12 October 2009

Future Forest Researchers: New Theories About Insect Infestation

Rising temperatures affect plants, herbivorous insects and predatory insects in different ways. It is therefore easier to predict the risk of future outbreaks of herbivorous insects by focusing on the interaction among species, rather than on the individual insect species.

This has been documented by four researchers in a recently published scientific article. Two of the researchers—Linda Martin and Helena Bylund—are participating in the Future Forests subproject: Fungi and Insect Damage.

It was during the application process for Future Forests that the idea for the article took form and co-operation with Åsa Bergren and Matthew P. Ayres at the Swedish University of Agricultural Sciences (Sveriges lantbruksuniversitet/SLU) was initiated.
“We believe that Future Forests have much to gain from using the theories we have expressed in this article. It will give the program a more accurate ability to predict the risk of future insect attack in the Swedish forests," says Christer Björkman.

Many organisms, particularly insects, are expanding their boundaries northward, according to several recent studies. The reason seems to be the warmer climate. Additionally, there is a widespread concern that the ongoing climate change will increase problems of insect pests in crops. This concern, however, has little support in actual observations.

Forecasts for the growing problems are sometimes the result of reasoning which is too simplistic. It briefly concludes along the lines that elevated temperatures lead to faster development from eggs, to more sexually mature insects multiplying exponentially to more generations of insects each year, which in turn results in outbreaks that are more serious.

Previously, it was known that plants, as well as herbivorous insects and predatory insects, respond positively to a temperature increase up to a certain critical point, after which increased temperature has negative effects. Now researchers are adding nuances when painting the ecological picture of what can be expected from plants, herbivores and carnivores in how they react very differently to a rise in temperature.
“The plants are expected to respond the least, herbivores a little bit more and carnivores are expected to have the most obvious reaction to increased temperature," says Åsa Berggren.

Physiological differences between plants and animals are the cause of this difference. Predator insects (e.g. the parasite hymenoptera) have an opportunity to not only respond physiologically, but also behaviorally (e.g. by more actively searching for food ) to changing circumstances.

“It is in other words not the response of individual species that is crucial, but the interaction between species and groups of organisms."

With such an approach, according to the researchers, it could be easier to answer questions about what will happen to the natural world in the future, particularly with regard to climate change impacts.

Mistra Mistra