The worsening effects of food supply on the climate

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 Ma and his colleagues at the Chinese Academy of Sciences in Shijiazhuang came to their conclusion after analysing existing data to estimate greenhouse gas emissions per unit of protein produced between 1961 and 2019. They chose protein instead of calories because it's a better indicator 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 drastically reduce emissions, not increase them.” Richard Waite He is a researcher at the World Resources Institute in Washington, D.C., but was not involved in the study.

“The continued and accelerating expansion of agricultural land since the turn of the century is of great concern as there is no path forward to limit warming to 1.5°C. [of global warming] “It's important to end deforestation as quickly as possible,” he says.

There are many reasons why climate emissions per unit of protein produced are no longer decreasing, Dan Leto For one thing, people around the world are eating more meat, which produces far more greenhouse gas emissions than plant-based foods, said Breakthrough Institute researcher David Schneider, who was not on the team.

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.”