The persistent warming of the oceans is causing an accelerated reduction in marine life, especially fish, according to a study published in the journal Nature Ecology & Evolution.
Analyzing 33,000 populations in the Northern Hemisphere between 1993 and 2021, the researchers concluded that fish biomass falls, on average, 7.2% for every 0.1°C increase in temperature per decade on the seabed.
The work isolated the impact of chronic warming from short-term fluctuations, such as marine heat waves.
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In some cases, these waves generate temporary “booms” in cold regions, where species are able to benefit from the momentary rise in temperature, while the same event worsens the situation in already hot areas. These specific gains, however, mask a trend of widespread biomass loss.
Experts consulted by the authors highlight that the situation adds to other factors of pressure on fishing stocks, such as overfishing.
FAO reports already indicate an increase in the proportion of overexploited stocks, and the new study suggests that the warming of the seas and the loss of oxygen are worsening a pre-existing crisis, making fisheries management even more complex.
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For marine scientists, the results reinforce the warning that “every fraction of a degree” in global temperature has a direct and measurable impact on ecosystems.
As the planet approaches exceeding the 1.5°C limit established in the Paris Agreement, pressure on fish populations is expected to intensify, with cascading effects on commercial fishing, food security and biodiversity.
The study’s authors argue that climate policies and fishery resource management consider not only the frequency of marine heat waves, but mainly the rate of bottom-ocean warming.
According to them, if the rate of warming continues to accelerate, the loss of biomass will be so widespread that no traditional management plan will be able to compensate for the damage to fish populations.
