Is “Insect Armageddon” for Real?

By Eric R. Eaton:

With so much misinformation and hyperbole streaming at us through social media, television, and other news outlets, many of us have become skeptical of almost everything. So, when an alarmist headline like “Scientists Warn of Insect Armageddon” crosses our screens, we are naturally leery. What exactly is the truth about the assertion that insect populations have dropped precipitously over the last twenty-five years or so?

Meadowlark with caterpillar. Ornithologists studying bird declines conclude that birds today are not eating as well as their predecessors. A 30-year German study shows a staggering drop in numbers of trapped insect specimens in 63 nature preserves. Photo: Eric R. Eaton

Part of the problem in assessing the validity of the situation is that much of the evidence is circumstantial or anecdotal. It is telling that the story broke in Europe, where there is a long history of scientific documentation; and where the historical loss of megafauna like bears, wolves, and bison has created a deep appreciation of all remaining species, including insects. Europeans are keenly aware of what species are threatened, and are heavily committed to preventing further extinctions. Citizen science is not a new concept, either, and more respect is accorded to “amateurs” there than it is to naturalists here in the U.S.

We can thank the volunteer members of the Entomological Society of Krefeld, Germany for sounding the alarm that resulted in the global news story. The group, which does include doctoral-level entomologists but also chemists and engineers, a school teacher, and other “non-professionals” in entomology, trapped insects regularly in sixty-three nature preserves in and near Krefeld over the course of nearly thirty years. The drop in numbers of specimens from start to present is truly staggering. The society keeps meticulous records, archiving the work and specimen collections of members now deceased or no longer participating in society activities. New recruits are mentored by older members, and encouraged to pursue studies in whatever group of insects excites them. It is a model of scientific leadership to be admired, and hopefully replicated everywhere.

The evidence provided by the Germans is compelling, and has been complemented by studies and observations made elsewhere. Australian scientists have noticed downward trends in insect survivorship in some butterfly and mosquito species in particular. Weather extremes, namely drought and excessive heat, have taken a toll, impacting insect populations at local levels at least. Enterprises that raise butterflies for exhibit in butterfly houses in Australia and other parts of the world, are suffering as a result of diminished breeding success. Failures include second generation survivorship of the blue and black Ulysses Swallowtail, one of the most spectacular insects in the world.

While the Australians still consider their contributions to the assessment of insect populations to be anecdotal, scientists in Canada have taken a different approach that is potentially much more quantifiable, and covers a much longer span of time. Ornithologists studying declines in the Whip-poor-will, a type of insect-eating bird, have been able to ascertain that the larger insects that once made up the principal diet of this species have declined in abundance. They measured this not by sampling the insects, but by analyzing the birds, including museum specimens decades old. It turns out that smaller insects accumulate different forms of the element nitrogen than do larger insects. This chemical fingerprint transfers over to insect predators like Whip-poor-wills. So, by comparing the nitrogen “signatures” of bird specimens from long ago to more recent specimens, scientists have concluded that today’s birds are not eating as well as their forefathers (and mothers). Populations of the Whip-poor-will are presently declining at a rate of about 3.5% per year.

What might be the root cause of such a rapid and extensive decline in insects? It is very likely a combination of many factors that can be traced largely to human impact. The conversion of natural habitat to housing, agriculture, and commercial enterprise is a primary concern. Global changes in climate that result in localized extremes in weather may drastically affect survivorship of insect populations both short term and long term. Continued, if not increased, use of pesticides results in the mortality of the whole spectrum of insects, not only those few pest species being targeted. Light pollution disrupts the nocturnal reproductive cycles of many species, especially the giant silkmoths. Water pollution makes streams, rivers, and lakes uninhabitable for a myriad of aquatic insects that are food for birds, bats, fish, and other animals. Collisions with vehicles are probably a vastly underestimated mortality factor, especially in rural and wilderness areas. Ironically, the collection of insects by scientists contributes little, if any, to the decimation of insects wrought by these other phenomena.

What can we do to turn the tide? We can simply be aware of the situation, and mindful of how our own personal actions might help or hurt the big picture of insect abundance. Knowledge is power, and we can share what we learn with others. While the overall trends may not be reversible, we can certainly slow them down dramatically by making wise choices.

Eric R. Eaton is principal author of the Kaufman Field Guide to Insects of North America and writes the blog “Bug Eric.” He lives in Colorado Springs with his wife, Heidi.