Species' temperature tolerances remain unchanged during past global warming and cooling

What is it about?

We tracked species' temperature tolerances across the last 700,000 years of global climate change, including 7 ice age cycles. We focused on a type of plankton called foraminifera, which is a key component of the base of marine food webs and of the carbon cycle. If a species adapted to environmental change in place, one would expect the temperatures observed at that species' locations to correspond to the global mean temperature at the time. Instead, species occupied the same temperature ranges regardless of the magnitude of global warming or cooling through time. These results suggest that when climate changes, marine species move to find habitats to which they are already adapted rather than staying in place and adjusting to new environmental conditions.

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Photo by Jeremy Bishop on Unsplash

Photo by Jeremy Bishop on Unsplash

Why is it important?

There are many unknowns and challenges in studying how species are responding to present-day climate change. By using the fossil record we can learn how species moved, adapted, or went extinct during past periods of climate change. Calcifying plankton have an exceptionally good fossil record, which means we can reconstruct their ecological history over a long time interval in more detail than for many other organisms. It is also important to learn about plankton because ultimately they support all large animals in marine food webs. Our conclusion that certain plankton don't change temperature tolerances even during ice ages suggests that ongoing global change could redistribute and reduce populations of plankton and other widely dispersing marine species.