per year (e.g. the Wet al., 2006a; 2006b; Rohde et al., 2006b) Tropics), there could be around 7000 t whereas sediment fluxes are relatively of surplus nitrogen annually. Reductions low from cropping land uses (especially in nitrogen fertiliser use has occurred sugarcane cultivation). This is due to in some regions over the past five to improvements in management practices ten years, but yields have also declined over the last 20 years (e.g. minimum tillage and as a result nitrogen surpluses are and trash blanketing in cane) (Rayment, still close to 70 kg/ha (Thorburn et al., 2003; Bainbridge et al., 2006b; Rohde 2007). Thus, the evidence of high stream et al., 2006a; Faithful et al., 2007). In concentrations of nitrogen in areas of the Wet Tropics (Johnstone catchment), sugarcane production described above is sediment fluxes from grazing areas are low not unexpected. due to high vegetation cover maintained While not studied as extensively, the throughout the year, with sediment export situation is similar in some important rates similar to those from areas of native horticultural crops. Nitrogen surplus is in rainforest. By contrast, fluxes from cropping the order of 200 kg/ha for bananas (Weier, areas (sugarcane and bananas) in this 1994; Moody and Aitken, 1996; Prove et catchment are around three to four times al., 1997), although this has been reduced higher than those from areas of native in recent years due to better fertiliser rainforest (Hunter and Walton, 2008). Urban management regimes for bananas (Armour development sites can also be local high et al., 2006, 2007b), and 100 kg/ha for impact sources of suspended sediment. capsicums (Moody and Aitken, 1996). Not Field studies in the Burdekin region (Virginia surprisingly, large amounts (~200 kg/ha) Park Station, Meadowvale Station and of N have been found in subsoils following the Bowen catchment) have shown that small crops in the Bundaberg region (Weier river sediment and particulate nutrient and Haines, 1998). concentrations in grazed areas are two to five times those in environmentally Phosphorus comparable non-grazed areas (Townsville Typically, most of the total phosphorus Field Training Area managed by the load in catchment waterways is associated Defence Department) (Post et al., 2006a, with the suspended sediment fraction 2006b). It is probable that hillslope and (and thus soil erosion processes), with gully erosion are both major sources in the <20% occurring in dissolved forms Dry Tropics, with bank erosion generally a (e.g. Bainbridge et al., 2007; Faithful smaller source of eroded sediment (Bartley et al., 2007; Hunter and Walton, 2008). et al., 2007c). Roth (2004) and Hawdon et However, there are exceptions (e.g. the al., (2008) have demonstrated evidence Mackay region), where relatively high of changed hillslope hydrology in grazed concentrations and loads of dissolved rangelands that resulted in increased runoff. phosphorus may occur, probably related Further work showed that patches bare of to locally-specific soil characteristics vegetation are particularly prone to erosion, (Bloesch and Rayment, 2006; Rhode resulting in high hillslope sediment yields et al., 2008). The downstream fate of (Bartley et al., 2007b, Bastin et al., 2008). phosphorus sorbed onto suspended Improved monitoring techniques are now sediment is dependent on environmental available to measure landscape leakiness conditions (e.g. pH, salinity, dissolved and patchiness with respect to runoff and oxygen concentrations) as well as the sediment (Abbott and Corfield, 2006). geochemical properties of the sediment There is reasonable understanding of spatial are still poorly understood. In certain variation in the contribution of sediments situations, the phosphorus may be and nutrients at the whole of GBR scale de-sorbed and released into the water (McKergow et al., 2005a; 2005b), which column, as reported by McCulloch et al., indicates that spatially targeted remediation (2003a) for anoxic sediment offshore from will achieve greater reductions than a the Johnstone catchment. blanket approach (Wilkinson, 2008). However, considerable uncertainty still exists in the relative source contributions within individual river catchments;

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef for example, different SedNet runs in 1.b.v. The priority source areas of 1.c. Key uncertainties related the Fitzroy basin have had a 30% range contaminants are now relatively to decline in water quality and (uncertainty) in the predicted contribution well known for GBR catchments. sources of pollutants of hillslope erosion (Wilkinson, 2008). In Several initiatives have attempted to The following points summarise the key addition, there is limited knowledge on identify the priority source areas of uncertainties associated with knowledge the relative importance of gully erosion contaminants in GBR catchments; related to the decline in water quality and compared with hillslope erosion in rangeland examples are described below. the sources of contaminants: grazing, the primary causes of gully erosion Further discussion of priority areas for in the landscape and the most effective • Due to time lags in system response management intervention is included in remedial management practices to stabilise and relatively short-term monitoring Section 5 (Part A). new and existing gullies. Broad assumptions information, estimates of contaminant are currently made in the sediment transport Analysis of data on fertiliser use, loss loads generated by model predictions models on gully extent and behaviour potential and transport in the Nutrient are subject to large uncertainties. leading to significant uncertainty in modelled Management Zones project (Brodie, Refinement of model approaches predictions in some locations (Bartley et al., 2007) has ranked fertilised agricultural that predict contaminant loads by 2007b; Herr and Kuhnert, 2007). areas of the coastal Wet Tropics and incorporating finer temporal resolution, Mackay Whitsunday as the hot-spot areas characterisation of hydrological Sediment particle sizes influence delivery for nutrients (mainly nitrogen) that pose processes, nutrient speciation and rates and system lags in delivery (i.e., the greatest risk to GBR reefs. better techniques for quantifying different rates of delivery for sand versus uncertainty is required. silt versus clay). Lags vary from short In the Dry Tropics, high suspended • There is a need to review and integrate (a few days) for clay to much longer sediment concentrations in streams land-based modelling of sediment timeframes (years) for silt and decadal derive from rangeland grazing, locally sources in the dry tropical catchments. timeframes for sand (Bartley et al., 2007b; specific catchment characteristics and In particular, the relative importance of Bainbridge et al., 2007). Different particle urban development sites, whereas gully erosion compared with hillslope sizes are important components of sediment fluxes are relatively low from erosion, the primary cause of gully different ecosystems; for example, sand is an cropping land uses due to improvements erosion in the landscape and the important element of riverbed environments in management practices over the last 20 most effective remedial management and beaches, while clay provides substratum years (refer also to Section 5 of Part A). practices to stabilise new and existing for mangrove communities. Projects have also identified catchment gullies requires further work. Broad hot-spots for sediment delivery (erosion). assumptions are currently made in For example, a modelling study on the Pesticides the sediment transport models on Burdekin ranked the east Burdekin, The herbicide residues most commonly gully extent and behaviour leading Bowen River and NW Burdekin sub- found in surface waters in the GBR region to significant uncertainty in modelled catchments as areas of highest delivery (diuron, atrazine, ametryn, hexazinone) predictions in some locations. derive largely from areas of sugarcane (Brodie et al., 2003; Fentie et al., 2006; • Identify major drivers, both natural cultivation (Rohde et al., 2006a; Faithful Kinsey-Henderson et al., 2007). This (soils and geology, elevation and et al., 2007; Lewis et al., 2007a) and for analysis has been confirmed to some rainfall intensity and duration) and/ atrazine from cropping relatively specific extent by monitoring studies that have or anthropogenic (land management to the Fitzroy (Packett et al., 2005). At a identified very high concentrations of such as stocking rates, fencing and local scale, diuron residues may also be suspended sediment from the Burdekin spelling and resultant ground cover), associated with its use as an anti-foulant sub-catchments Bowen River, Dry River of suspended sediment concentrations on boats (e.g. in marinas). Residues and Camel Creek (Bainbridge et al., from different dry tropical sub- of tebuthiuron are associated primarily 2007). In the Fitzroy catchment, modelled catchments (e.g. Burdekin and Fitzroy with the use of this product (Graslan) in estimates suggest a significant proportion Rivers). Developing load models grazing lands for woody weed control of the fine sediment delivered by the using available data has potential to (Bainbridge et al., 2007). river to the estuary and coastal marine environment is derived from the basaltic identify the effect of climate and land The capacity to predict contaminant loads soils of the western catchment (Douglas management on loads. through combined monitoring and modelling et al., 2005; Smith et al., 2006). • Knowledge of the residence times approaches is discussed further in Section 5. of different particle size fractions of suspended sediments transported Other through catchments and the Other sources of contaminants that may implications and timescales for be of concern to water quality in the GBR sediment delivery to the GBR lagoon. include disturbance of coastal areas and • A high degree of uncertainty exists in generation of acid sulphate soils (ASS) the role of groundwater transported (Powell and Martens, 2005; http://www. contaminants (especially nitrate) from nrw.qld.gov.au/land/ass/index.html). In paddock to coastal waters. recognition of these potential issues, the NRW has recently completed distribution mapping of ASS in Queensland.

8 2. Review scientific evidence for the presence, nature and extent of land-derived contaminants in GBR waters

Conclusion: Land derived are dispersed more rapidly and may be • At Low Isles, water clarity (measured by contaminants, including suspended trapped in the lagoon by biological uptake Secchi disc transparency) is now half sediments, nutrients and pesticides, are and persist in this particulate form for the value it was in 1928. However, the present in the GBR at concentrations years; most pesticide residues have short validity of this comparison is reduced likely to cause environmental harm. residence times (at most a few years) due as only two data sets are used for this to their chemical breakdown. assessment with little data produced Advances in monitoring and modelling between 1928 and the early 1990s. techniques in recent years have 2.a.iv. Large river discharge events enabled greater understanding of the (‘floods’) in the wet season are the • Coral cores record large increases in presence, nature and extent of land- major delivery mechanism of land- the delivery of suspended sediment derived contaminants in GBR waters. derived contaminants to the GBR. and nutrients to the GBR, following the Satellite imagery technology has enabled introduction of cattle and fertiliser to the In GBR waters, concentrations of dissolved observation of the extent of flood plumes catchments since the 1860s. inorganic nitrogen (nitrate, ammonium), to distances substantially further than was suspended sediment and dissolved previously understood. Recent efforts to inorganic phosphorus are many times higher collate long-term water quality data have in flood plumes than in non-flood waters. identified some trends in water quality with strong regional differences and it is 2.a.v. Correlations exist between river- now clear that the presence of pesticides discharged material and GBR in GBR waters is widespread. lagoon water quality. Coral cores have been demonstrated as a Phytoplankton biomass and pesticide useful indicator of changes in the delivery concentrations in the GBR lagoon are of contaminants to the GBR and records directly correlated with river nutrient and show strong correlation of increases in pesticide loads, respectively. In inshore contaminants with introduction of cattle waters, long-term mean chlorophyll and intensive fertiliser use. concentrations are high to the south compared with north of Port Douglas, 2.a. Lines of evidence coinciding with more intense land use south of Port Douglas. Offshore chlorophyll 2.a.i. Contaminants are dispersed widely concentrations are similar south and within the GBR. north of Port Douglas, suggesting that the Remote sensing demonstrates the pattern is not due to latitudinal differences. transport of river plume derived dissolved Limited evidence exists for a relationship matter across and along the GBR lagoon, between regional turbidity and river through the reef matrix and out to the suspended sediment discharge. Coral Sea. Particulate matter is dispersed 2.a.vi. Temporal changes are observed in less widely and tends to be trapped and contaminants in GBR waters. deposited inshore. Evidence of temporal change in 2.a.ii. Pesticides are present in the GBR. contaminants in GBR waters is limited Pesticide residues, especially herbicides, due to the small number of long-term are detected in many GBR waters. monitoring programs; however, some Pesticides at biologically active examples include: concentrations have been found up to 60 • Evidence for increasing concentrations km offshore in the wet season and in low but of suspended sediments, dissolved detectable concentrations in the dry season. organic nitrogen and dissolved organic 2.a.iii. Contaminants may have long phosphorus in Cairns lagoonal waters residency times in the GBR lagoon. between 1989 and 2005 (the only long- term water quality monitoring program Most sediment is trapped near the coast in the GBR lagoon). and hence has decadal residence times in the GBR lagoon. Dissolved nutrients

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef 2.b. The evidence base management practices interact to produce ecosystems. The model is currently this presumably fine-grained, washload the only available marine exposure 2.b.i. Contaminants are dispersed widely (non-settling) suspended sediment. Areas analysis that covers the entire GBR and within the GBR. of catchments producing this component of is a useful representation of the spatial The large increase in the availability of the suspended sediment load will be of high extent of the coastal areas that are likely new satellite remote sensing platforms management priority. Further discussion to be regularly exposed to land runoff. (e.g. MODIS, MERIS, ASTER, SPOT-5, of the correlation between river discharge However, the model did not consider QUICKBIRD, IKONOS, SEAWIFS) added water quality and GBR lagoon water quality the consequences of this exposure – for to existing platforms (LANDSAT, AVHRR) is included in Section 2 in Part A. example to coral reefs – which should be part of a complete risk assessment. allows daily tracking of flood plume Marine water quality monitoring is Research findings that could contribute to dispersal in the GBR lagoon. The use of undertaken as part of the Reef Plan a future risk assessment are included in such images, combined with traditional Marine Monitoring Program established Section 3. concurrent surface vessel sampling and in 2004 and led by the Great Barrier image analysis for parameters such as Reef Marine Park Authority (GBRMPA). suspended sediments and chlorophyll Monitoring at inshore sites includes: a (A. Dekker, pers comm.) allows to collection of water column nutrients and quantify the spatial extent of exposure of suspended sediment concentration data GBR reefs and other ecosystems (Brodie around inshore reefs during the wet and et al., 2006; Rohde et al., 2006a; Brodie dry seasons; deployment of automated et al., 2007a). long-term water quality loggers at several Figure 2 shows how remote sensing regional locations; sampling of pesticides images can be used to support evidence in the water column at >10 inshore reef of material transport in flood events. and island sites; collection of chlorophyll a Of particular note in Figure 2a, is the samples in the water column at more than presence in 2007 of an algal bloom 50 sites from Cape York to the Burnett and the presence of coloured dissolved Mary regions; and monitoring of seawater organic matter (CDOM) derived from temperature using continuous loggers at Burdekin and Wet Tropics river runoff 28 sites (Prange et al., 2007). Some of dispersing completely across the mid and these tasks are assisted by community outer shelf reefs of the GBR between groups and tourism operators. A flood Townsville and Port Douglas and well plume monitoring program was also into the Coral Sea (Brodie et al., 2007a). initiated in 2007 to measure water quality Figure 2b shows the high sedimentation conditions in flood plumes in as many area near the mouth of the Burdekin River regions as possible. Remote sensing in 2005 where most of the suspended techniques to measure chlorophyll, sediment drops out. This area, and the turbidity, colour dissolved organic plume generally, is affected by wind over matter and temperature are also being a 48-hour period. Figure 2c shows a developed under the program. plume extending offshore and to the north Models have been developed to associated with Fitzroy River discharge estimate the exposure of Great Barrier in a large event in 2008; the movement Reef inner-shelf reefs to terrestrial of the body of discoloured water initially runoff using ratings of volume and northwards and then to the south requires frequency of discharge from major further explanation. Figure 2d shows the rivers, the predominant distribution of extensive algal bloom off nutrient-rich river plumes in GBR waters, loads of Mackay Whitsunday Rivers in 2005. riverine contaminants, and distance of It is believed that only a small proportion reefs to river mouths (Devlin et al., 2003; (perhaps 5%) of the suspended sediment Maughan et al., 2008). Coastal and island load of major rivers is transported large areas at high risk of exposure to terrestrial distances in the marine environment runoff were identified adjacent to the during major discharge events (evident Wet Tropics region, from Tully to north from satellite images and flood plume of Cairns, and in the Whitsunday region. monitoring). Limited knowledge exists This model has a number of limitations; on the specific origin in catchments of for example, it assumes single, average this small, but high risk, component river discharge events and does not and how geology, soil type and land deal with temporal dynamics; and it only assessed coral reefs as exposed

10 a b

Figure 2. Satellite images of the GBR coast in flood conditions in a) Burdekin and etW Tropics rivers in 2007 (MODIS image, 13 February 2007: CSIRO); b) Burdekin River in 2005 (MODIS image, 28 and 29 January 2005: CSIRO); c) Fitzroy River in 2008 (MODIS image, 22 February 2008: ACTFR); d) Mackay Whitsunday Rivers in 2005 (Landsat (7) image, 2005: NRW).

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef 2.b.ii. Pesticides are present in the GBR. Smaller-scale hydrodynamic models have 60 km offshore (Rohde et al., 2006a; 2008) been used to estimate current transport in the wet season flood plume conditions. As most of the pesticides of concern to and mixing of contaminants in Keppel marine ecosystems mix conservatively Most of the sediment discharged from Bay (Herzfeld et al., 2006). Cross-shelf during flood plumes, the concentration rivers, especially the coarser fraction, is mixing, which is important to move in marine waters is closely related to the deposited and trapped on the shelf close contaminants from the coast out to mid- concentration discharged from the river to the river mouth. This has been clearly shelf reefs, has been measured indirectly (Rhode et al., 2006a). Pesticides have shown for the Fitzroy River (Bostock using radium isotopes (Hancock et al., recently been recognised as a greater et al., 2007; Ryan et al., 2007) and the 2006) and salinity (Wang et al., 2007). potential threat to GBR ecosystems Burdekin River (Orpin et al., 2004). (mangroves, wetland plant communities, Hydrodynamic modelling of the GBR Subsequently to deposition, sediment seagrass, coral reefs, phytoplankton Lagoon has recently been reviewed is resuspended by tidal and wind driven communities) than was realised before in a study of the adequacy of existing currents and carried northward by the 2003. Pesticide residues, especially receiving water models for the GBR long shore current and eventually trapped herbicides, are ubiquitous in many GBR (Webster et al., 2008a). It was concluded in northward facing bays (Lambeck region waterbodies including streams, that while hydrodynamic modelling and Woolfe, 2000). However, a small wetlands, estuaries, coastal and reefal is in a moderately advanced stage, proportion (13%) of riverine sediment waters (e.g. Packett et al., 2005; Rohde the applications of fine-sediment and output is delivered across the shelf to the et al., 2006a; Faithful et al., 2007; Lewis biogeochemical models are much more Coral Sea (Queensland Trough) (Francis et al., 2007a). In marine waters, residues limited. These latter models are more et al., 2007). at biologically active concentrations have complex and much more difficult to been found up to 60 km offshore (Rohde calibrate and verify than hydrodynamic et al., 2006a) in the wet season and in models. Process studies are needed to low but detectable concentrations in the support their development as well as data dry season (Shaw and Muller, 2005; collection strategies that can be used Prange et al., 2007). for calibration and validation. Studies and analyses designed to address 2.b.iii. Contaminants may have long these issues are required to understand residency times in the GBR lagoon. both the acute and chronic impacts of The GBR Lagoon is a system that contaminants on the GBR Lagoon and receives contaminant inputs, moves how reducing catchment loads might these around, stores some of it by provide benefits to the biogeochemical burying it or incorporating it into living and ecological function of the GBR. matter, transforms some of the material 2.b.iv. Large river discharge events and ultimately exports the remainder. (‘floods’) are the major delivery Our understanding and ability to model mechanism of land-derived transport processes including currents contaminants to the GBR. and mixing which are responsible for transporting contaminants is relatively The highest concentrations of land-based well understood (Webster et al., 2008a). contaminants are found in GBR waters Hydrodynamic models have been during flood plume events. Concentrations developed on the scale of the GBR of dissolved inorganic nitrogen (nitrate Lagoon to predict water movement and ammonium), suspended sediment, (Legrand et al., 2006; Lambrechts et al., dissolved inorganic phosphorus are found 2008) and investigate the fate of flood at levels many times those in non-flood plumes (King et al., 2002) and to examine conditions, including upwelling offshore exchange times through the year (Luick waters (Devlin et al., 2001; Furnas, 2003; et al., 2007). Most sediment is trapped Devlin and Brodie, 2005; Rohde et al., near the coast (Orpin et al., 2004; Devlin 2006a, 2008; Packett, 2007) and many and Brodie, 2005) and hence has decadal times the concentrations that would have residence times in the GBR lagoon. occurred in these river plumes before Dissolved nutrients are dispersed more catchment development. Pesticide rapidly and may be trapped in the lagoon residues, especially herbicides, are almost by biological uptake and persist in this ubiquitous in GBR estuaries, coastal and particulate form for years (Furnas et al., reefal waters (e.g. Packett et al., 2005; 2005). Most pesticide residues have short Rohde et al., 2006a; 2008; Faithful et residence times (at most a few years) due al., 2007; Lewis et al., 2007a). In marine to their chemical breakdown (Haynes et waters, residues at biologically active al., 2000). concentrations have been found up to

12 Figure 3. Map of the spatial distribution of particulate nitrogen in the GBR (De’ath and Fabricius, 2008).

2.b.v. Correlations exist between river York waters more than 100 years ago. of all major water quality parameters, discharged material and GBR Offshore concentrations of chlorophyll indicating distinct areas of long-term lagoon water quality. also vary from south to north, but elevated concentrations of particular insufficient evidence exists to indicate parameters (Figure 3 shows particulate Nutrient loads can be related to that this is directly related to terrestrial nitrogen distributions, and Figure 4 chlorophyll concentrations in marine influence over external factors such as shows spatial distribution of water quality waters. Results from chlorophyll a upwelling, currents and tidal mixing. variables across the six NRM regions). monitoring in the GBR lagoon show that chlorophyll a is currently (1991–2006) Water quality data from the GBR lagoon low (mean 0.2 μg/L) in Cape York inshore have been spatially analysed and waters and higher (0.3–0.7 μg/L) in integrated into a series of maps (De’ath, central and southern GBR inshore waters 2005; De’ath and Fabricius, 2008), which (Brodie et al., 2007b). The assumption are being made available through the is that inshore central and southern Marine and Tropical Science Research waters have increased in chlorophyll Facility (MTSRF) Risk Resilience and concentrations due to enhanced nutrient Response Atlas. The maps show the inputs from a position similar to Cape spatial distribution of mean concentrations

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef Figure 4. Map of the spatial distribution of water quality variables across the six NRM regions, for coastal (0–0.1 relative distance across), inshore (0.1–0.4 relative distance across), and offshore waters (0.4–1.0 relative distance across) (from De’ath and Fabricius, 2008). The colour ramp represents Secchi disk depth, the pie charts the mean values for each of the 18 NRM × cross-shelf regions of: chl = chlorophyll, Secchi = Secchi disk depth, ss = suspended solids, pn = particulate nitrogen, and pp = particulate phosphorus. Of note are the high concentrations of ss, pn and pp in the Burdekin and Wet Tropics regions, and the high chlorophyll values in the Burnett Mary region and the low values in the coastal regions of Cape York.

14 The fate of nutrients following the Fine sediments introduced to the GBR cessation of flood plumes is not clear-cut. lagoon by flood events undergo cycles of High DIN concentrations in plumes are settling and resuspension by the winds associated with elevated phytoplankton and tides and can be dispersed far from concentrations (Wooldridge et al., 2006; the river mouth. Larcombe and Woolfe Devlin and Brodie, 2005). What is less (1999) argue that chronic turbidity at coral well understood, is how the discharge of reefs due to suspension of fine sediments nutrients might cause a chronic impact on by tides and winds will not be significantly inshore reefs. Dissolved nutrients will be affected by changes in sediment inputs carried and mixed by currents, but some due to catchment management since will fuel the growth of sessile organisms the sediments pool in the lagoon is such as micro- and macroalgae and so large. Measurements in Keppel Bay be retained by the system. Nutrients (Radke et al., 2006) suggest that there associated with particles will follow is a relationship between turbidity and dynamics of settling, resuspension, burial, river discharge of sediment suspended and diagenesis processes that might associated with flood events. In the mouth ultimately release these nutrients in forms of the Fitzroy Estuary, where suspended suitable for plant growth. Measurements sediment concentrations show a strong in Keppel Bay suggest that ~1/3 of the tidal cycle, these concentrations are input particulate nitrogen and phosphorus higher in the period following riverine is buried in sediments, presumably in inputs than later in the year when riverine refractory form (Radke et al., 2006). inputs have ceased for six months. It Further, the biogeochemical modelling would appear that freshly introduced work in Keppel Bay (Robson et al., sediments are more readily suspendable. 2006a) suggested a significant missing Later, much of this suspendable sediment source of bioavailable nitrogen was moves into zones where it is less readily necessary in Keppel Bay in order to close suspended, such as in northern facing the budget of this nutrient. Laboratory bays or in the tidal creeks. Fine-sediment experiments on sediment cores collected transport is very difficult to model from the bay suggest that the source may effectively. The question as to whether have been benthic nitrification (Radke et increased suspended sediment loads al., 2006). For phosphorus, river inputs from increased erosion from agricultural appear to be retained close to the coast and urban development in major rivers in the central GBR and phosphorus inputs lead to increased regional turbidity due to upwelling events are a greater generated by resuspension in inshore contribution to shelf phosphorus budgets areas of the GBR lagoon (with depths than local river inputs over an average generally less than 10 m) is also being year (Monbet et al., 2007). examined in a current Marine and Tropical Sciences Research Facility (MTSRF) Recent research by Wallace et al., (2007) research program. Initial results from has also raised questions regarding the the Tully and Burdekin regions suggest fate of the dissolved organic nitrogen there is a period of increased turbidity (DON) fraction of the nitrogen load from for several months following each flood agriculturally developed catchments plume event (Wolanski et al., 2008). of the GBR catchment area. DON was previously considered to be relatively Pesticide concentrations in plume waters refractory and non-bioavailable on a very are directly correlated to pesticide limited theoretical basis. However, DON concentrations in river discharge as is a large component of the nitrogen the main process affecting plume load in many rivers and the degree of concentrations is dilution. This notion its bioavailability will be a critical factor is best supported by the information on in assessing the risk to both fresh mixing curves investigated in the Mackay and marine ecosystems from nitrogen Whitsunday region (Rohde et al., 2006a). driven eutrophication. In addition, the bioavailability of particulate nitrogen and phosphorus needs to be further investigated in the GBR catchments and lagoon.

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef Figure 5. Mn and Y concentrations in the coral core from 1813–1986. Yttrium concentration, like Ba, is interpreted to be an erosion indicator, steadily increasing after 1860–70. Manganese defines a different history. Elevated Mn concentrations coincide with major land settlement in the Burdekin catchment. The initial Mn spike in 1855–1856 is related to the establishment of the first sheep run in the southern Burdekin catchment. The peak Mn concentration coincides with the end of the American Civil War and the climax of rapid expansion of the sheep industry in the Burdekin catchment. The second major Mn peak in 1883–1884 coincides with, and may thus be related to, the expansion of the cattle industry or the beginning of the sugarcane industry on the lower Burdekin catchment. The return of Mn concentrations to pre-1850 levels coincides with the Federation Drought, which devastated sheep and cattle numbers throughout the catchment. An increase in Mn after World War II may be related to the further development of the cattle industry. Reproducibility of Mn by our method is shown for the (slightly heterogeneous) G.S.J. coral standard JCp-1. Also shown for comparison, are average and standard deviation of Mn in a mid-Holocene coral recovered from Nelly Bay, Magnetic Island. Source: Lewis et al., (2007b).

16 2.b.vi. Temporal changes are observed in Increases in nitrogen delivery, up to four- from resuspension in inshore areas of contaminants in GBR waters. fold, have also been demonstrated from the GBR lagoon. coral cores off Mackay associated with Increasing concentrations of suspended • Improved availability of high frequency, increasing fertiliser use for sugarcane sediment (TSS), dissolved organic low cost data through the application of cultivation in the Mackay region (Jupiter nitrogen (DON) and dissolved organic innovative monitoring techniques such et al., 2007; Marion, 2007). phosphorus (DOP) are evident in the only as remote sensing will enable more long-term repeated sampling program comprehensive assessment of the in the GBR lagoon for nutrients – the 2.c. Key uncertainties related presence and extent of contaminants in Cairns transect of Miles Furnas (AIMS). to presence, nature and the GBR. Concentrations of TSS increased from extent 1.6 to 3.7 mg/L, DOP from 1.1 to 16 μg/L The following points summarise the key and DON from 68 to 91 μg/L in the period uncertainties associated with knowledge 1989 to 2005 (Furnas et al., 2005). At related to the presence, nature and extent Low Isles, Secchi disc transparency has of land-derived contaminants in the GBR: almost halved from 11 in 1928 (during • Our conceptual and quantitative a 1-year study by the British Museum understanding of the transport and fate field expedition), to 6 m during current of nutrients and sediments is highly measurements (Wolanski et al., 2004). imperfect, particularly during The use of coral cores to show the non-flood times. presence of a ‘terrestrial signal’ in the • Hydrodynamic models of the GBR GBR, and hence changes in the delivery Lagoon are moderately advanced, but of materials from the land to the GBR models of the transport and fate of fine with catchment development, are now sediments and biogeochemical models well established. For example, the ratio of are much more limited. Process studies barium to calcium in corals offshore from as well as data collection strategies the Burdekin River indicated a five- to that can be used for calibration and ten-fold increase in suspended sediment validation are needed to support their loads following European settlement of development. Current models need the Burdekin catchment. This has been to link end of river to specific reef interpreted as indicating a large increase locations. in erosion and delivery of suspended • Satellite images and flood plume sediment to the mouth of the Burdekin monitoring suggest that some River, where the barium adsorbed onto suspended sediment is transported the sediment desorbs and is taken over large distances in the marine up by the coral. The barium replaces environment during major discharge calcium in the coral structure, resulting events. However, knowledge is limited in an altered ratio of Ba/Ca indicative of of the specific origin of this presumably a land-based influence (McCulloch et fine-grained, washload (non-settling) al., 2003b; Lewis et al., 2007b). Other suspended sediment, and how geology, metals including yttrium and manganese, soil type and land management which are used as indicators of erosion practices interact to produce it. and land settlement, also show changed concentration in coral cores after 1860 • While all terrigenous sediments and (Lewis et al., 2007b). Figure 5 shows an pesticides are land-derived, some of example of results from Magnetic Island the dissolved nutrients are sourced in the Burdekin region. from deepwater upwelling and from nitrogen fixing blue-green algae. Additional proxies in coral cores of past Improved nutrient budgets are needed water quality conditions are currently to quantify the relative contributions of being developed (Alibert et al., 2003; all sources. Wyndham et al., 2004; Sinclair, 2005; • Processes beyond gauging stations are Marion et al., 2005). Changes in poorly understood (i.e. what is entering the amount of water discharged due the coastal/estuarine interface and to vegetation change/loss and soil material transformation in estuaries). compaction in catchments have also been investigated using coral cores, and • It is unclear whether increased some dispute currently exists over the suspended sediment loads due to interpretation of this record (McCulloch, increased erosion from agricultural 2006; Lough, 2007). and urban development in major rivers leads to increased regional turbidity

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef 3. Review scientific evidence for causal relationships between water quality change and ecosystem health

Conclusion: There is strengthened 3.a.ii. Coral reefs. (aggregates of planktonic organic evidence of the causal relationship matter and fine sediment) increases The impacts of water quality on corals between water quality and coastal sedimentation stress and mortality in has been demonstrated through both field and marine ecosystem health. coral recruits. studies and laboratory experiments. Field Our understanding of the effects of studies have shown that: • Many pesticides found in the GBR exert land-sourced contaminants on GBR detrimental effects on zooxanthellae • Macroalgae increase and coral richness species and ecosystems has been photosynthesis and coral reproduction declines with increasing turbidity and expanded enormously in the period at trace concentrations. chlorophyll in the GBR (Lat 12–24º S). since 2003. However, the size of the • There are negative synergistic effects system and its temporal variability means • Links between nutrient enrichment and between herbicides and sediments that ‘representative’ monitoring and crown-of-thorns starfish population on crustose coralline algae that are measurement of conditions in the water outbreaks are now well supported. essential for successful coral recruitment. column and of ecosystem condition is Both the GBR and other reefs off high 3.a.iii. Mangroves. difficult. The impacts of water quality on islands exposed to terrestrial nutrient corals have been demonstrated through enrichment, and northern Pacific There is conflicting evidence concerning laboratory and field studies and data systems exposed to non-anthropogenic the cause of mangrove dieback in the synthesis and integration has enabled the nutrients show increased propensities Mackay region. Early research attributed development of trigger values/thresholds for outbreaks of crown-of-thorns starfish. an association with diuron, but affected of corals to water quality parameters. • Coral reef development diminishes mangroves have recovered despite diuron Knowledge related to the impacts of along a water quality gradient in the levels remaining high at some sites. water quality on seagrasses has been Whitsunday Islands. Changes include This suggests that the complexities of synthesised. Efforts to understand the the decline in the depth limit for coral cause and effect relationships for such synergistic effects of multiple stressors on growth from 25 m to 5 m water depth diebacks are yet to be fully resolved. corals and seagrasses have commenced. and a three-fold decline in the density However, the complexity of the of young corals, while the density 3.b. The evidence base relationship between nutrient enrichment, of coral-boring macro-bioeroders 3.b.i. Seagrass. coral reef decline, macroalgal proliferation, increases five-fold and macroalgal grazing fish abundance (and other cover increases six-fold along this The distribution and growth of seagrasses grazers) still prevents there being a clear water quality gradient. is dependent on a variety of factors consensus view on these relationships. • Coral cores from reefs off Mackay show such as temperature, salinity, nutrient that increasing exposure to nitrogen availability, substratum characteristics, 3.a. Lines of evidence from the Pioneer River is correlated and underwater light availability (turbidity). Terrigenous runoff, physical disturbance, 3.a.i. Seagrass. with poor reef condition and high macroalgal cover. low light and low nutrients, respectively, There is evidence of decline in seagrass are the main drivers of each of the • Inshore reefs off the Wet Tropics have health with increasing concentrations four seagrass habitat types found in lower coral and octocoral diversity of herbicides. The effects of nutrient Queensland and changes to any or all of than would be expected from their enrichment, turbidity, increased these factors may cause seagrass decline latitudinal location. temperature and synergistic effects are (Waycott et al., 2005). still poorly understood, especially for sub- Laboratory studies have shown that: The most common cause of seagrass tidal and deep-water seagrass beds. • Stress and mortality in corals exposed loss is the reduction of light availability to sedimentation increases with due to chronic increases in dissolved increasing organic content of the nutrients which leads to proliferation sediment. of algae, thereby reducing the amount • Coral calcification decreases with of light reaching the seagrass (e.g. elevated phosphate concentrations. phytoplankton, macroalgae or algal epiphytes on seagrass leaves and • The presence of muddy marine snow

18 stems), or chronic and pulsed increases not have a negative effect on seagrass have not yet reached critical levels for in suspended sediments and particles growth and distribution, as reported seagrasses. However, the limits of the leading to increased turbidity (Schaffelke in temperate regions (Mellors et al., ability of seagrasses to continue to absorb et al., 2005). In addition, changes of 2005). On the contrary, Udy et al. (1999) nutrients is not known and additional sediment characteristics may also play a observed an increase in seagrass experiments on interactions between critical role in seagrasses loss (Mellors et cover at Green Island between 1936 sedimentation, nutrients, light and al., 2005). and 1994, and attributed this increase temperature as other important drivers to a net increase in the total nutrient of plant growth are required. In addition, Herbicides (principally diuron) have pool available over 50 years of gradual nutrient analyses have been conducted been found in coastal and intertidal build-up of nutrients in the Cairns region. primarily on the smaller more ephemeral seagrasses adjacent to catchments with Recent data on seagrass tissue nutrient species. Larger more persistent species high agricultural use at levels shown to content (Halophila ovalis) collated by may be more sensitive to additional adversely affect seagrass productivity Mellors (2003) and Mellors et al., (2005) nutrients in this region and this should be (McMahon et al., 2005; Haynes et al., in Cleveland Bay shows an increase in assessed (CRC Reef Consortium, 2005). 2000). For example, diuron toxicity tissue nutrients over a 25-year period, trials on three tropical seagrass species The Reef Plan Marine Monitoring which circumstantially reflects increases (Halophila ovalis, Cymodocea serrulata Program includes a seagrass monitoring in fertiliser usage in the adjacent and Zostera capricorni) using Pulse- component, which involves monitoring Burdekin catchment. Amplitude-Modulated (PAM) fluorometry of intertidal seagrass meadows at 14 indicated that environmentally relevant Direct effects of higher nutrient sites along the GBR coast for percent levels of diuron (0.1–1.0 µg/l) exhibited availability on seagrass have been cover, species composition, reproductive some degree of toxicity to one or more observed in laboratory experiments. health (through seedbank monitoring) and of the tested seagrass species (Haynes Moderate levels of nitrate additions seagrass tissue nutrient status. Seagrass et al., 2000). These are comparable with (3.5 to 7.0 µM) promoted the decline surveys are undertaken at the end of diuron concentrations detected in several of the temperate seagrass species winter in October and following the wet GBR regions (Prange et al., 2007). Zostera marina (Burkholder et al., 1992; season in April. Additional information is Seagrasses are known to accumulate Short et al., 1995). Increased levels of also collected on sediment pesticide and heavy metals, but appear to be ammonia (1.85–5.41 µM) and phosphate absorbed nutrient concentrations within moderately resistant to the direct effects (0.22–0.50 µM) lead to a reduction in seagrass meadows and seagrass tissue of metals. However, the fauna associated shoot density and biomass of Z. marina nutrients (Prange et al., 2007). This task with seagrass meadows is considered (Short et al., 1995). The concentrations is assisted by the community-based to be highly sensitive to metal exposure measured in water samples taken in Seagrass-Watch program (Ward, 1989). flood plumes have consistently recorded (www.seagrasswatch.org). elevated dissolved inorganic nitrogen The effects of nutrients on GBR seagrass concentrations of 0.6 to 10 µM and health have proved more complex to phosphate levels of 0.13 to 1.98 µM understand but it is now clear that the (Brodie and Mitchell, 1992; Steven et al., effects are different to those shown for 1996; Brodie and Furnas, 1996; Devlin temperate seagrass and the threat from et al., 2001). These nutrient levels have increased nutrients may be less in tropical remained high in the inshore lagoon cases (Mellors et al., 2005; Schaffelke et for periods of several days to weeks. al., 2005; Waycott et al., 2005). To date, Approximate ranges for (non-flood) no major decline in seagrass abundance inshore water nutrient concentrations in the GBR region has been recorded or have been measured between non- attributed directly to increased nutrient detectable and 2 µM for dissolved availability, though localised declines inorganic nitrogen (predominantly have occurred in the Whitsunday and ammonia) and non-detectable and 0.2 µM Hervey Bay areas. In both cases, light for phosphate (Furnas et al., 1995; Brodie deprivation was implicated, by (i) algal and Furnas 1996; Devlin et al., 1997). overgrowth caused by nutrient enrichment from sewage effluent (Campbell and Other studies have shown that in the McKenzie, 2001) and (ii) smothering by GBR seagrass growth is limited by settling particles and high suspended nitrogen (Udy et al., 1999; Mellors, 2003). particle load from flood plumes (Campbell Both studies assessed the response of and McKenzie, 2004; Preen et al., 1995; seagrass to enhanced nutrient levels Longstaff and Dennison, 1999). and saw a response to both nitrogen and phosphorus, but nitrogen was The presence of high or low the primary limiting element. Thus, at concentrations of nutrients in the present, seagrasses have the capacity environment is one of the stressors on to absorb additional nutrients enhancing seagrass survival. Field research to date their growth and it would appear that in the GBR suggests that nutrients do the current nutrient loadings in the GBR

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef 3.b.ii. Corals. Studies where the predicted ecological • Reduced coral reef development in effects of poor water quality (elevated a water quality gradient through the Corals and water quality – field studies. delivery and/or concentrations of Whitsunday Island group (van Woesik Strong links between coral reef health suspended sediment, nutrients or et al., 1999). and water quality conditions have pesticides) have been borne out in the • A raft of physiological changes in corals been shown at local scales (reviewed field in the GBR include: have been documented along a water in Fabricius, 2005), at regional scales • Deepest depth of coral growth reduced quality gradient in the Whitsunday Island (van Woesik et al., 1999, Fabricius et from 25 m to 5 m depth, the number group (Cooper and Fabricius, 2007). al., 2005), and recently at a GBR-wide of young corals decreased three-fold, These sub-lethal changes are now being scale (De’ath and Fabricius, 2008). the density of coral-boring macro- developed into a bioindicator system to The effects of corals have been most bioeroders increased five-fold and investigate changes in the water quality frequently studied and effects of water macroalgal cover increased six-fold conditions and ecological status of quality on coral reproduction have along a water quality gradient in the inshore coral reefs. been reported repeatedly. However, Whitsundays (Cooper and Fabricius, • The species composition of foraminifera abundances of a range of other reef 2007, Fabricius et al., 2008, Cooper et (the ration between large, symbiont associated organisms have also been al., 2008). bearing and small, heterotrophic shown to change along water quality foraminifera) is being developed into a gradients. Figure 6 summarises the • Poor reef condition correlated with poor bioindicator system for the GBR. The results of a review of existing reef studies water quality conditions in Wet Tropics Foraminifera in Reef Assessment and from around the world to identify the main inshore reefs compared with reefs in Monitoring Index metric, previously effects of nutrient and sediment related similar physical locations near Cape developed for coral reefs in the parameters on key coral reef organism York, but which have good water quality Caribbean, shows a relationship with groups. The data suggests that nutrient (Fabricius et al., 2005). water quality conditions along the enrichment can lead to macroalgal • A sag in coral biodiversity in the region Whitsunday water quality gradient dominance if light levels are sufficient, between Townsville and Cooktown (Uthicke et al., 2006; Uthicke and but lead to a dominance by heterotrophic correlated with poor water quality Nobes, 2007). filter feeders if light becomes a limiting conditions in this area (Devantier et al., factor for macroalgae (Johannes et al., 2006). • The delivery of nitrogen from the Pioneer River to coastal reefs in the 1983; Birkeland, 1988). It also shows • Links between nutrient enrichment Mackay area as shown through coral that crustose coralline algae, which and crown of thorns starfish population core records is correlated with poor reef are essential settlement substratum for outbreaks are now well supported in both condition in areas of higher nitrogen coral larvae, are negatively related to anthropogenically enriched systems such delivery and a high proportion of sedimentation (Fabricius and De’ath, as the GBR (Brodie et al., 2005) and macroalgal cover (Jupiter et al., 2007). 2001), as later confirmed by laboratory naturally enriched systems such as the experiments (Harrington et al., 2005). northern Pacific (Houk et al., 2007).

Dissolved Light POM* Sedimentation inorg. nutr reduction

Crutose coraline algae

Bioeroders

Macroalgae

Heterotrophic filter feeders

Coral diseases

Coral predators

* including phytoplankton

Figure 6. Effects of the four main parameters of terrestrial runoff on organisms that interact with corals. High abundances crustose coralline algae as settlement substrata promote coral populations, whereas high abundances of the other groups are assumed to negatively affect coral populations. The arrows indicate the relative strength and direction of the response (arrows pointing up or down = increasing or decreasing, thick arrow = strong, medium = moderate, thin = weak effect); empty cells indicate that insufficient data are available. From Fabricius (2005).

20 While pollution effects on coral reefs at outbreaks of the coral eating COTS, and al., 2006). The full extent of organism local scales are well understood, links is further complicated by the naturally responses are poorly understood, as each at regional scales between increasing high variability in monsoonal river flood of the numerous inshore species has its sediment and nutrient loads in rivers, events. In addition, the relationship own tolerance limit at every life stage, and and the broadscale degradation of between macroalgal proliferation, nutrient interactions between the organisms add coral reefs, have been more difficult enrichment and the abundances of to the complexity. to demonstrate (Fabricius and De’ath, grazers (fishes and invertebrates) is 2004). This is due to a lack of large- complex and far from understood, and scale historic data and the confounding subject to scientific debate (McCook, effects of other disturbances such as 1999; McCook et al., 2001; Bellwood et bleaching, cyclones, fishing pressure and al., 2006; Hughes et al., 2005; Littler et

Figure 7. Relationship of macroalgal cover, and the taxonomic richness of hard corals, phototrophic and heterotrophic octocorals (soft corals and sea fans with and without zooxanthellae, respectively), along gradients in water clarity (measured as Secchi disk depth) and chlorophyll, while also controlling for relative distance across and along the shelf (from De’ath and Fabricius 2008). Substantial increases in macroalgal cover and losses in coral biodiversity are being observed at <10 m Secchi disk depth, and >0.45 µg L-1 chlorophyll. The red lines show the proposed water quality guideline values (10 m Secchi disk depth, and 0.45 µg L-1 chlorophyll).

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef However, recently relationships between In terms of ongoing monitoring of coral Though considerable knowledge data sets of water quality, and macroalgal reef health, the Reef Plan Marine has been gained from single species cover and the richness of hard corals and Monitoring Program includes an inshore exposure experiments in the laboratory, phototrophic and heterotrophic octocorals, reef monitoring component. Annual it is important to relate such laboratory were investigated at a GBR-wide scale underwater photographic surveys are studies to field settings and ecosystem (De’ath and Fabricius, 2008). The study undertaken along transects established responses. Detailed surveys at relatively showed that the four biotic indicators at 35 inshore reef sites. These surveys fine taxonomic resolution, when chosen are significantly related to GBR are an effective way of monitoring benthic cautiously interpreted in the context of water quality. Macroalgae increased and cover and reef community demographics. available biophysical environmental data hard coral richness and the richness of Coral settlement rates are also measured and biological knowledge of key species, phototrophic octocorals declined with after the annual coral spawning (using can provide important information on increasing turbidity and chlorophyll, settlement plates) in the Wet Tropics, the health and status of inshore coral after cross-shelf and long-shore effects Burdekin, Mackay-Whitsunday and reefs (Fabricius et al., 2005; Devantier were statistically removed (Figure 7). Fitzroy regions. Adult corals can tolerate et al., 2006), and laboratory experiments Heterotrophic octocorals slightly benefited poorer levels of water quality than new may then be used to investigate causal from high turbidity. Mean annual values coral recruits, thus one of the ways in relationships between water quality and of >10 m Secchi depth and <0.45 g L-1 which water quality is likely to impact reef the patterns observed in the field. chlorophyll were associated with low communities is through an effect on coral Recently, several conceptual models macroalgal cover and high richness of reproduction and recruitment (Prange et have been developed to articulate phototrophic octocorals and hard corals. al., 2007). known relationships to better underpin The study suggested these values to Corals and water quality monitoring programs and form the basis be useful water quality guideline values. – laboratory studies. for numerical modelling (Prange, 2007; These guidelines are presently exceeded Webster et al., 2008a; Haynes et al., on 650 of the 2800 gazetted reefs of A number of ecotoxicology-style 2007; Fabricius, 2007). the GBR. The models showed that experiments exist to investigate the compliance with these guideline values effects of various contaminants on 3.b.iii. Mangroves. (e.g. minimising agricultural runoff would selected target organism groups. Such The responses of marine plants likely reduce macroalgal cover by ~50% studies include the investigation of (mangroves, seagrass and macroalgae) and increase hard coral and octocoral nutrients on corals (Koop et al., 2001) and to changes in water quality in the GBR is richness by 40% and 70%, respectively, of sedimentation stress on corals (Philipp reviewed in Schaffelke et al. (2005). on these 650 reefs). GBRMPA is in the and Fabricius, 2003). Herbicides found The limited information of these process of refining the existing water in GBR waters have biological effects responses limits the ability to make quality guidelines that have previously on coral zooxanthellae at concentrations conclusions about responses across been developed for three GBR regions below 1 μg/L (e.g. Jones and Kerswell, community types; however, there (Moss et al., 2005; De’ath and Fabricius, 2003; Jones et al., 2003; Jones, 2005; are clear indications that declining 2008; GBRMPA, 2008). Negri et al., 2005; Markley et al., 2007; water quality negatively affects Cantin et al., 2007). The long-term This synthesised information GBR macrophytes. In addition, loss effect on ecosystem performance of the could support the completion of a or disturbance of habitat-building continuous presence of such residues comprehensive risk assessment for the macrophytes such as mangroves and is not known, but evidence is emerging ecosystems of the GBR that should seagrasses has serious downstream that some pesticides not only affect the include consideration of the relative effects for coastal water quality due to photosynthesis of the endosymbionts risk of different contaminants to GBR their capacity to assimilate nutrients and but also coral reproduction (Jones, ecosystems. Currently, the risk modelling to consolidate sediments. 2005; Negri et al., 2005; Markley et (such as Maughan et al., 2008; Wolanski al., 2007; Cantin et al., 2007). Lastly, Mangrove responses to nutrients and De’ath, 2005) assumes that all first evidence is emerging that the are complex, with examples of both contaminants of concern are of equal existence of synergistic effects may enhanced growth and associated risk, which is clearly not the case. This have to be carefully considered in dieback found in locations outside of the lack of knowledge prevents prioritisation estimates of tolerance thresholds GBR (e.g. Laegdsgaard and Morton, of management options for each of (and hence water quality targets). For 1998; Environmental Protection Agency the individual contaminants in the example, sedimentation effects on [EPA], 1998). As with the nuisance catchments, or at a cross-regional scale. crustose coralline algae are significantly algae, nutrients enhance growth To conduct a meaningful prioritisation, worsened when trace concentrations of mangrove plants. This has been knowledge of the degree of deviation from of herbicides occur in the sediments demonstrated in nutrient enrichment some assumed ‘natural’ condition and (Harrington et al., 2005). Other studies experiments, which also showed that elevation above trigger values/thresholds, have demonstrated that sedimentation nitrogen and phosphorus were growth- and potential consequences of such effects on corals worsen with increasing limiting differently at lower and higher enrichment need to be understood. organic enrichment of the sediments intertidal positions (Boto and Wellington, Currently, contaminant management (Weber et al., 2006), and with enrichment 1984). Nutrients derived from sewage is prioritised based on deviation from with marine snow (Fabricius et al., 2003; discharge can be beneficial for growth assumed ‘natural’ only. Wolanski et al., 2003). and productivity of mangroves (Clough

22 et al., 1983). However, under high have shown an overall improvement in • Knowledge of the response of the nutrient demand other chemicals, such the health of A. marina although herbicide GBR ecosystem to different events as herbicides, may be taken up at greater levels in sediments and pore water have in different areas, and the ability to rates along with extra nutrients (Duke remained high at some sites recover. Understanding the implications et al., 2003a). This synergistic effect (Wake, 2008). of combined scale and frequency of of increased nutrients has resulted in disturbance to GBR ecosystems. The dieback has also been attributed the increased phytotoxicity of specific to sedimentation (Kirkwood and • The relative risks to GBR herbicides (Hatzios and Penner, 1982). Dowling, 2002). ecosystems of individual terrestrial- High nutrient levels may also alter sourced contaminants. faunal communities that might affect These findings indicate that the causes • The complexity of the relationship the vulnerable trophic links between of such diebacks require further between nutrient enrichment, coral reef mangrove trees and fauna (Robertson et investigation and the complexities of decline, macroalgal proliferation and al., 1992). cause and effect relationships are yet to abundances of grazing fishes be fully resolved. Increased sediment loads in runoff from (and other grazers) still prevents there catchments affect mangrove distributions being a clear consensus view on this within estuaries as well as water quality 3.c. Key uncertainties related specific relationship. (Duke et al., 2003b). In recent decades, to causal relationships there have been unprecedented gains between water quality and in mangrove areas at the mouths of at ecosystem health least four GBR river estuaries, Trinity The following points summarise the key Inlet (Duke and Wolanski, 2001), uncertainties associated with knowledge Johnstone River (Russell and Hales, related to the causal relationships 1994), Pioneer River (Duke and Wolanski, between water quality change and 2001) and Fitzroy River (Duke et al., ecosystem health. 2003b). Although these rivers occupy a • While a limited number of models exist broad range of climatic and geographic that attempt to link marine ecosystem conditions, they each have characteristic health to end of catchment loads, and significant new mangrove stands. At further development is required as the mouth of the Fitzroy River, the area of a matter of urgency to assess the mangroves had been relatively constant influence of catchment management for a century but increased rapidly after actions on GBR health in a the 1970s. The increases were correlated comprehensive way. with concurrent human activities including increased clearing of vegetation in the • Synergistic effects of contaminants catchment, which increased sediment and external influences on GBR loads in runoff, and the construction of a ecosystems. major river barrage, which reduced river • Definition of acceptable/desired flows and flushing. thresholds for key indicators (i.e. coral, seagrass and biodiversity). An unusual species-specific dieback of Avicennia marina has been observed • Drivers of seagrass change and health, in the Mackay region since the mid- in particular the influence of declining 1990s (Duke and Bell, 2005; Duke et water quality, especially nutrients al., 2005 ). By 2002, it was estimated and turbidity. that 97% of the A. marina trees in the • The specific impacts of pesticides Pioneer River estuary were affected (particularly herbicides) on the GBR by moderate to severe dieback (Duke ecosystems. Presently there is a lack et al., 2003a). Laboratory studies have of toxicity data for organisms specific shown that mangroves are sensitive to to the GBR. Much of the current the root application of atrazine, diuron research has been focused particularly and ametryn (Photosystem II inhibiting on corals with comparatively little data herbicides) and Avicennia marina is on mangroves, seagrass and micro- more sensitive than other mangroves organisms. In addition, the synergistic tested (Bell and Duke, 2005). Although effects of mixtures of pesticides are the Mackay dieback was associated with relatively unknown, as well as the the levels of diuron and other herbicides effects of long-term exposure. present in mangrove sediments and pore • Understanding the response of water, and in stream/drain waters flowing estuarine systems to floods and the role into mangrove areas (Duke and Bell, of the coastal floodplain. 2005), two recent surveys of mangrove communities in the Pioneer River estuary

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef 4. Review existing scientific evidence for a decline in the quality of water in GBR catchment waterways leading to reduced instream ecosystem health

Conclusion: The health of freshwater 4.a. Lines of evidence 4.b. The evidence base ecosystems is impaired by agricultural land use, hydrological change, riparian 4.a.i. Priority factors affecting instream 4.b.i. Priority factors affecting instream degradation and weed infestation. ecosystem health are riparian ecosystem health are riparian vegetation condition, aquatic and vegetation condition, aquatic and Waterways of the GBR catchment include riparian weed prevalence, vegetation riparian weed prevalence, vegetation streams that drain forested uplands removal and habitat loss. removal and habitat loss. and the cultivated tablelands of the Wet Tropics, intermittent dry-land streams, These factors have been shown to be As described in Section 1, water quality lowland rivers and estuaries, and the more important factors reducing instream conditions in the GBR catchments lagoons and swamps of the floodplains. ecosystem health than water quality per se. in runoff events are reasonably well documented; water quality in the In the Wet Tropics, most systems are 4.a.ii. Concentrations of nutrients in fresh catchments through the non-event perennial, but in the Dry Tropics, streams waters in many catchments are periods is much less well documented. and wetlands may be intermittent, and proportional to the area of land It is this ambient or chronic water quality even large rivers may contract to isolated under agriculture. waterholes in the dry season. that is of greatest importance to the Elevated nutrient inputs from agricultural ecology of the rivers and wetlands, as Our understanding of the ecosystem sources are known to contribute to opposed to the short-term events that health of GBR waterways has been enhanced weed growth, vegetation change appear to drive water quality in coastal greatly enhanced by recent reports on and associated changes in instream waters. The relative importance of Wet Tropics streams (e.g. Arthington and community structure. ambient inputs to coastal ecosystem Pearson, 2007) and floodplain waterways processes is also not known. (Pearson et al., 2005), and on the riverine 4.a.iii. Agricultural development has led to waterholes and floodplains of the dry substantial damage to riparian and However, the most serious factors tropics (e.g. Perna and Burrows, 2005). wetland health in many catchments. affecting health in Wet Tropics streams and wetlands are changes to habitats, The GBR catchments support high These influences have negative including invasion by exotic weeds biodiversity and many endemic species of consequential effects on water quality and and loss of riparian vegetation, which freshwater fish (Pusey et al., 2004), some hence detrimental effects on instream biota. of the highest diversity of freshwater can cause major changes to waterway invertebrates in the world (Pearson et 4.a.iv. Concentrations of pesticides in morphology, habitat complexity, food al., 1986; Vinson and Hawkins, 2003; waterways are highest in areas of availability, gas exchange with the Pearson, 2005), and many species of intensive agricultural activity. atmosphere and, therefore, biodiversity. Organic effluents have been shown to aquatic plants (Mackay et al., 2007). The implications of elevated pesticide cause fish kills and a major decrease concentrations for community structure While the diversity of information on in biodiversity as a result of oxygen in freshwater ecosystems are potentially catchment freshwater health is increasing, depletion; and deposition of fine sediments severe but our knowledge is incomplete. much work is unpublished. Recent derived from agriculture and other sources reviews on within-catchment water quality 4.a.v. The condition of riverine waterholes in reduce biodiversity in streams. and ecosystem health have focused the Dry Tropics is largely determined The multitude of human impacts that on the Wet Tropics (e.g. Pearson and by cattle access. Stork, 2007; Connolly et al., 2007a, might affect catchment and GBR health 2007b; Pusey et al., 2007; Faithful et al., Cattle contaminate and disturb the is summarised in Figure 8. The most 2006); there has been less work on the waterholes causing deoxygenation important of these potential impacts is Dry Tropics, highlighting an important from excretia, increased turbidity, and land clearing (Pearson and Stork, 2007). information gap, although reports on the consequent loss of biodiversity. Burdekin and the Fitzroy systems are 4.a.vi. The condition and biodiversity of advancing our understanding of floodplain waterways are adversely those systems. affected by irrigation inputs and drainage. Sediments, nutrients from fertilisers and organic material have been shown to lead to oxygen depletion, enhanced weed growth, turbidity and hence biodiversity loss.

24 Human Natural influences processes

Rainfall and cloud capture Rainfall and cloud capture reduced by climate change feed pristine streams – more seasonal flows Perennial flows sustain high Loss of riparian vegetation biodiversity in streams severely alters stream habitat Riparian vegetation shades stream, Clearing of vegetation protects banks, input organic increases sediment and material and provides habitat nutrient input Downstream change as stream widens and deepens, Water infrastructure prevents with increasing instream plants, connectivity, severely alters and more fish species flows, affects water quality and biological processes Many small streams and ground water drain floodplain Irrigation alters flows and smaller catchments in wetlands Stream water quality Weed infestation reduces maintained by local processes connectivity and water quality Seasonal floods replenish Agriculture, grazing and urban extensive wetlands development add substantially Groundwater sustains to natural sediment and permanent wetlands nutrient loads Migratory species move Connectivity halted by water between stream, estuary, management activities – wetlands and reef weirs, drop-boards, culverts, etc Wetlands of different Agrichemicals boost nutrients character provide habitat for and add poisons numerous fish and prawns

Reef waters receive constant Floods carry materials into enhanced input of chemicals coastal waters, influencing Some resilience of reefs, sea grasses, etc., and sediment, with huge water quality up to thresholds, yet to be determined pulse during floods

Figure 8. Outline of processes from catchment to reef (adapted from Pearson and Stork, 2007).

However, in the Wet Tropics, there is little substrate it can have major effects it appears that introduced fishes do available land left to clear, so the issue is on benthic habitats and organisms, especially well in disturbed habitats, but more one of management of cleared land. by clogging substrate interstices and are not yet implicated in displacement of Changing land use is a growing concern microhabitats, and smothering plants natives in more pristine systems (Webb, because, as climate changes and as the and small animals (e.g. Connolly and 2003). economics of particular crops changes, Pearson, 2007). The dynamics of oxygen (and, new land uses may bring problems that Organic inputs to aquatic systems, such incidentally, pH) in catchment waterways have not yet been experienced. Even as effluents from sewage works or dairies, are complex and dependent on a the change in sugarcane harvesting, typically cause oxygen depletion through range of natural and human-influenced from the old method of burning first to bacterial respiration of organic materials, variables (Pearson et al., 2003). Natural remove trash, to the current approach of with subsequent loss of hypoxia-intolerant oxygen status can best be achieved by green cane harvesting, had unpredicted species of invertebrates and fish. In the maintaining riparian zones, curtailing impacts. Leaving the trash on the land Wet Tropics, sugar mill effluents were weed growth; by preventing the input had the major benefits of retaining organic once the main source of problems of nutrients and by removing blockages material, removing smoke impacts and (Pearson and Penridge, 1987), but there to flow. While the tropical Australian protecting the soil against erosion, but has been substantial effort to remove or invertebrate and fish fauna appear the interaction of rainfall with trash can clean up discharges to waterways. extremely resilient to low dissolved produce organic pollution in streams, oxygen status (Pearson et al., 2003; leading to fish kills. Fine-scale land Disturbance of riverbanks also occurs by Connolly et al., 2004), their tolerance and water management can alleviate access of feral animals, including pigs thresholds can be breached, as such problems. that can severely disturb the sediments evidenced by the occasional fish kills that and benthic fauna of shallow wetlands, Long-term turbidity in the water is often occur in floodplain waterways. Prolonged and also several species of fish, for caused by loss of riparian vegetation high sediment levels reduce diversity and example Tilapia (Webb, 2006). or cattle access, such as occurs in the abundance of stream biota such as fishes Burdekin River Dam (Lake Dalrymple) In the Wet Tropics, of major concern (Hortle and Pearson, 1990). and in the river downstream, and may are tilapia (Oreochromis mossambicus) have a long-term detrimental effect and other related cichlid fishes of African on normal processes. Moreover, if origin that, it is feared, might displace that suspended material settles to the native species (Burrows, 2004). Currently

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef 4.b.ii. Concentrations of nutrients in fresh years) and consequently have been nocturnal oxygen depletion and loss waters in many catchments are regularly used as indicators of water of biodiversity. Floodplain lagoons proportional to the area of land quality and ecosystem health (Rosenberg are also affected by inputs of organic under agriculture. and Resh, 1993). They are numerous materials (e.g. cane field wastes) that and ubiquitous, occurring in nearly all promote bacterial production and further The concentrations of dissolved nutrients water bodies and are easily sampled oxygen depletion. in stream water correlates with the using cheap, readily available equipment, proportion of agricultural land use in the The loss of riparian vegetation in making them ideal for this purpose. The catchments (e.g. Dillon and Kirchner, the GBR catchments is documented aquatic macroinvertebrates are typically 1975; Smart et al., 1985; Jordan et al., throughout Queensland in the Statewide diverse, with different species having 1997). Although streams are well flushed Landcover and Trees Study (SLATS) specific requirements for biophysical in Wet Tropics waterways, nutrient (e.g. Queensland Department of Natural conditions. As a consequence, their supplements from fertilisers are reflected Resources and Water [QNRW], 2007), distributions follow natural gradients in by algal productivity and consequent and at a local or regional scale through environmental conditions and they have changes in the fauna. In many disturbed specific, mostly short-term, assessments. been shown to respond to changes in streams the effects of increased nutrients Natural riparian (riverbank) vegetation in water quality and physical parameters are exacerbated because the clearing of GBR catchment typically includes forest associated with anthropogenic riparian vegetation increases light levels trees, shrubs and, with sufficient light disturbance (Connolly and Pearson, and encourages vigorous growth of penetration, some grasses and herbs. 2004). For example, they have been invasive weeds and the instream growth Where drainage is poor, species that are demonstrated to be sensitive to changes of algae and larger plants. tolerant of waterlogging may dominate. in water chemistry, including dissolved The benefits of riparian vegetation to For example, water hyacinth (Eichornia oxygen concentration (e.g. Connolly et normal ecosystem function are well crassipes) and salvinia (Salvinia al., 2004), pH (e.g. Rutt et al., 1990), documented (e.g. Pusey and Arthington, molesta) are two plants introduced salinity (e.g. Metzeling, 1993) and to be 2003). They include: habitat and habitat for their ornamental values, but which vulnerable to toxic contaminants such corridors for terrestrial animals and have become major weeds in the GBR as insecticides (e.g. Liess, 1994; Shultz plants; habitat for semi-aquatic animals; catchment waterways. They infest and Liess, 1995). They have also been shade; filtration mechanisms; organic lagoons and slow-flowing waterways, shown to respond to organic pollution inputs; bank stability; instream habitat eventually covering the whole water (e.g. Pearson and Penridge, 1987) and via roots and snags and basking sites body in a thick mat that blocks out light nutrient enrichment (e.g. Økelsrud and for reptiles. In the past, farmers were and prevents gas exchange, rendering Pearson, 2007; Pearson and Connolly, often encouraged to clear land right up to the waterway hypoxic and uninhabitable 2000). The clearing of riparian vegetation the river banks. It is now acknowledged for native plants, fish and other animals. and increases in sedimentation have that this policy was ill-conceived as the This growth is accelerated by increased also been shown to be detrimental to lost amenity values greatly outweighed nutrient input. In the Wet Tropics, the macroinvertebrate assemblages (e.g. the value of the land exposed. Despite major weed problem is para grass Ryan, 1991; Connolly and Pearson, 2007; broad acceptance of this assessment, (Brachiaria mutica), which grows in Harrison et al., 2008). restoration of riparian zones is only profusion wherever there is sufficient light 4.b.iii. Agricultural development has led occurring very slowly. and appropriate substrate. Its growth is to substantial damage to riparian enhanced by nutrients in the water. It now As part of the Queensland Wetlands and wetland health in many infests most minor drainage channels, Programme established in 2003 under catchments. small streams and river banks. It is a the Reef Plan, Queensland’s wetlands severe impediment to normal drainage, Various estimates of loss of freshwater have been mapped digitally by building on and has substantial effects on the wetlands in developed catchments along existing information, including water body morphology of waterways the GBR coast range between 70–90% mapping derived from satellite imagery, (Bunn et al., 1998). (EPA, 1999) while the condition of the regional ecosystem mapping and a remaining 10–30% range from moderate springs database (EPA, 2005). Wetlands Pearson and Penridge (1987) found to no value as fisheries resources (Veitch have been classified according to a range high abundances of macroinvertebrates and Sawynok, 2005). The most significant of criteria, including the type of ecological below the outfall of a sugar mill in the Wet reason for the reduction in the value system (riverine, estuarine etc), their Tropics. They associated the increase in of remaining wetlands to fisheries is degree of water permanency, and salinity. macroinvertebrate production with high changed catchment hydrology resulting in The result is a consistent wetland map at levels of nutrients and organic matter in loss of connectivity, habitat modification, a scale of 1:100 000, with finer detail in mill effluent. In experiments using artificial poor water quality and poor habitat some parts of Queensland (mainly coastal stream channels on the bank of a first quality. Wetland loss affects species regions) where appropriate mapping data order rainforest stream Pearson and whose lifecycle includes a marine phase exists. A wetland inventory is also being Connolly (2000) were able to increase (Veitch and Sawynok, 2005). developed to describe the listing and macroinvertebrate abundance by 75%. storage of wetland information from a Floodplain lagoons are affected by inputs Aquatic macroinvertebrates offer a range of sources including tenure, climate, of nutrients (from fertilisers) that promote time-integrated sample of environmental population, land use and field data. aquatic plant growth, and consequent conditions over their lifetime (weeks to

26 4.b.iv. Concentrations of pesticides in 4.c. Key uncertainties waterways are highest in areas of related to reduced intensive agricultural activity. instream health Some monitoring of pesticide The following points summarise the key concentrations has been done in uncertainties associated with knowledge the Wet Tropics that shows that the related to decline in the quality of water concentrations of pesticides in waterways in GBR catchment waterways leading to are highest in areas of intensive reduced instream ecosystem health. agricultural activity (e.g. Bainbridge et al., 2006a) but there is very little • Understanding of the fate and impacts information on the impacts of pesticides of pesticides in freshwater ecosystems. on native biota (exceptions include • Quantitative assessment of Kevan and Pearson, 1993). Clearly, our the different requirements for understanding of the fate and impacts of catchment management for improved pesticides is a major knowledge gap that instream health. needs addressing. • The greatest influence on streams and Weeds such as paragrass, which wetlands is caused by the ambient become a nuisance to farmers as a result concentrations in the non-flood periods. of accelerated growth through increased The short, sharp flush of material in the nutrient availability, are often managed flood periods have little influence on by mechanical or chemical means. This streams and wetlands, but produce the results in direct pesticide application to bulk of materials reaching the GBR; it waterways. The implications of these is the regular supply of nutrients that applications for instream or downstream occurs through the year on which weed ecosystem health have not been growth (for example) is dependent. adequately investigated. Those weeds are detrimental to instream health, smothering natural 4.b.v. The condition of riverine waterholes habitats, exacerbating hypoxic in the dry tropics is largely conditions and creating barriers to determined by cattle access. dispersal, but may provide an excellent The condition of riverine waterholes filter, reducing contaminants being reflects their local surroundings. In the dry delivered to the GBR. This hiatus needs tropics, the condition of riverine waterholes to be explicitly assessed and quantified. is largely determined by the availability It is possible, for example, that these of access to cattle, which contaminate beneficial effects of weeds are short- and greatly disturb remnant and refugial lived, as they are over-run by wet ecosystems, causing, among other things, season floods. deoxygenation and consequent loss of biodiversity (Burrows, 2003). 4.b.vi. The condition and biodiversity of floodplain waterways are adversely affected by irrigation inputs and drainage. Condition and biodiversity of floodplain waterholes are affected by irrigation inputs and drainage, particularly sediments, nutrients from fertilisers and organic material, which lead to oxygen depletion and biodiversity loss (Burrows and Butler, 2007).

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef 5. Review scientific evidence for the effectiveness of current or proposed management intervention in solving the problem

Conclusion: Current management 5.a. Lines of evidence GBR. While ‘win-win’ scenarios exist for interventions are not effectively some management interventions such as solving the problem. 5.a.i. Priority contaminants for the ‘6 Easy Steps’ nutrient management intervention are known for Water system in sugarcane, many practices Knowledge related to the effectiveness Quality Improvement Plan areas. involve net costs to producers, particularly of management interventions has moved in the shorter term. Economic and social forward in the last five years but there There is improved regional understanding impediments to practice change vary are still significant gaps that hinder the of management practices associated between regions, complicating the design capacity to identify the priorities for with the presence of contaminants in of policies to achieve practice change. investment and provide confidence in their waterways, including knowledge of likely water quality outcomes. The Water variability in risks across and within 5.a.v. Knowledge of the effectiveness of Quality Improvement Plans (WQIPs) in catchments and industries. However, restoration techniques is insufficient the GBR have provided a substantial prioritisation between the regions and to guide investment. driver to improve the availability and between industries at a GBR-wide scale The effectiveness of riparian vegetation accessibility of this information, and is lacking. and wetlands as potential filters of in defining which practices are most 5.a.ii. A range of measures for sediments, nutrients and pesticides is appropriate in certain locations for the managing sediment, nutrient and known for some cropping locations, most efficient biophysical, social and pesticide loss are available for but is limited for grazing areas. The economic outcomes. implementation across industries system understanding that is required Despite regional collaborative efforts and across regions in the to prioritise investment into riparian between industry, research, government GBR catchments. and wetland rehabilitation, taking into and the regional NRM bodies to develop Agricultural industry land management account social and economic factors, is Best Management Practices (BMP) for the systems such as Grazing Land extremely limited. Potential lags in system major industries (sugarcane, grazing and Management and fertiliser efficiency responses to management interventions horticulture) within the GBR catchments, techniques are established. are beginning to be quantified. there is still a lack of quantitative evidence 5.a.vi. Targets have been set at regional linking these BMPs with water quality 5.a.iii. Quantification of water quality scales based on best available benefits to downstream waterbodies. The outcomes of management science but GBR-wide targets linkage between the adoption of BMPs practices is inadequate. are lacking. and resultant improvements in water Management systems believed to be quality in a quantitative sense is unknown, effective (based on limited information) Targets for management actions, end of and an understanding of the timeframes are known for the sugarcane and grazing catchment loads and resource condition that changes in water quality are detected industries and some of these incorporate have been set through the GBR Water at different scales (i.e. paddock to sub- potential ‘win-win’ benefits (e.g. ‘6 Easy Quality Improvement Plans. The targets catchment monitoring). Steps’ nutrient management system in are thus far more robust than previously set but still require modification in the light There has been a small body of relevant sugarcane), although to variable degrees of new information. However, no targets social and economic research undertaken across regions and industries; less have been set at the GBR scale that to inform the management of the GBR; information is available for many of the would allow trade-offs in management evaluations of the existing social and regions’ diverse horticultural industries. actions across the GBR region to economic research already undertaken 5.a.iv. There are many social and be considered. in the GBR relating to water quality have economic impediments to the indicated that the research is relatively implementation of management 5.a.vii. The capacity to measure limited. In addition, much of the research interventions. effectiveness of management and development has often not been interventions has improved. well integrated with physical research There are multiple economic and social Several major monitoring and modelling and development, or does not provide a impediments to the implementation of partnerships have been established to comprehensive understanding of the social changes of management practices aimed measure water quality condition in the and economic issues across the GBR. at reducing contaminant loads to the

28 GBR catchments, including the Short Substantial issues still exist for sediment encouraged to follow a series of steps Term Modelling Project led by NRW and management in grazing lands. that tailor the fertiliser application rate to the Reef Plan catchment and marine the plant and soil requirements, and has The focus for sediment control and monitoring programs. Integration of benefits for productivity such as reduced reduction of erosion associated with these programs at the GBR paddock – to fertiliser application. Thorburn et al. rangeland grazing is in the Burdekin and catchment to reef scales – is lacking. (2003b) developed the N-Replacement Fitzroy catchments, and to a lesser extent system and this system has been trialled catchments in the Cape York and Burnett in several sugar areas within the GBR 5.b. The evidence base regions and upper parts of the Wet Tropics catchments (Thorburn et al., 2007; 5.b.i. Priority contaminants for catchments (Joo et al., 2005; Brodie et al., Webster et al., 2008b). Field trials have intervention are known for 2003; Furnas, 2003; Cogle et al., 2006). been positive, suggesting the assumptions WQIP areas. Hillslope, streambank and gully erosion behind the system are often valid. The dominate sediment delivery processes, Substantial variability exists in the main assumption is that soil nitrogen stores although further studies are required biophysical, social and economic can buffer the difference between the to demonstrate predominant erosion characteristics across the GBR amount of nitrogen needed by the crop and mechanisms in the catchments. Particulate catchments which influences the suitability the amount of nitrogen fertiliser applied. nutrients are also sourced from soil and application of management priorities. For example, if the yield of the coming erosion in grazing lands and can therefore A priority for recent research has been crop was larger than that of the previous be managed through soil erosion control. identification of the primary sources crop, additional nitrogen requirements of terrestrial contaminant runoff to the Dissolved inorganic nutrients are largely would be supplied from soil nitrogen stores. GBR through more detailed regional associated with fertiliser application in Conversely, these nitrogen stores would assessments to target management intensive cropping industries. For the be ‘topped up’ when a small crop followed interventions; the outcomes of these GBR region as a whole, management of a large one. This assumption means the assessments is addressed in Section 1a. these nutrient losses is essentially about concept of a ‘target yield’, as used in The most recent information has largely reducing fertiliser losses from sugarcane programs such as ‘6 Easy Steps’, is no been generated through the WQIP and to a lesser extent, horticulture (but longer necessary in determining fertiliser process undertaken for 17 of the 35 major noting that horticulture may be of major rates. Target yields are generally related to river catchments in the GBR region. For importance in some catchments). possible production, not actual production, example, in most of the Burdekin and and so can be a significant driver of high Herbicides are mostly derived from Fitzroy catchments where grazing is fertiliser application rates (relative to actual sugarcane applications (Rohde et al., the predominant land use, sediment is production) and high fertiliser and high 2006a) with some contributions from identified as the contaminant of greatest fertiliser surpluses (Beaudoin et al., 2005). cropping in the Fitzroy catchment (Packett concern (Burdekin WQIP – Mitchell et al., The success of the N-Replacement system et al., 2005), and woody weed control in 2007a; Fitzroy – Johnston, 2006), while is a potential saving in nitrogen fertiliser grazing lands. in the Tully catchment within the Wet applications of up to 40%, and a reduction Tropics, where intensive sugarcane and 5.b.ii. A range of measures for managing in the overall nitrogen surplus across the banana cropping is dominant, nitrogen sediment, nutrient and pesticide loss whole sugarcane industry of up to 60%. and pesticides are the key concern (Tully are available for implementation The N-Replacement research is currently WQIP – Kroon, 2008). Nutrients and across industries and across regions in the ‘proof-of-concept’ phase and plans pesticides are also of greatest concern in in the GBR catchments. are underway for developing the concept the lower Burdekin catchments (Mitchell into a practical management system. The principles for effective management et al., 2007a) and Mackay Whitsunday of sediment, nutrient and pesticide However, in contrast to recent region (Drewry et al., 2008) where land generation are well known and these are developments for sugarcane, little use is dominated by intensive cropping, incorporated into management practices consideration has been given so far predominantly sugarcane. The Burnett- being implemented across the GBR to similarly update fertiliser and other Baffle catchments incorporate a range of catchments. However, large uncertainties management practices for most of land uses including intensive cropping and exist regarding their profitability and short- the region’s horticultural industries. grazing; the WQIP process has identified and long-term impacts of implementation A review of fertility management in sediments, nutrients and pesticides as upon industries. Examples of methods horticulture and associated environmental important contaminants. The Black Ross designed and currently applied for issues (Hunter and Eldershaw, 1993) WQIP is dominated by urban land uses targeting specific problems are provides information and priorities where nutrients, pesticides, sediments and provided below. for improving fertiliser and pesticide heavy metals are of concern. management in these industries across There are several schemes available Improved management techniques in Queensland, including the GBR region. for managing fertiliser application in the intensive wet tropic areas have already This review should be updated and intensive cropping industries and these reduced sediment generation through its recommendations implemented so have been examined on a regional basis practices such as minimum tillage and that up-to-date information is available for each WQIP (e.g. Roebeling and green cane trash blanketing (Prove et al., on optimal fertiliser and pesticide Webster, 2007; Thorburn et al., 2008). 1997; Rayment, 2003), although there management practices for horticultural Examples include ‘6 Easy Steps’ (Shroeder remain relatively minor sediment issues industries in the region. et al., 2005) where cane farmers are in horticultural crops such as bananas.

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef In addition, the information needs to been demonstrated by Burrows (2003). of demonstrated time lags in system be provided for each industry and However, there has been little work on response to management changes is should take into account cross-regional managing grazing in riparian areas (with recorded in the Tully catchment. The Tully differences (e.g. in production systems the exception of fencing) and direct catchment is the least variable river in and climate). management is unlikely to be financially the GBR catchments, and yet very large viable in extensive grazing areas. changes in fertiliser use (increases) took Sediment control in the grazing Ongoing research (field experiments 14 years to be manifest as increasing industry is guided by the industry-led and modelling) is required regarding the nitrogen levels in the lower Tully River initiative, Grazing Land Management, influence of variable groundcover levels to a statistically robust trend (Mitchell or ‘GLM’. This initiative has developed and patterns for major landscapes within et al., 2001, 2006). This highlights the regionally-specific best management each region, and improved understanding importance of the need for innovative practices (BMPs). As with practices of the impact of significant flood events on monitoring and modelling techniques, for fertiliser management, each region sediment loads and defining the threshold and an improved understanding of the has also conducted an assessment of various management practices in these system dynamics to inform management of management practices suitable for events, is necessary to identify the best decisions. These issues are also reducing sediment runoff in priority sediment management practices for water discussed in Section 1. catchments; for example, BMPs for quality outcomes. grazing in the Burdekin are assessed The response of the system to these land and prioritised in Coughlin et al., (2007). Herbicide management is focused management changes is significantly Sediment control in these areas requires on better and more effective delivery influenced by system dynamics, increased vegetation cover, as well as techniques which reduce losses and depending on the contaminant and improved pasture condition and soil integrated pest management programs catchment systems. The major influences health to retain water, sediments and focused on reducing use. Current are summarised below (Waterhouse et nutrients on the land (Nelder, 2006; practices include zonal application and al., in press). Gordon, 2007). In principle, this means the use of hooded sprayers, and the • Sediment control mechanisms and applying the appropriate utilisation rates replacement of residual herbicides such targets in large catchments such as the of vegetation through better management as diuron by other less residual herbicides Burdekin are likely to encounter long of stocking rate (particularly in regard such as glyphosate. lag times in the system, depending to rainfall variability), wet season There are some examples of incidental on the soil and flow characteristics, spelling to improve pasture condition, interventions that have had benefit to and the time for riparian vegetation to forage budgeting to ensure cover levels water quality outcomes, such as green grow. However, fine sediments such as are adequate from year to year and cane trash blanketing, which while clays, which present the highest risk to preventing selective overgrazing of introduced to improve harvesting and GBR ecosystems, experience the least preferred areas in the landscape (Chilcott organic carbon content of soils, had system lags in transport. In addition, et al., 2003; Gordon and Nelson, 2007). the incidental benefit of reducing soil the variability in the systems in terms of However, recent unpublished work by erosion. A second example is evident with hydrology (decadal events) and climate Bartley et al., (2007c) suggests that the fertiliser application rates – in the last 10 mean that responses in the system majority of the sediments flowing into the years, at a time of reducing cane prices, are likely to be in decadal time scales creeks and rivers come from streambank fertiliser prices have risen, while fertiliser (Lewis et al., 2007b; Bartley et al., and gully erosion which will sometimes application rates have reduced. 2007a). need engineering solutions such as contour banks or ripping (as opposed 5.b.iii. Quantification of water quality • Fertiliser management in intensively to retaining walls or sediment traps) outcomes of management cropped areas such as the Wet Tropics and fencing riparian and gullied areas practices is inadequate. and the Mackay Whitsunday Region will to provide reduced grazing pressure, also experience significant lag times in While water quality outcomes are rather than changes in grazing land system response because of the sugar expected from the implementation of the management. Current practices largely crop cycles (six to seven years) and management practices outlined above, address hillslope erosion and further storage in soil and groundwater stores. there is limited evidence of measured work is required on management and Responses are likely to be multiple water quality outcomes from particular restoration techniques for gully erosion. years (i.e. five to ten years). Lags in practices in particular locations. groundwater transport and sub-surface There are also other means of addressing A major limitation in detecting transport (Rasiah et al., in prep; Rasiah sediment runoff in grazing lands. improvements in practices and et al., 2007; Armour et al., 2006) and Maintaining soil health, for example measurable outcomes in GBR ecosystem floodplain trapping (Wallace et al., in through reduced stocking pressure, is health is the ability to detect the signal of press; Karim et al., 2008; McJannet, also identified as an important contribution change in the system. This noise in the 2007) also have a significant influence to improving soil infiltration, and therefore signal is due to system variability, natural on the system. reducing surface water runoff and occurrence of sediments and nutrients • Herbicide management is expected sediment loss (Dawes-Gromadzki, 2005). in the system and limitations of the to be characterised by limited time The importance of off-stream watering capacity to monitor and model material lags because most of the herbicides as a means of reducing cattle impact transport and fate. A good example of concern have half-lives of less than on waterholes and lagoons has also

30 one year (e.g. 50 days). Significant al., 2003) and industries that are largely with the use of market-based instruments reductions in loads are expected to within receiving environments such as providing significant opportunities as be evident within two years of practice tourism and recreational fishing (Access they specifically integrate bio-physical change involving reductions in use Economics, 2007; Campbell and Murphy, and economic information (revealed by and loss. Changes in the presence of 2005; Marsden Jacob Associates, managers) of the benefit, costs and cost- herbicides due to improved practices 2008b). This variability in social and effectiveness of alternative management are also easier to identify in the system economic makeup further complicates interventions (Marsden Jacob as they are not present naturally, the measurement of the effectiveness Associates, 2008a). generating a clearer signal related to of proposed management interventions. There has been a small body of relevant practice change. While the understanding of cost social and economic research undertaken effectiveness of alternative management While vegetation management through to inform planning and management of interventions is still relatively rudimentary, maintenance or rehabilitation of water quality in the GBR (e.g. Windle it is generally better understood in grazing vegetated areas is considered to be and Rolfe, 2006; Hug and Larson, 2006; and sugar environments (Rolfe et al., a beneficial practice for water quality Larson and Stone-Jovicich, 2008; Larson, 2007, Donaghy et al., 2007, Roebeling, outcomes, direct measurements of in press), although many of the studies 2006; Roebeling et al., 2004, 2007; Alam long-term outcomes are difficult to find. have been regionally specific including et al., 2006). For example, Roebeling However, vegetation management in socio and economic assessments et al., (2007) analysed the water quality Queensland is probably one of the few completed to support water quality efficacy and the economic dynamics of examples of documented evidence of the planning in the Tully Murray catchments management practices in the effectiveness of a management action (Bohnet et al., 2007; Larson, 2006, Tully-Murray catchment. in Queensland through introduction of 2007), Burdekin region (Greiner et al., the Vegetation Management Act 1999. Based on the proposition that regional 2003; Greiner and Hall, 2006; Greiner The legislation restricted the amount of (i.e. private and social) benefits are et al., 2006), Mackay Whitsunday tree clearing that could be undertaken maximised where marginal private (Strahan, 2007) and Fitzroy (Preston on freehold and leasehold land. Figures costs equal marginal social benefits, the et al., 2007). These studies have from the Statewide Landcover and Trees studies showed that the cost-structure highlighted the substantial variability in Study (SLATS) showed the statewide around BMPs is such that a certain level the socioeconomic characteristics of the average annual rate for clearing of woody of improvement in water quality can be GBR catchment that ultimately influence vegetation in 2004–05 was 351 000 made at no cost (e.g. for sugar – a 25% the choice of management interventions hectares. This is 27% lower than in to 40% gain depending on adoption of for water quality outcomes. Integrating 2003–04 (482 000 ha) and 54% lower new fertiliser practices) but beyond that targeted social and economic analysis than the peak measured clearing rate point, costs for water quality improvement and research into the implementation of in 1999–2000 (758 000 ha). Reductions rise sharply. It showed that the current the Reef Plan should provide significant in clearing of more environmentally BMPs do not yet balance both production improvements in the understanding significant remnant woody vegetation and environmental goals. In addition, the of the cost effectiveness of alternative are even greater – 35%, down from spatial arrangement of industries in the management interventions (including 267 000 ha in 2003–04 to 172 000 ha in catchment was not optimal for improved variability) and the impediments to 2004–05 (QNRW, 2007). These figures water quality outcomes. Subsidies, change over time. demonstrate the effectiveness of the incentives and/or regulations will be The Reef Plan Marine Monitoring introduction of the legislation and in the needed to provide the business case Program includes a socio-economic short term, assumptions are made about for industries to develop and implement component. This involves reporting on: the outcomes in terms of water quality improved management practice settings market values of GBR industries and their and biodiversity values. and to guide spatial change in this, and inputs to regional economies; patterns many other GBR catchment locations. 5.b.iv. There are many social and of human use of the GBR particularly non- economic impediments to the There are significant barriers to the commercial recreational activities, tourism implementation of management adoption of practices that could materially and commercial fishing; and community interventions. reduce loads into GBR catchments. and visitor perceptions of, and satisfaction Similarly to the variability in the physical These barriers are economic such as with, GBR health (Prange et al., 2007). the private cost of changing practices impacts on loads from practice change A suitable indicator for assessing and social such as attitudes towards across and within industries of the the performance of management particular practices, skills required and GBR, there is significant evidence of interventions is the adoption rates of attitudes towards risk (Cary et al., 2001; variability in the economic and social various practices and tracking extension Preston et al., 2007; Donaghy et al., characteristics of regions across the efforts by region and industry. At this 2007). These constraints are often not GBR, between sectors, and often within stage, limited effort has been made to well understood. Because of the multiple sectors within regions. This variation benchmark these indicators (with some types of constraints to change and the applies to both industries contributing exceptions at a regional scale). This is variability of the constraints between to loads with the catchments such as a critical information need to inform the managers, a number of regulatory, grazing, sugar and horticulture (Marsden evaluation of Reef Rescue suasive and economic tools are being Jacob Associates, 2008a; Greiner et Plan investments. used to address water quality in the GBR,

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef 5.b.v. Knowledge of the effectiveness may be required to ensure these areas Despite the very considerable efforts of restoration techniques is retain this capability and do not become made in riparian rehabilitation, both in the insufficient to guide investment. contaminant sources; for example, as GBR region and elsewhere, there have shown for phosphorus in constructed been very few attempts to quantify the Rehabilitation of riparian zones and wetlands in the Burdekin region (Hunter benefits of these investments in terms wetlands and management in extensive and Hairsine, 2002). of improved water quality downstream. grazing lands is considered a priority Long-term monitoring studies are activity for improving water quality, In general, scientific knowledge of these needed at a sufficiently large (e.g. sub- particularly focused on the function riparian and wetland buffering functions catchment) scale to demonstrate that of these areas as filters of sediment, in cropping situations or in wetter more such benefits can be achieved following nutrients and pesticides. Rehabilitation intensive environments is relatively rehabilitation. However, some local is not an economic option for vast areas well developed and the principles have examples of monitoring effectiveness of in the rangelands – these riparian areas now been incorporated into software wetland systems do exist, for example still need to be managed under grazing that enables assessment of alternative in the Burdekin catchment (Burrows and (Coughlin et al., 2007). Large areas of management scenarios and identification Butler, 2007) and the Tully catchment riparian forest have been cleared over the of optimal locations for rehabilitation. For (McJannet, 2007). Recent research by last 30 years in the Burdekin (Lymburner example, the Riparian Nitrogen Model McJannet and others (unpublished) in and Dowe, 2006) and over the last 50 (RNM) (Rassam et al., 2008) enables the Tully catchment indicates that further years in the Fitzroy (Lymburner, 2001). users to identify sub-catchments and investigation is required to substantiate stream reaches where rehabilitation is From a management perspective, preliminary data showing the filter function likely to have greatest effect in reducing resources for rehabilitation are best that wetland systems provide in a wet downstream nitrate concentrations, and it directed to those parts of the catchment tropical floodplain environment. can also indicate the optimal buffer width where they can have greatest effect, required. The RNM has been successfully 5.b.vi. Targets have been set at regional recognizing that the functions and applied in the Tully catchment. A scales based on best available capabilities of riparian and wetland areas Riparian Particulate Model (RPM) has science but GBR- wide targets may differ depending on their position similarly been developed (Newham et are lacking. in the landscape (Hunter and Hairsine, al., 2005). It is also clear that in Wet 2002). For example, where hillslopes In the last three years, targets have Tropics catchments that it is best to drain directly into streams without the been set for management actions and have a mixture of grass and trees to trap presence of a floodplain, the riparian resource condition to support water overland flow of fine particulate matter zone will act to reduce sediment loads quality management in the Douglas, Tully- rather than just trees (McKergow et al., and associated contaminants carried Murray, Burdekin, Black-Ross, Mackay 2004a, 2004b). by overland flow. In smaller, frequently Whitsunday, Fitzroy and Burnett-Baffle ephemeral, streams the emphasis is The lack of locally-relevant data sets is catchments, mostly through the WQIP on filtering of overland flow. In larger a significant limitation to reducing the process. A consistent approach, reflected streams riparian vegetation has a major uncertainty of these model outputs. At a in Figure 9, has been adopted across the role in stabilising stream banks. Similarly, systems level, there is currently only a regions and significant advances have remedial management should target limited capability to optimise prioritisation been made in the rigour of the target riparian areas where shallow groundwater of sites for rehabilitation, not only from a setting process than earlier efforts (e.g. discharge of nitrate occurs, most likely in biophysical perspective but also taking Brodie et al., 2001). small to medium sized streams (Hunter into account social and economic factors. et al., 2006). Careful management

Water quality objectives Water quality objectives End-of-catchment based on achievable based on ecosystem water quality load target management scenarios health responses

Relevant WQIP tasks: - Identify critical sources and key pollutants - Identify total loads to achieve Water - Determine current receiving water - Describe management actions to achieve Quality Objectives (WQOs) quality condition maximum reduction in pollutant loads - Identify current estimated pollutant loads - Determine risk of impact by key pollutants - Describe management actions for - Identify source contributions of - Determine environmental Values and environmental flow objectives for estuaries pollutant loads WQOs for receiving waters - Understanding impacts of future growth - Timing for attainment and maintenance - Describe nutrient cycling processes and climate change of WQOs

Figure 9: Water quality target setting within the GBR and relevant tasks within the WQIPs.

32 However, as a result of the limitations associated with pesticide use in GBR careful consideration is required regarding in monitoring and modelling capacity catchments are currently being assessed location of management efforts. referred to in sections 1 and 3, water and a monitoring program developed for Much of the modelling performed to date quality targets are at present largely high risk waterways by QNRW. Marine has provided information on annual- driven by an understanding of what is water quality monitoring is undertaken as average conditions based on long-term achievable water quality change within part of the Reef Plan Marine Monitoring datasets and this type of modelling current land use systems and practices. Program led by the GBRMPA (Prange will continue to have its place (e.g. for The environmental tradeoffs in this et al., 2007) described in Sections 2 assessing likely impacts of alternative decision have not yet received much and 3. A comprehensive overview of planning/management options). However, attention because of the low confidence the location and extent of water quality the priority now is to develop more in our understanding of what is actually monitoring currently undertaken in the dynamic water quality models to analyse being discharged from catchments GBR catchments is provided in QNRW the large monitoring datasets being and how this relates to requirements (2008a). developed for several major catchments to sustain healthy GBR ecosystems. Estimates of the loads of contaminants of the GBR (Bartley et al., 2007b). The The implications for ecosystems of not discharged to the GBR that are not aims of such monitoring programs are meeting targets, and the lag time to captured in existing monitoring programs to identify the sources of contaminants change practices and realise water quality due to inadequacy of sampling sites and and to detect changes in contaminant benefits for the target adopted, have high methods have been made in a number concentrations and loads with time, in levels of uncertainty. of catchments. In the Tully catchment response to changes in land-management This is most apparent in the marine Wallace et al., (in press) showed that practices. Teasing out from the dataset environment, where relationships a large proportion of the total load of the effects of changed land management between water quality parameters and suspended sediment and nitrogen was is challenging particularly in large the resilience of GBR ecosystems is present in waters in overbank flow on complex catchments, where many factors, still emerging (refer to Section 3). The the floodplain and this was not included including climate change, co-determine establishment of the GBRMPA Water in load calculation made at Euramo water quality (Grayson, 2007). Models Quality Guidelines (GBRMPA, 2008) and (the lowest gauging station) in the river have to be calibrated with locally relevant the supporting science documentation channel. Similarly it is clear that much of data to interpret the monitoring data (e.g. (De’ath and Fabricius, 2008) provide a the nitrate lost from sugarcane fertiliser Hunter and Walton, 2008). Even so, substantial advancement towards setting in the lower Burdekin reaches the GBR because of the complexities and sizes of marine water quality targets; however, via small stream discharge and possibly catchments involved and the inevitable considerable work is required to define groundwater discharge and is thus not limitations of the models, it may not prove and measure desired water quality included in loads measured at Home possible to detect trends in the monitoring outcomes in the relatively short policy Hill in the Burdekin River (Brodie and data over the short- to medium-term. timeframes. Bainbridge, 2008). Similar ‘missing’ loads Model estimates that upscale from are obvious in Mackay-Whitsunday region 5.b.vii. The capacity to measure paddock to catchment scales are through small stream discharge (Rohde et effectiveness of management required to indicate the likely water quality al., 2008) and are likely in other regions. interventions has improved. improvements associated with changed Similarly, there is poor understanding of management practices, even if these Catchment and marine water quality the role of, or impact of, discharges of cannot be confirmed through monitoring monitoring programs have commenced contaminants from the coastal floodplain at that time. The time lags for trends to in priority catchments of the GBR as in dry season conditions. These chronic be detected in the monitoring data likely part of the Reef Plan arrangements. discharges are likely to include natural vary between contaminants and between Catchment and end of catchment load stream discharge and drainage catchments, depending on factors such water quality monitoring is led by QNRW from irrigation. as the dominant transport pathways and in collaboration with regional Natural SedNet modelling predicts that high levels transformation processes, the presence Resource Management (NRM) bodies in of suspended sediment trapping will occur of contaminant sinks (stores) and the 31 locations with a focus on sampling in in dams such as the Burdekin Falls Dam spatial distribution and extent of practice major runoff events, when these exports (Fentie et al., 2006) and the Paradise adoption. Field validation of modelled predominantly occur (Hunter and Walton, Dam (Henry and Marsh, 2006). This has increases to sediment and nutrient yields 2008). A number of monitoring programs significant implications for management is required using additional and more are undertaken at regional levels to of different parts of the catchment when direct proxies (perhaps sediment dating, support NRM planning and Water Quality considering overall sediment delivery; for review of fertiliser application tonnages). Improvement Plans, with comprehensive example, management could be targeted programs established in the Burdekin Improved understanding of the in catchments areas below the dam wall. (e.g. Bainbridge et al., 2007), Mackay uncertainties associated with existing However, recent studies using monitoring Whitsunday (e.g. Rohde et al., 2008) catchment transport modelling tools has data suggest that trapping in the Burdekin and Fitzroy (e.g. Packett et al., 2005) been an important component of recent Falls Dam is lower than modelled catchments for event monitoring. Many research, with the limitations summarised (average 60% instead of the modelled of these programs encourage community by Post et al. (2007) and Wilkinson et 80%) (Lewis et al., 2008) and therefore participation. The ecological risks al. (2008).

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef For example, sediment tracing work 5.c. Key uncertainties • The impact of woody weeds (e.g. underway in the Bowen River indicates related to management rubber vine) and the use of fire to much more gully erosion is occurring than effectiveness control weeds on sediment loss. model predictions, (Wilkinson, 2008). • Socioeconomic benchmarking of the Key uncertainties related to the This illustrates the need for broader data current adoption rates, extension efforts effectiveness of current or proposed collection on erosion rates and model and industry culture by region and management intervention in solving the validation. Limited gully mapping is an commodity. important source of model uncertainty problem include: • Development of a specific metric for in the Burdekin (Kuhnert et al., 2007) • Predictions of the efficacy and each sector group (e.g. grazing) aimed and the Fitzroy (Dougall et al., 2006b) efficiency of management interventions at measuring outcomes from actions to catchments. exist but quantitative assessments allow comparisons across sectors. based on field measurements are A comprehensive overview of the • Understanding the drivers that will lead generally limited. location and extent of water quality land managers to change practices for modelling activity undertaken in the GBR • Validation of effective and profitable water quality improvement. catchments to support Reef Plan planning management practices for the GBR • It is too difficult to pick up short-term or and implementation is provided in region’s agricultural industries, medium-term trends in water quality at QNRW (2008b). especially horticulture and grazing, large scales due to climate variability including environmental, social and A number of models are under and inherent difficulties in logistics economic perspectives. development that can assist in associated with monitoring at the right predicting the biophysical, social and • Capability to determine the relative spatial and temporal scales. Further economic outcomes of various policy importance of the location of the work is required to design and resource interventions, and therefore assist in works in the landscape in terms of optimal monitoring and modelling assessing management effectiveness. material delivery. programs in GBR catchments. For example, the ‘SEPIA’ model (Single • The relative importance of the type • Quantification of the downstream Entity Policy Impact Assessment of groundcover maintained in grazing benefits of management change/ Model) is being tested in the Burdekin, lands to minimise sediment loss, and restoration efforts and the return on Tully and Mossman catchments, and the efficiency of different groundcovers investment to land holders and funders, uses a range of input data including in managing hillslope erosion (i.e. at appropriate temporal and biophysical characteristics, economic ‘natural’ cover of trees and shrubs or spatial scales. drivers and landholder typologies to savannah, compared with pasture). • Quantification of the function of determine the probable outcome of • Impact of different grazing management wetlands and riparian vegetation as a set of policy options (Smajgl et al., practices on health and functioning filters for land- based materials in 2008); however, further model validation of riparian areas in extensive grazing different locations. is required. Bayesian approaches are lands, and management of riparian also being used to combine various areas, especially with regard to grazing land use and economic scenarios for and spelling. GBR water quality and climate change • The biophysical and economic outcomes (Wooldridge, 2007), and to effectiveness of gully erosion guide managers in prioritising investment remediation and management (Lynam et al., in review). measures to reduce gully sediment yields.

34 6. Discussing the implications of confounding influences including climate change and major land use change

Conclusion: Climate change and major events including heat periods and cold (Fabricius et al., 2008). Therefore, a land use change will have confounding snaps, more intense cyclones, and more predicted increase in the intensity of influences on GBR health. frequent droughts alternating with severe cyclones (Webster et al. 2005; Hoyos et flood. Overall, the changing climate as al. 2006; Kossin et al. 2007) will likely Comparisons of the degree of reef observed and/or predicted within the lead to a greater frequency of severe degradation and stage and severity of GBR region will therefore increase the reef damage at regional scales. human activity for the GBR compared frequency with which coral reefs are with other global reef systems shows Successful coral reproduction and being disturbed: that although the GBR is in relatively recruitment is needed to compensate for good condition, it is by no means • Increasing concentrations of CO2 in the the predicted increase in coral mortality pristine and some way along the path atmosphere also lead to a reduction in from bleaching events, cyclones, floods, to the degradation seen in many other the pH of the seawater, a phenomenon and crown-of-thorns outbreaks. Good reef systems (Pandolfi et al., 2003; termed ‘ocean acidification’. Ocean water quality is essential for successful Brodie et al., 2007a; Bruno and Selig, acidification reduces the ability of corals coral reproduction and the survival of 2007). The complexities between and other calcifying organisms to grow, coral recruits on inshore reefs, and for the impacts of water quality stresses and diminishes the capacity of coral keeping macroalgal cover low (reviewed compared with other stresses, such reefs to withstand erosion (Guinotte in Fabricius, 2005; Wooldridge et al., as climate change (bleaching, ocean and Fabry, 2008). 2006; and De’ath and Fabricius, 2008). Protecting the reefs against high levels acidification) and fishing/harvesting and • Chronically warmer waters lead to of nutrients, sediments and pesticides is their interaction, are yet to be resolved. changes in growth rates, altered food therefore considered essential to facilitate The current paradigm considers that a availability and ecological functions resilience during climate change. major correlation exists between acute in most species groups and GBR coral mortality following catastrophic ecosystems. Periods of extreme Another confounding influence is events such as cyclones, crown of thorns seawater temperatures (unusually high overfishing. Numerous studies have outbreaks and bleaching mortality, and or low) lead to coral bleaching and to a shown the important role of fishes lack of coral recovery in poor water greater susceptibility to diseases. It is in structuring benthic assemblages. quality conditions. In good water quality also likely that ecotoxicological effects Fishes strongly influence the balance conditions the coral recovers quickly; (e.g. from herbicide exposure are more between macroalgal and coral cover (e.g. in poor water quality conditions coral severe when organisms are already Hughes, 1994). Recent research has recovery is slow or non-existent due to stressed from high temperatures). shown that fish densities increase once lack of recruits, poor juvenile survivorship • Increased rainfall variability and reefs are being closed to fishing, clearly and competition from other benthic intensity of weather events (droughts, demonstrating that the densities of some organisms such as macroalgae and floods etc) will make land management targeted fish species are reduced way filter feeders. more difficult and increase the risk of below ‘pristine’ levels in many parts of The following section provides an soil erosion and loss, thereby resulting the GBR (Russ et al., 2008). Although overview of the current knowledge in increased loads of contaminants herbivorous fishes do not tend to be taken related to the implications of confounding into the GBR lagoon. Droughts lead to on the GBR, studies have shown that the influences on the GBR, with an emphasis reduced vegetation cover, making soils removal of top predators can alter trophic on the primary confounding influences more prone to erode and wash into structures in ecosystems (Graham et related to GBR water quality, climate the ocean during floods. The nutrient al., 2003), and such flow-on effects are change and major land use change. injection from drought-breaking floods poorly understood. This has been shown have been associated with the initiation to influence the rate at which coral reefs Climate change, water quality of primary outbreaks of crown-of-thorns recover after beaching events (Hughes et and GBR health starfish (Birkeland, 1982; Brodie et al., 2007). al., 2005). Changing hydrology may The present state of knowledge about the have severe effects on catchment vulnerability of GBR species and habitats water quality. to climate change has been reviewed in detail (Johnson and Marshall, 2007). • Storm energy increases with the cube Predicted changes in the climate both of wind speed and some forms of storm globally and for the GBR are an increase damage (e.g. the dislodgement of large in the frequency of extreme weather massive corals) are only observed at cyclone categories three or higher

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef Major land use change Projections are available regarding biofuel Given the uncertainties associated industries and indicate that they are not with the long-term impacts of water Given the potential climate change likely to grow substantially in terms of quality on the GBR in combination with scenarios and associated pressure for first generation biofuels. Peak oil and the confounding influences described industries to seek alternative and viable escalating petroleum prices are likely to above, the knowledge base to support ventures, major land use change in the have significant impacts on the land use management needs to be revisited GBR catchments is possible, which and management of the GBR, which will on at least a five-yearly cycle. It is is likely to have implications for the present both challenges and opportunities recommended that this discussion paper amount of contaminants discharged to to managing water quality. is updated in 2013, which coincides with the GBR. A number of scenarios can be the completion of the current planning The most significant management considered to be probable in the current cycle of the Reef Plan and the regional implication of these scenarios is the short- settings, although longer term scenarios water quality plans. (e.g. to 2050) are highly uncertain but term planning approaches that typify the have been attempted by Bohnet et al., management systems relevant to GBR (2008a, 2008b ). Likely examples and the water quality. Longer term projections projected consequences (based on per such as those piloted by Bohnet et al. hectare measure, not overall land area) (2008a) must be incorporated are estimated below. into planning.

Scenario Loss of sediment, nutrients, and pesticides

A shift from: fertilised cropping to another fertilised crop moderate change

A shift from: fertilised cropping to grazing, forestry or reserve large change, generally reduced

A shift from: grazing or forest to fertilised cropping large change, generally increased

36 Evaluate current research and advise on capabilities, Part B gaps and priority research needs

The current gaps and key uncertainties investment to support and guide Reef Eberhard et al., (2008). The process of related to water quality in the GBR Plan implementation. establishing a pilot Reef Water Quality have been highlighted in each of the Report Card in 2006–2008 (Vandergragt Of utmost importance, integration of Terms of Reference addressed above. et al., 2008) demonstrated the challenges the science for Reef Plan is the key to However, there are also several issues of providing an integrated assessment informing management decisions, and that are relevant to whole-of-system to inform management at a GBR scale requires additional skills in conceptual understanding that have not been where science coordination is lacking. and quantitative design and interrogation covered. Recent assessments of the that go beyond traditional fields of Conclusion: Effective science critical gaps in knowledge to support expertise. An integrated approach is coordination to collate, synthesise Reef Plan (e.g. Ferrier, 2007) highlight required to understand the whole system and integrate disparate knowledge that integration of the science is key that results in GBR water quality, and across disciplines is urgently needed. to addressing the complexities and includes relationships: uncertainties of the GBR system. This section provides the following • within and across catchments to the information for each of the areas of The present approach of delivering GBR, so that the linkages between research identified in the Terms components of the knowledge, without an catchment actions and GBR health, and of Reference: overarching effort to collate, synthesise within the components of the system and integrate this knowledge, is likely • Overview of the current major research (e.g. between water quality and coral to continue to fail to meet management projects. This is (not intended to provide health), can be quantified needs. Currently coordination and an exhaustive listing but highlight key integration of Reef Plan science is in a • between biophysical, social and projects that were initiated or completed parlous state. Inadequate management economic dimensions of the system so since 2003. that realistic targets and implementation of the large GBR water quality science • Commentary on the adequacy of the strategies can be developed and budget has led to implementation of existing research and capability. ad hoc projects, that are generally assessed • Identification of priority not coordinated or based on rational • across scales, so that the sum of research needs. priorities, has resulted in information catchment and regional activities can that is rarely integrated into knowledge be assessed to determine whether the or communicated to management. existing and proposed activities are Establishment of a central point of sufficient to achieve the Reef Plan goal. science coordination is required as a Further discussion of an approach to matter of urgency to enable science address these issues is provided in

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef 1. Assess water quality impacts

Current major research projects

Project Primary objectives

• To determine dose-response relationships and thresholds of potential concern for contaminant exposure of selected bioindicators; provide a better understanding of the MTSRF Project 3.7.1: Marine significance of such thresholds for reef water quality and ecosystem condition. and estuarine indicators and thresholds of concern • To progress the development of a composite indicator system to interpret water quality monitoring data and their link to ecosystem condition, and to improve estimates of river Katharina Fabricius, AIMS contaminant loads from discharge concentrations. Further information: http://www.rrrc.org.au/mtsrf/theme_3/project_3_7_1.html

• To characterise and obtain a distinct ‘fingerprint’ of the fine sediments (mud fraction) and dissolved materials entering the marine environment using their isotopic and elemental properties, and link these to their sources in the major terrestrial catchments. • To examine historical changes in the delivery of terrestrial materials, from the major MTSRF Project 3.7.2: river systems in the Townsville and Cairns regions, to the marine environment using Connectivity and risk: tracing materials from the upper coral and sediment cores. catchment to the reef • To determine the transport mechanism, residences time and fate of terrigenous sediments, nutrients and pesticides in the inshore and mid-reef regions of the GBR, Jon Brodie, ACTFR and develop and apply new technologies to specifically trace pathways of the key nutrient elements phosphorus and nitrogen from the terrestrial catchments, through estuaries, to inshore coastal zones and to the mid-reef of the Great Barrier Reef. Further information: http://www.rrrc.org.au/mtsrf/theme_3/project_3_7_2.html Davis et al. in press; Lewis et al. in press.

MTSRF Project 3.7.3: Freshwater • To develop physical, chemical and ecological indicators of freshwater ecosystem indicators and thresholds of health in the Wet and Dry Tropics. concern • To identify thresholds of potential concern relating to land use, water quality, riparian condition, habitat and food web structure in freshwater ecosystems of the Wet and Richard Pearson, JCU Dry Tropics. Angela Arthington, Griffith University Further information: http://www.rrrc.org.au/mtsrf/theme_3/project_3_7_3.html

38 • To assist in the assessment of the long-term effectiveness of the Reef Plan in reversing the decline in GBR water quality, through four sub-programmes: River mouth water quality monitoring, inshore marine water quality monitoring, marine biological Reef Plan Marine Monitoring monitoring, and socio-economic monitoring. Program • Marine biological monitoring includes monitoring benthic cover (algae, hard and soft corals), taxonomic composition and coral demographics (the size classes of corals). Multiple Providers, led by GBRMPA Coral settlement rates are also measured at reefs in three regions. Intertidal seagrass Coordination: Joelle Prange, meadows are monitored for percent cover, species composition, reproductive health RRRC and seagrass tissue nutrient status. This task is assisted by the community-based Seagrass-Watch programme (www.seagrasswatch.org). Further information: http://www.gbrmpa.gov.au/corp_site/key_issues/water_quality/marine_monitoring

To assess the effects of: • the herbicide diuron on the early life history stages of coral; Assessing the impacts of • chronic herbicide exposure on reproductive output of reef-building corals; pesticides on marine ecosystems • herbicides on photosynthesis and growth of tropical estuarine microalgae; and Andrew Negri, AIMS • insecticides and a fungicide at multiple coral life stages. Further information: Negri et al., (2005); Magnusson et al., (2008); Markey et al., (2007); Cantin et al., (2007)

• To develop new tools to assess and monitor the health of catchments and aquatic systems in both the Wet Tropics and GBR World Heritage Areas. CRC Catchment to Reef Program • The tools will enable land managers to mitigate the effects of human activities on – Complete water quality.

Multiple Providers, coordinated by • The three-year, $5 million project is now complete and is a joint initiative by CRC Reef CRC Reef and Rainforest CRC and Rainforest CRC. Further information: http://www.reef.crc.org.au/research/catchment_to_reef/C2Rresearch.htm

National Action Plan Water Quality Program: Water quality impacts on ecosystem health • To assess salinity and water quality impacts on Queensland freshwater ecosystems. (WQ06) – Complete Further information: http://www.wqonline.info/index.html Multiple providers

Adequacy of existing research Priority needs • Further development of understanding and capability of cause and effect relationships • Development of a marine and estuarine between water quality and ecosystem • Substantial progress has been made on material transport and biogeochemical health in freshwater ecosystems indicator development and assessment model coupled with a detailed including quantitative assessment of of marine water quality impacts hydrodynamic and eco-physiological the different requirements for catchment since 2003. model for the GBR for improved management for improved understanding of the relationship • Long-term funding commitments are instream health. required to continue to assess water between management actions and Reef • Understanding the response of quality impacts and confounding ecosystem response. estuarine systems to floods and the role influences. • Investigation of the impacts of of the coastal floodplain. • Very limited research connections synergistic effects of influences on GBR • The complexity of the relationship between catchment activities and ecosystem health including land based between nutrient enrichment, coral reef impacts. contaminants, climate change and other external drivers. reef decline, macroalgal proliferation • Most of the research has occurred at and abundances of grazing fishes (and • Improvement in understanding of single geographic scale and is therefore other grazers) still prevents there being the interactions of pesticides in GBR addressing components of the system a clear consensus view on this catchment and marine ecosystems. rather than connections between them. specific relationship.

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef 2. Quantify acceptable levels of pollution

Current major research projects Many of the projects listed in Section 1 of Part B also attempt to quantify acceptable levels of pollution in determining water quality impacts.

Project Primary objectives

• To provide technical background information and statistical data analysis for defining improved water quality guideline trigger values for the GBR Water Quality Guidelines. • To present spatial and seasonal characterisation of water quality conditions in the GBRMPA Water Quality NRM regions, spatial characterisation of proxies used for reef ecosystem health, Guidelines development project assesses relationships between water quality and reef ecosystem health, suggests Glenn De’ath and Katharina trigger values for water quality to protect ecosystem health and assesses predicted Fabricius, AIMS improvement in ecosystem health if the trigger values are implemented. Further information: refer to De’ath and Fabricius (2008)

Adequacy of existing research Priority needs and capability • Refer also to 1 Assess water quality • Targeted research on thresholds of impacts. concern for freshwater and marine • Completion of a risk assessment of ecosystems has commenced as part of the relative importance of sediments, the MTSRF program. nutrients and pesticides to marine • Data integration has occurred for the ecosystems at a regional scale. first time to support the development of • Definition of acceptable/desired water quality guidelines. thresholds for key indicators (i.e. coral, • Substantial progress in last 12 months seagrass and biodiversity). with publication of the report Water • Knowledge of the response of the Quality of the Great Barrier Reef: GBR ecosystem to different events Distributions, effects on Reef biota in different areas, and the ability to and trigger values for the protection recover. Understanding the implications of ecosystem health, (De’ath and of combined scale and frequency of Fabricius 2008) to support the disturbance to GBR ecosystems. establishment of GBR Water Quality Guidelines (GBRMPA, 2008). • Additional capability is required on statistical integration of datasets.

40 3. Locate and quantify the sources of pollution

Current major research projects Many of the projects listed in Section 5 of Part B regarding assessments of the effectiveness of management practices also provide information relevant to locating and quantifying sources of pollution.

Project Primary objectives

• The ultimate goal of the program is to assess the effectiveness of management actions on reducing contaminant loads. • The project involves load monitoring at 31 sites in ten priority (high-risk) catchments – the Normanby, Barron, Johnstone, Tully, Herbert, Burdekin, O’Connell, Pioneer, Fitzroy and Burnett. • The project proposes a combination of water quality monitoring and modelling NRW I5 End of Catchment Load activities: monitoring of current condition of various scales within each catchment; monitoring program determination of differences in measured water quality over time using various water quality and other climate and remote sensing information (modelling); determination David Roberts, NRW of the long-term annual average relative contributions to water quality within each catchment; and determination of the level of land use change and the relative changes in water quality these different land use management options have had on a sub- catchment and catchment scale, compared with climatic and catchment condition variability influences (modelling). Further information: http://www.reefplan.qld.gov.au/whosinvolved/activities_monitoring_ loads.shtm

Various monitoring programs designed to assess contaminant sources and resource condition. Tully WQIP David Haynes, Terrain NRM Further information: Kroon, (2008); Terrain NRM (2008) http://www.terrain.org.au/index.php?option=com_content&task=view&id=141&Itemid=52

• The project describes measurements of sediment and nutrient concentrations in flood waters on the Tully and Murray floodplains, including overbank flow. Sediment and nutrient transport on the Tully floodplain • The concentrations of contaminants during floods are also assessed and compared with those recorded during channelised flow. The findings have potentially significant Jim Wallace, CSIRO implications for future contaminant load monitoring and reporting programs. Further information: Wallace et al. (in press); Karim et al. (2008)

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef MTSRF Project 3.7.2: Connectivity and risk: tracing See description above in 1 Assess water quality impacts. Includes assessments in materials from the upper the Tully, Burdekin and Mackay Whitsunday regions. catchment to the reef Further information: http://www.rrrc.org.au/mtsrf/theme_3/project_3_7_2.html Jon Brodie, ACTFR

Various monitoring programs designed to assess contaminant sources and resource condition including: event monitoring; current condition of regional water Burdekin WQIP bodies; current condition and extent of riparian vegetation and wetlands, and their Ian Dight, Burdekin Dry Tropics effectiveness in trapping contaminants; fate of contaminants in the GBR; and NRM pesticide investigations in the Lower Burdekin. Further information: http://www.bdtnrm.org.au/cci/monitoring/

• The program identifies D condition lands in the Burdekin Rangelands using remote Burdekin Rangeland Condition sensing and rapid assessment ground-truthing. Monitoring project • The project has also identified areas that are at risk of slipping into D condition, and this information will be used by BDTNRM to prioritise areas for future on- Bob Karfs, DPIF; Brett Abbott, ground projects. CSIRO Further information: http://www.bdtnrm.org.au/projects/nap0024.html

Black-Ross WQIP Various monitoring programs were designed to assess contaminant sources and resource condition. Chris Manning, Townsville Regional Council Further information: http://www.creektocoral.org/cci/element2.html

Various monitoring programs were designed to assess contaminant sources Mackay Whitsunday WQIP and resource condition as part of the Healthy Waterways Integrated Will Higham, Mackay Whitsunday Monitoring Program. NRM Further information: http://www.mwnrm.org.au/programs/

Various monitoring programs were designed to assess contaminant sources and Fitzroy Regional NRM Plan resource condition.

Nathan Johnston, Fitzroy Basin Further information: http://www.fba.org.au/programs/regional_water_quality_monitoring_ Association and_reporting.html http://www.fba.org.au/programs/priority_neighbourhood_catchments_ water_quality_monitoring_program.html

Burnett-Baffle WQIP Various monitoring programs were designed to assess contaminant sources and resource condition. Sandra Grinter, Burnett Mary NRM Further information: http://www.bmrg.org.au/index.php

The project was initially part of the CRC for Coastal Zone Estuary and Waterway CRC for Coastal Zone Estuary Management and studied biogeochemistry, primary production and material and Waterway Management - transport of various water quality parameters in the Fitzroy Estuary. Complete Further information: http://www.ozcoasts.org.au/search_data/crc_pubs.jsp Multiple Providers Webster et al., 2006; Herzfeld et al., 2006; Robson et al., 2006a, 2006b; Douglas et al., 2005; Margvelashvili et al., 2003; Webster et al., 2003

Receiving waters receiving model Recent work by CSIRO with the FBA aims to link catchment material transport for the Fitzroy Estuary models with these estuary models.

Barbara Robson, CSIRO Further information: Robson and Brando, 2008

42 DEWHA Project 9: Remote- To assist GBR WQIPs by providing remote sensing capability to monitor chlorophyll, sensing of GBR Waters to assist suspended sediment, water clarity and the colour dissolved organic matter. Involves performance monitoring of Water the continued development of regionally appropriate algorithms for accurately Quality Improvement Plans in Far reporting these parameters and the development of methods of reporting the North Queensland information in ways useful to WQIP reporting and adaptive implementation.

Vittorio Brando, CSIRO Further information: [email protected]

Nutrient Management Zones (NMZs) are geographical areas identified as high risk Reef Plan Nutrient Management in terms of nutrient loss to waterways. By identifying NMZs, effort and assistance Zones project (D8) to improve nutrient management on farms can be focused to improve the quality of water entering waterways and the GBR lagoon. Rebecca Paine, Department of Primary Industries and Fisheries Further information: Brodie (2007); http://www.reefplan.qld.gov.au/library/pdf/D8_FAQs.pdf

• The QScape project seeks to improve knowledge of how changes in land use, land management and climate affect land condition, water quality and ecosystem health, and additionally to contribute associated research products to other land, vegetation NRW QScape Modelling Initiative and water resources research. • QScape is virtual in organisation, integrating expertise from across existing NRW Ken Brooks, Department of Natural Resource Sciences and regional science, with some direct supplementation of Natural Resources and Water new remote sensing and modelling staff. QScape seeks to provide a flexible series of modular components for a variety of uses. Further information: [email protected]

National Action Plan Water Quality Program: Modelling To use spatial and temporal models to provide regions with user-friendly outputs landscape processes, related to landscape processes and the impacts of management practices on water management impacts and quality. catchment loads (WQ03) –Complete Further information: http://www.wqonline.info/index.html Multiple providers

Adequacy of existing research groundwater to loads and consideration • Understanding of the relationship and capability of the role of groundwater transported between increased suspended contaminants (especially nitrate) from sediment loads caused by increased • Immense improvements in last five to paddock to coastal waters. erosion from agricultural and urban six years through targeted monitoring development in major rivers and and modelling programs in many • Investigation of the relative importance increased regional turbidity from catchments. of gully erosion compared with hillslope erosion and whether targeted resuspension in inshore areas of the • Lack of whole-of-GBR approach for all management is required, including GBR lagoon. contaminants even though knowledge review and integration of land-based • Improved conceptual and quantitative may be adequate at some WQIP scales modelling of sediment sources in the understanding of the transport and or across GBR catchments for a single dry tropical catchments. fate of nutrients and sediments in the contaminant (e.g. Nutrient GBR, particularly during non-flood Management Zones). • Identification of major drivers of suspended sediment concentrations, times, through the development of • Inconsistent information across regions both natural and/or anthropogenic, from process studies and implementation of and land uses. different dry tropical sub-catchments, supporting monitoring strategies. • Long-term efforts are required. and identification of the specific origin • Analysis of the function of the coastal/ Priority needs of fine-grained, washload (non-settling) estuarine interface in contaminant suspended sediment that may be transport and transformation. • Refinement of model approaches transported large distances offshore. • Further development of high frequency, that predict contaminant loads by • Improved nutrient budgets are needed low cost data through the application incorporating finer temporal resolution, to quantify the relative contributions of innovative monitoring techniques characterisation of hydrological of all sources in GBR waters; while all such as remote sensing to enable more processes, nutrient speciation and terrigenous sediments and pesticides comprehensive assessment of the better techniques for quantifying are land-derived, some of the dissolved presence and extent of contaminants in uncertainty. nutrients are sourced from deepwater the GBR. • Determination of the relative upwelling and from nitrogen fixing blue- contributions of surface runoff and green algae.

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef 4. Identifying management practices to reduce pollution from key sources

Current major research projects Refer also to Section 5 of Part B below regarding assessing management effectiveness.

Project Primary objectives

DEWHA Project 11: The Model To make available to producers and management agencies model farming Farms Project: Systematic enterprises that demonstrate the economic and GBR water quality benefits of implementation of nutrient and new generation farming systems, where those farming systems incorporating all sediment source controls on wet applicable BMP and the development of new and evolving technologies, over a and dry tropical cane farms full sugarcane production cycle (three to five years). Case study areas – lower Multiple providers, led by Adam Burdekin and Tully. West, Department of Primary Further information: [email protected] Industries and Fisheries

• To compare grazing management strategies under variable rainfall conditions. Wambiana grazing management: Impact of grazing • To demonstrate the benefits of sustainable management of grazing lands through strategies and variable rainfall trial of variable stocking rates and measurement of pasture condition, biodiversity, on pasture composition soil condition and surface runoff water quality.

Peter O’Reagain, DPI&F Further information: http://savanna.cdu.edu.au/publications/savanna_links_issue33.html?tid=250863

• To test approaches to reduce nitrogen fertiliser application in sugarcane industry and Improved environmental to trial the N-Replacement concept. outcomes and profitability • The project involved on-farm experiments from the Wet Tropics of Queensland to through innovative management of nitrogen (SRDC project northern New South Wales, covering a range of soil types and cane varieties. CSE011; SRDC component • Further validation of the approach is underway in GBR catchments. complete) Further information: Peter Thorburn, CSIRO http://www.csiro.au/files/files/pjdh.pdf; Thorburn et al. (2003a, b; 2007), http://www.srdc.gov.au/ProjectReports/ViewReports.aspx?ProjectNo=CSE011

• To develop a range of proven farm management options for improved water, nutrient and crop management that will maintain or increase profitability, while controlling Adopting systems approaches to rising water tables, reducing the risk of irrigation-induced salinity and improving off- water and nutrient management farm water quality. for future cane production in the • To carry out assessments of the economic feasibility of the proven farm management Burdekin (CSE012) – Complete options within the context of future water pricing and water allocation scenarios in the 2008 Lower Burdekin. Multiple providers, funded by • To establish industry reference sites with grower participation to provide robust SRDC benchmarks and to assist in the dissemination of project learnings. Further information: http://www.srdc.gov.au/ProjectReports/ViewReports.aspx?ProjectNo=CSE012

44 Sustainable grazing for a To implement grazing land best management practices (full wet season spelling healthy Burdekin catchment – and forage budgeting) on Virginia Park Station in the Burdekin catchment in order Complete 2006 (MLA project to examine the impact of these practices on land condition recovery, landscape NBP.314) health and the consequent leakiness of water, sediment, and nutrients both from the hillslope and the catchment. Multiple providers, led by David Post, CSIRO and Peter Further information: Post et al., 2006 O’Reagain, DPI&F http://www.clw.csiro.au/publications/science/2006/sr62-06.pdf

• To improve on-farm profitability (reducing fertiliser costs by $60/ha or 65 c/t of cane) and ensure greater environmental accountability and responsibility through accelerated adoption of integrated nutrient management. • To improve knowledge of the constraints to the adoption of best-practice nutrient management using grower surveys. Accelerated adoption of best- • To develop a Soil Capability and Management Package (SCAMP) for improving practice nutrient management on-farm management decision-making and facilitate the use of nutrient management – Complete 2008 plans at block and farm scales and the implementation of soil/site specific fertiliser Multiple providers, funded applications using a participative approach. by SRDC, led by Bernard • To assess the risks of on- and off-site impacts of land management practices using Schroeder, BSES vulnerability maps at catchment scale. • To demonstrate the benefits of best nutrient management practices with on-farm strip trials. Further information: http://www.srdc.gov.au/ProjectReports/ViewReports.aspx?ProjectNo=BSS268

• AgSIP was a state-level investment program of the National Action Plan for Salinity and Water Quality. The program ran from August 2004 until June 2007. Sustainable Agriculture State- • To develop new processes, tools and frameworks to facilitate agricultural practice level Investment Program change where needed in order to help regional NRM groups design, refine, (AgSIP) – various projects – deliver and review their regional investment strategies and natural resource Complete 2007 management plans. • The project involved looking at existing practices, developing new recommended Multiple providers practices where needed, filling data gaps, designing integrated landscape monitoring systems, and developing better training and decision-support tools across cotton, cane grazing and horticulture industries.

Adequacy of existing research Priority needs • Assessment of the relative importance and capability of the type of groundcover maintained • Completion of robust triple bottom line in grazing lands to minimise sediment • Substantial improvements in the last evaluations of current and proposed loss, and the efficiency of different five years. management actions as a basis to groundcovers in managing hillslope design more cost-efficient management • WQIPs are the first attempt to target erosion (i.e. ‘natural’ cover of trees and interventions in the future. ‘key contaminants’ in a restricted area. shrubs or savannah, compared Established qualitatively good practices • Development of new land management to pasture). but quantitative assessments practices for improved water quality • Development and testing of sustainable are inadequate. outcomes. grazing and fire management • Grazing land management practices • Investigation of the social/economic/ guidelines for riparian and frontage will successfully deal with hillslope institutional aspects of delivering country in the extensive dry rangelands. erosion, while riparian vegetation practice change. management is able to minimise • Establishment of capability to determine streambank erosion, but practices the relative importance of the location related to management of gully erosion of the works in the landscape in terms requires further investigation. of material delivery.

Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef 5. Assess the effectiveness of actions to reduce pollution

Current major research projects Refer also to Section 4 in Part B regarding identification of management practices, many of these projects test the effectiveness of the actions.

Project Primary objectives

DEWHA Project 4.2: Implementing agricultural source To target components of the Douglas Shire Fertiliser Management Strategy and the controls through accredited Farm Douglas Shire Cane Drain management Strategy as identified in the Douglas WQIP. Management Systems in the These and other BMPs will be implemented and monitored. Mossman Mill District Further information: [email protected] Peter Bradley, Terrain NRM

Douglas WQIP Fertiliser To test variable nitrogen fertiliser application rates in sugarcane in Mossman and management trials assess the water quality and economic benefits.

Tony Webster, CSIRO Further information: [email protected]

Mackay Whitsunday management To assess sediment, nutrient and herbicide runoff from canefarming practices in the practices (rainfall simulator) Mackay Whitsunday region: a field-based rainfall simulation study of management experiment practices Ken Rohde, Department of Further information: Masters et al., 2008 Natural Resources and Water

To develop a detailed understanding of the potential for wetlands on the Tully- Wetland filter function Murray floodplain to regulate and filter agricultural runoff before it drains to the GBR lagoon. David McJannet, CSIRO Further information: http://csiro.au/science/ps3ox.html; McJannet (2007

• Evaluate the socio-economic constraints to and risks associated with the adoption of MTSRF Project 3.7.5: Socio- land use and management options for water quality improvement at the private and economic constraints to and social level. incentives for the adoption of land use and management options for • Identify and assess instruments that are most cost-effective in promoting the adoption water quality of these ‘best’ land use and management options by community embedded agents in rural and urban areas in North Queensland’s catchments. Martijn van Grieken, CSIRO Further information: http://www.rrrc.org.au/mtsrf/theme_3/project_3_7_5.html

The SEPIA (Single Entity Policy Impact Assessment) model simulates land-use Case study applications of a decision making enacted by agents involved in agricultural production. The current Single Entity Policy Impact application includes sugarcane, tree fruit, and beef cattle (grazing) producers, and Assessment model is applied in the Douglas Shire, Burdekin region and Tully catchments. Alex Smajgl, CSIRO Further information: http://www.csiro.au/news/newsletters/0411_water/story1.htm

DEWHA Project 6: Decision Reduce nutrient loadings to the GBR by working with producer reference groups Support Tools for Nutrient and industry associations in the Johnstone, Tully and Don/Burdekin catchments Management in Tropical to develop science-based tools for improved nutrient management in tropical Horticulture horticulture.

Phil Moody, NRW Further information: [email protected]

46 Adequacy of existing research Priority needs and capability • Establishment of a GBR-wide initiative • Significant gaps in quantitative to effectively validate management knowledge of the effectiveness of practices across land uses in the GBR practices – rudimentary knowledge catchments, including the efficacy across practices. of practices in regionally specific • Substantial uncertainty between the applications, from the perspective of relationship of improved water quality water quality outcomes and profitability. at a paddock scale, reduced loads and • Establishment of modelling and the effect on the GBR, and therefore, monitoring systems that quantify the uncertainty in exact target setting to responses of the catchment socio- achieve specific GBR outcomes. ecological system to management • Limited investigation of the tradeoffs interventions. (if any) between BMPs, profitability • Commencement of a GBR-wide and production, especially in extensive monitoring program to undertake socio- grazing lands. economic benchmarking of the current • Major opportunity to measure the adoption rates, extension efforts and effectiveness of improvements through industry culture by region Reef Rescue investment. and commodity. • Development of a specific metric for each sector group (e.g. grazing) aimed at measuring outcomes from actions to allow comparisons across sectors. • Assessment of the drivers that will lead land managers to change practices for water quality improvement. • Investigation of the design of optimal monitoring and modelling programs in GBR catchments that enable detection of short- or medium-term trends in water quality at large spatial and temporal scales.

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Synthesis of evidence to support the Scientific Consensus Statement on Water Quality in the Great Barrier Reef DPC1658