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Ocean ecosystems are more sensitive to climate change

Climate change is having a bigger impact on animals and plants in the ocean than those on land, according to new research.

This could be because organisms that live on land are better able to avoid the negative consequences of global warming than their ocean counterparts.

Researchers have been examining the impact of temperature on biodiversity, or the variety of life on Earth. They studied life in temperate regions: the places on Earth in between the sub-tropics and the polar circles where temperatures tend to be moderate, such as Europe and North America.

Using a vast database at the University of St Andrews they examined ecosystems around the globe, looking at changes in the number of species and the total number of individuals over time, then matched these against changes in air and ocean temperatures.

The collaboration was led by scientists from the University of Helsinki, the University of St Andrews and Radboud University and published in Nature Ecology and Evolution.

Conor Waldock is a co-author on the paper, which he worked on while completing his PhD at the Museum. He is now a post-doctoral researcher at the Swiss Federal Institute of Technology in Zurich.

He says, 'We wanted to know whether we can see the influence of global warming on animal and plant life by comparing the changes in biodiversity in areas that have warmed rapidly to those that haven't had as much warming.

'Some places are experiencing much more sudden increases in temperature than others, so this was a bit like performing a giant natural experiment.'

Studying biodiversity

Biodiversity is changing all the time and can be difficult to track. Biodiversity refers to much more than just individual animals and plants. It includes all living things and their communities: the oceans, deserts, forests and ice caps that they live in. It's important that nature is diverse, because diversity makes ecosystems more resilient to changes.

However, in some areas, man-made climate change is changing biodiversity at unprecedented rates. This year is set to be the hottest year on Earth on record. Ice caps are melting faster than ever, and wildfires and floods have caused devastation across the globe in the last year alone.

Species and ecosystems can be fragile, so even small changes in temperature can have large consequences. Just a tiny increase can tip some animals and plants into extinction.

That's why studies like this one are so crucial. It is not just important to preserve nature for its own sake. Humanity's future relies on biodiversity as well. For instance, hundreds of millions of people rely on seafood as their main source of protein. Continued warming and more acidic waters will substantially alter marine food chains.

Our suffering oceans

Biodiversity is changing more quickly in the ocean. In temperate marine areas, the study found that the numbers of organisms decrease as the water gets warmer.

However, the number of different species found in these areas increase as the temperature does. At first that increase seems surprising, but as the study focused only on temperate ecosystems, this is probably caused by an influx of warm-water animals migrating to new areas that are now becoming more suitable.

The study did not see the same consistent changes on land, despite a larger increase in temperature.

That's not to say that temperature change is not affecting biodiversity on land. It may be that animals and plants on land have a wider tolerance and more strategies to survive warming temperatures compared to ocean organisms.

Conor explains, 'We discovered that changes to ocean life more closely matched patterns of global warming compared to life on land - suggesting marine ecosystems may be highly sensitive to warming.

'This appears surprising because the oceans only warmed half as much as the land in our study, but we expect that species on land have more strategies to avoid the impacts of increased temperature, for example by escaping to higher altitudes or persisting in pockets of cooler climates.'

Lead researcher Laura Antão, from the Research Centre for Ecological Change at the University of Helsinki, adds, 'We know that biodiversity change is a complex phenomenon, and that temperature is a major factor affecting species distributions and survival.

'Our study provides a clear picture of the change in the numbers of species and individuals against changes in temperature, where we see mostly gains in the ocean coinciding with warming in these temperate locations. But we also see nuance in the responses, and this is very valuable, as it shows that biodiversity change is not the same everywhere.'