Whilst many activities require vegetation clearing, the habitat of a threatened species should never be cleared. Threatened species living in a small area are particularly vulnerable to vegetation clearing, which may destroy their entire habitat.
When compared with other states of Australia, a relatively small proportion of natural vegetation in the Northern Territory (and Cape York) has been cleared. However, specific habitats are threatened because of their proximity to urban centres, or the fertility of their soils. Significant portions of these habitats need protection from clearing.
Though restricted in area, clearing for urban and rural residential development, and the associated degradation of surrounding environments, can significantly affect threatened species that are found in small areas. Urban expansion, followed by an increase in fire and the spread of Buffel Grass, is responsible for the almost complete disappearance of Bednall’s Land Snail from its former distribution in the Alice Springs area. Similarly, the Alice Springs sub-population of Minnie Daisy is currently threatened by developments on the southern side of Alice Springs. Although the area in which this species grows is too steep for development, disturbance from nearby house yards and roads is likely to lead to increased Buffel Grass invasion and changes to fire regimes.
Clearing for urban, rural and industrial development and sand mining in the Darwin area is a significant threat to a number of species that are only known from one or two locations. This includes ground-dwelling orchids, bladderworts, a typhonium and Glenluckie Helicteres. Even if some habitat is retained for these species, activities associated with development are likely to lead to degradation through weed invasion, escape of garden plants, and grazing by a range of animals kept on hobby-farms. Where threatened species occur in areas designated for clearing and development, large areas should be set aside to offer protection from these threats, and ameliorative measures undertaken to mitigate the impacts.
Clearing for mining operations is also a significant activity on Groote Island and on the Gove Peninsula.
Forest and woodland habitats on fertile soils in the Top End are threatened by clearing for agriculture and horticulture. Many native plants and animals are only found in these more productive habitats, and so are potentially threatened by any reduction in their extent as a result of clearing. Plants that may be threatened by clearing of tall forests and woodlands on the Tiwi Islands include two species of the arum-like typhonium. Clearing of forests also destroys essential habitat features found only in mature vegetation communities that take years to develop. This is particularly true of tall trees, which are important for nesting birds like Red Goshawks, and large tree hollows, which are important for Masked Owls.
Tiwi Island rainforests are of high conservation significance as they support a rich flora including several threatened plants such as Dendromyza, Mapania, Mitrella, Native Walnut, Quandong, Tarennoidea, Tiwi Islands Waxflower and Xylopia. These species are at risk where rainforest patches adjoin woodlands designated for plantation development if adequate buffers are not included in clearing operations. For example opening of the canopy could cause desiccation of epiphytic orchids such as Thrixspermum congestum.
The Daly River region is another area where there is considerable pressure to clear vegetation for agriculture because of its arable soils and access to perennial water supplies. Masked Owls and Northern Brush-tailed Phascogales are among the species that could be at risk if these developments proceed without care.
If clearing is necessary, landholders must apply for a permit, which will involve demonstrating that no threatened species will be adversely affected by the proposed action. If there are no threatened species in the area, and clearing is approved, steps can be taken to minimise effects on wildlife. At least one-third of any land type or vegetation community should be retained to provide habitat for that particular species. Clearing along streams, around wetlands, or on steep slopes or erodible soils should be avoided altogether.
Wildlife corridors can reduce habitat fragmentation and maintain landscape connectivity. The cleared area should be managed to ensure it does not become infested with weeds that may then colonise the surrounding native vegetation. Consultation with the Department of Natural Resources, Environment, the Arts and Sport is advisable for the latest vegetation management requirements in the local area.