Climate Change Affects Insect Distribution

As climate change progresses in the coming decades, it is likely to have "profound implications" for the distribution of insects and other invertebrates around the globe, according to a new study.

As warm-blooded animals, humans have been able to adapt to varying weather conditions and are found on every continent on Earth. Conversely, cold-blooded (ectothermic) animals, such as insects, must live in climates where the ambient temperature allows their biological processes to function.

A group of researchers set out to answer whether the average temperature of an area or the frequency of extreme temperature conditions in an area have the biggest impact on species distribution, according to the press release.

The study, led by Johannes Overgaard from Aarhus University, Denmark with Michael R. Kearney and Ary A. Hoffmann from Melbourne University, Australia, demonstrated that extreme temperature events is the main factor in defining distribution of both tropical and temperate species. Their findings are published in Global Change Biology.

In their experiment, the team tested 10 fruit fly species of the genus Drosophila that are adapted to tropical and temperate regions of Australia. They began by finding the optimum temperatures for the species, and then found the boundaries for their tolerance of hot and cold temperatures.

"This is the first time ever where we have been able to compare the effects of extremes and changes in average conditions in a rigorous manner across a group of species," said Hoffmann.

After the team knew the optimum and extreme tolerances of the species, they compared the species' distribution in Australia to the temperatures recorded in the country to see if average temperature or extreme temperatures played a larger role in deciding distribution.

"The answer was unambiguous: it is the species' tolerance to very cold or hot days that define their present distribution," said Overgaard.

Therefore the team was able to conclude that extreme weather events, not an increase in average temperature, costs insects their lives and will most affect distribution.

Using their findings the team was able to model distributions of insect distributions based on climate change predictions for the next 100 years.

"Climate change will result in fewer cold days and nights, and thus allow species to move toward higher latitudes. However climate change also leads to a higher incidence to extremely hot days and our model therefore predicts that the distribution of these species will be reduced to less than half their present distribution," said Overgaard.