The consequences of climate change are so complex: The North Atlantic right whales, which are threatened with extinction, are being driven from their protected habitat into dangerous waters by changing ocean currents, report marine biologists. There they are more likely to collide with ships and get entangled in fishing utensils. Without further protective measures, the tragic story of this whale species is likely to end in total loss in the coming decades, the researchers say.
Once upon a time, many thousands of northern Atlantic right whales swam (Eubalaena glacialis) along the coasts of Europe and North America – but that changed quickly in the era of commercial whaling. The whales, which can weigh up to 100 tons, were the target of the harpoons, because they swim particularly leisurely. Its popularity among whalers also shaped the English name of this species: “right whale” – “real whale”. In the end, except for a few animals, the North Atlantic Cape population was slaughtered.
The species was placed under protection as early as 1930 – but since then its population has hardly recovered compared to other whales. Since the small population in the area of ​​the east coast of the USA has recently been shrinking, the northern right whale has been listed as “critically endangered” in the IUCN’s list of threatened species since 2020. The researchers led by Charles Greene from Cornell University in Ithaca also illustrate the downward trend in their study with numbers: According to them, the population has shrunk significantly, especially since 2010. At the beginning of the decade there were still over 500 animals – now the experts estimate the population at only 356 whales.
Shrinking remainder
But what is bothering these whales? It was already known that northern right whales particularly often collide with ships and get tangled in fishing lines – with fatal results. The scientists are now showing that these threats are linked to a consequence of climate change: As their data shows, the warming water in the Gulf of Maine is increasingly driving the animals from this protected marine region into the unsafe Gulf of St. Lawrence.
“Most of the warming in the Gulf of Maine isn’t coming from the atmosphere or the ocean surface, as you might think,” says Greene. Instead, the cause is a change in water movements in the North Atlantic, which ultimately also goes back to climate change. As the researchers explain, the Gulf of Maine is shaped by the warm waters of the Gulf Stream. In the past ten years, however, the current has changed a lot. “Due to the warming of the climate, the overturning circulation is slowing, so that the Gulf Stream moves north and feeds even warmer and salty water into the Gulf of Maine,” says Greene.
Evasion with fatal consequences
This effect harms the northern capers indirectly, explain the marine biologists: The warming leads to a decline in the populations of tiny crustaceans in the Gulf of Maine, which serve as food for the whales. As the scientists report, there are signs that this loss of food has reduced the calving rates of the whales and eventually forced the animals to leave their traditional midsummer foraging grounds in the Gulf of Maine. Apparently they move to the north: Since 2015, more and more northern right whales have been observed foraging in the cooler waters of the Gulf of Saint Lawrence.
But these are problematic new hunting grounds, because while the Bay of Maine is comparatively calm and special efforts are made to protect marine animals there, there are busy shipping routes through the Gulf of St. Lawrence and also the danger from fishing utensils are increased there. The effect of emigration is already clearly noticeable in this context, say the scientists: There have been many deaths among northern capers in the Gulf of Saint Lawrence in recent years.
“More animals die every year,” says lead author Erin Meyer-Gutbrod from the University of South Carolina in Columbia. Without a trend reversal, the population will continue to shrink and the species will probably become extinct in the coming decades, fear the marine biologists. Your only hope now are new guidelines for rope-free gear, as well as the enforcement of speed limits for ships and money for the installation of surveillance systems. “The protective measures would have to be tightened quickly, however, before this species goes back so far that there is no turning back,” says Meyer-Gutbrod.
Source: Cornell University, Article: Oceanography, doi: 10.5670 / oceanog.2021.308