Climate Change Is Freezing Earth’s Fauna in Place Andriy Onufriyenko – Getty Images
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Species turnover accompanies changes to ecosystems, and as climate change accelerates, this process should happen faster as animals under stress venture into new ecological niches.
But a new study finds that the opposite is actually occurring as climate change decreases the numbers of potential colonizers.
Scientists from Queen Mary University of London discovered this trend while analyzing millions of survey records from freshwater, marine, and terrestrial environments.
Species turnover is a ubiquitous phenomenon, but environmental shifts can speed up or slow down the process. In the face of accelerating anthropogenic climate change, scientists expect the overall number of species being replaced in Earth’s various ecosystems to increase. As species face extirpation in one place, the theory goes, they’ll move into new ecological niches and supercharge turnover rates there.
However, a new study published in the journal Nature Communications finds convincing evidence that worldwide species turnover has actually been slowing down. In the research, Emmanuel Nwankwo and Axel Rossberg from Queen Mary University of London analyzed a massive open-source dataset called BioTIME database of surveys, which contains nearly 9 million species-identification records for freshwater, marine, and terrestrial ecosystems.
While the database stretches back to the 19th century, the researchers focused on data pertaining to the 1970s onward in an effort to capture modern trends. What they found is that in one-to-five-year periods, there was an average turnover slowdown of one-third across all ecosystems—contrary to theoretical expectations.
“Nature functions like a self-repairing engine, constantly swapping out old parts for new ones,” Nwankwo, lead author of the study, said in a press statement. “But we found this engine is now grinding to a halt.”
So what exactly is going on here? Well, researchers describe a somewhat counterintuitive state of ecosystem affairs they dubbed the “multiple attractors” phase. Instead of passively reacting to environmental changes, during this phase species are constantly turning over in an ecosystem, which researchers describe as an “unending game of rock-paper-scissors” or a “revolving door” of species turnover. The X-factor is the widespread degradation of the environment caused by anthropogenic climate change. It’s shrinking the regional pools of candidate replacement species, so potential colonizers of new ecological niches are disappearing—and not getting replaced.
“The observed slowing of turnover, we argue, could be understood…as resulting because anthropogenic environmental degradation or declines of regional species pools reduce the number of potential colonizers driving turnover,” the authors write. “Although one can expect environmental drivers to dominate species turnover eventually as climate change accelerates further, for now such attribution should be done with caution.”
This means that a lack of change in local species isn’t necessarily an indicator of good ecosystem health. The authors caution that ecosystems are immensely complex and estimates of total species turnover can be affected by short-term climate variability (i.e. El Niño or the Southern Oscillation phenomenon) or even by variations in the methodologies used to analyze the datasets. But the evidence suggests that environmental shifts related to climate change are proving even more deleterious to Earth’s ecosystem dynamics than scientists expected.
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