As temperatures go up, insect populations go down

As most Australians would tell you, hot temperatures and swarms of insects tend to go hand in hand. But with 2016 expected to be the warmest year on record — and 2017 already hot on its heels, if the past couple of weeks have been anything to go by — scientists have discovered that rising temperatures are in fact damaging insects’ ability to reproduce.

Studying fruit flies, researchers at The University of Sheffield found that being exposed to mild heat as a juvenile negatively affects an insect’s chances of producing offspring as an adult. Explaining the results, lead investigator Dr Rhonda Snook said, “Juvenile insects are extremely susceptible to environmental changes as they don’t move around much because they are either larvae — like butterfly caterpillars — or they don’t yet have wings to fly away.”

The researchers also found that the extent of the negative effects varied depending on where the insect population is based. Insects which evolve in countries at low latitudes, such as Spain, cope better with above average temperature rises compared to those living at high latitudes, such as Sweden.

“We are now interested in finding out what genes differ between Spanish and Swedish populations that allow the Spanish flies to cope better,” said Dr Snook.

“Identifying genes that are linked to increased and decreased reproduction is something which may be very useful not only in understanding how insects will cope with climate change but from the perspective of controlling insect pests.”

Published in the Journal of Evolutionary Biology, the study was described by Dr Snook as “unique”, with the juvenile insects only exposed to mild heat but the impacts studied into adulthood. She said, “The results show that even small increases in temperature may still cause populations to decline because — while these insects don’t die because of the mild heat — they produce fewer offspring.

“We already knew that insects are feeling the effect of climate change, but we now know they are felt at much lower temperatures,” said Dr Snook.

Image courtesy of Philip McErlean under CC BY-ND 2.0