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Posted 25 February 2009

A recent US report reviewing ecological thresholds and climate change has highlighted the potential for interactions between climate change and invasive species to cause abrupt, irreversible changes in ecosystems.

Commissioned by the U.S. Geological Survey the report emphasises the importance of understanding ecological thresholds to develop adaptation strategies for climate change.

One highlighted example is in Alaska, where multiple climate change effects have dramatically changed wetlands, tundra, fisheries and forests.

During the 1990s, milder winters and warmer temperatures allowed the spruce bark beetle to complete its life cycle in one year instead of two, allowing it to multiply to higher numbers than usual.

Combined with a nine year drought, which had stressed spruce trees, the resulting infestation caused large-scale forest die-off.

Forests of inland Alaska are now threatened by an outbreak of spruce budworms, incapable of reproducing in the region before 1990. Partly as a result of tree death, there have been severe fires, which emit large amounts of greenhouse gases. Fires are predicted to greatly increase in this region under climate change.

The authors warn that such complex interactions exceed our predictive capabilities and that management policies developed during relatively stable climate conditions may be “inadequate for a variable world with more surprises”.

In response, the authors say we need better understanding of ecological thresholds and the consequences of crossing them as well as management strategies to deal with them.

“In a world being altered by climate change, natural resource managers may also have to be increasingly nimble, and adjust their goals for desired states of resources away from static, historic benchmarks and focus on increased resilience, biodiversity, and adaptive capacity as measures of success,” the authors say.

The Invasive Species Council will be developing policy recommendations that require identification of potential transformative interactions of climate change and invasive species, as well as priority actions to prevent the crossing of ecological thresholds.

One priority for Australian ecosystems is limiting the use and spread of flammable invasive pasture grasses that create positive feedback loops between fire and invasion, which will probably be exacerbated under climate change.

Source
Fagre, D. B., C. W. Charles, C. D. Alen, et al. 2009. Thresholds of Climate Change in Ecosystems. A Report by the Us Climate Change Science Program and the Subcommittee on Global Change Research. U.S. Geological Survey.