An analysis of more than 300 marine plant, animal, plankton, and fish species found that they’ve increasingly moved towards the poles as the climate grew warmer over the last century. Their abundance has also been changing as the species adapt to shifts in suitable living areas.
One of the silver linings of the study is that the warming is opening up new habitats towards the pole, which cold-water species are taking advantage of. Species towards the Equator, however, are declining as large swaths of their habitat become too warm to tolerate.
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“We drew together an extensive collection of survey records that reported how species abundances have changed over the last century, as the world’s oceans warmed by over 1°C,” says Martin Genner, Professor of Evolutionary Ecology at the University of Bristol’s School of Biological Sciences, who guided the research.
“We then identified the location of each study in relation to the full global distribution of the species and asked if abundance changes depended on where a species was studied.”
The metastudy was carried out by researchers from the Universities of Bristol and Exeter, and reviewed 540 previously-published records. Louise Rutterford from Bristol School of Biological Sciences, co-author of the paper, explains that they predicted that each species would increase in abundance towards the poles, and decrease towards the “equatorward side of its range, as temperatures become too warm to survive”. Their prediction proved to be true.
For example, populations of Atlantic herring and Adélie penguins were both declining in abundance at the warmer edges of their ranges and increasing in abundance at the cooler edges of their ranges. Some marine species do seem to benefit, overall, from a warmer climate, as they can now thrive closer to the poles, in areas that were previously too cold to bear.
“Meanwhile, some marine life suffers as it is not able to adapt fast enough to survive warming, and this is most noticeable in populations nearer the equator. This is concerning as both increasing and decreasing abundances may have harmful knock-on effects for the wider ecosystem,” Rutterford adds.
Overall, the findings strongly suggest that such changes will continue — and perhaps amplify — in the future, as temperatures are predicted to rise past 1.5°C over pre-industrial levels by 2050. The team believes this will translate into opportunities, such as larger catches of warm-water species, but also hazards, such as greater populations of warm-water parasites around aquaculture. These changes could also lead to greater instability in marine ecosystems.