Climate change has led to a 21% reduction in global agricultural productivity growth since 1961, equivalent to completely losing the last 7 years of advances in productivity, according to new research from the University of Maryland and Cornell and Stanford universities. 

The study, published last week in Nature Climate Change, is the first to quantify the man-made effects of climate change on global agricultural productivity, showing agriculture is particularly vulnerable in warmer regions like Africa, Latin America and the Caribbean. 

“Our study suggests climate and weather-related factors have already had a large impact on agricultural productivity,” said Robert Chambers, professor in the Department of Agricultural and Resource Economics (AREC) at UMD and an eminent agricultural productivity researcher. “We used the model in this paper to estimate what total factor productivity patterns would have looked like in the absence of climate change.” 

Total factor productivity is a calculation that measures the growth of an industry, such as agriculture. Chambers and lead author Ariel Ortiz-Bobea M.S. ’11, Ph.D. ’13, now at Cornell, have been pioneering new productivity calculations in agriculture to include weather data, improving their accuracy. 

“When a farmer makes an economic decision like what to plant in June, we won’t necessarily know the outcome of that decision until six months later,” Chambers said. “So there is a distinct break between input and output, and random events like weather can severely affect that. Agricultural productivity measurement hasn’t historically incorporated weather data, but we want to see the trends for these inputs that are out of the farmer’s control.”

In this case, weather data was an integral part of the model that examined productivity in both the presence and absence of climate change. While Chambers’ previous work on the topic, published in Science Advances, details the specific regional effects of climate change on U.S. agricultural productivity, the new paper has a global focus. 

“The impacts for the U.S. are measurable and negative, but they appear to be much smaller than for other regions, in particular Africa,” said Chambers. 

In fact, the study finds that while global agricultural productivity growth has slowed by about 21% in the last 60 years, many warmer climate regions dropped 26-34%. The United States seems to be less affected, with productivity growth slipping 5-15%. 

"Some people think about climate change as a distant problem, something that should concern primarily future generations," said Ortiz-Bobea. “Overall, our study finds that anthropogenic climate change is already having a disproportionate impact on poorer countries that depend primarily on agriculture. It appears that technological progress has not yet translated into more climate resilience.”

Such questions will only become more pressing in coming decades., Chambers said.

“We are projected to have almost 10 billion people to feed by 2050, so making sure our productivity is not just stable but growing faster than ever before is a serious concern.”