Temperature, precipitation, habitat loss, and more: The multiple, interacting forces of climate change are driving dramatic shifts in insect populations and biodiversity. Scientists gathered this month at a symposium at Entomology 2025 to share current research on climate change and insect biodiversity and identify persistent knowledge gaps. Emily Schmitt, a researcher at the University of New Mexico, shared that nearly half of the grasshopper populations in the northern Chihuahuan Desert are in significant decline. Shown here is a Dactylotum bicolor grasshopper. (Photo by David Lightfoot, Ph.D., Museum of Southwestern Biology)

By Carolyn Bernhardt

On a crisp November day in Portland, Oregon, experts gathered for a symposium at Entomology 2025 to explore how climate change affects both insect populations and the ecosystems they call home. Across seven talks and a panel discussion as part of a symposium titled “Exploring the Nature of Climate Change Impacts on Insect Biodiversity,” several key themes emerged, such as the persistent value of hands-on sample collection and boots-on-the-ground observation in the age of artificial intelligence (AI).

And, while insects are highly adaptable, some species will fare better than others in increasingly warm, dry, and volatile environments. Drought also emerged as a major, underappreciated driver of declines. Researchers also noted that climate change acts through multiple interacting forces—temperature, precipitation, habitat loss, and more—but most studies examine these factors in isolation. Overall, the symposium highlighted persistent knowledge gaps that can only be addressed through integrated research approaches.

“Sometimes You Have to Go Outside and Look.”

“Projected changes in climate in the western United States of high relevance to insects,” presented by Erica Fleishman, Ph.D., Oregon State University

Erica Fleishman kicked off the symposium by putting the West’s shifting climate into practical terms. “There’s a lot we still can’t see,” she said, referring to the gaps in weather monitoring across rugged, remote Western terrain.

Her talk knit weather data, land-use patterns, and insect dynamics into a pattern that’s increasingly difficult to ignore. Temperatures are rising in every season, snowpack is shrinking, and heat waves now arrive like unwelcome houseguests that stay too long. Meanwhile, rapid swings between abundance and scarcity—like the wet winter preceding an unexpectedly warm spring in early 2025—are becoming the new normal, with insects absorbing both direct and indirect consequences.

And, she said, the human element matters. As more people move into natural areas already primed for wildfire, they’re “turning up” the risk in places where the ecosystems are already stressed. She also made a point to note AI and models cannot replace direct field observation, closing with a sentiment from a former mentor: “Sometimes, to understand what’s going on, you have to go outside and look.”

When Plants Respond to Climate Change, Insects Follow

“Plant responses to climate change in California and current climate-adaptive management approaches,” presented by James Thorne, Ph.D., University of California, Davis

Whereas Fleishman zoomed out to the West as a whole, James Thorne zoomed in slightly. California’s vegetation, Thorne said, is reshuffling in response to rising temperatures, fire, and drought.

Across the state, warming temperatures are shifting the timing of flowering for roughly 29 key woody plants, while increasing tree mortality and altering their elevational ranges. Drought- and fire-resistant trees are also dying off, largely due to disappearing freezes, coupled with surging populations of invasive species and pathogens. And seedlings are struggling to establish quickly enough to replace these robust trees. A key tree species affected by all of this is the valley oak, which supports about 4,600 insect species.

He also touched on a lively debate brewing in restoration circles: Which genetic sources should we be planting for long-term resilience? Restoration practitioners disagree on seed-source strategy, with annual/shrub specialists and forestry specialists holding opposite philosophies—and landscape genomics may finally help reconcile them. “Plantscape genomics offer an amazing opportunity to engage in [understanding] which populations of [tree] species are resilient or not,” he said.

More Than the Average: Grasshoppers Show Why Climate Variability Matters

“Climate sensitivity of desert grasshoppers,” presented by Emily Schmitt, University of New Mexico

Emily Schmitt took everyone to the Chihuahuan Desert, where decades of monitoring offer clarity on how grasshoppers respond to the ups and downs of climate, not just its overall direction. The research has shown that nearly half of the grasshopper populations in the northern Chihuahuan Desert are in significant decline. In some cases, Schmitt said, variance is costly; in others, beneficial. But, for most species, results were not straightforward.

At New Mexico’s Sevilleta National Refuge, Schmitt and her collaborators have monitored about 70 grasshopper species across three ecosystems—plains grasslands, desert grasslands, and desert shrubland—for 33 years. Grasshoppers, dominant herbivores averaging 3,000 individuals per hectare (up to 6,000 in wet years), show mixed trends: 45% of populations have declined, 38% have remained stable, and 17% have increased. Long-term drought, rising aridity, and increased climate variability, she said, are key drivers behind these shifts.

At New Mexico’s Sevilleta National Refuge, researchers have monitored about 70 grasshopper species across three ecosystems—plains grasslands, desert grasslands (shown here), and desert shrubland—for 33 years. (Photo by Emily Schmitt)

For most grasshopper species, the impact of climate variability depends on average conditions—increased variance can be harmful under certain mean conditions, while decreased variance can be beneficial. The majority of species studied showed this context-dependent response.

The scientists suspect that life-history traits—body size, dispersal ability, and how closely a species is tied to particular environmental conditions—could be a key factor. Additionally, they are curious to explore whether certain life stages are more vulnerable than others. Future research will focus on these hypotheses.

Schmitt reminded attendees that the average response across variable climates is not the same as the response across average climates, underscoring how climate extremes may be just as important as long-term trends.

Waves of Drought

“Droughts as a driver of insect population declines,” presented by David Wagner, Ph.D., University of Connecticut

David Wagner didn’t sugarcoat things, citing drought as the biggest driver of insect decline globally. He explained how water scarcity kills insects outright through desiccation, but the indirect effects can be just as deadly: depleted nectar sources, weakened host plants, shrinking water tables, and altered soil chemistry.

In southern Arizona, butterfly counts have collapsed across several long-term monitoring sites, plummeting by up to 90%. Acting in step with Fleishman’s advice to go outside and look, Wagner revisited the same spot he did in graduate school for the Patagonia Arizona Annual Butterfly Count and noted an enormous drop in abundance from what he recalled decades prior. Ground temperatures in exposed areas have hit 180 degrees Fahrenheit—far beyond any insect’s tolerance.

He argued for integrating more research on insect consumers, such as birds and bats, which are often the first to signal ecosystem-level shifts. The approach also spares researchers the need to collect insect data from the populations themselves, leaving the few that remain alone to (hopefully) survive.

A companion presentation by co-author Madeline Shaw reinforced his point: drought research is heavily skewed toward a handful of regions, leaving significant knowledge gaps.

The EntoGEM project, Shaw said, conducted a systematic review of the literature to map insect population trends and identify key knowledge gaps, particularly regarding drought impacts. Nine reviewers screened abstracts against established criteria, ultimately selecting just over 100 studies from an initial pool of more than 1,000, while discarding over 800 that didn’t meet the standards.

The review revealed that aridity and drought remain understudied compared with water levels. That research is often biased toward specific study sites and institutions, though the most valuable data came from around 30-degree latitudes. Secondary effects of drought, which can trigger cascading ecological impacts, are especially underrepresented, as most studies examined only a single effect. Looking ahead, the team plans to incorporate studies published since 2020 and refine their search strategy to capture research that may have been overlooked in the first review.

Land Use Amplifies Climate Effects

“Global scale impacts of climate change and land use-climate change interactions on insect biodiversity,” presented by Charlie Outhwaite, Ph.D., Zoological Society of London

Charlie Outhwaite brought the room back to a global scale, calling for researchers to study the intersection of multiple effects on insects simultaneously, such as land use and climate change, rather than in isolation as they typically do. “Pressures on biodiversity rarely work in isolation,” she said, “But that is often how we assess them.” Climate affects land use and vice versa, so their interactions can lead to greater changes in biodiversity.

Using a collection of studies, called PREDICTS, that have examined biodiversity across different land uses and land-use intensities at various sites, the team analyzed more than 6,000 sites (ranging from forest vegetation to cropland and beyond), 264 studies, and nearly 18,000 insect species. They looked at primary vegetation, secondary vegetation, and low- and high-intensity agriculture.

Echoing Schmitt’s sentiments, Outhwaite noted that the team found a lot of nuance hiding in averages. In high-intensity agricultural regions, insects lose both abundance and species richness faster as climate stress increases. Natural habitat can soften those losses, but according to this research, this was mostly only possible in landscapes with low-intensity agriculture. The work also highlights a mismatch in research coverage: Some insect groups are well studied (such as butterflies), while others remain data-poor.

Christopher Halsch, Ph.D., Binghamton University, has studied how insect responses to warming vary by overwintering stage, finding that overwintering strategy is a powerful predictor of how insects will respond to warming winters and increasing temperature variability. Shown here is a Polites sonora butterfly, sometimes known as a Sonora skipper, observed near Castle Peak in the Sierra Nevada mountains of California. (Photo by Christopher Halsch, Ph.D.)

Learning About Climate Change’s Impacts From Butterfly Sleep

“Insect overwintering modulates responses to temperature change,” presented by Christopher Halsch, Ph.D., Binghamton University

Christopher Halsch brought the focus to winter—the season warming faster than any other, especially at high elevations and latitudes—presenting findings from research he and his team conducted on Donner Pass in the Sierra Nevada mountains. The team investigated how insect responses to warming vary by overwintering stage. Halsch’s talk positioned overwintering as the bottleneck through which different species pass at various life stages. Some overwinter as eggs, others as larvae, pupae, or adults, and each stage carries a unique thermal sensitivity.

Halsch’s work suggests that the overwintering strategy is a powerful predictor of how insects will respond to warming winters and increasing temperature variability. For example, warmer minimum temperatures, especially for those who overwinter as eggs, meant fewer butterflies. Additionally, the combination of temperature and snow had a massive effect on how many butterflies emerged at winter’s end, with more snow being a positive. Halsch suspects this finding was due to snow insulating overwintering species.

Christopher Halsch, Ph.D., Binghamton University, has conducted research on insect overwintering strategies at high elevations in the Sierra Nevada mountains of California. (Photo by Christopher Halsch, Ph.D.)

Patchy Landscapes, Clear Next Steps

The symposium at once called attention to as-yet uncharted research areas and offered researchers a few clear paths to follow. For one thing, water is paramount, both to insects directly and the vegetation they feed on or live in. However, plants often respond to climate shifts first, triggering cascading effects across whole insect communities. No matter what, field observation remains essential.

By the symposium’s end, attendees left with a long list of must-see observations for their “go outside and look” list—and plenty of fresh perspectives to notice along the way.

Carolyn Bernhardt, M.A., is a freelance science writer and editor based in Portland, Oregon. Email: [email protected].