Around 15,000 rainforest patches occur scattered through the Top End growing in fire protected areas where moisture is available through the year. They are generally associated with groundwater springs or perennial streams. Despite the large number of stands, rainforest (or monsoon forest) habitat makes up a tiny proportion of the Northern Territory, covering less than 0.1% of its land area. However, rainforests support a great variety of wildlife. They are home to nearly 600 plant species, including 28 threatened plants that are rarely, if ever, found in other habitats. The main reason these species are considered threatened is that they are found in very few places: their future survival may be at risk if one or more rainforest patches are damaged.
By contrast, there are very few threatened vertebrate animals restricted to rainforests, and of the 30 birds, 12 mammals, 9 reptiles and 7 frogs found primarily in rainforest, only two - the Arnhem and Carpentarian Rock-rat - are considered threatened. However, Masked Owl, Oenpelli Python and Bare-rumped Sheath-tailed Bat are commonly found in rainforests, so could be adversely affected by any loss of rainforest habitat.
Threats and management
Fire incursions from the surrounding drier forests and woodlands are perhaps the greatest threat to rainforests in the Northern Territory, affecting around one third of rainforest patches. So managing fuel loads to prevent fire incursions is essential for the
protection of rainforests and the threatened species that live in them. Further information is needed for the strategic fire management of rainforest pockets in remote areas, particularly about the distribution and extent of these rainforest stands.
Around one-fifth of rainforest patches surveyed so far have been found to be weedinfested. While few aggressive weeds have invaded rainforests, there are a number that could be detrimental to rainforest health if they did so. Weeds, particularly introduced perennial tussock grasses, on the edges of rainforests are a significant problem as they increase both fuel loads and fire hazard. Greatest among these threats are Gamba Grass and Guinea Grass.
Damage caused by feral animals is also a significant problem for Northern Territory rainforests, with 20% of surveyed patches suffering severe damage from water buffalo and 10% from pigs. Even more patches may be affected by buffalo as the numbers of this feral animal are again on the rise. Buffalo, cattle and pigs degrade rainforests by grazing and trampling plants. Buffalo and cattle compact the soil, and pigs dig it up, looking for edible roots and tubers. This type of damage is particularly a problem for ground dwelling plants, including several orchids, but may also prevent the recruitment of larger rainforest plants. Pigs also feed on fallen rainforest fruits and could have a substantial impact on seedling regeneration. Another threat to rainforests that has come to light fairly recently is the draw-down of aquifers. This not only dries out rainforest patches, but also increases their vulnerability to fire. Desiccation and fire as a result of unsustainable water extraction threaten Darwin Palm in the Darwin rural area. Increasing pressure to extract water for agriculture and rural residential developments, along with climate change, could see the drying out of more rainforest patches, threatening even more rainforest species.
- This factsheet, by the Bureau of Rural Science, describes Australian rainforests, where they are found, management issues, their tenure by State and Territory, and their values and uses (wood, and environmental, indigenous and other uses). (PDF file, 2.0 MB)