Ocean warming is posing a threat to fish population which is a crucial source of food as well as the income of millions of people worldwide as stated in the new research published on Thursday.
According to the study, due to human-caused climate change, the amount of seafood shrank by 4.1 % between 1930 and 2010.
“That 4 percent decline sounds small, but it’s 1.4 million metric tons of fish from 1930 to 2010,” said Chris Free, the lead author of the study, published in the journal Science.
Scientists warned that the world’s food supplies would be under pressure due to global warming in coming decades and that would lead to less ocean fish in the future. The new findings considering the historical data suggest that apart from the factors like overfishing, the severe impact of climate on seafood is already visible and the declines had already begun.
According to the Food and Agriculture Organization of the United Nations, fish make up 17 percent of the protein intake of the global population as 70 percent of the protein intake of the people living in some coastal and island countries.
“Fish provide a vital source of protein for over half of the global population, and some 56 million people worldwide are supported in some way by marine fisheries,” Dr. Free said.
Fish populations in the northeast Atlantic Ocean and the Sea of Japan, declined by 35 percent over the period of the study as the ocean warming hit some regions hard.
“The ecosystems in East Asia have seen some of the largest declines in fisheries productivity,” Dr. Free said. “And that region is home to some of the largest growing human populations and populations that are highly dependent on seafood.”
Marine life has been the target of some of the most drastic effects of climate change. The 93 percent of the heat absorbed by the oceans gets trapped by the greenhouse gases pumped into the atmosphere by the humans.
As the condition is changing with the fast increase in ocean temperatures than what estimated earlier, fish are also shifting in search of their preferred temperatures from the place they live at present. Both the fish and the sources of food they depend on may get destroyed due to high ocean temperatures.
“Fish are like Goldilocks: They don’t like their water too hot or too cold,” said Malin L. Pinsky, an associate professor in the School of Environmental and Biological Sciences at Rutgers University and a co-author of the new study.
United Nations developed a measure quantifying the amount of food that repeatedly harvested from a base population of fish and the researchers focused on sustainable catches using this measure. “Fisheries are like a bank account, and we’re trying to live off the interest,” Dr. Pinsky said.
“This is going to be one of those groundbreaking studies that gets cited over and over again,” said Trevor Branch, an associate professor at the University of Washington’s School of Aquatic and Fishery Sciences, who was not involved in the study. “Most of what I’ve seen before in terms of climate-change impacts have been speculative, in terms of, ‘We think this is what’s going to happen in the future.’ This one’s different.”
A data set consisting of 235 fish populations, located in 38 ecological regions was used by the researchers for study. The detailed data told them about the location of the fish and also their reaction towards the environmental effects like the change of water temperatures.
After comparing that data to records, it showed the changes in ocean temperatures over time broke down by the various regions. The regional analyses were critical as some parts of the ocean warmed faster than other parts.
“We then connected those to which populations responded positively, negatively, and which didn’t respond at all,” Dr. Pinsky explained.
Some other trends also revealed from the data. The matter that was especially troubling to the researchers was, the fish populations in the colder parts of their ranges tended to fare better compared to those located in warmer areas as the extra heat was too much for those fish. It may be for the data they used was less detailed in the tropics. Fish losses in those regions may have been higher than in the areas the study focused on, Dr. Pinsky said.
Overfishing made warm areas fared even worse. Fish become even more vulnerable to temperature changes as overfishing damages the ecosystem and their reproduction ability. The researchers suggested that improving the overall management of fisheries and guarding against overfishing can help. However, the ultimate solution lies in halting or at least slowing climate change.
A separate study, published Wednesday in the journal Science Advances, found that the goal of the Paris climate agreement of limiting warming to 2.7 degrees Fahrenheit, or 1.5 degrees Celsius, above preindustrial levels could result in extra revenue of billions of dollars for fisheries globally and especially in developing world, where many people depend on fish for protein.
“We hope that this highlights the importance of accounting for the fact that climate change is driving shifts in productivity,” Dr. Free said of his research. “Fishery managers need to come up with new innovative ways of accounting for those shifts. That includes reducing catch limits in warm negative years, but it can also include increasing catch limits in cooler positive years. Having regulations that are adaptive to climate change is going to be important for maximizing food potential.”