Fish populations are declining as the oceans are warm, putting at risk key sources of food and income for millions of people around the world, according to a new study published Thursday.
The study found that the amount of seafood that people could sustainably harvest from a wide range of species shrank 4.1 percent from 1930 to 2010, the victim of man-made climate change. This is 1.4 million metric tons of fish from 1930 to 2010, says Chris Frey, the lead author of the study, who appeared in the journal Science.
Scientists warn that global warming will put pressure on global food supplies in the coming decades. But the new findings, which separate the effects of water warming from other factors, such as overfishing, suggest that climate change already has a major impact on seafood.
"Fish provide a vital source of protein to more than half of the world's population and some 56 million people around the world are somehow supported by sea fishing," Dr Frei said.
While the oceans have warmed up, some regions have been particularly badly affected. In the northeast of the Atlantic Ocean and the Japanese Sea, fish populations have dropped by as much as 35% over the survey period .
"Ecosystems in East Asia have some of the biggest declines in the productivity of fisheries," Dr Frei said. "And this region is home to some of the largest human populations and populations that are heavily dependent on seafood."
Now, he is a post-graduate student at the University of California, Santa Barbara, and Dr Svoboden begins his research while he is Ph.D. Climate Fwd: Our email newsletter.
Marine life has been subjected to some of the most drastic consequences of climate change. The oceans have absorbed 93% of the heat that is captured by the greenhouse gases that people pump into the atmosphere.
A study published in January, also in science, found that ocean temperatures were rising much faster than previous estimates.
Against the backdrop of these changing conditions, fish move where they live in search of their preferred temperatures. The high ocean temperatures can kill both the fish and the food sources they depend on.
"The fish are like a goldfish: they do not like their water too hot or too cold," says Malin L. Pinski, associate professor at the Rutgers University School of Environmental and Biological Sciences, and co-author of the new study.
About a quarter of the surveyed fish extends its range . On the side of the Atlantic coast of the United States, the sustainable catch of the Black Sea bass has increased by 6% during the survey period. The Atlantic herring is abundant.
But half of the regions also do not do well. The northeastern Atlantic, the home of cod, fish and chips, saw a 34% decline in sustainable catches.
Above all fish populations declined rather than increased over the eight decades of the survey.
Researchers focused on sustainable catches using a measure developed by the United Nations that quantifies the amount of food that can be harvested repeatedly from the main fish population. "Fisheries are like a bank account, and we are trying to live out of interest," said Dr Pinsky.
Several previous studies predicted that climate change will result in fewer ocean fish in the future, but new research looked at historical data to find that the downturn has already begun.
"This will be one of these groundbreaking studies that is re-quoted," said Trevor Branch, an associate professor at the Washington School of Water and Fish Science, who did not participate in the study. "Most of what I've seen before in terms of impacts on climate change is speculative in terms of:" We think this will happen in the future. This is different. "
Researchers used a dataset of 235 fish populations located in 38 ecological regions around the world. Detailed data told them not only where the fish were, but how they responded to environmental impacts like changing water temperatures.
The team compares this data with records showing how ocean temperature has changed over time, broken down by region. These regional analyzes are important because some parts of the ocean have warmed faster than others.
"We then linked those who responded positively, negatively and who did not respond," said Dr. Pinsky. 19659002] The data revealed some other trends. Fish populations in the colder parts of their areas are better than those in the warmer areas – for these fish the extra heat is too high. This is particularly worrying for researchers, as the data they use is less detailed in the tropics. Fish losses in these regions may have been higher than in the regions for which the study was focused, Dr. Pinsky said. Researchers predict that overfishing makes fish even more vulnerable to temperature changes, damaging their ability to replicate and damaging the ecosystem.
Protecting against overfishing and improving overall fisheries management can help. But ultimately, they say, the solution lies in delaying or stopping climate change.
A separate study published in Science Advances on Wednesday found that limiting warming to 2.7 degrees Fahrenheit or 1.5 degrees Celsius above levels – the Paris Climate Agreement goal – could to generate billions of dollars of additional revenue for fishing worldwide. Much of this will be in the developing world, where many people rely on fish for protein.
"We hope this highlights the importance of taking into account that climate change is a driving change in productivity", his research. "Fisheries managers need to find new innovative ways to take account of these changes. This includes lowering catch limits in warmer negative years, but may include increasing catch limits in cooler positive years. Regulations that are adaptive to climate change will be really important to increase the potential of food. "