Over the last few decades, warming ocean temperatures have caused marine species to move to new places. They are leaving some places where temperatures have become too warm for them. And they are invading new places that have now become inhabitable due to increasing temperatures. For example, on both sides of the North Atlantic (the U.S. northeast coast and western European coast), scientists have found that cod have shifted their distribution to higher latitudes, as have several other commercially valuable fish species. In these areas, fishermen are also starting to see more warmer-water fish, like black sea bass in the northeast U.S. and red mullet in northern Europe1.
Temperatures are increasing both on land and in the oceans because our burning of fossil fuels is putting too much carbon dioxide into the atmosphere, and carbon dioxide traps heat. As temperatures continue to rise, we can expect to see more species on the move. The big questions are how will this affect species diversity (abundance and types of species), fisheries, and coastal communities?
Well, a recent study by a team of international scientists from North America, Europe, and Australia helps shed light on these questions. The group of scientists mapped shifts in ocean temperatures around the globe from 1960 to 2009. And they projected how temperatures would continue to shift out to 2100. The scientists use this information to predict where species will move to, since species movements are likely to track shifting climates. The scientists identify migration corridors that species in search of new homes will likely follow, as well as migration barriers.
The scientists’ study shows that equatorial or tropical regions are particularly vulnerable to a loss of species diversity. Rising ocean temperatures in this region will force tropical species to move to cooler locations. And since there are no species to replace them, the abundance and types of species in these areas will decline. The scientists call these areas “climate sources”.
The scientists also found that in many places, coastlines will block species migration routes and may prevent further movement into cooler habitats. In these “coastal sink” areas some species may go locally extinct. But species from warmer areas may move in and replace lost species.
Areas identified as “migration corridors” are likely to see an influx of species from various different habitats. In these areas species diversity may increase. But it will also lead to new species interactions, which may affect the structure of food webs and ecosystems.
Professor Mike Burrows of the Scottish Association for Maine Science led the study. He says that mapping these areas around the globe, “shows those places where biodiversity may be compromised by climate change, alongside all the other threats to life in an increasingly crowded and developed world.” Communities likely to see large shifts in the species living off their coast may need to adapt to new fish. Coastal communities where species will decline may need to diversify their sources of food and income.
The full study “Geographical limits to species-range shifts are suggested by climate velocity” was published in Nature and can be accessed here.
To learn more about how rising ocean temperatures are affecting ocean species and habitats, please visit Blue Ocean Institute’s Ocean Warming page.
Elizabeth Brown is a research scientist at Blue Ocean Institute.