Looking through the fossil record representing the past 540 million years, Peter Mayhew and colleagues found that some historical periods of global warming greeted the world not with mass extinction, but with a boom in biodiversity. By looking through the record of fossilized marine invertebrates–creatures such as squid, snails, crabs, worms, sea stars and anemones–the researchers calculated how many different species lived during each historical period. They then correlated these estimates against records of historical ocean water temperatures. Taking these two sets of information together, the scientists argued that when the temperature goes up, so too does the number of species on the planet.
The reason for the jump, Mayhew told Nature, is that a little bit of warming would lead to an expansion of tropical habitats. The tropics tend to harbor more species in a given amount of space than mid-latitudes or polar environments, so more tropical area could lead to more types of species overall.
The scientists cautioned, though, that “he rate of change is very important.” Nature says:
For diversity to rise, he explains, new species need to evolve. And that takes between thousands and millions of years — much slower than the rate at which extinctions are likely to occur with today’s rapid change.
Another qualifer: This research only applies for sure to spineless sea creatures, not necessarily to all life on Earth. As such, the boom in biodiversity that accompanies some gentle global warming likely won’t be seen with the current aggressive rate of anthropogenic warming. Indeed, sea life is already being affected by modern change, thanks to the dual impacts of warming and ocean acidification. A recent report puts a fifth of all invertebrates at risk of extinction.