Nullarbor bioregion

Description Figure 2 Western Australian Rangeland Monitoring System monitoring Area: 197 220 km2 sites and pastoral tenure in the The Nullarbor bioregion is dominated by broad, WA part of the Nullarbor bioregion gently undulating limestone . The vegetation is predominantly chenopod, with a number of bluebush and saltbush species, sometimes with a scattered WA overstorey of western myall or mulga. The plains are NT progressively more wooded in the northern and western parts of the bioregion. Perennial grasses are common where fires have removed the chenopod vegetation. Soils are calcareous shallow loams and calcareous loamy bioregion boundary earths. Pastoralism is the predominant land use within pastoral tenure Western , while conservation reserves occupy WARMS monitoring site most of the bioregion on the South Australian side. There are no major population centres in the Monitoring sites and pastoral tenure bioregion. Yalata is one of the smaller centres. Data sources available Data sources include:

Location n Western Australian Rangeland Monitoring The Nullarbor bioregion is located in the southern System (WARMS), which provides high reliability rangelands of (WA; 70% of the for reporting change, with a large number of Interim Biogeographic Regionalisation for Australia sites in the central band, Nullarbor (NUL2) (IBRA) area) and (SA; 30% of sub-IBRA, quantitative data, and a focus on longer- bioregion). Figures 1 and 2 show the location lived plant species, which helps to filter short- of the Nullarbor bioregion. term seasonal variability n domestic stocking density, which provides Figure 1 Location of the Nullarbor moderate reliability bioregion n fire extent, intensity and frequency, which provides high reliability

n dust

n distance from water

n distribution and relative abundance of invasive animals and weeds

n land use

n conservation estate

n land values.

NullarborLocati bioregionon of Nulla rbor bioregion 1 Climate Nullarbor 2 sub-IBRA

The climate of the Nullarbor bioregion is arid to Resource capture index semiarid. Spatially averaged median (1890–2005) When seasonal quality was above average, 32% of rainfall is 192 mm (April to March rainfall year; sites showed a decline in the resource capture index, see Figure 3). Note that rainfall data are for the while 57% of sites showed an increase when seasonal whole Nullarbor bioregion. quality was below average. Figure 3 Decile rainfall for the period No 1991–1992 to 2004–2005 change: 10 Decline: 0.90 ≤ Increase: 9 Seasonal Number RCI < RCI < RCI ≥ 8 quality of sites 0.90 1.10 1.10 7 6 Above median 5 average 19 32% 32% 37% 4 3 Average 83 23% 39% 39%

Rainfall decile 2 1 Below 0 average 14 14% 29% 57% 1991-92 1993-94 1995-96 1997-98 1999-00 2001-02 2003-04 Rainfall year RCI = resource capture index

Annual rainfall is for the 12‑month period 1 April Population growth rate to 31 March. No sites experienced a decline in the density of Seasonal quality based on decile rainfall throughout longer-lived perennial vegetation when seasonal quality the 1992–2005 reporting period was above average. was above average, and 86% of sites showed an Recent years (2002–2003 to 2004–2005) have seen increase when seasonal quality was below average. declining rainfall (although still above the median). On average, there was a 20% increase in density Spatially averaged, the Nullarbor bioregion received and virtually no sites suffered substantial decline.

14 consecutive years of median or above rainfall. No This is almost certainly the best sequence of rainfall change: on record, better even than the mid-1970s or the density first decade of the twentieth century. Decline: between Increase: Seasonal Number density < 95% and density ≥ Note that regional averaging of rainfall conceals spatial quality of sites 95% 105% 105% variability. Some parts of the bioregion experienced Above better seasonal quality and others worse during the average 19 0% 32% 68% 1992–2005 period. For example, much of the western Average 83 17% 28% 55% part of the bioregion was declared to be under Below average 14 0% 14% 86% exceptional circumstances (drought) in 2003, with this declaration extended in 2006. There are no suitable data for reporting change for the SA part of the Nullarbor bioregion. Landscape function Change in landscape function can be reported in a Sustainable management number of ways using WARMS data. The information in the following sections is based on the resource Critical stock forage capture index and population growth rate (for Decreaser shrubs declined in density at 5% of sites consistency with reporting by other jurisdictions). in the central band, Nullarbor Plain (NUL2) sub- Reporting is for the central band, Nullarbor Plain IBRA following above-average seasonal quality. They (NUL2) sub-IBRA only based on the distribution increased at 90% of sites following below-average of WARMS sites. seasonal quality.

2 Rangelands 2008 — Taking the Pulse Distance from stock water The percentage area of pastoral lease country in WA within three kilometres of permanent and semi- permanent sources of stock water for each sub-IBRA is: Seasonal Species

quality group Number of sites Decline: density < 0.95 No change: 0.95 ≤ density < 1.05 Increase: density ≥ 1.05 Northern band, Carlisle 11.9% (5.5% of Above Decreaser 19 5% 26% 68% (NUL1) sub-IBRA analysed) average Intermediate 19 0% 79% 21% Central band, Nullarbor 10.2% (53.1% of Increaser 7 n/a n/a n/a Plain (NUL2) sub-IBRA analysed)

Average Decreaser 76 22% 22% 55% IBRA = Interim Biogeographic Regionalisation for Australia; Intermediate 73 6% 38% 29% NUL = Nullarbor Increaser 15 7% 67% 27% Note that this analysis does not include the locations Below Decreaser 10 0% 10% 90% of natural waters, although these are rare in the average Intermediate 9 n/a n/a n/a Nullarbor bioregion. It is not possible to report Increaser 1 n/a n/a n/a change in watered area for the 1992–2005 period.

There are no suitable data for reporting change There is no commercial pastoralism in the SA part for the SA part of the Nullarbor bioregion. of the bioregion.

Plant species richness Weeds No WARMS sites had decreased species richness of Weeds known to occur in the Nullarbor bioregion include: native perennial plants following above-average seasonal quality and 21% of sites had increased species Common name Scientific name richness following below-average seasonal quality. African boxthorn Lycium ferocissimum African love grass Eragrostis curvula No Bathurst burr Xanthium spinosum change: Patersons curse Echium plantagineum Decline: 0.80 ≤ Increase: Wild mignonette Reseda luteola richness richness richness Seasonal Number index index < index See www.anra.gov.au for distribution maps quality of sites < 0.80 1.20 ≥ 1.20 Above average 9 0% 53% 47% Components of total Average 83 2% 69% 29% grazing pressure Below average 14 0% 79% 21% Domestic stocking density There are no suitable data for reporting change for Approximately 32% of the Nullarbor bioregion is the SA part of the Nullarbor bioregion. commercially grazed, almost exclusively in WA. Data from the Australian Bureau of Statistics showed that Change in woody cover domestic stocking density was below the 1983–1991 Based on WARMS data, cover of woody species average throughout 1992 to 2004 and decreased increased by one-third on average and remained the appreciably between 2000 and 2001. In both 2001 same or increased on most sites (83%). On only 1% and 2004, stocking density was approximately 65% of sites did cover drop below 50% of the initially of the 1983–1991 average. These changes bear little recorded value. direct relationship with seasonal quality indicated by decile rainfall (see Figure 3, above). Note that spatial There are no suitable data for reporting change averaging across grazed areas of the bioregion conceals for the SA part of the Nullarbor bioregion. likely actual variation in stocking density trends.

Nullarbor bioregion 3 Kangaroos Biodiversity There are no suitable data for reporting change More than 15% of the Nullarbor bioregion area is in kangaroo populations. protected (Collaborative Australian Protected Areas Database, Biodiversity Working Group indicator: Invasive animals Protected areas; see Section 7 of Chapter 3 of Invasive animal species known to occur in the Rangelands 2008 — Taking the Pulse). Nullarbor bioregion include: For the SA part of the bioregion, there are more

Common name Scientific name than 500 flora survey sites and approximately Fox Vulpes vulpes 10 000 flora records of about 630 taxa (Biodiversity Working Group indicator: Flora surveys). There are Rabbit Oryctolagus cuniculus more than 3500 bird records, 1000 reptile records Wild dog Canis spp. and 600 mammal records (Biodiversity Working Feral cat Felis cattus Group indicator: Fauna surveys). Starling Sturnus vulgaris Camel Camelus dromedaries In this bioregion, there are (Biodiversity Working Horse Equus caballus Group indicator: Threatened species):

See www.anra.gov.au for distribution maps n 3 threatened plant species

n 8 threatened mammal species Products that support reporting n 3 threatened bird species. of landscape function and sustainable management Socioeconomic characteristics Fire Land use and value Data for the whole bioregion show that fires cause Approximately 32% of the Nullarbor bioregion is major, long-lasting changes in the vegetation of the commercially grazed, exclusively in WA. This area Nullarbor bioregion. Typically, the chenopod shrubs has not changed appreciably over the 1992–2005 are replaced by perennial grasses following fire. This reporting period. occurred especially along the trans-Australian railway line, completed in the early 20th century, and in the In WA, there have been very few property sales mid-1970s following a sequence of very high rainfall. during the 1992–2005 period and it is not possible to report realistic change in the average ‘lease and Fire was insignificant during the 1997–2005 period, improvement’ value of pastoral land. with a maximum of 0.5% of the bioregion area burnt in 2000. Key management issues The fires that were recorded occurred in the hot or dry months of the year and so were likely to be and features more intense. Key features and issues of the Nullarbor bioregion include the following: Dust n WA (issues relate to the central band, Nullarbor Based on data for the whole bioregion, the mean Dust plain [NUL2] sub-IBRA): Storm Index value (1992–2005) was 1.64, which is considered low. Dust levels were relatively higher in – The Nullarbor as a whole experienced the eastern part of the bioregion (SA) than in WA. an exceptional sequence of above-average rainfall through the 1990s and early 2000s.

4 Rangelands 2008 — Taking the Pulse Notwithstanding this, western parts of the n SA: bioregion were declared for exceptional – The Alinytjara Wilurara Natural Resource circumstances (drought) in 2003 and this Management Board, recently formed under the was extended in 2006. South Australian Natural Resources Management – Over approximately the past decade, the Act 2004, has statutory responsibility for the cover and density of shrubs and trees on monitoring and evaluation of the Aboriginal WARMS sites increased. lands in SA. – Grazing-sensitive species were not adversely – Lack of water, both potable and of stock affected on WARMS sites over approximately quality, is the major limiter to development. the past decade. – Much of the area has been modified by – Native shrub species richness on WARMS extensive fires in the past. sites increased slightly over approximately – All of the bioregion is held as Aboriginal land the past decade. or conservation reserve. – Wild dog numbers and their impacts have – Increasing tourism pressure (whale watching, increased markedly in recent years. surfing, fishing) along the coastal fringe is evident. – High numbers of kangaroos contribute a significant proportion of total grazing pressure. – About 16.1% of the bioregion within WA is within the conservation estate.

Nullarbor bioregion 5