Are insects declining alarmingly? Yes, he says. Is it more complex than the impending global collapse? Also yes.
Forister, who studies butterflies in the western United States, points out two species that represent very different situations.
Commonly found in southern parts of the United States, Mexico, and Central America, the gulf mother-of-pearl butterfly is now blooming in California because people there cultivate its host, the passion vine, a popular ornamental plant.
In contrast, the great marble butterfly, which lives on invasive mustard plants, was widespread until its population crashed, likely a victim of the triple impact of climate change, habitat loss, and pesticides.
Forister’s study specifically focuses on how climate change affects butterflies. Species struggle with forest fires, drought, and extreme weather events, and while previous theories have suggested that butterflies could simply move up or down mountain slopes in mountainous areas to take advantage of better conditions, at least this does not seem to be the case for all species.
Other species, including the famous monarch butterfly, fared better than expected in the summers of 2011 to 2015, when warmer conditions gave them more time to reproduce. But that has not stopped the ongoing decline of monarchs in the west. (Learn why western monarchs were denied protection of endangered species.)
How we can help
Amid devastating statistics, Forister and Wagner say there is hope.
Germany pledged nearly $ 120 million (£ 88 million) in 2019 for insect conservation, monitoring and research. Costa Rica has supported international organizations that are spending $ 100 million (£ 73 million) on the inventory and sequencing of pieces of DNA in “every multicellular creature in the country” for over a decade, “which is particularly important for the myriad of unknown tropical insects Wagner writes in the introductory essay of the report.
Citizen scientists are stepping up to expand the knowledge base. An app, iNaturalist, where users upload images for identification and categorization, is becoming one of the greatest sources of insect viewing.
Solutions to overarching problems like climate change require laws and new guidelines, but individuals can make a difference to insects in their backyards, neighborhoods and communities, say Wagner and Forister. (Read about how bumblebees become extinct in a time of climactic chaos.)
One way is to reduce the use of pesticides and herbicides on lawns. Better still, consider converting part of your lawn into a natural area. Insect habitat could increase by more than four million acres in the U.S. if every home, school, and park were to convert 10 percent of its lawns, writes entomologist Akito Y. Kawahara of the University of Florida at Gainesville in the PNAS report . Grow native plants and limit outdoor lighting, which attracts and often kills nocturnal insects.
It’s even easier to uncover hives in gardens and bare earth for bee nests in the fall, says Lusha Tronstad, an invertebrate zoologist at the Wyoming Natural Diversity Database who studies the decline of the western bumblebee and was not part of the report. Do not rake leaves before winter.
“People can be a little lazy, and that benefits insects,” she says.