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Posted May 2009

An important 2008 CSIRO review of the impacts of climate change on Australia’s national reserve system highlighted interactions with invasive species.

Authors Michael Dunlop and Peter Brown noted that exotic species are one of the reasons future climate change will be unlike any experienced previously.

The arrival of new species (both native and exotic) are one of four “wicked” threats that will be affected by climate change and will be particularly hard to manage because of strong biophysical and social dimensions (the others are altered fire regimes, land use change and altered hydrology).

They outline three models of biodiversity responses to climate change, all of which may have a role:

1. Relative abundance model: The combination of many impacts will lead to changes not in species composition but in their relative abundance and ecosystem structure and function. One important feature may be rapid increases in the abundance of exotic species in present “sleeper populations”.

2. Rapid distribution change model: A small proportion of species respond rapidly to altered conditions by range changes followed by local population expansion. Mechanisms include “response to fire (fire pioneers); CO2 (increased competitive ability); reduced frost and snow (released constraints); warmer, wetter or drier conditions affecting growth and competition; increased dispersal in storms and floods.” Some of the dispersed species will have a major impact and potentially transform ecosystems.

3.  Gradual distribution shift model: Species will shift gradually in response to changes in bioclimatic habitats. They will respond differently, so communities and ecosystems will change.

The researchers note that the third is the most prevalent mental model, intuitively appealing and allowing for simple, directional predictions. Although this model dominates many assessments of the impacts of climate change on biodiversity and protected areas, they caution that “the strong bias in the literature and consciousness of interested parties toward the third model does not reflect relative likelihood or importance”.

Dunlop and Brown’s recommendations include the need to assess the potential for exotic species to become invasive or ecologically significant under climate change and to implement plans to manage threatening processes, including controlling potential source populations of potentially invasive exotic species and increasing restrictions on the entry of exotic domestic, agricultural and horticultural species to Australia and their distribution around the country.

They also recommend developing a framework for assessing the consequences and management of new native and exotic species arriving in regions that considers their positive and negative impacts.

References
Dunlop M, Brown PR. 2008. Implications of climate change for Australia’s National Reserve System: A preliminary assessment. Report to the Department of Climate Change. Canberra: Department of Climate Change. www.climatechange.gov.au/impacts/publications/nrs-report.html

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