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When Thomas Lovejoy traveled to the Amazon as a young biologist in 1965, massive highways, farms, and ranches had hardly yet crisscrossed the jungle. Stunned by the rainforest’s riches (and by the colorful manakins—his favorite birds), he later coined the concept “biological diversity” that described what he saw.

As development encroached in the region, he launched to understand the ecosystem's respose. Forty years later, the experiment remains the world’s  look at the real-world effects of habitat fragmentation. Though the initial forest clear-cutting occurred decades ago, the effects are still playing out.

Over a long and varied career, the “godfather of biodiversity,” as Lovejoy is now , turned his attention beyond Brazil. As the threat of climate change emerged, his 1992  became the first to examine its biological consequences in detail. Now in his late 70s, he is still speaking and publishing words of warning and advice as the planet continues warming—that includes a new book, in January, that follows-up on that earlier work.  

Sporting a flock of colorful birds on one of his trademark bowties, Lovejoy joined  to accept its 2019 Environmental Leadership Award . In an interview, Lovejoy spoke about his recent efforts to urge action as time left to avoid irreversible ecological crisis whittles away. 

���Ϲ���: In the new book you co-edited, , what’s different since the last edition came out? What more do we know about how climate change affects the planet's species? 

Lovejoy: In the first book, which was actually 1992, all you could do is look at the geologic path to try and guess. In the second, in 2005, you could just basically see the footprint of climate change anywhere you looked on the planet. By this one, you could see enough impacts around the world to conclude pretty clearly that more than 1.5 degrees of warming would be really bad for the biology of the planet—and make it basically impossible to manage biologically. The reason is, with more climate change, ecosystems literally start to come apart. It’s very hard to predict how any particular one will be impacted, because modeling doesn't tell you. It's all about the idiosyncratic relationships between species.

The cover of our book is a musk oxen because when they forage in winter, instead of having to brush snow away to get to the vegetation, it's very often frozen ice. So they are raising underweight calves.

We all know what's happening with coral reefs. We all know what's happening with coniferous forests in North America, where the balance [of the ecosystem] tipped in favor of the bark beetle. Those are just the first kinds of examples of what’s going to be happening all over the place, and at a greater scale. So, don't ever let anyone tell you that 2 degrees [of warming] is OK.

A: Is it the uncertainty around these ecological tipping points that's most scary? That we don't know when we will hit points of no return.

L: In ecosystems, it's really hard to predict where they will be, so the best thing to do is not go there. That's the idea of trying to stop at 1.5 degrees. Of course, there's this really good news in one sense. In January 2018, there were new estimates of how much carbon was in the atmosphere from destroyed and degraded ecosystems. It turns out to be much bigger than anyone had thought—literally equal to what remains in extant ecosystems, which gives you a real sense of scale. But it also represents an opportunity for ecosystem restoration, to pull that carbon dioxide and avoid a lot of the associated global warming.

That's a really, really important conclusion. In it is the seeds of people beginning to understand that the planet actually works as a linked physical and biological system. Quite wonderfully, it takes this challenge from being something that people say — "well, what can I possibly do?"—to one where everybody can do things like plant trees or help restore wetlands and pull some of that carbon back.

A: You  about certain levels of deforestation at which the Amazon rainforest ecosystem risks flipping to savanna, because the hydrological cyle can’t sustain itself. Do you see climate change increasing this risk?

L: What's spooky, but also interesting, is that there is a negative synergy going on between deforestation, climate change, and extensive and unprecedented use of fire. There have been historic droughts, in 2005, 2010, 2016, which Carlos Nobre, the leading climate scientist in South America, and I agree are probably the first flickers of that tipping point. The good news is that you can build back a margin of safety by  doing reforestation. But it's really close. So action is needed now.

A: Your habitat fragementation study in the Amazon is now 40 years old. You told me earlier you're now thinking about its future. What are you working on?

L: There is literally no place on the planet, other than this particular experiment, where people will be able to follow the consequences of habitat fragmentation over time. Most of the studies have been sort of snapshots. That led me to realize that this [work] has to go on longer than I would be around.

That has led to the creation of the , with a joint U.S. and Brazilian board, with the beginnings of some endowments and a lot of fundraising ahead. But the idea is to institutionalize this for its science and environmental implications, for the capacity-building to train students, and also to continue to bring these semi-mythical creatures called decision makers to the Amazon forest to understand its biodiversity. 

A: In April, you were also one of many co-authors of a new Global Deal for Nature proposal. It puts forward ambitious goals that grapple with both species loss and global warming. What’s the thinking behind it?

L: that was published was the first time we put together, essentially, a map of biodiversity conservation goals together with the elements of the natural world that we need to have a sustainable planet — so some of the ecosystem restoration side of things. Basically, it’s both biodiversity goals but also: 'How do you manage the rest of nature in such a way that those targets will have a viable future?’

A: At ���Ϲ���, we all know your quote about birds: “If you take care of birds, you take care of most of the environmental problems of the world.” Right now, are you optimistic or pessimistic about the future for birds?

L: I don't think there's any choice in the matter. One has to be optimistic. If one is pessimistic, one is not likely to try hard enough. If you are optimistic, you will look for ways to secure the future of birds and biological diversity on the planet.

This interview has been lightly condensed and edited for clarity.