Entomologists issue warning about effects of climate change on insects
UMD entomologist Anahí Espíndola says insects are under threat, but there is still time to change course
Peer-Reviewed PublicationIMAGE: BEES ARE IMPORTANT POLLINATORS, BUT THEY ARE BEING THREATENED BY CLIMATE CHANGE, WHICH CAN AFFECT THEIR RANGES, THEIR INTERACTIONS WITH OTHER SPECIES AND THE PHENOLOGIES OF THE PLANTS THEY DEPEND ON. view more
CREDIT: ANAHÍ ESPÍNDOLA
In a new scientific review, a team of 70 scientists from 19 countries warned that if no steps are taken to shield insects from the consequences of climate change, it will “drastically reduce our ability to build a sustainable future based on healthy, functional ecosystems.”
Citing research from around the world, the team painted a bleak picture of the short- and long-term effects of climate change on insects, many of which have been in a state of decline for decades. Global warming and extreme weather events are already threatening some insects with extinction—and it will only get worse if current trends continue, scientists say. Some insects will be forced to move to cooler climes to survive, while others will face impacts to their fertility, life cycle and interactions with other species.
Such drastic disruptions to ecosystems could ultimately come back to bite people, explained Anahí Espíndola, an assistant professor of entomology at the University of Maryland and one of the paper’s co-authors.
“We need to realize, as humans, that we are one species out of millions of species, and there's no reason for us to assume that we’re never going to go extinct,” Espíndola said. “These changes to insects can affect our species in pretty drastic ways.”
Insects play a central role in ecosystems by recycling nutrients and nourishing other organisms further up the food chain, including humans. In addition, much of the world’s food supply depends on pollinators like bees and butterflies, and healthy ecosystems help keep the number of pests and disease-carrying insects in check.
These are just a few of the ecosystem services that could be compromised by climate change, the team of scientists cautioned. Unlike mammals, many insects are ectotherms, which means they are unable to regulate their own body temperature. Because they are so dependent on external conditions, they may respond to climate change more acutely than other animals.
One way that insects cope with climate change is by shifting their range, or permanently relocating to places with lower temperatures. According to one study cited by Espíndola and other scientists, the ranges of nearly half of all insect species will diminish by 50% or more if the planet heats up 3.2°C. If warming is limited to 1.5°C—the goal of the global Paris Agreement on climate change—the ranges of 6% of insects will be affected.
Espíndola, who studies the ways in which species respond to environmental changes over time, contributed to the sections of the paper that address range shifts. She explained that drastic changes to a species’ range can jeopardize their genetic diversity, potentially hampering their ability to adapt and survive.
On the other hand, climate change may make some insects more pervasive—to the detriment of human health and agriculture. Global warming is expected to expand the geographical range of some disease vectors (such as mosquitoes) and crop-eating pests.
“Many pests are actually pretty generalist, so that means they are able to feed on many different types of plants,” Espíndola said. “And those are the insects that—based on the data—seem to be the least negatively affected by climate change.”
The team noted that the effects of climate change are often compounded by other human-caused impacts, such as habitat loss, pollution and the introduction of invasive species. Combined, these stressors make it more difficult for insects to adapt to changes in their environment.
Though these effects are already being felt by insects, it is not too late to take action. The paper outlined steps that policymakers and the public can take to protect insects and their habitats. Scientists recommended “transformative action” in six areas: phasing out fossil fuels, curbing air pollutants, restoring and permanently protecting ecosystems, promoting mostly plant-based diets, moving towards a circular economy and stabilizing the global human population.
The paper’s lead author, Jeffrey Harvey of the Netherlands Institute of Ecology (NIOO-KNAW) and Vrije Universiteit Amsterdam, said in a statement that urgent action is needed to protect insects and the ecosystems they support.
“Insects are tough little critters, and we should be relieved that there is still room to correct our mistakes,” Harvey said. “We really need to enact policies to stabilize the global climate. In the meantime, at both government and individual levels, we can all pitch in and make urban and rural landscapes more insect-friendly.”
The paper suggested ways that individuals can help, including managing public, private or urban gardens and other green spaces in a more ecologically-friendly way—for instance, incorporating native plants into the mix and avoiding pesticides and significant changes in land usage when possible.
Espíndola also stressed the value of encouraging neighbors, friends and family to take similar steps, explaining that it’s an easy yet effective way to amplify one’s impact.
“It is true that these small actions are very powerful,” Espíndola said. “They are even more powerful when they are not isolated.”
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Their paper, titled “Scientists’ warning on climate change and insects,” was published in Ecological Monographs on Nov. 7, 2022.
JOURNAL
Ecological Monographs
METHOD OF RESEARCH
Systematic review
SUBJECT OF RESEARCH
Animals
ARTICLE TITLE
Scientists' warning on climate change and insects
ARTICLE PUBLICATION DATE
7-Nov-2022
‘Insects need our help in a warming world, now’
70 scientists’ warning on climate change effects
Peer-Reviewed PublicationIMAGE: CLIMATE-CHANGE IMPACTS ON INSECTS CAN BE CATEGORISED INTO TWO MAJOR GROUPS: GRADUAL LONG-TERM CHANGE AND EXTREME EVENTS THAT WILL INCREASE IN FREQUENCY AND SEVERITY. INTERVENTIONS INCLUDE FORMAL MITIGATION OF CHANGE THROUGH POLICY AND PUBLIC APPROACHES WHICH IN TURN HELP TO REDUCE IMPACTS IN VARIOUS WAYS. view more
CREDIT: SCIENTISTS' WARNING ON CLIMATE CHANGE AND INSECTS
‘If no action is taken to better understand and reduce the impact of climate change on insects, we will drastically limit our chances of a sustainable future with healthy ecosystems.’ This warning in a very topical paper in Ecological Monographs comes from 70 scientists from 19 countries around the world. But, they also provide ways to help insects in a warming world complete with management strategies.
Yes, we’ve heard about insect decline before. But no, we haven’t done much to stop it on a worldwide scale. Climate change is at the top of the world’s to-do list. Something that coincides very well with the COP 27 climate change conference in Egypt from 6 - 18 November.
Gradual change plus extremes
‘Climate change aggravates other human-mediated environmental problems,’ says Jeffrey Harvey from the Netherlands Institute of Ecology (NIOO-KNAW) and Vrije Universiteit Amsterdam. ‘Including habitat loss and fragmentation, various forms of pollution, overharvesting and invasive species.’ He leads the major paper by an international team of scientists. Together, they provide a convincing overview of the role of climate change and climatic extremes in driving insect decline.
The paper is part of the Scientists’ Warning series. ‘Insects play critical roles in so many ecosystems, but we are rapidly losing at least part of them,’ Harvey stresses the urgency. And this seems the case especially in temperate regions. The authors emphasise that both longer-term events and short-term extremes are harming insects in several ways.
‘The gradual increase in global surface temperature impacts insects in their physiology, behaviour, phenology, distribution and species interactions.’ Harvey adds: ‘But also, more and longer lasting extreme events leave their traces.’ Hot and cold spells, fires, droughts, floods.
Piling up
Evidence of the effects is piling up, and it’s all presented in this review. For instance, fruit flies, butterflies and flour beetles can survive heat waves, but males or females become sterilised and thus unable to reproduce. They become ‘living dead’. Bumblebees in particular prove very sensitive to heat, and climate change is now considered the main factor in the decline of several North American species.
‘Cold-blooded insects are among the groups of organisms most seriously affected by climate change, because their body temperature and metabolism are strongly linked with the temperature of the surrounding air,’ says Harvey.
One major concern with insect decline in a warming world is that plants – on which insects depend for food and shelter – are similarly affected by climate change. And as insect numbers dwindle, it in turn works its way higher up the food chain. This has happened to many birds, for instance, over the past decades.
Supporting the global economy
Think pollination, pest control, nutrient cycling and decomposition of waste. Insects represent the overwhelming bulk of biodiversity, and perform vitally important services that sustain human civilisation, all worth staggering amounts of money (billions of dollars) annually to the global economy. Another reason to act on climate change. Harvey: ‘The late renowned ant ecologist Edward O. Wilson, once argued that ‘it is the little things that run the world’. And they do!’
‘Over time, insects must adjust their seasonal life-cycles and distributions as the world warms,’ says Harvey. ‘However, their ability to do this is hindered by other human-caused threats such as habitat destruction and fragmentation, and pesticides.’ Furthermore, heatwaves and droughts can drastically harm insect populations in the short term, making insects less able to adapt to more gradual warming. ‘Warming over different time scales poses different kinds of threats to insects.’
What to do
Importantly, the scientists not only describe the problems, but also discuss a range of solutions and management strategies. These may help to buffer insects against climate warming. Individual people can help by caring for lots of different wild plants, providing food and areas where insects can shelter to ride out climate extremes. And by reducing the use of pesticides and other chemicals. ‘At the larger scale, we need to address climate change. Rewilding programmes also need to consider micro-scale ecosystems which focus on the conservation of small animals like insects.’
‘Insects are tough little critters and we should be relieved that there is still room to correct our mistakes,’ according to Harvey. But time is running out. ‘We really need to enact policies to stabilise the global climate. In the meantime, at both government and individual levels, we can all pitch in and make urban and rural landscapes more insect-friendly.’
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With more than 200 staff members and students, the Netherlands Institute of Ecology (NIOO-KNAW) is one of the largest research institutes of the Royal Netherlands Academy of Arts and Sciences (KNAW). The institute specialises in water and land ecology with three major themes: biodiversity, climate change and the sustainable use of land and water. The institute is located in an innovative and sustainable research building in Wageningen, the Netherlands. NIOO has an impressive research history that stretches back more than 65 years and spans the entire country, and beyond.
JOURNAL
Ecological Monographs
METHOD OF RESEARCH
Systematic review
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Scientists' warning on climate change and insects
ARTICLE PUBLICATION DATE
7-Nov-2022
Solutions for impacted insects 
Local environmental characteristics can either harm or benefit insects (left panel), especially when insects are exposed to climatic extremes such as droughts and heatwaves. Ecologically targeted management strategies (right panel) can help insects to adapt to climate change and other human-caused environmental problems.
CREDIT
Scientists' warning on climate change and insects
Impacted insects (IMAGE)
Examples of impacted insects: emperor dragonfly, Quino Checkerspot butterfly, yellow-banded bumblebee and hyperparasitoid Gelis agilis (from upper left to lower right).
CREDIT
Tim Bekaert, Andrew Fisher (USFWS volunteer biologist), Rob Foster, Tibor Bukovinszky (NVWA Wageningen University & Research) / Scientists' warning on climate change and insects
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