What climate change is really doing to animals—her revelations will shock you

Butterflies, Fieldwork, and Surprising Discoveries

Camille Parmesan became a prominent figure in global ecology by being the first to prove tangible climate change impacts on a wild species—the Edith’s checkerspot butterfly. Her fame is now not only tied to researching biodiversity’s future in a warming world, or sharing the Nobel Peace Prize with her IPCC colleagues, but also her status as a scientific refugee in Europe.

There were two points in her life when she chose to move countries, simply to continue her climate research in a supportive political setting—first leaving Trump’s America in 2016, then post-Brexit Britain. She now leads the CNRS theoretical and experimental ecology research station in Moulis, in southwest France.

Speaking with Parmesan reveals insights into protecting unpredictable biodiversity, addressing increased species hybridization, and responding to ever-present climate skepticism.

The Conversation: Your early work on Edith’s checkerspot habitats quickly earned international recognition. Specifically, how did you show that a butterfly could be affected by climate change? What tools did you use?

Camille Parmesan: A pick-up, a tent, a butterfly net, strong reading glasses to spot tiny eggs and caterpillar damage on leaves, a notebook and pencil for field notes! Out in the field, that’s all you need.

Before hitting the field, though, she spent a year combing through museums across the United States, some in Canada, even London and Paris, gathering every scrap of data on Edith’s checkerspot. She hunted for details like “It was here, one mile (about 1.6 km) from Parsons Road, on June 19, 1952,” because these butterflies live in small, sedentary populations. At the time, without digital archives, she had to hand-record data from pinned specimens. Then came the fieldwork: visiting every site during the butterfly’s short, month-long flying season, estimating when they’d be active at each location to time her surveys.

You look for adults first, but if you see none, you don’t give up—you search for eggs, webs spun by young caterpillars, leaf damage from post-hibernation larvae…

Just as crucial: evaluating the habitat—is there enough healthy host and nectar plants for the butterflies? If a site had inadequate habitat, she excluded it, striving to isolate the impact of climate change from other factors like habitat loss or pollution. At big sites, she sometimes checked 900+ plants before a single survey felt complete.

The Conversation: When you return to those sites decades later, do you notice things you couldn’t see at the start of your research?

C.P.: Let’s say I look at things I never thought to look at 40 years ago—or even that my husband Michael (biologist Michael C. Singer) didn’t look at 50 years back. We found, for instance, that eggs are now laid slightly higher up on the plants—a hugely important adaptation to climate change.

Now, eggs are placed higher because the ground is simply too hot. Last summer, Parmesan measured ground temperatures of 78°C (over 170°F). Caterpillars that fall off simply die. Butterflies will sometimes land and leave immediately because it’s too hot for their feet—they prefer to settle on vegetation or even on people! Early on, it never seemed important where the eggs were laid, which is why careful observation of your organism and its environment is crucial. She laments seeing eager young biologists wanting to rush, collect specimens, grind them up in the lab, run genetic tests. That’s all good, but without time spent observing species in their habitats, you can’t connect lab results to what really happens in the wild.

Biodiversity in Motion: Conservation’s New Frontier

Thanks to the work of Parmesan and her colleagues, we know living organisms are powerfully affected by climate change, and many species must shift their ranges to survive. But it’s hard to predict where they’ll hang on in the future. So, what do we protect—and where?

C.P.: This is the big question bugging conservation biologists. Go to a conservation biology meeting, and you’ll see plenty of people getting depressed, because nobody knows what to do.

Color differences in Edith’s checkerspot at low altitude (left) and high altitude (right) are linked to climate adaptation: darker wings heat up faster in the sun, crucial in cooler climates.

Parmesan urges a mindset shift: treat conservation more like a diversified insurance portfolio. We can’t foretell the future, so we need flexible, adaptable plans, adjusting as we observe new realities. She and her team recently published a paper suggesting we adopt certain decision-making strategies from famously unpredictable fields like economics or water resource planning. With today’s computers, you can simulate a thousand possible futures: If we do X, what happens? Some scenarios look good, some bad, some mixed. The task: find the “robust” set of measures that work reasonably well across most scenarios.

In their ecosystem conservation models (about 700 scenarios for 22 species), just protecting the places where a species is now almost never guarantees survival—only 1-2% of scenarios predict the species will persist in the same spot in the future.

So what if you protect not only current sites, but also sites where the species is thought likely to occur 30%, 50%, 70% of the time? By combining protections for a range of potential habitats, you can often cover half the areas where models predict long-term persistence—far more robust than clinging to the present. Traditional conservation areas are still useful, but often not enough.

Size matters, too. The bigger and more diverse protected lands are—especially for regions rich in species diversity—the better. As changing species leave, newcomers may arrive. Ecological hotspots will likely keep their role, but with communities of entirely new species, thanks to features like mountains, valleys, and a mosaic of microclimates.

Between these areas, Parmesan stresses the importance of “corridors” that let creatures move without certain death. In wheat fields, for example, everything crossing is likely to die. Creating winding strips of semi-natural habitat, or establishing wide buffer zones along rivers, helps species move safely: “It doesn’t have to be perfect habitat—just don’t make it deadly,” she notes.

Even domestic gardens can play a part: leaving part of your yard unmown, letting nettles or brambles flourish, creates mini-corridors for wildlife. Road edges can do the job too. Fiscal incentives (tax breaks for undeveloped land, for instance) could encourage landowners to help out. The whole point is, don’t put all your eggs in one conservation basket.

Protecting every possible future site isn’t realistic—too expensive, too complex. Instead, aim for a resilient set of sites, within what’s financially and socially feasible, so when the climate stabilizes, surviving species have somewhere to recolonize and thrive.

Hybridization: A New Twist in the Story of Survival

There’s a new conservation dilemma: increased hybridization. As species shift across the landscape, they meet and mingle as never before. Polar bears, driven from their melting sea-ice homes, increasingly encounter grizzlies and brown bears—and sometimes interbreed, with hybrid cubs as a result.

Historically, conservation biology wanted to prevent hybridization, aiming to preserve differences in behavior, appearance, diet, and genetics. Hybrids—even when viable—are often less resilient. Nevertheless, with climate change constantly forcing species together, keeping them apart is, as Parmesan admits, a lost cause. It’s time for a new approach: focusing on preserving as much genetic diversity as possible, no matter the form it takes.

Populations with wide genetic variation can evolve and adapt much more quickly. Fighting hybridization could actually make adaptation to climate change harder. The goal, then, is to hang onto as many genes as possible, even if it means losing distinct species. After all, in past warm periods, polar bears and grizzlies mixed, and when conditions cooled again, polar bears re-emerged far more quickly than if they’d had to re-evolve from scratch—their key genes persisted, quietly, inside brown bear populations.

Boundaries of Adaptation—and Hope

For non-scientists, the situation can feel contradictory: nature is full of dramatic adaptation (trees changing chemistry, butterflies changing color), yet biodiversity is plunging worldwide. How to resolve this paradox?

C.P.: The current speed of climate change is a huge part of the puzzle. And every species has a pretty fixed physiological niche—a “climate space,” a particular mix of rainfall, humidity, dryness. Once they hit that wall—they die. We don’t really understand why those limits are so strict.

For other stressors, like copper pollution or noise, many species can adapt genetically, though not all. Some pests thrive in urban jungles. But with climate change, most species lack the genetic variation to keep up. Only hybridization or (painfully slow) mutation can bring in new adaptive traits. We’d need a million or two million years for today’s species to evolve for the oncoming climate.

Back in the Pleistocene Ice Ages, with global temperature swings of 10-12°C, species coped by moving. But in the even wilder Eocene, with sky-high CO2 and extreme heat, species went extinct if they couldn’t shift far enough. Evolution at this scale takes hundreds of thousands—sometimes millions—of years, not a few centuries.

Still, hope remains for some highly threatened populations, as Parmesan explains:

“Populations that seem highly exposed to climate change can nonetheless resist extinction. So it’s worth protecting them, reducing other stresses, and monitoring their adaptation capacity.”

Take the Quino checkerspot, a genetically distinct Edith’s checkerspot found in southern California. Hit hard by climate change and urban sprawl, most of its populations vanished. In the early 2000s, Parmesan and her husband joined its conservation planning, arguing that only protecting current, lowland habitats was futile. They suggested safeguarding higher-altitude sites—even where the butterfly didn’t yet exist.

Potential host plants were already present at elevation. Introducing lowland butterflies to these unfamiliar plants showed they liked them—no evolutionary leap needed. Tribes and the US Forest Service embraced the highland conservation sites. One degraded area with a restored clay-lined vernal pool (“spring pond”) and native Plantago erecta host plants, soon saw the return not only of Quino checkerspot, but nearly every threatened species it was designed to protect, within three years. Many weren’t even deliberately reintroduced—they just showed up!

Some checkerspots even made it to higher ground by themselves, surpassing expectations for a butterfly not known for marathon flights. A corridor doesn’t need to support a full population—it just needs to let individuals pass without killing them.

When Science Crosses Borders—And Families Don’t

Parmesan herself has experienced a kind of scientific migration, seeking political environments where she could work freely. In France, she’s been portrayed as a “scientific refugee” and asked to speak about it. In the US? Curiosity among colleagues, but little media attention.

C.P.: What’s interesting is that the US media never picked up on this. All the attention came from outside the US—from Canada and Europe. I don’t think Americans realize the current damage to academia, education, and research.”

She observes that Americans sometimes assume no one would ever want to leave the US for research opportunities elsewhere. Yet, as she notes, the US once brimmed with research funding from agencies, philanthropists, and NGOs—funding which abruptly dried up.

Climate Change, Health, and the Art of Conversation

One way to get people’s attention about biodiversity conservation? Link it to health. Parmesan started in the medical field herself, before switching to ecology. As soon as her research began revealing just how widely species were moving, her first thought was: “Diseases are going to move too.”

Her lab has traced the spread of leishmaniasis northward in Texas due to climate change, and the IPCC has tracked tropical diseases—malaria, dengue, and three others—emerging in Nepal for the first time on record. The culprit? Not new farming, but shifting climate.

New diseases are emerging further north, affecting mostly Inuit communities—which, Parmesan points out, may explain why politicians downplay it. In Europe, the tiger mosquito now spreads in France with its associated illnesses. Leishmaniasis is already present; more species are expected. Tick-borne illnesses are also advancing north in Europe. These are already clear effects of climate change on human health—even if most people aren’t aware yet.

But even for her, climate change can be hard to discuss with family:

C.P.: In my family, the only option is to not talk about it—and everyone’s fine with that. We love each other, we want to get along, we avoid divisive topics. If climate change comes up, it gets awkward fast, reminding us why we don’t bring it up. I’m sorry about that, but I don’t want to lose my family. If they ever want to know more, they know where to find me.”

Still, Parmesan has found common ground with people of very different beliefs, like Texas’s National Evangelical Association. United by a wish to protect biodiversity—whether as God’s creation or simply Earth’s inherent worth—they collaborated on climate education videos. The results? “Fantastic,” she says.

This article is published as part of the 20th anniversary of France’s National Research Agency (ANR). Camille Parmesan is a laureate of the ANR’s Priority Research Program “Make Our Planet Great Again” for France 2030, supporting fundamental and applied research across all fields, and leading national efforts in higher education and research under France 2030.