Altered fire regimes

The most substantial threat to the biodiversity of the IPAs is the changed fire regime.  For millennia fire has been the single most powerful land management tool available to indigenous landowners. It was used to great effect, shaping the fauna and flora of the tropics and ensuring a sustained seasonal harvest for the people who controlled it. The arrival of Europeans brought changes to the traditional patterns of burning as Aboriginal people moved from their homelands to centralized communities and the frequency of fire in the landscape decreased while the intensity increased (Warddeken Land Management Limited 2009b).

The change from benign and “healthy” fire regimes under customary management to increasingly unsustainable fire regimes dominated by frequent, intense and extensive fires has had a major detrimental impact on biodiversity. The current regime is substantially reducing the extent of the endangered Arnhem Plateau Sandstone Shrubland Complex heathlands and the abundance of a range of fire-sensitive plant species (e.g. Callitris intratropica, Petraeomyrtus punciea). It is also causing damage to monsoon rainforest patches and the Allosyncarpia forests, which are endemic to the Arnhem Plateau (Russell-Smith 2006). The current fire regime may also be detrimentally affecting a range of animal species, including granivorous birds as well as small mammals (Franklin 1999, Woinarski et al. 2001). A marked decline in the abundance and richness of savanna woodland and rock-dwelling mammals has now been documented repeatedly in northern Australia, and fire is thought to be a primary correlate to this effect.

Feral animals

Feral pigs, the Asian water buffalo, cattle and cane toads are known to be impacting on biodiversity values in the IPAs (Fordham et al. 2006, Griffiths and Pardon 2002). Water buffalo and pigs are having a large impact on fragile coastal wetlands and they act as vectors for the spread of weeds. Buffalo destroy rainforest patches and breech coastal levees, leading to saltwater incursion of wetlands. Pigs are a major predator of marine turtle nests. The cane toad is thought to have caused the collapse of northern quoll and yellow-spotted goanna populations (Woinarski et al. 2007). Other feral animals that are a source of concern include European bees, feral ants, black rats, tramp ants and cats.

Exotic plants

The major threat from exotic plants lies in grassy weeds such as Gamba Grass and Mission Grass. These have a high biomass, cure late in the year and as a consequence cause significant damage to the environment by increasing the scale of uncontrolled fires. These weeds are increasing rapidly in extent and density. Localized outbreaks of Mimosa pigra have been controlled to date, but reinfestation is an ongoing threat. As a declared Weed of National Significance it forms impenetrable thickets hindering and substantially changing native plant and animal communities.  Other serious environmental weeds such as Alligator Weed, Salvinia and Prickly Acacia are recorded in adjacent regions to the IPAs.

Diminishing presence of people on country and knowledge transfer

Cultural heritage management issues of the region are inextricably linked to the diminishing presence of people on country and the imminent passing of the final generation to have lived at least part of their lives in a traditional manner. Time is the most pressing threat to traditional ecological and cultural knowledge and it is vital to record knowledge held by senior land owners. The loss of cultural knowledge about the biodiversity of the region is also a critical issue. A small number of elderly Aboriginal experts retain a large body of knowledge essential to management of the area. The need to record this knowledge and to assist its customary flow to younger generations for incorporation into contemporary Aboriginal land management is vital. These threats are magnified by the lack of management resources available and the logistical difficulties and costs of undertaking management in such a remote and rugged landscape.

Inadequate documentation

In contrast to other areas of Arnhem Land there has been minimal research and documentation of cultural and archaeological sites, and many of the art and archaeological sites have not been seen by living people and are un-researched (Warddeken Land Management Limited 2009a). There is a consequent lack of records of cultural sites or information relating to them, including their custodians. This is of the highest priority given the small number of people with knowledge of these sites. Without a good record of the cultural landscape there is no buffer against intergenerational gaps in knowledge transfer.

Physical destruction of cultural sites

Damage to sites in this region is principally attributable to fire and the actions of feral animals. Where vegetation or litter builds up against art sites they are at threat from fire. Intense fire can cause severe exfoliation of sandstone surfaces resulting in obliteration of paintings. Currently many rock art sites are heavily overgrown and at risk of irreparable fire damage. Termites and wasps also build nests on painted surfaces and large feral animals such as buffalo and horses rub on painted walls and raise dust.

Climate change

Climate change is an overarching threat to the IPAs and a specific threat to the preservation of cultural heritage sites. Rising sea levels are and will increasingly threaten coastal sites such as middens, more contemporary occupation sites and hunting and harvesting areas such as reefs and mudflats, and on floodplains.

References

Bawinanga Aboriginal Corporation (2009). Djelk Indigenous Protected Area - Central Northern Arnhem Land Management Plan 2009.

Fordham, D., Georges, A., Corey B., and Brook, B. W. (2006). Feral pig predation threatens the indigenous harvest and local persistence of snake-necked turtles in northern Australia. Biological Conservation 133: 379-388.

Franklin, D.C. (1999). Evidence of disarray amongst granivorous bird assemblages in the savannas of northern Australia, a region of sparse human settlement. Biological Conservation 90: 153–68.

Griffiths, A.D., and Pardon, L.G. (2002). Feral animal abundance and spatial extent of damage from the Gumadir River catchment, western Arnhem Land, Rep. No. Technical Report No. 2. Key Centre for Tropical Wildlife Management, Darwin.

Russell-Smith, J. (2006). Distributional pattern of plant species endemic to the Northern Territory, Australia. Australian Journal of Botany 54: 627–640.

Warddeken Land Management Limited (2009a). Warddeken Indigenous Protected Area Arnhem Land Plateau, Northern Territory Management Plan 2009-2013.

Woinarski, J.C.Z., Milne, D.J., and Wanganeen, G. (2001). Changes in mammal populations in relatively intact landscapes of Kakadu National Park, Northern Territory, Australia. Australian Ecology 26: 360-370.

Woinarski, J.C.Z, Mackey, B., Nix, B., and Trail, B. (2007). The Nature of Northern Australia: its natural values, ecological processes and future prospects. Canberra: Australian National University.