Every year, the number of insects flying over, crawling on, or burrowing in some parts of the planet drops by a percentage point or two. That means areas of severe decline could lose as much as much as a third of all their insects in two decades.
That’s the bad news, scientists reveal today in Proceedings of the National Academy of Sciences (PNAS). Dozens of insect experts contributed to a series of reports in the journal on just how bugs are faring around the world, for better or worse.
The good news—if good news is to be found—is that not all insects are declining so quickly. Some are even flourishing. And most important, researchers say, there’s hope for keeping our planet buzzing with its most abundant and diverse creatures.
The insect world, estimated at up to 10 million species, is suffering from more than one problem. Threats range from deforestation, climate change, and invasive species to industrialized agriculture, and even light pollution. (Read more: Where have all the insects gone?)
“Death by a thousand cuts,” is how David Wagner, a University of Connecticut entomologist, who contributed to the new report, puts it.
Robust insect populations are vital for a variety of reasons, ranging from how they support the world’s food supply to how they create backyard flowers through pollination. Although most of us would prefer not to encounter many of the planet’s tiniest creatures, their role in our lives can’t be overstated. Nor can the need to make saving insects a priority, scientists say.
“Insects, like every bit of the natural world, are declining,” says Matthew Forister, an insect ecologist at the University of Nevada, Reno, who also contributed to the report. “But it’s clear insects have a possibility to rebound. It’s grim, but it’s not too late.”
Beyond the hyperbole
Reports of global insect decline aren’t new. During the past few years, a growing body of studies and news stories has drawn attention to the problem in starkly different terms—declarations of insect Armageddon on the one hand to reports challenging notions of a pending apocalypse for the six-legged on the other.
Wagner says he and other researchers who contributed to the new report aim to move beyond the hyperbole by analyzing as much research as possible concerning insects’ current global status.
“This is a much more bridled, careful, critical assessment,” he says, than some of the previous reports highlighting extreme losses in particular regions and extrapolating them across the globe.
Are insects declining at an alarming rate? Yes, he says. Is it more complex than imminent global collapse? Also yes.
As an example, Forister, who studies butterflies in the western U.S., points to two species representing very different situations.
The gulf fritillary, generally found in southern portions of the U.S., Mexico, and Central America, is now flourishing in California because people there cultivate its host, the passion vine, a popular ornamental plant.
By contrast, the large marble butterfly, which thrives on invasive mustard plants, was widespread until its population crashed, likely victim of the triple whammy of climate change, habitat loss, and pesticides.
Forister’s study focuses specifically on how climate change affects butterflies. Species are struggling with wildfires, drought, and extreme weather events, and while earlier theories posited that butterflies in mountainous regions might simply move up or down mountainsides to take advantage of better conditions, that doesn’t seem to be the case, at least not for all species.
Other species, including the famous monarch butterfly, did better than expected during the summers of 2011 to 2015, when warmer conditions gave them more time to reproduce. But that didn’t stop the continuing decline of monarchs in the West. (Learn why western monarchs have been denied endangered species protections.)
How we can help
In the midst of devastating-sounding statistics, Forister and Wagner say there’s hope.
Germany pledged almost $120 million to insect conservation, monitoring, and research in 2019. Costa Rica endorsed international organizations spending $100 million to inventory and sequence portions of the DNA of “every multicellular creature in the country over a decade,” which will be particularly important for the countless unknown tropical insects, Wagner writes in the report’s introductory essay.
Citizen scientists are stepping up to help expand the knowledge base. An app, iNaturalist, where users upload images for identification and categorization, is becoming one of the largest sources of insect observations.
Solutions to overarching problems such as climate change require legislation and new policies, but individuals themselves can make a difference for insects in their backyards, neighborhoods, and communities, Wagner and Forister say. (Read how bumblebees are going extinct in a time of climate chaos.)
One way is to curb use of pesticides and herbicides on lawns. Better yet, consider converting some of your lawn to a natural area. Habitat for insects could increase by more than four million acres in the U.S. if every home, school, and park converted 10 percent of its lawns, entomologist Akito Y. Kawahara, of the University of Florida in Gainesville, writes in the PNAS report. Grow native plants and limit exterior lighting that attracts and often kills nocturnal insects.
Even more simply, leave sticks in gardens and some bare earth uncovered in the fall for bee nests, says Lusha Tronstad, an invertebrate zoologist with the Wyoming Natural Diversity Database who is studying the decline of the western bumblebee and was not involved in the report. Don’t rake up leaves before winter.
“People can be a little lazier, and that will benefit insects,” she says. (Here are nine ways to support bees and other pollinators at home.)
Tronstad also notes that a species’ fate can change rapidly for the better or worse. The western bumblebee has declined by 93 percent in just over two decades.
Meanwhile, the endangered Karner blue butterfly, named by novelist and entomologist Vladimir Nabokov, has been responding well to restoration efforts, Wagner says. The small butterfly has long suffered from fire suppression and residential and commercial development in its sandy habitat from the edges of the Great Lakes to New England. Efforts to plant and promote lupine – which the adults and larvae need – and other habitat improvement projects are helping.
Will small, personal changes like restricting pesticide use on your lawn prevent the worst effects of climate change? No, Forister says. But it will make a difference in your local insect populations, and those differences add up.