Global Warming Good for Biodiversity? Only at a Big Cost

A study just out in Proceedings of the National Academy of Sciences is both important and confusing — important for people who know how to read through a scientific paper, and confusing for the rest of us. It’s confusing because the bottom line is that biodiversity — that is, the richness of species — is likely to improve in a warmer world. Since ecosystems with high biodiversity are the healthiest and most resilient, this is presumably a good thing.

But it doesn’t seem to square with what scientists have been saying for some time: that we’re losing biodiversity as the Earth warms. In fact, many say that the planet is in the midst of a sixth mass extinction, of the same sort that wiped out the dinosaurs 65 million years ago.

A wall of biodiversity at the American Museum of Natural History, New York City.
Credit: Dano/flickr      

One major reason is the global warming triggered by our burning of fossil fuels, although land use changes as we build cities and roads and eradicate rainforests is another big factor.

The key to this seeming paradox is time. “Increases in global diversity take millions of years, and in the meantime we expect extinctions to occur,” co-author Tim Benton, of the University of Leeds, said in a press release.”

In previous research, the same scientists had concluded that a warmer world would feature less biodiversity. Their evidence came in the form of ancient marine fossils: if you look at back at the past 540 million years or so of the planet’s history, there seemed to be fewer species during periods when the Earth’s temperature was higher. This seemed odd, since today there’s more biodiversity around Earth’s warm equator than there is in temperate and polar region.

Now, however, the researchers are saying, in essence, “never mind.” It’s not that the earlier research was wrong, exactly. It was just based on data of uneven quality. Scientists had counted all the species they could find in the fossil record and came up with a correlation between warm climates and a paltry numbers of species.

This time around, they took account of the fact that some periods in the fossil record have been much more thoroughly sampled than others. When you rely only on the well-sampled periods, it turns out that warm climates tend to have more species after all.

What this means is that global warming could ultimately end up being a good thing for the planet. But things are likely to be awfully unpleasant for existing species along the way, and that includes the human race.