Today, a global food crisis is looming as the world population increases, more people shift towards meat and dairy intensive diets and more cropland is diverted to grow biofuel crops1,2,3,4. How will we meet these growing demands, especially when recent crop-production trends were insufficient to do so, and many regions are showing significant stagnation and declines in yield improvement?

Looking forward, we must first ensure that areas still increasing yields do not falter, while at the same time improving management practices to reduce impacts on the environment4. Next, we have to identify why yield gains for our most important cereal crops are stagnating in more than a quarter of our croplands. Can we reverse the yield stagnation in these areas? At the field to country scale, there are numerous studies showing that both biophysical and socio-economic causes, often not mutually exclusive, are the drivers of these yield changes. The lack of readily available data regarding all possible drivers of global agriculture at the level of our analysis precludes any effort to ascribe the causes behind the observed yield trends. However, below we discuss some of the reported field to country-scale causes of yield changes with an emphasis on Europe, Asia-Australasia and Africa; these are the continents where yield stagnation appears particularly widespread (Fig. 2).

In the Americas, maize yield stagnation is especially widespread only in Mexico. Here reduced fallow periods in areas of shifting cultivation without concomitant adoption of modern management practices15, or non-introduction/adoption of non-local but high-yielding maize seeds by farmers16, may be responsible. In the United States, greater adoption of no-till practice by farmers in the semi-arid areas of the Great Plains has coincided with intensified crop rotations17 (for example, wheat-maize rotations as opposed to a fallow following wheat). Farmer net incomes may have consequently increased, but intensified crop rotations may have also led to increased yield variability and crop failures17 in an area of already limited water resources18. Our analysis shows widespread yield stagnation in these regions, especially for wheat (Fig. 2a and c).

In Europe, wheat yields may have declined because of climate changes in some countries of Western Europe10, though elsewhere in more northern countries, the warmer climate may have led to fewer low yield years, and even expansion of wheat areas14,19. Elsewhere in Europe, warmer temperatures may have had no effect on boosting either maize and wheat yields20. Confounding the climate-change effects in Europe are socio-economic and policy decisions to reduce farmer remuneration for intensive cultivation, or to reduce the environmental burden6,7,10,21,22, which may have reduced farmer inputs leading to yield stagnation11 but improved environmental quality23. However, there are clearly both regional/country and crop specificities. There may now be fewer incentives to boost wheat yields in Western European countries11 (namely in France, Germany and United Kingdom), which correlates with our results showing widespread areas where yield increases have ceased (∼80% of the wheat areas in France and Germany, and ∼99% in the United Kingdom). However, maize yields are increasing almost everywhere in France and Germany (∼90% and 100% of maize-growing areas, respectively). Spain, Portugal and Italy on the other hand have a larger fraction of their wheat areas showing yield increases (82%, 89%, and 76%, respectively) compared with maize (48%, 65%, and 41%, respectively).

In Asia and Australia, yields of wheat and rice may have stagnated as shown in our analysis (see Fig. 2b) due to a combination of factors that are location-specific, including climate-change-related heat stress24,25, increased night time temperatures26, depletion of soil fertility and salinization12,27, soil erosion27, increasing competition for water resources28, pest and disease build-up27 and a lack of capital29 to buy more expensive inputs while the real crop prices declined30. Wheat yields may have stagnated in Bangladesh31, and in parts of India also because of current cultivars approaching their yield potentials32. The effect of water scarcity for irrigation, falling groundwater water tables18,27,33 and soil-quality depletion may be even more pronounced for rice34,35, leading to the widespread rice-yield stagnation (Fig. 2b). The need for new wheat cultivars is another major challenge; specifically, varieties are needed that are heat- and water logging-tolerant for growing conditions in South Asia where wheat follows rice in the crop rotation, and frost-tolerant varieties for the growing conditions in East Asia27. Similarly, rice cultivars that provide high yields in nutrient-deficient soils36 are needed to boost yields. Changing the length and type of crop rotation with better management could also boost Asian rice and wheat yields37.

In Africa, crop yields may have stagnated due to a complex combination of factors, many of which may ultimately be due to socio-economic limitation. Specific constraints to crop yield increases include variability of dry spells and lack of field-water management strategies in the drier parts of the continent38, absence of significant irrigation infrastructure39,40, low nutrient application and absence of fallows to restore soil fertility levels41,42, lack of availability of suitable high-yielding crop varieties that in turn could be related to institutional and political conditions42,43,44, and the lack of farmer expertise in appropriate agronomic practices42. However, when combinations of socio-economic factors align to overcome the biophysical limitations, significant yields gains are achieved45. For example, landscape-scale modelling results39, field trials46 and policy experiments47, all demonstrate that fairly small increase in inputs is sufficient to double maize yields in Africa.

Although we have found widespread yield stagnation, an increase in the number of crops per cropping cycle or intercropping with other crops48,49,50 can increase net food supply and farmer incomes17. Indeed, global harvested areas have increased at nearly three times the rate of global croplands areas since 19854. In some areas, farmers may have prioritized livestock over grain crops, and in other regions, yields may have stagnated, but the total factor productivity (the ratio of the total output to the total input) increased21,51. However, globally, there remain many regions where both the growth in yields and total factor productivity of agriculture remain low, perhaps because of a lack of established agricultural research and investment51.

At the global scale, yields are being affected by both biophysical52,53 and socioeconomic22,29,40 factors. Differences in crop performance create yield gaps4,5,32,39 that could be overcome by adoption of best management practices54,55,39. Understanding how changes to management practices (including fertilizer application, irrigation, pest management and others) could close yield gaps39 is critical to addressing stagnating yields on our most important croplands. Failure to identify and alleviate causes of yield stagnation, collapse and never improving yields will have an impact on the future of global food security.

Our global analysis shows that maize, rice, wheat and soybean crops are continuing to experience yield increases in 61–76% of their global harvested areas. This implies that between 24–39% of these cropland areas are no longer witnessing yield increases; the spatial extent of such rice and wheat areas is now particularly extensive (37% and 39% of global areas, respectively). In all, 43% of global rice and 44% of global wheat production are currently from these areas, not witnessing yield increases, raising the important question of how future demands, at least in these two commodities, would be met.

More troubling is our finding that for the top-three global rice producers–China, India and Indonesia, yield gains are not occurring across 79%, 37% and 81% of their rice cropland areas. China, India and the United States–the top-three wheat producers–similarly are not witnessing yield increases in 56%, 70%, and 36% of their wheat cropland areas, respectively. The spatial extent for the top-three global producers of soybean under these yield conditions is much lower, but China, the second largest global maize producer, now has more than half its area not witnessing yield gains (Table 1). China and India, the world’s two most populous countries3, are now hotspots of yield stagnation with more than a third of their maize, rice, wheat and soybean areas not witnessing yield improvement with the problem being more acute in China. For some crops in these two countries, the spatial extent of yield stagnation is more than half the cropped area.

It is thus quite clear from these results that considerable investment in agriculture is needed in the coming decades to meet the challenges of the growing demand for food; simultaneously, we have to maintain a livable environment4. Although this study suggests that we have been losing ground on maintaining growth in agricultural production, there are promising paths to pursue in the years ahead56.