An unusually large influx of tiny insects called aphids have been sucking away Dallas-area pecan trees in recent weeks. After they’re full, they “excrete” the waste out of their rear ends and onto cars, driveways and sidewalks. “Texas is covered in a sticky, gooey goo,” declared a Dallas Morning News headline. Other news outlets offered tips on how to clean up the mess.
It’s not just Texans who need to be exterminated. Scientists who study the relationship between insects and plants have long predicted that a warm climate would favor aphids and other plant-eating pests. The Texas drought, occurring as the state experiences rising temperatures under the influence of climate change, is just one example. Elsewhere, growing populations of herbivorous insects are disrupting farms and the food supply chain, causing problems far more serious than sticky windshields.
Discussions of climate change and its impact on animals are often limited to large, charismatic species such as polar bears and sea turtles. Butterflies and pollinators might deserve mentions, but in general insects get far less attention than species that easily translate into stuffed animals. This is an understandable but serious oversight that must change if we are to have any chance of mitigating hundreds of billions of dollars in potential losses.
Insects, unlike sea turtles, provide services critical to the functioning of the environment and human societies. According to a 2015 study, 5% to 8% of global crop production—worth as much as $577 billion—depends on pollination. A less obvious but no less important service is the processing of manure into fertilizer, a function performed by many organisms. A recent study indicates that the manure eating services provided by just one, the simple manure sweeper, save the U.S. cattle industry about $380 million annually in manure recovery services. Other ecosystem services provided by insects, including pest control, are much more difficult to price. Forensic entomology, the science of using insects to investigate deaths at crime scenes, is highly dependent on decades of data on corpse decomposition rates tied to specific temperatures. And what price will Texans pay for a swarm of aphid-eating ladybugs to stop the goo?
Alas, these crucial organisms face what some prominent scientists have recently come to call the “insect apocalypse.” Last year, a group of scientists estimated that insect abundance is declining by 1% to 2% per year due to a range of stressors, including insecticides, herbicides and climate change. This year, another study assessed samples from nearly 20,000 different insects and found a 63% decrease in insects in climate-stressed agricultural areas, where most of the natural habitat has been removed (removal of trees intensifies, among other warming effects). Another recent study found that the increasing frequency of unusually hot days in North America and Europe is contributing to higher local bumble bee extinction rates. And in forensic entomology, a growing body of research suggests that disappearing and migrating insect species—like the weevil—undermine the utility of the investigative method, potentially hindering law enforcement.
Not every insect species will suffer losses as a result of a changing climate, and many that won’t are exactly the kind of bugs that humans would rather do without. Many pests, especially the crop-munching varieties, are beneficiaries of climate change. In 2013, scientists noted that the home ranges of many pests have shifted to historically cooler regions since at least 1960. That shift continues. Scientists estimated this year that a warmer climate is contributing to a 70% expansion in American habitat for the brown marmorated stink bug, a common and devastating agricultural pest.
Greater amounts of precipitation generated by warming oceans also affect harmful insect populations. For example, over the past 15 years, the western Indian Ocean has experienced historically powerful cyclones. In 2019 and 2020, the rains from those events created ideal conditions for locusts to breed, hatch, develop and eventually damage hundreds of thousands of hectares of sorghum, maize and wheat in Ethiopia alone.
There are also more subtle ways in which climate change can promote pests and the destruction of economically significant plants. One study found that increases in temperature were accompanied by an increase in the number of maize stem borers, a pest common in parts of Africa, and a decrease in the parasites that feed on them. This disconnect, in turn, led to greater devastation of maize crops. Drought, such as Texas has faced, can weaken a plant’s natural defenses and thereby attract pests, while higher CO2 levels can reduce the nutritional value of plants. “If insects face a plant that won’t give them all the nutrients they need, they will consume more,” explained Esther Ndumi Ngumbi, an assistant professor of entomology at the University of Illinois. “This is another unfortunate side effect of drought,” says Ngumbi, who studies the relationship between plants and insects and spoke to me by phone.
Her research is also focused on the impact of pests on farmers, and she is disturbed by what she has observed, especially among small farmers in emerging markets. “A Kenyan farmer works one acre of land. If insects come, if drought comes, it takes away their crop, which means they can’t provide for their family.” In more developed regions, the farms are larger, but the impact is still significant, especially as consumers face higher inflation.
Research efforts to develop and distribute – for free – drought-resistant crops are a critical step in addressing the growth of pests on fields. But this is a longer term process. For now, Ngumbi would like to see a global effort to better monitor for pests and notify farmers before they migrate to their fields. In addition, she and others argue that crop diversification, rather than single-crop monocultures, can help slow down pests.
None of these steps can reverse the impact of climate change on insects. But they can prepare people for the consequences that are already happening and inspire long-term thinking about adaptation. If we don’t talk about it, we’re not going to do anything about it, and doing nothing will only benefit the pests. This should bother everyone.
More from other writers at Bloomberg Opinion:
Our Climate Future May Be Decided in Gridlock: David Fickling
How to pay the urgent climate action bill: Antonio Guterres
Beleaguered East Africa just can’t catch a break: Bobby Ghosh
This column does not necessarily reflect the opinion of the editors or Bloomberg LP and its owners.
Adam Minter is a Bloomberg opinion columnist covering Asia, technology and the environment. He is recently author of “Secondhand: Travels in the New Global Garage Sale.”
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