Indicator: BD-10 Examples of native species whose populations have declined where various invasive species have established resident populations

Data

Bird Atlas surveys reviewed by Garnett et al. (2002) show that increases in habitat modification and the relative abundance of introduced bird species correlated with decreases in native bird abundance and distribution. The highest abundance of introduced bird species, principally exotic species, occur in the extensively modified parts of south-east Australia and eastern Tasmania where they now make up 15% of all species (National Land and Water Resources Audit (2002).

Source: Garnett ST, Crowley GM and Barrett GB (2002), Birds, in "Australian Terrestrial Biodiversity Assessment", National Land and Water Resources Audit, Commonwealth of Australia, Canberra.

What the data mean

The examples found show that habitat modification impacts on both native and naturalised species populations.

Data Limitations

In the absence of any indicator which isolates the pressure of species behaving invasively from other pressures which may just favour the introduced species at the expense of the native species, the indicator aims to identify correlations between the proliferation of species that are considered to be invasive in certain environments and the decline of native species. It sheds little light on the impact of naturalised species on native species.

The two examples found relate only to birds.

Issues for which this is an indicator and why

Biodiversity — Pressures on biodiversity - Invasive species 

A spatial correlation between declines in native species and establishment of introduced populations does not automatically imply a cause and effect relationship, especially where there are other pressures, such as habitat modification, which could be the common cause of both changes. However, compiling data on such correlations may enable the development of studies which control for other pressures and thus provide insight into the actual impact of naturalised species.

Other indicators for this issue:

Land — Direct pressure of human activities on the land - Species introduction and species change 

Changes in population and/or distribution of either native or introduced species may be indicative of more general changes in land condition, whether the cause of the change is habitat modification, species introduction, or any other pressure. Compiling data on such correlations may also enable the development of studies which control for other pressures and thus provide insight into the actual impact of naturalised species on land condition.

Other indicators for this issue:

Inland Waters — Response of biota - Invasive species 

Changes in population and/or distribution of either native or introduced species may be indicative of more general changes in the condition of freshwater systems, whether the cause of the change is habitat modification, species introduction, or any other pressure. Compiling data on such correlations may also enable the development of studies which control for other pressures and thus provide insight into the actual impact of naturalised species on condition of inland waters.

Other indicators for this issue:

Coasts and Oceans — Direct pressure of human activities on coasts and oceans - Direct pressure of coastal activities (other than shipping and fishing) 

Changes in population and/or distribution of either native or introduced marine species may be indicative of more general changes in the condition of coastal and marine systems, whether the cause of the change is habitat modification, species introduction, or any other pressure. Compiling data on such correlations may also enable the development of studies which control for other pressures and thus provide insight into the actual impact of species introduced by coastal activities on the condition of coasts and oceans.

Other indicators for this issue:

Further Information