It’s not just Texans who should be blushing. Scientists studying the relationship between insects and plants have long predicted that a warming climate would benefit aphids and other plant-eating pests. The Texas drought, which is occurring as the state experiences rising temperatures due to climate change, is just one example. Elsewhere, rising populations of plant-eating insects are disrupting farms and the food chain, causing far more serious problems than sticky windshields.
Discussions of climate change and its impact on animals are often limited to large and charismatic species such as polar bears and sea turtles. Butterflies and pollinators may get mentions, but generally insects get less attention than species that easily translate into stuffed animals. This is an understandable but serious oversight that must be changed if we are to have any chance of mitigating hundreds of billions of dollars in potential losses.
Insects, unlike sea turtles, provide essential services for the functioning of the environment and human societies. According to a 2015 study, between 5% and 8% of the world’s crop production—worth $577 trillion—depends on pollination. A less obvious but no less important service is the composting of feces, a function many organisms perform. A recent study suggests that single, beetle-only, dung-eating services save the U.S. cattle industry about $380 million annually in dung recycling services. Other ecosystem services provided by insects, including pest control, are much more difficult to put a price on. Forensic entomology, the science of using insects to investigate deaths at crime scenes, relies on decades of data on the rates of decomposition of corpses linked to certain temperatures. And what price would Texans pay for a bunch of debt-eating ladybugs to stop the goo?
Alas, these crucial organisms are facing what some leading scientists have recently begun to call the “insect apocalypse.” Last year, a group of scientists estimated that insect abundance is declining by 1-2% per year due to a number of stressors, including insecticides, herbicides and climate change. This year, a separate study evaluated samples from nearly 20,000 different insects and found a 63% decline in insects in climate-stressed agricultural areas where the most natural habitat has been removed (removal of trees increases warming effects, among other things). Another recent study found that the frequency of unusually hot days in North America and Europe increases the rate of local bee extinction. And in forensic entomology, a growing body of research suggests that disappearing and migrating insect species, such as the housefly, are undermining the utility of the investigative method, potentially hindering law enforcement.
Not all insect species will experience losses due to a changing climate, and many that do not are the types of bugs that humans would prefer. Many pests, especially the crop-eating variety, benefit from climate change. In 2013, scientists found that the home ranges of many pests have historically been shifting to cooler regions since at least the 1960s. That change continues. Scientists estimated that a warmer climate this year was contributing to a 70 percent expansion in U.S. habitat of the brown stink bug, a common and devastating agricultural pest.
The increased amount of precipitation produced by warming oceans also affects harmful bug populations. For example, in the last 15 years the western Indian Ocean has experienced historically strong cyclones. In 2019 and 2020, the rains from these events created perfect conditions for locusts to breed, grow, develop and ultimately damage hundreds of thousands of hectares of sorghum, maize and wheat in Ethiopia alone.
There are also more subtle means by which climate change promotes the destruction of pest and economically significant plants. One study found that rising temperatures led to an increase in the number of maize stem borers, a common pest in parts of Africa, and a decrease in the parasites that feed on them. This disconnect, in turn, led to greater destruction of maize crops. Drought, which Texas has experienced, can weaken the plant’s natural defenses, thereby attracting pests, and higher CO2 levels can decrease the plant’s nutritional value. “If insects are faced with a plant that won’t provide them with all the nutrients they need, they will consume more,” explains Esther Ndumi Ngumbi, an assistant professor of entomology at the University of Illinois. “That’s another unfortunate consequence of the drought,” said Ngumbi, who studied the relationship between plants and insects and spoke to me over the phone.
Her research also focuses on the impacts of pests on farmers, and she is concerned about what she sees, especially among small farmers in emerging markets. “A Kenyan farmer cultivates one hectare. If the insects come, if the drought comes, that takes away their harvest, which means they can’t feed their family.” In more developed regions, farms are larger, but the impacts are still significant, especially as consumers face higher inflation.
Research efforts to develop and disseminate drought-resistant crops for free is a critical step in combating the growth of pests on agricultural land. But that is a longer term process. For now, Ngumbi would like to see a global effort to better control the pests and notify farmers before they migrate to their land. In addition, he and others argue that crop diversification, rather than single-crop monocultures, can help slow down pests.
None of these steps can reverse the effects of climate change on insects. But they can prepare humans for the consequences that are already happening and encourage reflection on long-term adaptation. If we don’t talk about it, we won’t do anything, and doing nothing will only benefit the pests. That should crack everyone up.
More from other Bloomberg writers:
Our climate future may be decided in Gridlock: David Fickling
How Basic Climate Action Urgent Bill: Antonio Guterres
Beleaguered East Africa Just Can’t Catch a Break: Bobby Ghosh
This column does not necessarily reflect the views of the editorial board or Bloomberg LP and its owners.
Adam Minter is a Bloomberg Opinion columnist covering Asia, technology and the environment. Most recently, he is the author of “Secondhand: Travels in the New Global Garage Sale.”
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