Rising ocean temperatures are pushing marine species towards the poles

• Rising ocean temperatures are pushing marine species away from the equator and towards to poles, a new study has found.
• This was true not just of fish, but also seabirds, marine invertebrates and plankton.
• Both increases and decreases in populations can have adverse effects on the ecosystem.

Marine species are relocating towards the poles due to rising ocean temperatures, scientists have said.

The researchers, including scientists from the universities of Bristol and Exeter, looked at data on over 300 marine plants, birds and animals spanning more than a century.They found a “general pattern” where species showed increasing population densities towards the poles but declines in numbers in the habitats near the equator.

The team believes its findings, published in the journal Current Biology, indicate rising temperatures have led to widespread changes in the population size and distribution of marine species.

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Martin Genner, an evolutionary ecologist at the University of Bristol and senior study author, said: “The main surprise is how pervasive the effects were. We found the same trend across all groups of marine life we looked at, from plankton to marine invertebrates, and from fish to seabirds.”

The world’s oceans have warmed by an average of 1°C since pre-industrial times, the researchers said.To find out how this temperature change has affected marine life, the team reviewed 540 published records of species abundance changes – their occupancy trend over time.

This is concerning as both increasing and decreasing abundances may have harmful knock-on effects for the wider ecosystem

Louise Rutterford, study author

They found certain species to be thriving well in the cooler regions of the oceans, with rising temperatures opening up previously inaccessible habitats. For example, the researchers said, the populations of Atlantic herring and Adelie penguins were both declining in abundance near the equator but increasing in abundance towards the polar regions.

But they found conditions of habitats near the equator were too warm to tolerate.

Louise Rutterford, a study author based at both Exeter and Bristol universities, said: “Some marine species appear to benefit from climate change, particularly some populations at the poleward limits that are now able to thrive.

“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.”

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With warming predicted to increase up to 1.5°C over pre-industrial levels by 2050, the researchers said species are likely to undergo further shifts in population distribution in coming decades.

Prof Genner said: “This matters because it means that climate change is not only leading to abundance changes, but intrinsically affecting the performance of species locally.

“We see species such as Emperor penguin becoming less abundant as water becomes too warm at their equatorward edge, and we see some fish such as European seabass thriving at their poleward edge where historically they were uncommon.”