The oceans may be heating up more slowly than the continents, but animals and plants in the oceans are reacting much faster to the new conditions than organisms on land. This is the surprising conclusion drawn by an international group of researchers of which Prof. Dr. Wolfgang Kießling of FAU is a member. The scientists have published their findings in the online journal Nature Climate Change (doi10.1038/nclimate1958).
About 71 percent of the Earth’s surface are covered in water; however, large parts of the oceans are still uncharted territory. Very little was known so far about how animals and plants in the world’s oceans react to the higher water temperatures caused by climate change. It would seem plausible that marine organisms are affected less by climate change since it causes the temperatures on land to rise three times faster than water temperatures. However, scientists led by Prof. Kießling, Chair of Palaeoenvironmental Studies, have found the exact opposite to be the case. The reactions of marine organisms to rising temperatures are far more severe than on land. Furthermore, researchers have proven an undeniable connection between climate change and the changes in the oceans. The regions where the highest temperature differences have been measured in the past years have also seen the most dramatic changes.
For their analysis, the researchers evaluated 1735 studies from all over the world that examine which changes climate change causes in marine plants and animals. Their first insight: aquatic organisms near the equator are moving towards the poles to avoid the higher temperatures, into areas that were too cold only a few years ago. And not only that, their habitats are shifting more than ten times faster than those of land animals. Every ten years, marine habitats move an average of 72 kilometres towards the poles, while on land the average distance is six kilometres. The ‘fastest’ organisms in this regard are phytoplankton and zooplankton – which includes diatoms and copepods – as well as fish larvae.
A further insight: there are also big observable changes in the area of phenology. This is the term used for all flora and fauna-related events that are subject to seasonal influences. When do starlings return from the south? When do snowdrop shoots grow? When do hedgehogs seek out their wintering grounds? Here the researchers found that typical maritime spring events – such as the appearance of plankton bloom and the breeding season of seafowl – take place an average of four days earlier per ten years. On land, the difference is approximately two and a half days. The largest change is visible in zooplankton and teleost fishes, whose spring starts eleven days earlier every ten years.
The consequences of these changes are yet to be examined. ‘Certain fish species moving their habitat further towards the North or South Pole doesn’t necessarily mean that there are no fish left in their original habitats,’ explains palaeobiologist Kießling. ‘However, it is becoming difficult to replace the emigrating species near the equator with immigrants.’
Prof. Dr. Wolfgang Kießling
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