The Crazy Reason Climate Change May Contribute To Infertility
When we hear about couples who are having difficulty getting pregnant, people are often quick to assume that it’s because women are waiting longer and longer to have children. After all, female fertility naturally declines with age. But research is revealing that fertility rates may be dipping for reasons that are far more complicated than that—some of which may be out of our control.
While this research is quite preliminary, a new study in the Journal of Evolutionary Biology suggests that certain animal species may find it increasingly difficult to reproduce if temperatures become more extreme.
For the study, researchers exposed moths to different temperatures up until the point they were ready to mate. The higher the temperature that male moths were exposed to, the shorter their sperm—which diminishes sperm's effectiveness. The heat also made both males and females less likely to engage in sex.
Some of this makes sense when you think about male anatomy: “It is well known that the reason testes are usually located outside the body cavity in male mammals is because sperm is damaged by excessive heat inside the body,” said Graziella Iossa, study author, in a news release. “However, it is now becoming clear that when subjected to heat stress, males become infertile before females do.”
Of course, it may seem like a bit of a stretch to extrapolate this moth research to humans. After all, many of us have the luxury of relaxing in air conditioned apartments when a heat wave strikes. But other research suggests there may be something to the connection between climate change and infertility.
A 2018 study analyzing 80 years of U.S. birth data found that high temperatures have a significant negative effect on fertility and birth rates in humans, too. While August and September—nine months after the coldest part of the year—are two of the busiest months for births in the U.S., the conception trend goes the opposite direction for hot months. “If you look nine months after a heat wave in August, the following May you see significantly fewer births,” said Alan Barreca, UCLA environmental economist and study author, in a news release.
Barreca suspects that the reason for this is heat’s negative effect on male fertility and sperm production—just like with the moths. And while it may be tempting to think that couples are simply less likely to get busy when it’s sweltering outside, other research by Barreca suggests people are actually more likely to have sex.
More research is certainly needed to confirm a connection between male infertility and climate change–induced temperature hikes, but these studies offer a fascinating look into the complexity of fertility issues (and the fact that infertility is by no means just a women’s issue) as well as the widespread impact of increasing global temperatures.
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