Researchers from Harvard University in the United States have suggested that wheat yields could be levelling off. Many organisations, including the UN Food and Agriculture Organisation have said that more food needs to be produced using fewer inputs in the near future and across a number of global regions in order to achieve sustainability and eliminate hunger.

Harvard scientists Marena Lin and Peter Huybers undertook their research in response to calls from development organisations and agriculturalists, who have stated that increases in food production will have to take place on existing agricultural land, meaning crop yields will need to increase if the world is to feed a projected population of 9 billion by the middle of the century. The boons which helped food production grow as a result of the Green Revolution in the middle of last century include "improved cultivars and management techniques, as well as from the use of chemical fertilizers, irrigation, and pesticides."

Although wheat yields have risen in a mostly linear fashion since that time, the researchers said, statistical tests show yields are no longer increasing in many parts of the world. They studied data from 47 different regions and found yields had reached a plateau in half of the samples. The majority of levelling was in developed countries, including the United Kingdom, France and Germany.

A number of possible causes for the transition were suggested by the researchers, including that government "Policies appear to have disincentivized yield increases relative to other objectives," though they added, "The effects of climate change and of yields nearing their maximum potential may also be important."

Although reaching maximum yield potential and reducing chemical inputs could explain the situation in Europe, in India and Bangladesh, where increasing amounts of fertilizers are being used, the same pattern is apparent. This discovery led the researchers to speculate that stagnation "Could be due to the effects of climate change, which may be expected to decrease yield potential."

The researchers said their modelling was more accurate than most, and revealed they had developed a new statistical test to measure the yield time series. Stagnating yields were identified in 27 of the 47 countries studied, which together account for 75 per cent of global wheat production.

The researchers said there remains scope for improvement, through technological innovation, policy revisions and more equitable development, which it is hoped would lead to yield increases in regions where data is unavailable and yields are not reaching their potential. They concluded optimistically that "Level wheat yields are generally found in regions with adequate food security, whereas regions with historically greater food insecurity generally show continued increases—and local yield increases are more effective at alleviating local food insecurity."

The study, published in Environmental research Letters, can be read here.

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