Review: John Terborgh on the Insect Apocalypse
Last week we considered the work of Rachel Carson, whose 1962 book Silent Spring sounded the alarm about the danger of pesticide use and is sometimes credited with launching the modern environmental movement. Today we hear from John Terborgh, a senior scholar and researcher on tropical ecology and conservation, that our assault on insect life remains a potentially catastrophic threat to natural systems.
A large study carried out in sixty-three German nature reserves between 1989 and 2016 revealed a stunning 75 percent decrease in the mass of captured insects within the study’s boundaries. Dave Goulson’s new book, Silent Earth: Averting the Insect Apocalypse, is a timely and important work documenting these breathtaking declines in insect abundance. The author writes from the vantage of his own corner of the world, the United Kingdom, but evidence that insects are vanishing globally is coming in from North America, Europe, Puerto Rico, and elsewhere.
Why we should care about insects? Most broadly, because biodiversity is insect diversity: there are more species of insects than of all other organisms combined. It would be enough to weigh the interests of insects themselves, but insects also perform many vital functions in the larger ecology. These include the pollination of a majority of the plant species on earth, the dispersal of seeds, the processing of organic matter that recycles nutrients to the soil, and the regulation of other populations through predation and parasitism. Most crucially for us vertebrates, insects and their arthropod kin provide sustenance for innumerable mammals, reptiles, amphibians, and birds. Without insects, much of the rest of nature would collapse. We may already be seeing signs of that collapse in the estimate that North America has lost three billion birds over the last half century, 30 percent of the 1970 population.
Why is this happening? There are many potential reasons, each the subject of a chapter in Silent Earth: habitat loss; homogenization of agricultural landscapes; overuse of fertilizers; introduction of competitors, predators, and pathogens; disorienting night lights; and, of course, climate change. But leading the list are pesticides and agricultural chemicals more broadly. I was shocked to read that more than seventeen pesticide applications are in use in the crop fields of the UK every year, making it inevitable that much of the countryside is contaminated.
While such prima facie evidence might seem compelling, connecting the dots on the causes of insect decline is a challenge. Critics doubt that chemicals applied locally could have wider impacts across the landscape. But this is what the skeptics said when Rachel Carson raised the alarm about controlling insect populations with DDT. It took ten years of research to demonstrate the persuasive case for DDT’s destructiveness by showing beyond dispute that DDT was bioconcentrating at the top of the food chain and directly causing reproductive failure in bald eagles and other charismatic birds via eggshell thinning.
