Species may not be able to evolve fast enough to keep up with global warming, scientists have warned.
Researchers in Norway measured how quickly a tropical fish species can adapt to warming oceans – and predict that some will not survive.
The researchers at the Norwegian University of Science and Technology (NTNU) followed 20,000 zebrafish over four years and six generations.
They found that the creatures can adapt to warmer temperatures, but that the adaptation may not be quick enough to keep up with the pace of global warming.
Fredrik Jutfelt, an associate professor at NTNU’s department of biology, said: "We see that zebrafish can develop heat tolerance, and we have developed lines of zebrafish that can better withstand the heat. That's good news.
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"The problem is that evolution takes many generations. Evolution only increased the heat tolerance in the fish by 0.04 degrees C per generation.
“This is slower than the warming experienced by many fish in many places. It looks like evolution is slower than global warming in this case.”
The research was published in Proceedings of the National Academy of Science, PNAS.
"This is the largest artificial evolution experiment that has been performed on vertebrates with a focus on heat tolerance,” Jutfelt said.
The research group used zebrafish that were caught in the wild for their experiments.
The fish were then deliberately bred based on their ability to cope with the most extreme warm periods.
Evolution means that the individuals which are best adapted to environmental conditions produce more fertile offspring than other members of their species.
Over several generations, these changes can accumulate and alter the species itself.
One group of zebrafish also spent two weeks in warmer water prior to artificial selection, to see if evolution could increase their capacity to acclimatise
Jutfelt said: "It's unlikely that some zebrafish populations, and other tropical fish species, will be able to cope with the temperatures that the planet may experience by the end of this century.
“Some species that already live at the limit of what they can tolerate may not be saved by evolution. That is surprising and sad, and it means it is important that we stop warming the planet.”
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