Pest plants, pest animals and pathogens have been identified by every state and territory as a key threat to biodiversity generally, and to threatened species specifically. Almost all states and territories also note that data on the distribution and abundance of pest plants and animals, and management effectiveness for these pests are poor. For states that provide assessment grades similar to those used by the Australian Government, the state for pest plants and animals is considered poor to very poor, and the trend is deteriorating (South Australian natural resource management [NRM] report card, Victorian SoE, Australian Capital Territory SoE). Similar concerns have been raised regarding lack of data on pest plants and animals on much of the Indigenous estate. In general, landowners or land managers are legally responsible for the control of pest plants and animals, which can create an onerous demand on resources. In particular, many Indigenous land managers, with the notable exception of Land and Sea Rangers, have inadequate capacity to meet that obligation.
The impact of invasive species is the most frequently cited threat to EPBC Act–listed species. Of the 21 key threatening processes listed under the EPBC Act, 12 describe declines in native species and/or ecological communities caused by 1 or more invasive taxa, including cats, rabbits, goats, rats, cane toads, foxes, feral pigs, gamba grass, escaped garden plants, red imported fire ants and yellow crazy ants. A further 3 are concerned with threats arising from pathogens—the rootrot fungus Phytophthora cinnamomi; psittacine circoviral (beak and feather) disease, affecting endangered parrots; and chitrid fungus disease, affecting amphibians.
In February 2013, novel biota were listed as a key threatening process under the EPBC Act. The key threatening process listing covers 6 major groups of novel biota and associated processes that are affecting biodiversity:
- competition, predation, or herbivory and habitat degradation by vertebrate pests
- competition, predation, or herbivory and habitat degradation by invertebrate pests
- competition, habitat loss and degradation caused by terrestrial weeds
- competition, habitat loss and degradation caused by aquatic weeds and algae
- competition, predation, or herbivory and habitat degradation by marine pests
- mortality, habitat loss and degradation caused by pathogens.
Novel biota encompass those invasive taxa that are separately listed as key threatening processes, as well as other novel biota that are already established in Australia and species with the potential to become invasive in the future.
In April 2014, ‘Aggressive exclusion of birds from potential woodland and forest habitat by overabundant noisy miners (Manorina melanocephala)’ was listed as a key threatening process. The native noisy miner has benefited from extensive fragmentation of woodland habitat with high edge:interior ratios and is considered a pest species. Noisy miners live in large colonies and, in areas where they are abundant, aggressively defend their territory by physically attacking other birds. The abundance of other native woodland birds is demonstrably lower in areas where noisy miners are present, and the effects of the noisy miner are substantially greater than the effects of other recognised threats such as grazing or habitat removal.