play an important ecological role in many of ’s tropical and sub-tropical environments. In several areas, mangroves also have strong social and cultural significance. DBCA’s Biodiversity and Conservation Science is carrying out a State-wide monitoring program to keep a long-term watch on the health and extent of mangroves, to observe changes in their condition caused by factors associated with climate change, and in order to respond to direct human-caused threats. by Kevin Bancroft t is estimated that there are 352,000 and Kimberley regions, respectively. Previous page unique flowering species on Structurally, areas range from Main Mangrove forests line the Kimberley coast. Earth, of which approximately 140 sparsely treed stands no taller than five I Photo – David Bettini species are found in marine environments. metres in Shark Bay, to dense forests of up Inset left DBCA scientists are monitoring the True mangroves – plant species that occur to 20 metres tall in the Kimberley. health of mangroves throughout the State. only in mangrove forests and are not Photo – Kathy Murray/DBCA found in terrestrial communities – account UNSUNG HEROES Inset right Mangrove heron. for 69 of these species. Of these, 41 are Mangroves serve an important Photo – Jiri Lochman found in Australia, and nearly half in ecological role. They protect the shoreline Above left Grey mangroves are found in Western Australia. from coastal erosion, particularly in the Bunbury. tropical areas where cyclones and severe Photo – Cliff Winfield SPECIES DIVERSITY monsoonal storms routinely occur. They Mangroves have adaptations also have a substantial capacity to convert Above Some mangroves species have special above-ground roots. that enable them to survive in salty atmospheric carbon dioxide and other Photo – Kevin Bancroft/DBCA environments. For example, special greenhouse gases into oxygen and can glands in their leaves excrete excess salt, fix the carbon in the muddy, oxygen- and enable mangroves to expel up to poor substrate that supports them, for 90 per cent of the salt content taken in thousands of years. They also have the through their root systems. Also, some potential to sequester (capture) up to and the mangrove free-tailed bat (Ozimops species have special above-ground roots, six times more carbon than rainforests. cobourgianus), northern brushtail possums called pneumatophores, which transport Indeed, the average carbon captured (Trichosurus arnhemensis), native rodents oxygen throughout the plant to regions by one hectare of mangroves, including such Melomys burtoni and more than 200 located in low-oxygen muddy sediments. soil carbon, has been estimated at bird species such as the great-billed heron Mangroves occur in both tropical and around 1000 tonnes – about the same (Ardea sumatrana), mangrove heron subtropical areas. They vary in height from amount as the annual carbon emission of (Butorides striata), the mangrove kingfisher less than a metre up to 20 metres tall, and approximately 700 cars. (Halcyon chloris), pied cormorant usually occur above mean sea level in the The structural complexity of (Phalacrocorax varius) and the mangrove intertidal zone of marine and estuarine mangroves provides nursery habitat, flyeater (Gerygone levigaster). environments. However, the most inland shelter, nesting and foraging habitat Mangroves also have cultural occurrence of mangroves in WA is at for numerous resident and transient significance and are used for food, Mandora Marsh wetlands in Walyarta invertebrate, fish, bird, reptile and medicines, shelter and as a wood resource. Conservation Park, approximately mammal species, including prized Traditional owners harvest the mangrove 60 kilometres inland from Eighty Mile recreational species such as barramundi snail (Nerita spp.), ‘long bums’ whelks Beach. (Lates calcarifer), mangrove jacks (Lutjanus (Telescopium telescopium and Terebralia In WA, mangroves occur in stands of a argentimaculatus) and mud crabs (Scylla spp.), fish, turtles and mud crabs for food, single species, such as the grey mangrove serrata and S. olivacea). Other species that while the leaves of the mangrove myrtle (Avicennia marina) found in Bunbury utilise mangroves include the estuarine (Osbornia octodonta) are rubbed on the (see also ‘Kaleidoscope’ on page 53), the crocodile (Crocodylus porosus), green skin to repel insects and chewed to relieve Abrolhos Islands and Shark Bay areas, turtles (Chelonia mydas), flying foxes toothaches. The Aboriginal people of the or in multispecies assemblages of up to (Pteropus spp.), microbats such as the Dampier Peninsula traditionally sought eight or even 20 species in the Pilbara northern pipistrelle (Pipistrellus westralis) out a particular mangrove – the kapok

50 LANDSCOPE Above Mangrove loss. Photo – Kevin Bancroft/DBCA

mangrove (Camptostemon schultzii), and changing rainfall patterns, and increased Further investigation of satellite data used its wood to construct rafts, paddles, storm intensity and frequency. With the showed this loss was not gradual, and a and spears for hunting of dugong, fish and exception of the Rowley Shoals Marine significant mortality event occurred in turtles. Park, mangroves are present in all CALM February 2011. Carnarvon climatology Act marine conservation reserves north and environmental data suggests that the MONITORING MANGROVES of and including Shark Bay Marine Park. In loss of mangroves coincided with four IN WA each of the reserves, the department uses environmental pressures. Firstly, there DBCA’s Biodiversity and Conservation satellite imagery and aerial photography were record-high sea levels peaking in 2011, Science has established a State-wide together with on-ground surveys to assess which would have drowned the mangroves monitoring program, to evaluate the the health of the mangroves, based on two that were already at their maximum condition of mangroves and to detect key condition indicators – spatial extent depths. Secondly, prolonged record-high the effects of pressures on mangrove (area) and canopy density. air temperatures were experienced, and sustained high seawater temperatures would communities. WA mangroves are subject EVALUATING CHANGES to lower levels of human-caused pressures, have added further pressure to the already- such as from coastal development and Routine monitoring between 2010 and nutrient enrichment and sediment run-off 2015 in Shark Bay Marine Park highlighted from agriculture and industrialisation, than losses in spatial extent and in canopy Hear about mangrove other more densely populated areas in density, particularly along the Carnarvon monitoring Australia. The main pressure on Western coast. In 2010, Carnarvon coast mangroves Scan this QR code Australian mangrove communities spanned approximately 850 hectares, or visit Parks and Wildlife comes from long-term changes in climate but, by 2015, this was reduced to Service’s ‘LANDSCOPE’ conditions, such as rising sea levels, approximately 720 hectares – a loss of playlist on YouTube. rising seawater and air temperatures, about 15 per cent.

LANDSCOPE 51 “DBCA’s primary focus for mangrove conservation is to minimise the loss of diversity and spatial extent, caused by human activity.”

stressed mangroves. Lastly, the worst and Lalang-garram / Camden Sound flooding of the Gascoyne and Wooramel marine parks, respectively. In both rivers since 1960 eroded mangrove habitat marine conservation reserves, significant and smothered other areas with terrestrial increases in rainfall and moderate air sediments. Prolonged high air and seawater temperatures have provided optimum temperatures, and low rainfalls would have growing conditions for the mangrove further hampered recovery in some areas. communities. A minor mangrove loss (less than two hectares) was also observed at Big GROWING FORWARD Lagoon, in Francois Peron National Park, WA’s mangrove communities, in during routine monitoring. Subsequent general, are not under immediate direct field investigation revealed that the cause threat from human activity. However, was a flock of nesting cormorants that they are susceptible to human-induced were directly impacting the mangroves climate change. DBCA’s primary focus for Above left Grey mangroves at Roebuck Bay in through defoliation and by depositing high mangrove conservation is to minimise the Broome. levels of nutrients via their guano. loss of diversity and spatial extent caused Photo – Damon Annison Losses in mangrove spatial extent in by human activity. Ningaloo Marine Park in 2015 and 2016 In the same way that humans monitor Top Kevin Bancroft and marine ranger – vessel were attributed to a short-term drop in sea their blood pressure to identify heart mate Adrian Lane examining mangroves. Photo – Daniel Barrow/DBCA level and increasing sediment interstitial disease, DBCA researchers will continue water salinity – the water in between sand to monitor changes in mangrove spatial Above Club mangroves. grains. Declines in mangrove spatial extent extent and canopy density to indicate Photo – Kevin Bancroft/DBCA and canopy densities have been observed the health of these ecosystems. Further in the Montebello/Barrow Islands Marine research is required to understand Below Stilted mangrove is one species that grows in WA. Conservation Reserves since 2011. These the potential effects of sea level rise, Photo – Sue Osborne/DBCA are more than likely related to a short- sediment interstitial salinity, and to obtain term drop in sea level, increasing sediment estimates of the area of inundation from porewater salinity and higher-than-average rising sea levels, which may influence atmospheric temperatures since 2012. mangrove inshore migration. DBCA is In contrast to these Gascoyne and currently exploring the use of remotely Pilbara reserves, the mangroves in the piloted aircraft technology (drones) to Kimberley (Eighty Mile Beach and Lalang- obtain valuable on-ground data at larger garram / Camden Sound marine parks), spatial scales and at sites inaccessible Kevin Bancroft has been involved experienced increases in distribution and by field staff. Ongoing monitoring using in marine conservation and management in canopy cover. Between 1989 and 2015, established techniques, combined with with the department and its predecessors there has been an increase of 214 hectares these innovative new approaches, will for 20 years. He can be contacted on (08) 9219 9792 or by email (about 25 per cent) and 2909 hectares enable the continued evaluation of these ([email protected]). (about 12 per cent) at Eighty Mile Beach valuable mangrove ecosystems.

52 LANDSCOPE