This is the question that researchers from Germany and the US have been trying to answer in the hope that lessons learned from the past can help inform future policy. Their study, published in the journal Environmental Research Letters (ERL), found that, with all else being equal, if yields had remained the same as their 1961 values, additional land the size of Australia would have been needed to grow crops.

“We used a decomposition approach to try and identify the main drivers in the change of land use over the last 50 years,” explained Veronika Huber from the Potsdam Institute for Climate Impact Research, Germany. “This is a technique often used in climate economics, but not so often in this context. Our work builds on previous decomposition studies, but we used the novel method of secondary decompositions to study the contribution of individual crop types and we also looked at a comprehensive set of national data. Our study also includes international trade.”

Huber and her colleagues looked at four major drivers for cropland expansion since 1961: human population growth; rising per-capita caloric consumption; processing losses (including conversion of vegetal into animal products and non-food use of crops); and yield gains.

“Since 1961, the world’s population has grown by three billion people,” said Huber. “As the population is set to grow by the same amount by the end of the century, we wanted to quantify the effect of these different drivers in order to rank them and perhaps help set research priorities for the future.”

The team found that yield increases have largely kept pace with the increase in population. If these rates of yield improvements were sustained into the future, and population growth slowed down as projected by the UN, the pressure to expand cropland, even under further moderate increases of per-capita food consumption, would gradually subside.

But Huber warns that the research also showed there have been recent increases in processing losses that might emerge as new important drivers of cropland expansion. “These increases in processing losses are most likely due to increased meat consumption and bioenergy production,” she said. “We also need to bear in mind that, while our research gives a measure of what has happened in the past, disruptions due to climate change could mean that the drivers for cropland expansion may not follow the same pattern in the future.”

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