Invasive species are one of the two major threats to biodiversity (the other being habitat loss and fragmentation). More than half of the key threatening processes listed under Federal legislation relate to invasive species.
Around 15% of plants in Australia have been introduced from other countries, and about a quarter of these are already serious environmental or agricultural weeds, or have the potential to become serious weeds. Weeds displace, outcompete and smother native vegetation. They can reduce the diversity of native plant species in an area, altering the structure and composition of vegetation communities. In turn, this affects the food, shelter and other resources available for native animals. Weeds can also alter other elements of the ecosystem, by causing changes in water flow, run-off, nutrient cycles and fire regimes. Major weeds in the GER corridor include lantana, which is considered one of the worst environmental weeds in the world, and bitou bush, a serious weed of coastal areas. Disturbance from construction of roads, fences and other infrastructure, increased nutrient levels in soil from fertilisers or urban runoff and inappropriate grazing and fire management are all major causes of weed invasion.
Major animal pest species in the Great Eastern Ranges include predators such as foxes, wild dogs and cats. These species prey on small mammals, birds, frogs, reptiles and invertebrates, and are thought to be involved in the extinction or decline of many small to medium-sized native animals. Feral herbivores, including rabbits, goats, horses and deer, cause overgrazing and degradation of native vegetation and the land. For example, in the Australian Alps, large feral herbivores, especially horses, cause serious damage by trampling and grazing in fragile alpine ecosystems. Pest species also compete with native species for resources like nest sites, food and shelter, and can spread diseases.
Combating invasive species in the GER corridor
GER works with landowners and the general public to provide education about pest animals and weeds, and to support and improve management of invasive species across tenures. For example, GER’s 2013-14 grant program supported the National Parks Association of NSW’s Citizen Science project, which engaged landholders to use remote infra-red motion detection cameras to assess the effects of pest species control on small native mammals. Another GER project in Bathurst, NSW, involves a partnership between Greening Australia and the Bathurst Local Aboriginal Land Council to eradicate invasive species from Aboriginal Land at Mt Panorama.
In addition, GER projects and partnerships that protect intact native vegetation and restore degraded habitat may indirectly help to reduce the impact and spread of invasive species. This is because disturbed and fragmented areas tend to have a greater abundance of invasive species than more intact ecosystems, whilst a healthy, biodiverse ecosystem is generally more resilient to invasion by exotic species.