Wheat yields have levelled off in many countries around the world, even in regions of greater food insecurity such as India and Bangladesh, say researchers in the US.
"With the major exception of India, the majority of levelling in wheat yields occurs within developed nations, including the United Kingdom, France and Germany," said Lin. "This levelling coincides with policies in these countries, which appear to have disincentivized yield increases relative to other objectives. It is interesting to note that in these cases, the levelling wheat yield is probably due to management decisions, rather than the reaching of a yield limit."
In India and Bangladesh, however, there seem to be different factors at play. In these two countries, which have greater food insecurity and have been using increasing amounts of fertilizers, wheat yields are also levelling off. "This could be due to the effects of climate change, which may be expected to decrease yield potential," said Lin. "Also, wheat yields in India and Bangladesh are near their estimated yield potential." She also pointed out that developing countries were more likely to be excluded from this analysis due to poor data quality and may show different trends, perhaps corresponding more with management factors.
Of the 50 regions that Lin and Huybers tested for yield stagnation, 27 show yields that have levelled off when performing the test at the 80% confidence level. Using 2007 numbers, wheat accounts for 19% of the total calories of food produced, and the 47 countries sampled in their analysis account for 75% of total global wheat production.