By Daniel Klein
BU News Service
People rarely give much thought to insects. They’re small, unsightly, innocuous at the best of times and unbearable at worst. No one has ever invited ants, mosquitos or flies to a picnic. No one has ever lost sleep because they didn’t have bedbugs. Even the word “bug” means “to bother,” and almost completely encapsulates humanity’s relationship with the class of creatures called insecta.
The planet teems with insects — billions more than any other terrestrial animal. Scientists estimate that for every human on the planet, there are 200 million insects. They eat, and are eaten, by almost everything. Their size and number make them the foundation upon which the world’s food chain rests. So what happens if the bugs aren’t there?
Insect populations are declining, according to Martin Sorg, an entomologist from the Krefeld Entomological Association in Germany. For decades, his team has tracked insect populations in nature preserves throughout Germany. They’re responsible for one of the few multi-species studies of insect populations. During their observations between 1989 and 2013, they saw three quarters of the insects disappear.
A similar study by Rothamstead Research, an agricultural research center in the United Kingdom, showed parallel declines.
Even without broad surveys, the discrete data from species-specific studies paints a distressing picture. A 2016 study by the University of Helsinki found significant decreases in butterfly and moth populations from Finland and a noticeable drop in biodiversity. A Masaryk University study measured substantial declines in stoneflies in the Czech Republic and a 2012 paper published in Insect Conservation and Diversity estimated an 81 percent decline in the monarch butterfly populations in the American midwest.
These losses reverberate throughout ecosystems. The American Audubon Society noted declines in bird species in a 2006 study, while across the pond, the Royal Society for the Protection of Birds issued a similar report in 2009. A 2010 study of bird populations by the Society of Canadian Ornithologists found a dramatic reduction in North American insectivorous bird species between the years of 1966 and 2006. The authors concluded that “declines in aerial insectivore populations are linked to changes in populations of flying insects, and these changes might be indicative of underlying ecosystem changes.”
Unsurprisingly, amphibian and bat populations are also suffering. The worldwide loss of amphibian species has occupied science news for years, although the causes are still unclear. It’s easy to lament the decline and extinction of a charismatic frog (like the now-extinct one below), but it’s far more difficult to feel outrage over the loss of a beetle, even if the latter is the cause of the former.
Far more pressing are the declines in insect species we rely on: bees and other pollinators. In the United States alone, insect pollinators provide ecological services worth over 57 billion dollars, according to a 2006 report in BioScience. Many parts of the world have already seen dramatic losses in pollinators with drastic and unsustainable consequences. A 2016 Huffington Post story showed workers of rural Hanyuan county in China hand-pollinating their fruit trees after an insect die-off linked to pesticide use. This is not the only time humans have replaced pollinators — farmers have hand-pollinated vanilla for centuries, as its original pollinator, the Melipona bee, no longer exists in the quantities necessary for cultivation.
With a problem this broad, it’s difficult to isolate and unambiguously identify the causes, which is why it’s so noteworthy when someone does. In 1962, Rachel Carson published the book “Silent Spring,” providing an unflinching look into the environmental hazards of the pesticide DDT. As a result of her exhaustive research, the United States banned the use of DDT in 1972. Today it’s banned or restricted in most countries.
Studies suggest that neonicotinoid pesticides disproportionately contribute to insect declines. These nicotine-based compounds have been linked to declines in insectivorous bird populations, according to several studies recently published in Nature. Additionally, a 2015 study in the Journal of Applied Ecology tracked the wide path of neonicotinoids through the food chain, with effects far beyond the insects they’re meant to target.
Many ecologists have blamed neonicotinoids for the worldwide decrease in bee populations. Despite lobbying efforts by farmers and chemical concerns, the EU has thus far refused to lift their temporary ban on neonicotinoids. Unfortunately for the insects, neonicotinoids linger on far after their initial use and can have deleterious effects even in non-lethal doses. A 2017 study in Science sampled honey from around the world with worrying results: 75 percent of their samples contained neonicotinoid compounds. Honey is one of the clearest indicators of environmental contamination, as bees range widely and unwittingly bring poisons back to the hive.
Unfortunately, pesticides are not the only possible culprit — habitat loss cannot be ignored. Many of the longest-term studies, including a 2008 Lund University study which recorded change in land use over the past two centuries, indicate that habitat loss is a significant factor in insect decline. Forty-four percent of the butterfly species observed in the early 1900s were extinct as of their 2001-2005 survey. Many of these butterflies lived only in certain small forests, which now no longer exist.
Scientific rigor demands ecologists collect more data before conclusively blaming one cause for insect decline. Despite the patchwork coverage, the data is worrisome. On the anecdotal side, James Traniello, a Professor of Biology at Boston University, noticed declining insect populations on his New Hampshire farm.
“Thirty years ago — always, and with great abundance — [there would be] beautiful pyrotechnic displays,” Traniello said.” I would see fireflies, my kids used to go out with mayonnaise jars, bring ‘em into the house and all that. Roughly, I would say about 15 years ago, they started to decline. And within the past several years, 8 to 10 years ago, I just stopped seeing them.”
Scientists can’t yet definitively confirm the widespread loss of insects, but this trend echoes other indisputable signs of biodiversity and natural habitat loss in general. And while scientists can guess what might happen as species die and ecosystems collapse, the natural world is complicated and interconnected. Species die when their food sources go extinct, when the climate changes, when their nesting sites turn into shopping malls, when another species out competes them, or hundreds of other reasons. We simply don’t understand enough to know all of the ways in which species rely on each other. We can only do our best to protect them — even the bugs.