That doesn’t mean climate change won’t affect tropical forests of today. It already is. And it definitely doesn’t mean humans needn’t worry about global warming. Climate change will be the end of the world as we know it. But it also will be the beginning of another.
Mass extinctions will open ecological niches, and environmental changes will create new ones. New creatures will evolve to fill them, guided by unforeseen selection pressures. What this new world will look like, exactly, is impossible to predict, and humans aren’t guaranteed to survive in it. (And that’s if civilization somehow manages to survive the climate disasters coming its way in the meantime, from superstorms to sea-level rise to agriculture-destroying droughts). Still, experiments like Winter’s offer a glimpse.
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Adapting to a warmer world will be long and painful process for the rainforest, and many species won’t make it through. Even so, “there will still be tropical forests in 2100,” says Simon Lewis, a plant ecologist at University College London and the University of Leeds. They will probably even contain many of the same species ecologists know today, including some of the trees in Winter’s experiments.
It’s the relationships between those species, and the role each plays in the ecosystem, that will change—and, in turn, transform the entire forest. “The forests that come out of this change are probably going to be much different than the kinds of forests we have today,” says Christopher Dick, an evolutionary geneticist who studies tropical trees at the University of Michigan.
Winter’s data hints at one such change in forest structure. The three species that did the best under the highest temperature regime were the coralwood tree (Adenanthera pavonina) a species of fig tree called Ficus insipida, and the balsa tree (Ochroma pyramidale). Each is what Winter called “pioneer species,” fast-growing trees that can quickly move into cleared areas and take over. (F. insipida ups the ante, beginning life as vine that climbs up dead trees—and also living ones, eventually strangling them.)
These kinds of species are vital to a healthy rainforest, helping it regenerate after destructive events like a flood or the death and collapse of a large tree (when those things fall, they take out everything around them). But a mature rainforest needs the species that show up later, too. Those tend to be larger and longer-lived, stabilizing the forest and serving as ecological linchpins for insects, birds, monkeys, vines, and the rest of the ecosystem for decades or even centuries. And it was those so-called “climax species” that suffered the most under higher temperatures in Winter’s experiments.
That suggests that as climax tree species die in a warmer forest, they won’t be replaced. “One would expect that tropical futures of the future would be dominated by those nimble species that can disperse very well,” Lewis says. Pioneer trees that will put down roots anywhere, vines that grow into every nook and cranny, small rodents that reproduce quickly and scurry far, birds that can fly over vast swaths of land and aren’t too picky about where they nest. But that’s a small subset of the thousands of species found in tropical forests today. Without the rest of them, the rainforest will be a much simpler place.