International
Gaël Mariani et al. / 2020

World - Let More Big Fish Sink: Fisheries Prevent Blue Carbon Sequestration—Half in Unprofitable Areas

Contrary to most terrestrial organisms, which release their carbon into the atmosphere after death, carcasses of large marine fish sink and sequester carbon in the deep ocean.

Yet, fisheries have extracted a massive amount of this “blue carbon,” contributing to additional atmospheric CO2 emissions. Here, we used historical catches and fuel consumption to show that ocean fisheries have released a minimum of 0.73 billion metric tons of CO2 (GtCO2) in the atmosphere since 1950. Globally, 43.5% of the blue carbon extracted by fisheries in the high seas comes from areas that would be economically unprofitable without subsidies. Limiting blue carbon extraction by fisheries, particularly on unprofitable areas, would reduce CO2 emissions by burning less fuel and reactivating a natural carbon pump through the rebuilding of fish stocks and the increase of carcasses deadfall.

INTRODUCTION

The continuous increase in CO2 emissions from fossil fuel burning and other human activities is rising atmospheric CO2 concentration [270 parts per million (ppm) before the preindustrial period versus 410 ppm now] and altering global climate with deleterious consequences on ecosystems, human health, and the economies (1, 2). In response, the Paris Agreement, adopted in 2015 at the 21st Conference of Parties under the United Nations’ Framework Convention on Climate Change, has the objective to limit global warming below 2°C relative to preindustrial levels by keeping atmospheric CO2 concentration below 490 ppm by 2100 (3). Meeting this target will require multiple and urgent efforts to reduce CO2 emissions, promote carbon sequestration, and develop negative-emission technologies.

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