Plants and Animals of Arnhem Land

By John Woinarski, Parks & Wildlife Commission of the NT

Documenting biodiversity

There has been relatively little documentation of the biodiversity and conservation values of Arnhem Land. With few exceptions, most of the published information derives from a few collecting expeditions (most notably the landmark 1948 American-Australian Scientific Expedition) and as ancillary information collected during anthropological studies (most notably by Donald Thomson in the 1930s).

The most notable of the exceptions are ongoing surveys of crocodile populations in many of the river systems; waterbirds, coastal shorebirds and breeding sites for seabirds and marine turtles (mostly not yet published); extensive floristic inventories of rainforests by fire ecologists Jeremy Russell-Smith and Diane Lucas; intensive studies of the movement patterns, distribution and factors affecting survival in marine turtles by Rod Kennett (Centre for Indigenous Cultural and Natural Resource Management, Northern Territory University) and Dhimurru Aboriginal Land Management Corporation; and wildlife inventories of Cape Arnhem Peninsula, the Wessel and English Company island groups, and Arafura Swamp catchment by the Parks and Wildlife Commission of the Northern Territory, in collaboration with Aboriginal landowners.

The information gathered across these studies is piecemeal and sketchy, even by northern Australian standards. In contrast to this slim chronicle of published information, traditional Aboriginal landowners have maintained an extraordinarily detailed knowledge of their environments and biota across most of Arnhem Land.

Eucalypt open forests (typically Darwin stringybark and Darwin woollybutt) dominate extensive areas of Arnhem Land. Many of the animals associated with these eucalypt forests such as the brushtail possum Trichosurus vulpecula , northern brown bandicoot Isoodon macrourus , agile wallaby Macropus agilis , delicate mouse Pseudomys delicatulus , red-collared lorikeet Trichoglossus haematodus , brown honeyeater Lichmera indistincta , silver-crowned friarbird Philemon argenticeps , weebill Smicrornis brevirostris and white-bellied cuckoo-shrike Coracina papuensis are widespread in Arnhem Land. (Click on the species name to see a list of research findings).

In contrast, some species common in eucalypt forests elsewhere in the Top End are either comparatively rare or absent from most of Arnhem Land: these include many of the finches, some raptors and the fawn antechinus Antechinus bellus.

Rivers and floodplains

East of the East Alligator River, most of the rivers of Arnhem Land are relatively small, and the floodplains relatively restricted. The Goyder/Glyde system is the most distinctive, including the vast Arafura Swamp, the most extensive melaleuca wetland in Australia. This is an important breeding site for magpie geese and other waterfowl, and the swampland and adjacent areas contain many highly restricted plant species.

Coastal areas

Coastal areas of Arnhem Land include some of the best developed sandsheet and sand-dune formations in northern Australia, especially at Cape Arnhem Peninsula and on Groote Eylandt. These support some distinctive heathlands, and some localised animal species, including the Northern Hopping-Mouse Notomys aquilo and the burrowing skinks Lerista stylis and L. carpentariae . Mangroves are also well-developed along much of the shoreline of Arnhem Land, and support a rich associated biota including the False Water-rat Xeromys myoides, Mangrove Monitor Varanus indicus, Chestnut Rail Eulabeornis castaneoventris and Mangrove Golden Whistler Pachycephala melanura .

Environmental challenges

The lack of development and broad-scale habitat modification is the primary conservation asset of Arnhem Land. The environment remains extensive and its diverse components functionally inter-connected. This is one of the least disturbed environments in Australia, if not the world.

However, there are increasing inroads into this asset. Many weeds are spreading into the region, even into remote areas such as the Arafura Swamp. Feral animals, most notably pigs, water buffalo and cane toads have changed the ecology of some significant areas, and their spread is continuing more or less unabated. Notwithstanding the traditional land management practices of much of the area's Aboriginal population, many areas are now very rarely visited and suffer from the effects of a fire management vacuum. As the economic productivity of most of the region is relatively low, there are few resources available for tackling these emerging land-management problems.

The most important resource is a strong sense of responsibility for land held by many Aboriginal landowners. In some parts of Arnhem Land, this accountability for looking after the land has led to the formation of local area based Aboriginal ranger corps, charged with land management and supported by the local communities and grants from some federal and Territory agencies.