Scientists have warned of an ‘insect apocalypse’ in recent years, noting sharp declines in specific areas – particularly in Europe. A new study shows that these warnings may be exaggerated and are not representative of what happens to insects on a larger scale. Credit: UGA
Long-term ecological site study shows no changes in net insects.
Scientists have warned in recent years about an ‘insect apocalypse’ and noted sharp declines in specific areas – particularly in Europe. A new study shows that these warnings may be exaggerated and are not representative of what happens to insects on a larger scale.
Bill Snyder, a professor of agroecology at the University of Georgia, tried to find out if the so-called “insect apocalypse” would really happen, and if so, it had already begun. Some scientists say that it may only be 30 years before all the insects become extinct, so this is a very important and timely question for agriculture and conservation.
Snyder and a team of researchers from UGA, Hendrix College and the U.S. Department of Agriculture used more than 5,300 data points for insects and other arthropods – collected over four to 36 years on monitoring sites representing 68 natural and managed areas – to search for evidence of declines across the United States.
Some groups and sites showed increases or decreases in abundance and diversity, but many remained unusual, with some net abundance and biodiversity trends generally indistinguishable from zero. This lack of overall elevation or decline was consistent across arthropod feeding groups, and was similar for severely disturbed relatively natural sites. These results were recently published in Natural ecology and evolution.
Local observations
The idea for the study began last year with a cross-country road trip for Snyder from Washington state to his new home in Georgia.
‘I had the same observation as a lot of people. We had our drive through the country – you don’t see as many insects sitting on your car as vines. ”
When he arrived at his home in Bishop, Georgia, it seemed like a different story.
“I noticed that the lights outside were full of insects, as much as I remember as a child,” he said. ‘People have this idea – it seems [there are] fewer insects – but what is the evidence? “
Filled black circles represent LTER pages with arthropod data included in the study. Colors on the underlying map indicate ecoregions as defined by the USDA Forest Service.
There is some alarming evidence that European honeybees have problems, but Snyder was envious when insects are in decline everywhere. “We are so many things off insects,” he said. “If insects disappear, it would be really, really bad. Perhaps it is the end of human existence. ”
He discusses the subject with another biologist and friend, Matthew Moran at Hendrix College, and they recall the network of the US National Science Foundation of LTER sites, Long-Term Ecological Research (LTER), which were founded in 1980 and includes a network of 25 monitoring locations across each of the country’s largest ecoregions.
Ecological sampling
The NSF LTER data are publicly available but have not previously been collected in a single dataset to be examined for evidence of broad-scale density and change in biodiversity over time to date.
Arthropod data sampled by the team include locusts in the Konza Prairie in Kansas; ground arthropods in the Sevilleta desert / grassland in New Mexico; mosquito larvae in Baltimore, Maryland; macroinvertebrates and crayfish in Northern Temperate Lakes in Wisconsin; aphids in the Midwestern FS; crabs in coastal ecosystems in Georgia; sign at Harvard Forest in Massachusetts; predators in Hubbard Brook, New Hampshire; arthropods in Phoenix, Arizona; and stream insects in the Arctic in Alaska.
The team compared the samples with data on human footprint index, which includes multiple factors such as insecticides, light pollution and built environments to see if there were general trends.
“No matter what factor we looked at, nothing could explain the trends in a satisfactory way,” said Michael Crossley, a postdoctoral researcher in the UGA department of entomology and lead author of the study. ‘We just took all the data and, as you can see, there are so many things up and down. Even when we broke it out into functional groups there was not a clear story, as predators decrease as herbivores increase. “
“This is an implication for conservation and one for scientists, who have called for more data due to under-sampling in certain areas or certain insects. We took the opportunity to apply this wealth to data that has not yet been used, “explained Crossley, an agricultural entomologist who uses molecular and geospatial tools to understand pest ecology and evolution and improve management outcomes.” “There should be more datasets that we do not even know about. We want to continue digging to get a better idea of what’s going on.”
Good and bad news
To answer Snyder’s broad question of, “Are there general declines?” No, according to the study. “But we will not ignore small changes,” Snyder said. “It is worth distinguishing between the two problems.”
Particular species of insects that we rely on for important ecosystem services of pollution, natural pest control and decomposition remain untimely in decline in North America, the authors note.
In Europe, where studies have found dramatic insect decay, there may be a greater, longer-term impact on insects than the US, which has a lower population density, according to Snyder.
“It’s not the worst thing in the world to take a breath,” Snyder suggested. “There has been a lot of environmental policy and change. Many of the insecticides currently used in agriculture are narrow-minded. Some of those effects seem to work. ”
When it comes to conservation, there is always room for everyone to save and do their part.
“It’s hard to tell when you’re one householder when you have an effect when you plant more flowers in your garden,” he said. ‘Maybe some of these things we do are starting to have a beneficial effect. This can be a bit of a hopeful message that things people do to protect bees, butterflies and other insects actually work. ”
Reference: “No Net Abundance and Variety of Insects Declines on US Long Term Ecological Research Sites” by Michael S. Crossley, Amanda R. Meier, Emily M. Baldwin, Lauren L. Berry, Leah C. Crenshaw, Glen L. Hartman , Doris Lagos-Kutz, David H. Nichols, Krishna Patel, Sofia Varriano, William E. Snyder and Matthew D. Moran, August 10, 2020, Natural ecology and evolution.
DOI: 10.1038 / s41559-020-1269-4
