More heat waves, less babies? Climate change can make male fertility disappear, say scientists, Europe News & Top stories

LONDON (THOMSON REUTERS FOUNDATION) – Fathers would have long advised to wear boxer shorts and avoid hot tubs, to prevent too much heat damaging their reproductive abilities.

Now the same effect – but caused by stronger heat waves as a result of climate change – is perhaps behind huge falls in numbers of insects, according to scientists, in a study published on Tuesday, November 13 in the journal Nature Communications.

They discovered that male red flower beetles exposed to a heat wave in the lab had half the expected number of offspring and that exposure to a second heatwave, 10 days later, virtually sterilized the men.

Male flounder beetles conceived by heat-damaged fathers also lived shorter lives and were far less successful in reproducing, said Matt Gage, a biologist at the University of East Anglia and head of the research team.

Although less vermin in your flower sounds like good news, it seems that the same principles can also be applied in the food chain, including possibly also for people.

"We have known for hundreds of years that male fertility is sensitive to heat," Gage told the Thomson Reuters Foundation.

But in particular: "the transgenerational effect was very surprising" in the new study, he said.

"In fact, we heat the planet and that keeps us from reproducing."

A 2017 study, published in the journal Science, found that flying insect populations in German nature reserves had submerged more than 75 percent in about 30 years.

The Gage team believes this can be linked to an increasing number of heat waves in those decades – a concern for the planet's biodiversity – and potentially to potential parents – because climate change brings hotter and longer heat waves.

Birth rates among people are already dipping in very hot periods, and not only because the prospect of a particularly sweaty rendezvous can sound pretty unattractive, scientists believe.

A study published in this year's Demography magazine found that "sexual behavior was probably not the explanatory factor" behind the falls in conception during heat waves, Gage said.

Instead, excess heat may have damaged the sperm, leading to the risk of genetic damage and less likely to make a successful pregnancy, he said.

Can doctors one day give warnings to potential parents to get pregnant during heat waves, to prevent potential genetic damage?

Gage does not know that for sure.

"We would like to know the mechanism of this transgenerational damage," he said. "We know that radiation causes mutations in the offspring, and it is possible that heat does similar things."

Anyway, the findings of the new study "are very important to understand how species respond to climate change," he noted.

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