If emissions continue to rise rapidly, nearly 90% of the world's population are projected to be exposed to losses of food production.
The world needs to urgently cut its planet-warming greenhouse gas emissions to avoid a "perfect storm" that will lead to simultaneous falls in food production from both farming and marine fisheries, researchers said.
If emissions continue to rise rapidly, nearly "90% of the world's population ... are projected to be exposed to losses of food production in both sectors" by 2100, according to a new study by researchers from countries such as France, the United States and Canada.
This amounts to about 7.2 billion people. In contrast, less than 3% of the population, or 0.2 billion people, live in regions that would experience simultaneous productivity gains.
"Climate change has put humanity on a dangerous path that will become increasingly difficult to reverse if greenhouse gas emissions are not taken much more seriously," Lauric Thiault, the paper's co-author, told the Thomson Reuters Foundation.
Almost 200 countries agreed in Paris in 2015 to curb temperature rises caused by burning fossil fuels, felling forests and other activities that emit greenhouse gases.
But economic development and industrialization around the world has resulted in an expansion of fossil fuel infrastructure, such as power plants and pipelines.
Earlier this week, a report by the World Meteorological Organization said greenhouse gases in the atmosphere hit a new record in 2018.
Future climate projections show tropical areas, particularly in Latin America, Central and Southern Africa, and Southeast Asia, would "disproportionately face" losses in both farming and marine fishery sectors, according to the new study, published on Wednesday in the journal Science Advances.
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"These areas are generally highly dependent on agriculture and fisheries for employment, food security, or revenue," it added.
This is the first study to provide a global picture of how climate change would affect food production both on land and in the sea, said Thiault, from France's National Center for Scientific Research.
While it is already known that climate change would affect agriculture, the extent and magnitude of simultaneous losses was a surprise, but there are "unequivocal benefits" of achieving the 2015 Paris Agreement, he said.
Next week, representatives from nearly 200 countries are meeting in Madrid to flesh out rules for implementing the accord, which requires curbing emissions to limit temperature rises to "well below" 2 degrees Celsius (3.6°F).
Achieving this would lead to gains in both farming and fisheries for the most vulnerable countries as well as nations with large per capita emissions such as the U.S., China and Saudi Arabia, the paper said.