Some fishes have to travel farther to adapt to a changing climate

December 2nd, 2011 by Technical University of Denmark

Even though the oceans warm up slower than land, a recent study, The Pace of Shifting Climate in Marine and Terrestrial Ecosystems, published in the scientific journal, Science, shows that marine life has to move their ranges just as quickly as species on land to cope with the changing temperatures.

This is the first time that the rate at which marine species have to change to cope with global warming has been quantified.

Animals and plants are optimally adapted to their surroundings. Therefore, when temperatures change due to global warming, plants and animals have to find ways of coping.

One way to cope can be to relocate to areas with temperatures like those the species are used to.

Another option is for the animals or plants to change the timing of seasonal events like hibernation, breeding, spawning or migration.

“It is well-known that plants and animals can cope with global warming by relocating or changing when, for example, they hibernate or breed.

But until now, nobody has looked at how fast these changes would occur,” says Senior Research Scientist Keith Brander from the National Institute of Aquatic Resources (DTU Aqua) in Denmark who is one of the authors of the study.

Seventeen experts from around the world gathered information from global temperature records from the last 50 years as well as from over 300 scientific papers concerning how increasing temperatures affect animals and plants on land and in the sea.

Spring temperatures arrived 5 to 10 days per decade earlier in the North Sea but by less in the Mediterranean and were delayed in the Black Sea. Figure: Burrows et al. 2011.(click map to expand)

“Even though temperatures on land have increased faster than in the oceans, the rate at which species relocated or changed the timing of, for example, their breeding or hibernation was just as high in the oceans as it was on land,” said Keith Brander from DTU Aqua, who came up with the initial idea to look at how quickly species in the sea could be expected to change as a response to global warming.

The study shows that in order to keep up with the observed climate warming over the past 50 years, the world’s plants and animals would have moved around 2.5 km each year on average to track their optimal temperatures.

But regional variations mean that in many areas marine species must respond much more rapidly to the changing climate than species on land.

Some southern European fish species are extending their range northwards. Since 2000 three species of Seriola jack (family carangidae) have been recorded in Guernsey waters for the first time (click image to expand - ©RLLord)

“Because of the faster increase of temperatures on land, you might expect the species to change quicker on land than in the sea. This study shows that this is not true at all,” said Keith Brander.

“On land, species can find different temperatures by moving a shorter way than species in the ocean. For example, by relocating to higher altitudes in mountains.

In the oceans, temperatures are much more even. Here, if the temperature increases, the species would have to move a much larger distance to find the right temperature,” he said.

The average temperature in the Danish seas has increased by 1.5⁰ C over the last 30 years and to track these changes, marine species have had to relocate.

“Some species in the Danish waters have had to move their ranges around 10 km each year during the last 50 years in order to cope with the changing water temperature,” says Keith Brander.

The increasing water temperature and the species relocating have meant an increased number of animal and plant species in the North Sea.

The white seabream and the two-banded seabream have recently been recorded in Guernsey waters for the first time (click image to expand - ©RLLord)

“With regards to number of animal and plant species, the biodiversity in the North Sea has increased during the last 30 years due to global warming,” said Keith Brander.

He explained that species adapted to live in warmer waters now find the Danish water temperatures suitable while some of the species adapted to live in colder waters are apparently able to adapt to the higher temperature.

But not all fish species adapted to colder waters thrive in the warmer Danish waters.

“The numbers of the flatfish, the common sole, has been increasing in Danish waters. The sole is distributed all the way down to Africa, and thrives in the warmer Danish waters.

In contrast, the European plaice is a flatfish species adapted to living in colder waters, and we see that the numbers of European plaice in Danish waters are going down compared to sole numbers.

Yet, it is not a simple picture. For instance, a cold-water species, like the Atlantic cod, is able to stay in Danish waters by adapting to changing temperatures by moving the time when they spawn,” said Keith Brander.

“Today, Danish marine species are not threatened by global warming. But that can change. A hundred years from now, some Danish marine species might be in trouble”.


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