Raising cattle produces huge amounts of greenhouse gases
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As the world’s population grows, the only way to reduce agriculture’s huge greenhouse gas emissions is to make food production more efficient. Unfortunately, efficiency gains have stagnated since 2010, and as food demand continues to grow, agricultural emissions and deforestation are likely to skyrocket.
Lin Ma and his colleagues at the Chinese Academy of Sciences in Shijiazhuang came to this conclusion after analysing existing data estimating greenhouse gas emissions per unit of protein produced between 1961 and 2019. They chose protein instead of calories because it’s a better measure of food quality, Ma says.
Between 1961 and around 2010, emissions per unit of protein fell by two-thirds, the team says. But since then, there has been no further improvement and there are even signs of an increase. Agriculture is responsible for about a third of all greenhouse gas emissions, and food demand is projected to increase by up to 50% by 2050. If agriculture’s climate efficiency does not improve further, emissions from agriculture will also increase by 50%, the researchers warn.
Moreover, without improvements in agricultural efficiency, the only way to increase production is to clear more land for farming, which will lead to further deforestation and biodiversity loss, they say.
“That’s very bad news. We need to dramatically reduce emissions, not increase them,” said Richard Waite of the World Resources Institute in Washington, D.C., who was not involved in the study.
“The continued and accelerating expansion of agricultural land this century is extremely worrying because keeping[global warming]to 1.5°C depends on ending deforestation as quickly as possible,” he said.
There are many reasons why greenhouse gas emissions per unit of protein produced haven’t fallen, says Dan Leight of the Breakthrough Institute, who was not on the team. One is that people around the world are eating more meat, which produces far more greenhouse gas emissions than plant-based foods.
The fact that large amounts of agricultural crops are now being converted to fuel rather than food could also be a factor, he says. “The rise in crop-based biofuels likely explains some of the slowdown in decarbonization we find in the paper,” as biofuel crops grown for energy are chosen for their calorie content rather than their protein content, reducing the efficiency that Ma’s team measures.
Another potential factor is the increase in extreme weather events that are affecting crop yields and food prices around the world, which the study did not take into account, Ma said. “But we suspect the impact of extreme weather on crop yields was relatively small before 2019.”
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