Climate change and habitat loss from big farming combine to suppress global insect populations, with each problem exacerbating the other, a new study finds.
While insects occasionally annoy humans, they are also key in pollinating plants to feed humans, making the soil more fertile and including the beautiful butterflies and fireflies. Scientists have noticed dramatic declines in both the total number of insects and the diversity of insect species, calling it slow-motion death with 1,000 cuts. The cuts include pesticides and light pollution.
Large single-crop farming that leaves less habitat and leafy food for insects plus higher temperatures from climate change is a big problem for insects, but a new study in the journal Nature Wednesday based on more than 750,000 samples from 18,000 different insect species says it doesn’t. only two threats act independently. How habitat loss and climate change interact is what really destroys insect populations.
In about half of the cases where insect numbers dropped dramatically, the researchers found climate change and habitat loss from agriculture augmented each other. In more than a quarter of cases of biodiversity loss, meaning fewer species, the same dynamic is at work.
“We know insects are under threat. We are now getting a much bigger deal on what they are threatened with and by how much,” said study author Charlotte Outhwaite, an ecologist at University College of London.
“In these cases, habitat loss and climate change can often be worse than if they acted alone, because one can make the other’s impact worse and vice versa,” Outhwaite said. “We lose part of the picture if we just look at these things individually.”
For example, monoculture farming often reduces the shade of trees, making them hotter in certain places. On top of that comes climate change, he said. Then insects that need heat dissipation or need to move north for cooler climates can run into problems with the lack of proper habitat from large farms.
This is especially a problem in countries such as Indonesia and Brazil, where forests are being cleared and temperatures are warming higher than any other part of the world, Outhwaite said.
That’s tough on insects like pesky midges.
“Cocoa is pollinated primarily by midges and people don’t like midges. You know they’re the nuisances that bite you, they’re bugging you at picnics,” Outhwaite says. “But if you love chocolate, you have to appreciate it because without them, we would have less cocoa.”
The same can be said of bees, which are struggling with climate change warming and single-crop farming, Outhwaite said.
Insect pollinators are responsible for about a third of the human diet, according to the US Department of Agriculture. And 2 out of 5 invertebrate pollinating species, such as bees and butterflies, are on the path to extinction, according to a 2016 UN science report.
What makes this study important is that it is the first to link climate change and industrial agriculture together in explaining harm to insects, said University of Connecticut entomologist David Wagner, who was not part of the study. Because the study used so many different samples and species and looked around the world, that gives the findings more credibility, Wagner said.