Mass Casualties From Climate Change

Until recently, scientists hadn’t been able to successfully project the effects of climate change—but not for lack of trying. Predictive studies have never quite agreed with one another, since researchers use different models of climate change that predict different numbers of extinct species (with results ranging from 0 to 54 percent).

Mark Urban, an ecologist at the University of Connecticut, took the predictions one step further by analyzing the extinction models of 131 previous studies. He found that one pattern was clear: as the rate of global warming increases, more species go extinct. So when Urban looked at the case of extreme global warming (4 degrees Celsius or higher) in his meta-model, he discovered that 16 percent of earth's species could disappear. His findings were published in Science this week.

In an article for Vox, Brad Plumer explained the caveats to this study, which include the possibility that climate change helps some species at the expense of others. He writes: 

“Likewise, as ecosystems shift, plants and animals will start interacting in new and hard-to-predict ways. Will that increase or decrease extinction risks? It's hard to say. ‘You can imagine a species that, as it moves, it gains a new predator — which increases its extinction risk," Urban explains. "But what if, at the same time, it also finds new prey, which decreases its extinction risk? So you get these very complicated interactions.’

Finally, humans are a real wild card here. As animals try to shift their habitat in response to warmer temperatures, we might end up blocking them from moving — say, because we've built roads or cities in their path. That could increase extinction risks. Or, alternatively, we could try to take conservation measures that help species adapt — say, by stitching forest fragments together, as Duke University biologist Stuart Pimm outlined more fully in this interview.”

Urban also tells Plumer that there are risks other than extinction:

“We're also seeing substantial changes in abundances and ranges. So even if we didn’t have a single extinction, we'd be looking at a substantial reorganization of biodiversity around the world. And that will have many effects, some detrimental to other species and human interests.”

The Audubon Birds and Climate Report projects a similar effect in North American birds. Some species could lose their seasonal ranges due to global warming; others could thrive. If both cases, the balance between overlapping populations could be upended.

Read the full story at Vox.