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Nature (2023)Cite this article
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Achieving food-system sustainability is a multidimensional challenge. In China, a doubling of crop production since 1990 has compromised other dimensions of sustainability1,2. Although the country is promoting various interventions to enhance production efficiency and reduce environmental impacts3, there is little understanding of whether crop switching can achieve more sustainable cropping systems and whether coordinated action is needed to avoid tradeoffs. Here we combine high-resolution data on crop-specific yields, harvested areas, environmental footprints and farmer incomes to first quantify the current state of crop-production sustainability. Under varying levels of inter-ministerial and central coordination, we perform spatial optimizations that redistribute crops to meet a suite of agricultural sustainable development targets. With a siloed approach—in which each government ministry seeks to improve a single sustainability outcome in isolation—crop switching could realize large individual benefits but produce tradeoffs for other dimensions and between regions. In cases of central coordination—in which tradeoffs are prevented—we find marked co-benefits for environmental-impact reductions (blue water (−4.5% to −18.5%), green water (−4.4% to −9.5%), greenhouse gases (GHGs) (−1.7% to −7.7%), fertilizers (−5.2% to −10.9%), pesticides (−4.3% to −10.8%)) and increased farmer incomes (+2.9% to +7.5%). These outcomes of centrally coordinated crop switching can contribute substantially (23–40% across dimensions) towards China’s 2030 agricultural sustainable development targets and potentially produce global resource savings. This integrated approach can inform feasible targeted agricultural interventions that achieve sustainability co-benefits across several dimensions.
The Green Revolution brought about unprecedented increases in global food supply to meet rapidly rising demand. Yet the promotion of relatively few high-yielding crops and accompanying input-intensive practices has led to serious compromises for nutrition security and the environment4. The development of agriculture in China has followed these same patterns. The country has made marked gains in its agricultural productivity over the past several decades, increasing national crop production by +107% since 1990 alone1. Despite a population of more than 1.4 billion people, the increase in China’s food demand has largely been met by domestic increases in agricultural production, except for soybean1. Yet attaining these high levels of food production has meant mounting environmental challenges across the country. In recent decades, groundwater levels have dropped at alarming rates2, agricultural GHG emissions have increased1, the intensity of fertilizer application has increased substantially1 and pesticide pollution has become more widespread1.
In recognition of these clear tradeoffs, the Chinese government is considering a suite of interventions to improve the sustainability of agriculture without compromising the sector’s high levels of production3. These strategies include developing ‘high-standard farmland’ to improve agriculture productivity while reducing input use (for example, water, fertilizer), implementing ‘water-saving projects’ to improve water-use efficiency and extending technologies for soil testing and nutrient recommendations to reduce fertilizer use, among others. Although all of these solutions promise to reduce the environmental burden of agriculture, they tend to focus on singular outcomes and are based on the assumption that crops are already grown in the locations in which they are most agro-climatically suited and most resource-efficient. Yet recent research has made it increasingly clear that current cropping patterns are suboptimal across several outcomes and that crop switching (that is, changes in crop distribution and/or crop rotations) may offer promise for improving agricultural sustainability. Recent global studies5,6,7,8 have shown that crop redistribution can reduce irrigation (that is, blue) water demand (−12% to −21%) and blue-water scarcity and protect the natural environment and biodiversity while improving or maintaining food production. Several other analyses have recently been performed at the country level, which is necessary to account for policy-relevant factors that can influence the extent to which an agricultural solution is feasible. In India, crop redistribution has been shown to improve dietary nutrient supply, climate resilience and net farmer incomes and reduce natural-resource use and GHG emissions9,10,11. In the United States, studies found that crop switching can reduce blue-water demand12 and climate-related crop losses13. Other research has shown the promise of diversifying crop rotations14,15. In China, field-based experiments in the North China Plain have shown that crop rotations alternative to conventional maize–wheat systems can reduce groundwater depletion and increase economic output14. Long-term evidence from North America has also shown the superior climate resilience of more diversified rotations15. Yet whether and to what extent crop switching would yield similar benefits for agricultural sustainability for the entire country of China remains unquantified.
Crop switching is a promising strategy to complement other sustainable farm-management solutions. The Chinese government has also recognized redistributing crops as a way to enhance the sustainable development of the agriculture sector3,16. For example, in early 2000, a crop-switching research project led by the National Development and Reform Commission (NDRC) put forward regional agriculture development directions based on historical analysis16. More recently, China’s National Sustainable Agriculture Development Plan (2015–2030) also gave general directions by dividing China into three regions: with more emphasis on food production than sustainability (for example, in the Yangtze River region), with equal emphasis on food production and sustainability (for example, in the Northwest) and more emphasis on sustainability than food production (for example, in the Tibetan Plateau)3. To meet these policy priorities, it is therefore essential to quantitatively evaluate where and to what extent crop switching—in an economically feasible way—may contribute to China’s sustainable development targets without compromising food supply. Furthermore, because China alone accounts for large fractions of the global population (19%)1, primary crop production (19%)1, natural-resource use (for example, fertilizers (25%), pesticides (10%), irrigation (13%), cropland (9%))1,17, agrifood-system-related GHGs (12%)1 and farmers (16%)1, efforts undertaken in China to improve its sustainable development goals will have far-reaching implications towards addressing global food security and sustainability challenges.
Here we quantify and assess opportunities for crop switching across China, focusing on 13 crops that collectively account for 94% of China’s primary crop production and 90% of its harvested area18. We combine gridded (5 arcmin) crop-specific data (circa the year 2010) on rainfed and irrigated yields and harvested areas19 with each crop’s water-requirement estimates, GHGs intensity20, fertilizer application rate21, pesticide use21 and farmer net profit21. Using these data, we estimate several sustainability dimensions prioritized in China’s sustainable agriculture plans22, namely, production quantity, water demand, GHG emissions, fertilizer use, pesticide use and economic output of current crop production. We then construct a linear optimization model to simulate the contribution of crop switching to sustainable agricultural development and assess tradeoffs and co-benefits across several dimensions and different regions. Each optimization run assigns priority to one of the following objectives: minimize water demand; minimize GHGs; minimize fertilizer use; minimize pesticides; maximize farmer incomes; or maximize benefits across all dimensions simultaneously—based on three different levels of governmental cooperation (that is, siloed, cross-ministry coordination and central government coordination) (Table 1). Our optimizations reallocate harvested areas between crops and alter cropping rotations with the constraints that: (1) national supply of all crops cannot decrease—a constraint reflecting national self-sufficiency targets; (2) farmer incomes within each grid cell cannot decrease—ensuring that farmer profitability is not adversely affected; (3) only crops grown at present within a grid cell can be planted there; (4) the harvested area within each grid cell is held constant—preventing agricultural expansion; and (5) cropping calendars of rotating crops cannot overlap in time. We also test the uncertainties of relaxing these constraints. Finally, we quantify the outcomes of optimized crop switching and compare the magnitude of benefits to relevant sustainable development targets for China. Such evaluations of several outcomes are essential for identifying interventions capable of improving the multidimensional sustainability of agriculture.
