In this interview, Jill Stoddard, Editor-in-Chief of the Global Observatory, talks with Brad Cardinale about the scale and irreversibility of the biodiversity crisis.

Dr. Cardinale is an ecologist who focuses on the conservation and restoration of biodiversity in natural systems, as well as the ecological design of human-engineered systems that benefit from the use of native species and biodiversity. He is Head of the Department of Ecosystem Science and Management and Penn State University.

The interview has been edited for clarity and length.

Recently, I spoke with a Yale economist who said climate change is not the biggest issue affecting our survival right now.

I would agree with that. Climate change will have a substantial, somewhat more immediate impact on humanity, though I would personally be much more concerned about biodiversity loss. I don’t want to minimize the impacts of climate change, but there are ways to adapt, and it is also reversible. We know that if we stop fossil fuel consumption, we can reduce emissions. We also know how to pull carbon out of the atmosphere. And there is an enormous amount of money and attention being put toward this.

Biodiversity loss isn’t reversible like climate change. Once a species goes extinct, it’s gone forever. And everything you eat, drink, and breathe comes from a species somewhere, and if you lose those species, your ability to eat, drink, and breathe might be permanently damaged, and that could be irreversible as well. We can’t genetically engineer our way out of it at the moment.

How bad is the crisis?

In your and my lifetime, we are on track to lose about one-third of all species that exist on the planet. That’s unevenly distributed among species, so mammals, for instance, are in a much greater threat than, say, certain kinds of insects.

If we continue on the current path, where we are taking away natural habitats, reducing species population sizes, and threatening species with things like pollution, climate change and poaching/over-harvesting, the projection is that we will be at the point of a mass extinction within about two or three human generations. And a mass extinction is defined as a 75 percent loss of all species on the planet, so imagine that your great-great-grandchildren are in a period that’s comparable to when we lost the dinosaurs from the planet.

So I think the crisis is pretty bad—though I do think the facts can get overblown by some who claim we are currently in the midst of a mass extinction.

In 2016, the biologist E.O. Wilson said, “We really don’t know that much about biodiversity.” So how do we know which species are… I don’t want to say important, but critical to our survival? Or should we work to save every species?

Nobody in their right mind would say we have to conserve everything. First of all, it’s impossible. We don’t have enough time, people, or money. In addition, we have the problem that we haven’t yet discovered everything. But once it’s discovered and we add it to our mathematical models, we can get an idea of which ones (and how many) are the most important. Right now, we have pretty good experiments and mathematical models that can tell us exactly how many species are required to maintain productive ecosystems—meaning ecosystems that can maintain fertile soils, and grow plants where the plants can feed both humans and wildlife.

We can also calculate the number of species we need to conserve in order to maintain ecological processes that produce goods and services, such as the production of wood and food and pest control. We’ve only developed these calculations in the past couple of decades, and we are now pretty close to being able to say which species are the highest priority, and which are perhaps the lowest priority.

For plants and animals that prove to be less important to humans, there is the big question of, are there other reasons for us to conserve them? We don’t have infinite knowledge and we’re not quite sure whether or not one that seems unimportant now has a function we haven’t discovered yet. Or if it will become important in the future when the climate changes and suddenly it’s the one that makes up for an extinct species.

So we have uncertainties that we’re wrestling with, but maybe I can provide a different perspective from E.O. Wilson—who liked to inspire people through these statements about the wonder of biodiversity—that it’s not as if we don’t have knowledge. The science has evolved a lot, even though it’s imperfect.

Though to his point, we’ve only scientifically categorized just over a million species, while the estimate is that there are well over nine million multi-cellular species, and maybe a trillion different kinds of prokaryotes like bacteria, viruses, the vast majority of which we’ve never even seen on Earth.

So, we can’t save everything. How do we know what we should we focus on?

There are calls from the United Nations and others to set aside a certain fraction of the Earth’s land surface and the world’s oceans to simply provide refuges and habitats for species regardless of how humans prioritize or use them. This is probably the most important conservation initiative if we want to save biodiversity and leave those biological options available for us when we don’t know everything that species do.

Keep in mind, we are constantly revising the estimates of how much land and water are needed to conserve the world’s biodiversity, and we’re revising them as countries who had previously committed to what were called the Aichi targets. And so the United Nations, along with partners, are redefining what those goals should be and seeing if we can get commitments from countries. Current calls are to set aside 30 percent of the Earth’s land surface for things other than just humans, and to set aside roughly an equal amount of marine protected areas that will save biodiversity in the marine environments.

These numbers differ according to who’s leading the initiative. E.O. Wilson called for 50 percent of the world’s surface to be set aside—the so-called Half Earth project. His argument is that half is needed for humanity to have cities to live in and produce food, and half is needed to save even a reasonable fraction of the world’s species needs, and should be set aside for purposes of conservation.

Do you think that the approach offered by frameworks like the United Nations COP 15 is enough?

I think any global problem—climate change, plastic pollution in oceans, biodiversity—requires agreements and actions that occur at levels that range from local involvement in decision-making to more regional government decision-making to international agreements. And COP 15 is intended to form international agreements and set goals that the majority of countries will agree on and aspire to, and I think having those goals certainly initiates national policies and actions that are critically important for achieving biodiversity conservation.

But they’re insufficient in the sense that, ultimately, biodiversity conservation comes down to local decisions and local actions, and the local people who oversee or use those resources are going to be the ones that either have to protect them or change their behaviors.

These international agreements can set targets and they can incentivize, but we also need the bottom-up approach. In my country, it’s the state governments that set policies and laws that incentivize certain forms of change. Unless those occur simultaneously, we’re just not going to reach those goals. So, is COP 15 important? Absolutely. Is it enough? No.

Are we at least headed in the right direction?

Well, one big change that has happened in the past two decades is that conservation has moved away from the idea of setting aside land or water where everybody is kept out, or where visitors can go in but nobody can touch anything or take anything out. Now it’s more focused on whether we can get agreements among the people who locally manage the habitat to harvest in a way that’s more sustainable, so the area has a net population growth of endangered species. It’s about integrating people’s needs and land management and sustainable development. And even if we use the land, we do so in a way that ensures the survival of endangered species over time—and that’s been key to getting buy-in, particularly in developing nations where people still rely on those resources.

It will be a big challenge to get international agreements where both developing and less developed nations can agree on conservation goals. But all of the data suggests that, once we get agreement, then we head in the right direction. As of a few years ago, we were close to achieving the goals for creating marine protected areas, which were created mostly in rich developed nations. However, our terrestrial levels are falling well short of the 30 percent land that was set aside for initial targets and way short of the Half Earth project that E.O. Wilson and others advocate for. Nevertheless, we are setting aside more and more protected areas and terrestrial land surface, and we are including indigenous lands as part of those areas where we know that they’ve been better managed for natural resources and sustainable growth than they have in the past.

There’s also been a recognition that the historical approach to conservation has been unjust. We’ve often kicked people out of land that was theirs to begin with in order to make a national park or a reserve. If you’re a fisherman whose livelihood depends on a marine protected area that gets taken away from you, then we as conservationists are having major impacts on people’s livelihoods, and that just doesn’t work. The same applies in developing nations. You can’t just go into a developing nation and say, “You can’t cut down your forest anymore,” when in fact, their ability to build a viable economy depends on it. You can’t just say, “We want you to protect lions,” when in fact there’s conflict, and lions are eating people’s livestock.

Are there countries where the local or national government has integrated biodiversity into their national plans, or come up with some innovative ideas to protect their biodiversity?

I’ll try to give a couple of examples from different regions that are making at least some effort. Costa Rica might be the best-known example. Their number one form of income for the entire country is ecotourism, so in protecting nature, they’ve created a whole economy that the country revolves around. There are numerous examples now where people’s well-being and nature’s well-being can go hand-in-hand, and that’s a fundamental shift in the way we now think about conservation.

Canada and Australia, who have historically taken land away from indigenous and aboriginal people’s control, are now giving the land back to those cultures that had once maintained them, partly because it’s the right thing to do from a perspective of justice, and partly because it also helps meet the international goals for biodiversity conservation. A few years ago, Justin Trudeau converted a decent amount of land in Canada back to indigenous people’s management in part as a way to reach international goals for biodiversity conservation.

China has “green sponges” in many of its cities, which are these very large natural areas that can absorb water. It’s an important win-win during a period where China is undergoing rapid development. China is accomplishing its own goals through green infrastructure and biodiversity, because it recognizes that if you have pavement everywhere, it causes extensive flooding and a lot of loss of life and property damage. China also recognizes the importance of conservation and is starting to become a leader in conservation by setting aside green spaces and national parks.

And in Africa, Namibia is perhaps the best example where the World Wildlife Fund (WWF) is working with local peoples to establish ecotourism and conservancies that generate new revenue for local peoples, building on models like Costa Rica, where people from richer nations are willing to spend money to just have a chance to see rhinos and lions, and not necessarily shoot and kill them.

Are there places where adaption and mitigation efforts around climate and biodiversity overlap so that when designing policy, there are efforts that help both?

A lot of people talk about how climate change is going to be the single biggest contributor to biodiversity loss. I’m pretty skeptical of that, as it’s based on models whose assumptions have proven to be flawed. The models do seem to suggest that we’re going to lose a lot of species because they won’t have a place that is the right temperature for their existence. But what is not in the models is that some species can adapt, so for instance, lizards can go under a rock and thermally regulate. Other animals can have changes morphologically, and physically. So, are climate change and biodiversity related to each other biologically, physically, chemically? I think the case for that is less so.

But should climate change and biodiversity loss be considered together? The answer is a yes and no. Yes, they should be integrated because they’re the two biggest forms of environmental change in the modern era. Yes, they should be integrated from the sense that things are going to shift around the globe and that’s going to have major social disruption and major economic impacts. But no, in the sense that climate change is probably not going to be the dominant contributor to the world’s extinctions.

When looking at slowing climate change, individual actions will have some impact, but the real impacts need to come through policy and larger investments. Is that also true with biodiversity loss? If I’m an individual, are there things I can do?

Sure. Here are a couple of things individuals can do. One is, speak your values with your purchasing, and be conscientious of what you’re purchasing. The single biggest contributor to biodiversity loss is habitat loss, and habitat loss very often is driven by what people purchase or buy. An example is the coffee you buy—shade-grown coffee is better for the environment and its biodiversity than coffee purchased from a company that destroys an entire rainforest to grow coffee plants. Also, a lot of things contain palm oil, but every time you purchase it, more of a rainforest is cut down and, as a result, orangutans are being killed. In some instances, there are organizations that will help you with purchasing. An example of that is the Monterey Bay Aquarium Seafood guide that you can put in your wallet and take to the store to help you purchase sustainably grown seafood.

The second thing is, if you’re so inclined, donate to an organization that’s involved in conservation and protection—there’s a lot of them out there. The Nature Conservancy and World Wildlife Fund are sort of the big global leaders, but almost every location has a local organization that’s trying to conserve or manage local forests or local streams or local habitats, so donate or get involved.

And then the third thing is, vote wisely. In political systems that have elections, elected officials are the ones that set policy.

Of course, people’s reasons for caring about biodiversity are very different. Some really respond to this idea that species and the variety of species are essential to our quality of life because it cleans up our water, protects us against storms, provides us with food. Other people respond to it as a generational thing—nature was really important to their family because they used to go fishing together or get together at a cabin, and nature was a backdrop for family.

And then some people, including those in my family, couldn’t care less about those two things, but when the Pope comes out and says, “We need to protect God’s creation,” they’re like, “Well, I’ll listen to the Pope because we’re Catholic.” So some want to protect it because of a religious or spiritual idea that it was a creation, and we are stewards of it.