Heatwaves driven by climate change making insects infertile, new study suggests

Heatwaves appear to be sterilising male insects, a discovery that has serious implications in a world of rising temperatures and mass extinctions.

A new study found heatwave conditions slashed sperm production in beetles by three quarters and halved the amount of offspring they could produce.

With massive insect declines already recorded by scientists from Germany to Puerto Rico, the findings present another massive source of concern for scientists.

Heatwaves such as the ones that struck much of the northern hemisphere this summer are thought to be on the rise, and getting more intense as the average worldwide temperature creeps up.

The scientists suggested their findings could even have repercussions for humans, as past work has hinted that heat shock has the power to induce infertility to mammals as well.

“We know that biodiversity is suffering under climate change, but the specific causes and sensitivities are hard to pin down,” said Professor Matt Gage from the University of East Anglia, who led the research.

“We've shown in this work that sperm function is an especially sensitive trait when the environment heats up, and in a model system representing a huge amount of global biodiversity.”

Beetles such as the red flour beetle used in the research comprise a staggering quarter of all biodiversity on Earth, with around 400,000 species described to date.

In the team’s study, which was published in the journal Nature Communications, beetles were exposed to simulated heatwaves 5-7C above optimum conditions for five days.

They then followed this work up with experiments to assess the damage caused to reproductive success and sperm function, as well as long-term effects on offspring.

After the initial exposure cut the chances of reproducing, a second heatwave rendered them virtually sterile – producing just 1 per cent of the offspring produced under normal conditions.

“Insects in nature are likely to experience multiple heatwave events, which could become a problem for population productivity if male reproduction cannot adapt or recover,” said Kirs Sales, a PhD student who led the research.

To make matters worse the effects of heat stress seem to cross generations. The offspring of heatwave-shocked fathers lived shorter lives, and the sons produced fewer offspring of their own.

Recent studies have shown insect declines of up to 75 per cent in some areas, an effect that has been linked to everything from overuse of pesticides to habitat destruction.

With insects playing a vital role supporting global biodiversity and pollinating plants, scientists have warned that their loss will trigger “ecological Armageddon”.

“Since sperm function is essential for reproduction and population viability, these findings could provide one explanation for why biodiversity is suffering under climate change,” said Professor Gage.

“Heatwaves are particularly damaging extreme weather events. Local extinctions are known to occur when temperature changes become too intense.

“We wanted to know why this happens. And one answer could be related to sperm."