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Posted May 2009

Jessica Hellman, from the University of Notre Dame, and colleagues have identified five categories of interactions between climate change and invasive species, operating at different stages of the “invasion pathway”.

1. Altered transport
Climate change may alter patterns of transport of invasive species. It could link new geographic regions by altering commerce or tourism or changing the demand for nursery species. Pathways of international transport could change and extreme weather or different weather patterns could increase the dispersal of some species. Climate change may increase the ability of organisms to survive in ballast water. Fish for sport may be introduced into new areas as warming occurs, and native species may be moved to increase their prospects of survival.

2. Altered climatic constraints
Climate constraints to colonisation by invasive species may be reduced: warmer temperatures may facilitate establishment, reduce competitive resistance from native species or increase the competitiveness of an invasive species. Hellman and colleagues note that invasive species are more likely than noninvasive species to have traits, such as broad environmental tolerances and long distance dispersal, that favor them in a changing environment.

3. Altered distributions
Climate change is likely to alter the distribution of invasive species by changing environmental constraints to spread. In northeast US, aquatic invasive species such as water hyacinth (Eichhornia crassipes) are likely to survive milder winters and increase their reproductive output.

4. Altered impacts
Impacts of invasive species will be affected. For example, invasive Tamarix species, which use more water than native riparian plants, may exacerbate predicted water shortages in southwest USA.

5. Altered effectiveness of management
Finally, the effectiveness of management will change. Increased carbon dioxide increases the tolerance of some weeds to some herbicides. Biocontrol agents may either increase or decrease in impact.  In the US, one of the most effective biocontrol agents for alligator weed (Alternanthera philoxeroides) may spread to affect more of the weed if temperatures increase (but the weed will also spread).

References
Hellmann JJ, Byers JE, Bierwagen BG, Dukes JS. 2008. Five potential consequences of climate change for invasive species. Conservation Biology 22: 534-543.

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