Biodiversity loss

Biodiversity loss — driven by habitat destruction, pollution, climate change, and invasive species — threatens ecosystems, economies, and human well-being. Rapid species decline disrupts essential ecosystem services like pollination and water purification, while the loss of genetic diversity reduces nature’s ability to adapt to changing conditions, exacerbating the effects of climate change.

In this wide-ranging interview with AGCI, Dr. Camille Parmesan, Director of the CNRS Station for Experimental and Theoretical Ecology (SETE), in Moulis, France, explores the profound impacts of biodiversity loss on ecosystem resilience and sheds light on the vital role biodiversity plays in stabilizing the climate and maintaining the health of our planet, highlighting the need for conservation efforts and more sustainable practices.

AGCI: How is biodiversity loss a global change issue, and where is it occurring?

Camille Parmesan: Global change encompasses all the different human activities that are altering the natural environment. It’s a very broad term. One of the impacts of global change is biodiversity loss — species are being lost through habitat destruction, urban expansion, planting crops, pesticide overflow, and all the different types of pollution that humans create. Climate change is the latest human impact, but humans are also transporting plants and animals all over the world, creating invasive species in different areas. We’re in a human-dominated landscape now. Even 20 years ago, ecologists didn’t like to talk about pristine areas anymore, because none of us actually believe any area is pristine. And that shocks the public, because they say, “Oh, no, I went into Yosemite National Park and it was so beautiful.” Well, did you notice all the forest fires around you? Climate change is driving an increase in areas burned. They may look at the Mediterranean wild oats in the valley and see this beautiful sea of gold, but they’re not native to California and have killed off most of the local biodiversity. So the public doesn’t perceive anything like the level of destruction of natural biodiversity that exists.

Where is it worse? Well, Europe looks in better shape than, say, parts of Africa, where a lot of traditional old growth forest is being destroyed — but that’s because Europe destroyed its biodiversity 200 years ago. Humans have destroyed nature globally. We know where biodiversity loss is occurring most rapidly today. Africa, parts of Latin America, Brazil have had a real upsurge in habitat destruction. But no area on Earth is “blameless.” I mean, where you have people, people have destroyed nature.

AGCI:  How does the loss of biodiversity impact people’s lives and communities?

CP: Some biodiversity loss is very visible. That land used to be a beautiful park, and now it’s an office building. But that’s just the most obvious way we’re affecting biodiversity. There are so many more hidden ways — they’re not hidden to the wildlife, but they’re hidden to human eyes. Bringing in species from other continents and other oceans, for example. You get beautiful tropical fish for your aquarium, and then the kids grow up and no longer take care of it, so you just dump the aquarium into the local lake or stream. And you think, “What harm is that going to do?” And then suddenly, this thing ends up outcompeting all the local fish, and you’ve got a big problem. That happens a lot, and by the time the public is aware of it, it’s already a disaster, like with the zebra mussel in the Great Lakes in the USA.

It may take a few years or decades, but the ecosystem often no longer functions the way it did historically because you’ve changed the species present. Often, human activities end up simplifying systems, so you have fewer species, fewer links. Those simpler systems tend to not provide what we call “ecosystem services” to the same extent as the very diverse ancestral systems. They’re more fragile. And they’re less resilient to extreme climate events like drought and heat waves, which are becoming increasingly common with climate change.

Where you have people, people have destroyed nature.

Dr. Camille Parmesan

I was coordinating lead author of chapter two of the last Intergovernmental Panel on Climate Change (IPCC) report, which looked at how climate change is impacting terrestrial ecosystems. We concluded that one of the most important consequences of all the other global change forces was that it was making these systems less resilient to climate change. And that large systems with their traditional biodiversity intact were able to handle these climate shocks better than systems that had been invaded by an exotic species or had a lot of fragmentation from roads and urban expansion.

At this point, we have nearly runaway climate change. It is nowhere near being stabilized. Even though individual countries have done really well, globally greenhouse gas emissions are ratcheting up more than ever. And therefore, trying to stabilize the climate is getting more and more difficult.

And what was interesting is we were all coming together toward the same conclusions, that it’s no longer enough just to stop all emissions now. In order to stabilize the climate, we also have to suck up CO2 because we have too high levels of greenhouse gasses in the atmosphere.

So how do you suck up CO2? There are technological approaches, machines or chemical reactions that can take CO2 from the airspace and store it as a liquid or solid. But these are nowhere near scaled up to being able to actually reduce the level of CO2 in the atmosphere. What can do that? Well, plants have been doing this a long time and they’re really, really good at it! So in order to suck up large amounts of CO2 from the atmosphere, we have got to get our plant systems, our ecosystems, into better shape.

To date, the natural world has already sucked up something like half of the CO2 that humans have put out. But the capacity of our oceans and forests and grasslands to be a carbon sink and put CO2 into long-term storage has weakened. The wilds in the Amazon may look totally healthy and undisturbed, but they’re now sucking up less CO2. The oceans are becoming a weaker sink. Some of those huge permafrost-frozen peatlands in the Arctic that historically were a massive sink have flipped into being a source of CO2. That’s what we call a positive climate feedback. In other words, a native system started out healthy, but by warming that system up, through increasing drought periods and strange climate events of all kinds, that system is now actually releasing more CO2 than it sucks up. It’s become an overall net carbon source. And our conclusion was that the only systems that can suck up enough CO2 from the global atmosphere to make a difference are native ecosystems, natural ecosystems. So it’s imperative that we restore these degraded ecosystems quickly enough that in another 100 years, when those technological fixes come into place, they will be able to start helping us to stabilize the climate.

AGCI: How does your own work relate to understanding and addressing biodiversity loss as a global change issue?

My own field is the impacts of climate change. But now, no ecologist can work on just one global change factor because every natural system is being impacted by multiple activities simultaneously. So I try to focus on the systems that are least affected by all these other things. They haven’t had habitat outright destroyed. They don’t have a lot of invasive species. But even there, when humans come in, just putting a road in and dividing two pieces of land can cause the loss of individual species. And that’s very difficult to get across to the public. Roads act as a firebreak, so they can prevent natural fire from going through. They act as a barrier to dispersal. Animals, even tiny insects, try to cross a road and they get hit by a car and killed. It’s the number one cause of mortality of some animals in some areas. Even the butterflies I work on, they fly right at car height and the cars come along and hit them.

There’s this huge initiative in the USA for roadless areas. Conservation biologists realize that preventing roads going in could do more to save an area from all these subtle forms of destruction than almost anything we could do. If you could just keep the roads out and keep a large, intact area, it would be resilient to a lot of these other problems.

I actually wear two hats. On the one hand, I’m a field biologist and I work on Edith’s checkerspot butterflies and their host plants in the western USA. This single species and related species in Europe have told us so much about how climate change is impacting wild populations and the diversity of ways species can respond. This species has a long history of scientific research, so we know a lot about it. It’s very variable. From Mexico to Canada, it looks different everywhere you go.

And deeper than that, it has very different adaptations everywhere you go. And what we’re seeing in this single species is that some populations have genetically evolved to eat invasive species, which is great. Instead of going extinct, they’re able to shift from the traditional host plant to the invasive species. But what we found is that having done that makes them more susceptible to human land management changes. So this population we have been studying for 20 years went extinct because it shifted to the exotic host plant. Humans changed cattle ranching and this exotic host plant (a plantain) became unsuitable because taking the cattle off caused the grass to grow high and caterpillars could no longer use the plantain, so the whole population went extinct. If they had stayed on the traditional hosts (which were on the forest edge and never grazed), they would have been fine.

We’re also seeing evolution in response to climate change. Populations have changed the height at which they lay their eggs because the ground is literally getting too hot and it’s killing the eggs off. So you’ve had this very strong selection for them to raise their eggs up. Fantastic. This species is going to survive. Well, not so simple, because as you raise the eggs up, they get eaten by grazing deer. You’re seeing this very rapid evolution, which, as a scientist, is really exciting. But at the same time, that rapid evolution is making them more vulnerable to something else. So even where species are able to evolve in response to climate change, they’re not out of the woods. And that’s what we didn’t know.  We’re going back to our site this summer to see how the risk of being eaten vs. the risk of dying of heat are playing out in this population. People kept saying, if they can evolve, then they’ll be fine. But what we’re showing with our fieldwork is no, life isn’t that simple.

My second hat was spawned because of my work with IPCC. I started working with IPCC back in 1997 on the Third Assessment Report, when there wasn’t even a chapter for impacts on species. Everything was at the biogeochemical, ecosystem-level changes. So we had to bung together conclusions in weird places in the report because we didn’t have a chapter. Now it’s very well recognized, but at that time, we were trying to come up with just a simple statement in summary for policymakers: Climate change is affecting wild species.

We had to pull together all the literature because no one had pulled it together before. And that got me into the world of meta-analyses, working with other people’s data and pulling it together into a single synthetic conclusion that you can apply at a larger scale. So for the next decade, I was pretty much a meta-analysis person.

To do a meta-analysis on impacts of climate change, you really have to dig deeply into exactly where that data was gathered to tease apart the impact of climate change from all these other global change activities — habitat destruction, invasive species, pollution, pesticides, etc. You have to go into each study, often interview the person who did the study, where and how it was conducted. And now, with so many thousands of studies being published, and a lot of them not properly indicating the details we would need to know to be able to put it into a proper meta-analysis, we contented ourselves with a more traditional review approach. I’m still doing large synthetic studies, but I’m very, very happy the last few years to be getting back to doing the field work in California because we’re still finding out just amazing insight into the impacts of climate change from this one butterfly.

AGCI:  What do you see as the most important part of your work, and why?

CP: That’s not an easy question because each hat has a very important component. The most important thing we’re learning from the field work is that wild species are more resilient than we thought. That resilience gives us hope and buys us time, but it’s not going to prevent species from going extinct.

The most important thing we’re learning from the field work is that wild species are more resilient than we thought. That resilience gives us hope and buys us time, but it’s not going to prevent species from going extinct.

Dr. Camille Parmesan

One thing we’re seeing from all these hundreds of species moving around, trying to track climate space as it shifts geographically around the world, is hybridizations between distinct ecotypes, distinct subspecies, and even completely different species. The iconic one is grizzly bears and polar bears starting to hybridize. And the world of conservation is freaking out about this because managers have worked their lifetime to preserve the uniqueness of their system and their species within it. And in their minds, they’re seeing that destroyed by other species moving in and getting hybrids between them. Because I do these huge, global meta-analyses and syntheses, I see that climate change is having this massive impact on wild plants and animals around the world, and no single group is immune. There’s no such thing as a place on Earth immune from the impacts of climate change, or a type of species, a taxonomic group, that hasn’t been affected.

And yet we know, on the other hand, that resilience comes from diversity. The more a natural system or an individual species has its historical diversity, the more resilient it is to climate change. The more genetic diversity a population has, the more that population is resilient to climate change. At all these levels, diversity is the key. And we argued in a recent publication that as you hybridize things, it appears that you’re losing diversity. But if you think of diversity in a broader sense, that hybrid may be holding the genes for both of those species. So when we do stabilize the climate, you’ve got them there. The genes are hiding. With the help of modern genetics, we’re able to do much better estimates of what’s happened over the last several 100,000 years or more. And what we’re seeing is the polar bear actually disappeared several times from the paleo record during a few brief, warm spells. But it re-emerges very quickly once the climate gets cold again. So increasingly we believe that hybridization can preserve genetic diversity in a hidden way that may help those species reemerge when we stabilize the climate.

I’m very much promoting restoring areas that have been degraded to increase the protected areas even more. Or keep them in a managed state where they have healthy diversity. Allowing this flow of species, allowing the hybridizations in the hopes that nature will preserve its diversity in ways that we can’t see and allow it to come back more quickly if and when we ever do stabilize the climate. To me, one of the most important things I’m doing is pulling together what’s happening with Edith’s checkerspots to tell us what may be important for preservation of biodiversity at a global scale. It’s these insights from what’s happening in the field and recognizing the implications for the global transitions that we’re seeing — that linking, I think, is one thing I do best and one thing that a lot of people don’t have the experience to be able to do.

AGCI: What do you see as the biggest biodiversity challenges on the planet today?

CP:  One thing that’s really obvious is population growth. Paul Ehrlich came out with The Population Bomb in 1968 and said one of the biggest problems globally is population growth. And he’s still right. It is the biggest problem to stabilize the climate, to keep the quality of life high for the people that are here. Population growth is a huge issue, and it’s incredibly politically divisive. We had huge arguments with governments about the extent to which we could support this in our IPCC Summary for Policymakers. All the different global change factors affecting wildlife and biodiversity would be relieved by stopping population growth. Stabilizing the population numbers and even reducing it, that’s all you’d have to do, and a lot of these problems would fix themselves.

The second big problem, which is very related, is how do you keep 30 percent to 50 percent of the planet as natural, healthy ecosystems — which we argued is necessary for stabilizing climate, both in the oceans and on land — how do you do that and feed this ever-growing global population? In one way, it seems so easy to fix. Many nations have stable populations and have healthy economies and it’s not a problem. But globally, the population is certainly not stabilizing.

I think a lot can be done to improve our food systems to be more amenable to some level of natural biodiversity. It’s not going to be the same as a big, intact, healthy ecosystem. But you can have farmlands and ranch lands that are managed much more sustainably than they are now, that can have reasonable biodiversity. Where we live now in southern France, we bought a 100-acre farm and put cattle on it. We have a farmer manage it for us. We’re interested in butterflies and very quickly found out that you have to keep the meadows open because otherwise it’s all forest. And much of the biodiversity is meadow biodiversity. The flowers, the insects, the birds are reliant on meadows, and those meadows have to be maintained. You either have to cut it for hay or have something graze it. So we decided to just watch it for a year. And we did a little survey and found two dozen different butterflies that are resident on the farm, two of which were incredibly rare on a European-wide level. And so we went to the farmer and found out he uses very traditional methods: no commercial fertilizers, no pesticides. The grazing is very low impact, there’s no overgrazing. He cuts the hay very traditionally; it’s allowed to dry in the field, so all the seeds drop. And we found out that you can produce food —  in this case, beef — and have incredible biodiversity.

Now that is kind of special to this area and to the climate we have. The IPCC had a whole chapter five on food and agriculture. And it was great working with the authors of that group because we were concluding the same thing: When you intermix native species with domesticated species, you can create a more resilient source of food. So you’re mixing native nut trees and fruit trees with low-level shrubs, tomatoes, and things like this. By keeping a buffer area that’s natural habitat around that, you increase the pollination of the crops that you’re trying to grow. By lowering or eliminating pesticides, you’re keeping the native pollinators healthy. And systems that are managed in this more traditional, more sustainable way tend to be small, diverse plots that are more resilient to climate shocks. Those are the places where if you get a drought or heatwave, they will lose some things, but they’ll always have a crop, something that has managed to survive through that. Whereas the big wheatfield next door gets entirely lost.

Even in food systems, diversity matters. And there are ways of doing this that can go hand in hand with preserving quite a lot of the local biodiversity. Not all of it. You have some species that are native to very deep old-growth rainforests that you’ll lose when you start putting food in. But an awful lot of diversity can be mixed in with food management. The yield tends to be lower, but a lower yield that’s steadier year to year is better than a boom-and-bust monoculture crop that is not resilient to climate shocks and needs huge inputs of fertilizer and pesticide. It’s just a very different way of thinking about how we live in this world.

AGCI:  What do you see as some of the most exciting opportunities to address those challenges in the coming decades?

CP: Ecotourism can be a solid economic base for a region or a country. When I first started working on this 30 years ago, ecotourism was very new and untested. We need to be doing it a lot better than we’re doing. It has to be done carefully and with more than the economy in mind. You’ve got to have people understanding the natural systems and trying to keep the ecotourism at a level and approach that is not in conflict with local biodiversity. I think some places are doing it really well and some places are absolutely not. So it is an opportunity, but it’s not being done right a lot of the time.

AGCI: Why should all people care about biodiversity loss whether or not they’re seeing its impacts locally?

CP: They need to care about it because their lives are dependent on it. People aren’t seeing the connection between the food they get in the grocery store, the clean water they get out of the tap, the clean air they’re breathing, and all the big, natural ecosystems that are providing all of that. And that is a tough one. I’m working on a human-nature interaction project with a psychologist, a young postdoc interested in conservation and biodiversity. And she was worried about the life her four-year-old daughter was going to grow up into. She developed these educational modules in real schools with real children. And I said, I bet we can teach five-year-olds about climate change. And, lo and behold, we did it, teaching them in an outdoor classroom in a natural area. Like, here’s a tree, that’s carbon. Here’s a lump of coal, that’s carbon. Five-year-olds get it.

She really got me more into that literature, and it’s very, very clear in a meta-analysis that we published, that when humans really spend time in nature, either doing yoga or walking through, they literally have better health. This was from thousands of people and around 250 studies around the world. And not just correlational studies, but experimental studies showing that when you get people to be mindful, to just go out and be in nature and close their eyes and think about what they’re hearing or open their eyes and think about what they’re looking at, it’s like a meditation. When they forget their job, forget whatever they’re stressed about, forget their financial worries and just be there in nature, they have better blood pressure, they feel better, they have more energy, they feel more relaxed. And it’s fabulous to see the data. Just spend an hour every Saturday in your local park, really being there — not doing anything, not on your iPhone, not talking to someone — just be there and see the effect it has. And it turns out it has a highly significant positive effect on individual health and well-being. I would have thought that, but it was just fabulous to be part of that meta-analysis and see it’s the power of nature. It’s wonderful.

Dr. Camille Parmesan is Director of the CNRS Station for Experimental and Theoretical Ecology (SETE, in Moulis, France) and brought to France as a “Make Our Planet Great Again” Laureate. Her research focuses on the impacts of climate change on wild plants and animals and spans from field-based work on butterflies to synthetic analyses of global impacts on a broad range of species across terrestrial and marine biomes. Her 2003 paper in Nature was ranked the most highly cited paper in the field of climate change (Carbon Brief, 2015), and she was named the 2nd highest-cited author in climate change (T Reuters). She is an elected Fellow of the European Academy of Sciences, Fellow of the Ecological Society of America and Honorary Fellow of the Royal Entomological Society. She received the Conservation Achievement Award by the National Wildlife Federation and was named “Outstanding Woman Working on Climate Change,” by IUCN. She has worked with the Intergovernmental Panel on Climate Change for over 25 years, and shares in the IPCC’s Nobel Peace Prize (2007) and Gulbenkian Prize for Humanity (2022). She was a Coordinating Lead Author for the Intergovernmental Panel on Climate Change (IPCC) 6th Assessment Report (2022). Professor Parmesan also has affiliations with the University of Plymouth (UK) and the University of Texas at Austin (USA). 

See Dr. Parmesan’s AGCI workshop participation and presentations.