This past summer, my wife and I took a lovely walk around Echo Lake in New Hampshire. What struck us, and we mentioned to a ranger, was the dearth of bird song. Despite the general solitude, all we heard was an occasional song in the distance. The only birds we saw were some ducks in the lake. Earlier this summer, we were in the Sierra Nevada mountains in California. We could not help but notice the huge number of dead and dying trees. Back home near Chicago, it is difficult to ignore the decline in the number of insects. In years past, insects of all kinds would gather around our back-porch light at night. Now there seem to be but a few. This is despite our newly established native plantings.
These are all anecdotal, but it is hard to ignore the impression that things in the living world are increasingly out of whack. Now our circumstantial observations are being increasingly backed by hard data. Although as pointed by Ed Yong in the Atlantic (Feb. 19, 2019), fears that insects will totally disappear are overblown, there is increasing evidence of the decline of insect numbers. Recent studies from Germany and Puerto Rico have indicated significant losses. A metanalysis by Sánchez-Bayo and Wyckhuys (2019. Biological Conservation 232: 8–27) suggests that 40% of the world’s insect species are threatened with extinction in the near future. While there is considerable justifiable criticism of these numbers, there does to be a consensus that insects are in decline, but also that the far more data is needed to accurately assess numbers and assign causes. A sober FAQ statement from the Entomological Society of America is a must read (http://www.entsoc.org/sites/default/files/files/Science-Policy/2019/Global%20Insect%20Biodiversity%20FAQs.pdf).
On September 19 the bad news on birds appeared. In a widely publicized paper in Science, Kenneth Rosenberg and his co-authors reported on changes in North American bird populations since 1970. Much of their analysis was based on the annual bird counts conducted by citizen-scientists, such as the Audubon Society Christmas Bird Count, as well as weather station radar images of migrating bird flocks. Together, these data suggest that bird abundance has declined by about 30% since 1970, or about 3 billion (yes, billion) fewer birds. Grassland species have been especially hard hit, with a 53% decline. Even introduced and common birds are not exempt; although my backyard is overrun by house sparrows, they too are decreasing (they are also declining precipitously in their native Europe, possibly due to disease). The authors also remind us that even once abundant birds, such as the passenger pigeon, are not immune to extinction. As for causes, they indicate that: “Pervasiveness of avian loss across biomes and bird families suggests multiple and interacting threats.” Certainly, the decline of insects and birds are not unrelated, with both common causes and interactions (insectivorous birds have been badly hit). We are losing the sweet sound of bird songs.
As mentioned in an earlier post, every year I teach an honor’s seminar on the Sixth Extinction, based on Elizabeth Kolbert’s excellent book. This semester I am also leading a discussion of it among a group of STEM majors and faculty. When the book first came out, Kolbert was interviewed by Jon Stewart on the Daily Show. They agreed that the book contained very little “good news.” In the decade since it came out, the news has not gotten any better.
Prompted by the amazing Greta Thunberg, young people throughout the world have marched and demanded action on climate change. This is wonderful. But we should not forget that climate change is only part of the human impact on the world; we should especially not forget the ongoing decline in plant and animal life. We should not only take action to reduce emissions, we also need to demand protection of the organisms we share the world with.
(note: the title is from Shakespeare’s Sonnet 73. It was also the title of a 1976 award winning post-apocalyptic novel by Kate Wilhelm).