The major vertebrate pests cause direct short-term economic losses of at least $500 million per year (and quite possibly over $1 billion per year), mainly in lost agricultural production. Overgrazing and browsing by introduced herbivores also contributes to land degradation, which lowers the future productive capacity in many areas, but there is no estimate of the economic cost of this degradation. In addition, grazing, predation and competition by non-native vertebrates are recognised as major threats to many endangered native species and communities. These costs have also not been quantified. Some introduced species can also act as vectors or reservoirs for diseases affecting livestock, native species or people. This again is a largely unquantified cost, although a potentially high one, particularly in relation to the impact of exotic diseases. These have trade and quarantine implications as well as direct costs due to mortality and morbidity and disease control measures.
There are at least 30 species of non-native pest vertebrates in Australia (see table below) and all areas of Australia have at least one pest animal (eg. feral cats are distributed throughout Australia and rabbits and foxes occur in most parts of the mainland south of the Tropic of Capricorn). However, while it is clearly not economic, nor necessary, to establish a detailed sampling framework throughout the country monitoring will be necessary where investment is occurring so that progress towards targets can be measured. Some States and Territories are establishing set transects and other monitoring frameworks.
Ideally, the impact of pest animals should be measured in terms of damage to valued resources rather than in terms of pest animal numbers or population density. However, due to the difficulty and expense of measuring pest animal impact (particularly long-term effects caused by herbivorous pest animals), pest animal population density will usually be measured and related to population density and environmental damage where pest density:resource damage relationships are known for particular situations.
|Author||Natural Resource Management|
|Publisher||Department of the Environment and Heritage|
|Region||Australia - national|