Agricultural intensification has dramatically increased in recent decades, outstripping rates of agricultural expansion, and has been responsible for most of the yield increases of the past few decades. In the past 50 years, the world’s irrigated cropland area roughly doubled, while global fertilizer use increased by 500%. Intensification has also caused water degradation, increased energy use, and widespread pollution. Of particular concern is that some 70% of global freshwater withdrawals are devoted to irrigation. Furthermore, rain-fed agriculture is the world’s largest user of water. In addition, fertilizer use, manure application, and leguminous crops have dramatically disrupted global nitrogen and phosphorus cycles, with associated impacts on water quality, aquatic ecosystems and marine fisheries. Both agricultural expansion and intensification are also major contributors to climate change. Agriculture is responsible for 30–35% of global greenhouse gas emissions, largely from tropical deforestation, methane emissions from livestock and rice cultivation, and nitrous oxide emissions from fertilized soils. We can draw important conclusions from these trends. First, the expansion of agriculture in the tropics is reducing biodiversity, increasing greenhouse gas emissions, and depleting critical ecosystem services. Yet this expansion has done relatively little to add to global food supplies; most production gains have been achieved through intensification. Second, the costs and benefits of agricultural intensification vary greatly, often depending on geographic conditions and agronomic practices. This suggests that some forms of intensification are better than others at balancing food production and environmental protection.Until recently,raspberry container growing most agricultural paradigms have focused on improving production, often to the detriment of the environment.
Likewise, many environmental conservation strategies have not sought to improve food production. However, to achieve global food security and environmental sustainability, agricultural systems must be transformed to address both challenges .First, the transformation of agriculture must deliver sufficient food and nutrition to the world. To meet the projected demands of population growth and increasing consumption, we must roughly double food supplies in the next few decades1–3. We must also improve distribution and access, which will require further changes in the food system. The transformation of agriculture should also cut greenhouse gas emissions from land use and farming by at least 80% ; reduce biodiversity and habitat losses; reduce unsustainable water withdrawals, especially where water has competing demands; and phase out water pollution from agricultural chemicals. Other environmental issues must also be addressed, but these four under gird the relationship between agriculture and the environment and should be addressed as necessary first steps. An influential series of recent reports has suggested possible solutions to our interwoven food security and environmental challenges. Below, we consider the potential strengths and weaknesses of four proposed strategies.The expansion of agriculture into sensitive ecosystems has far-reaching effects on biodiversity, carbon storage and important environmental services. This is particularly true when tropical forests are cleared for agriculture, estimated to cause 5–10 million hectares of forest loss annually. Slowing the expansion of agriculture, particularly into tropical forests, will be an important first step in shifting agriculture onto a more sustainable path. But will ending the expansion of agriculture negatively affect food supplies? Our analysis suggests that the food production benefits of tropical deforestation are often limited, especially compared to the environmental damages accrued.
First of all, many regions cleared for agriculture in the tropics have low yields compared with their temperate counterparts. The authors of ref. 21 considered crop production and carbon emissions resulting from deforestation and demonstrated that the balance of production gains to carbon losses was often poor in tropical landscapes . Regions of tropical agriculture that do have high yields—particularly areas of sugarcane, oil palm and soybeans—typically do not contribute much to the world’s total calorie or protein supplies, especially when crops are used for feed or bio-fuels. Nevertheless, such crops do provide income, and thereby contribute to poverty alleviation and food security to some sectors of the population. Although ceasing the expansion of agriculture into tropical forests might have a negative—but probably small—impact on global crop production, losses can be offset elsewhere in the food system. Agricultural production potential that is ‘lost’ by halting deforestation could be offset by reducing losses of productive farmland and improving yields on existing croplands. Though the ‘indirect land use’ effects of bio-fuel production are thought to increase pressure on tropical forests, it may also be true that increasing food production in non-tropical zones might reduce pressures on tropical forests. Economic drivers hold great sway over deforestation. Ecologically friendly economic incentives could play an important part in slowing forest loss: the proposed Reducing Emissions from Deforestation and Degradation programme, market certification, and ecotourism all provide opportunities to benefit economically from forest protection.Increasing food production without agricultural expansion implies that we must increase production on our existing agricultural lands. The best places to improve crop yields may be on under performing landscapes, where yields are currently below average. Recent analyses have found large yield variations across the world, even among regions with similar growing conditions, suggesting the existence of ‘yield gaps’ .
Here we define a yield gap as the difference between crop yields observed at any given location and the crop’s potential yield at the same location given current agricultural practices and technologies. Much of the world experiences yield gaps where productivity may be limited by management. There are significant opportunities to increase yields across many parts of Africa, Latin America and Eastern Europe, where nutrient and water limitations seem to be strongest . Better deployment of existing crop varieties with improved management should be able to close many yield gaps, while continued improvements in crop genetics will probably increase potential yields into the future. Closing yield gaps could substantially increase global food supplies. Our analysis shows that bringing yields to within 95% of their potential for 16 important food and feed crops could add 2.3 billion tonnes of new production, a 58% increase . Even if yields for these 16 crops were brought up to only 75% of their potential, global production would increase by 1.1 billion tonnes , a 28% increase. Additional gains in productivity, focused on increasing the maximum yield of key crops, are likely to be driven by genetic improvements. Significant opportunities may also exist to improve yield and the resilience of cropping systems by improving ‘orphan crops’ and preserving crop diversity, which have received relatively little investment to date. To close global yield gaps, the interwoven challenges of production and environment must again be addressed: conventional approaches to intensive agriculture, especially the unbridled use of irrigation and fertilizers, have been major causes of environmental degradation. Closing yield gaps without environmental degradation will require new approaches, including reforming conventional agriculture and adopting lessons from organic systems and precision agriculture. In addition, closing yield gaps will require overcoming considerable economic and social challenges, including the distribution of agricultural inputs and seed varieties and improving market infrastructure.Moving forward, we must find more sustainable pathways for intensification that increase crop production while greatly reducing unsustainable uses of water, nutrients and agricultural chemicals. Irrigation is currently responsible for water withdrawals of about 2,800 km3 per year from groundwater, lakes and rivers. Irrigation is used on about 24% of croplands and is responsible for delivering 34% of agricultural production17. In fact, without irrigation, global cereal production would decrease by an estimated 20% , so more land would be required to produce the same amount of food. However,blueberry plant pot the benefits and impacts of irrigation are not evenly distributed. We find that, when irrigated, 16 staple crops use an average of 0.3 litres per kilocalorie . However, these water requirements are skewed: 80% of irrigated crops require less than 0.4 litres per kilocalorie, while the remaining 20% require 0.7 litres per kilocalorie or more. Where water is scarce, good water and land management practices can increase irrigation efficiency. For example, curtailing off-field evaporative losses from water storage and transport and reducing on-field losses through mulching and reduced tillage will increase the value of irrigation water. Chemical fertilizers, manure and leguminous crops have also been key to agricultural intensification. However, they have also led to widespread nutrient pollution and the degradation of lakes, rivers and coastal oceans. In addition, the release of nitrous oxide from fertilized fields contributes to climate change. Excess nutrients also incur energy costs associated with converting atmospheric nitrogen and mining phosphorus. Even though excess nutrients cause environmental problems in some parts of the world, insufficient nutrients are a major agronomic problem in others. Many yield gaps are mainly due to insufficient nutrient availability .
This ‘Goldilocks’ problem of nutrients is one of the key issues facing agriculture today. Building on recent analyses of crop production, fertilizer use and nutrient cycling, we examine patterns of agricultural nitrogen and phosphorus balance across the world. Specifically, we show areas of excess nutrients resulting from imbalances between nutrient inputs , harvest removal and environmental losses . We further analyse the efficiency of nutrient use by comparing applied nutrients to yield for 16 major crops . Our analysis reveals ‘hotspots’ of low nutrient use efficiency and large volumes of excess nutrients . Nutrient excesses are especially large in China66, Northern India, the USA and Western Europe. We also find that only 10% of the world’s croplands account for 32% of the global nitrogen surplus and 40% of the phosphorus surplus. Targeted policy and management in these regions could improve the balance between yields and the environment. Such actions include reducing excessive fertilizer use, improving manure management, and capturing excess nutrients through recycling, wetland restoration and other practices. Taken together, these results illustrate many opportunities to improve the water and nutrient efficiency of agriculture without reducing food production. Targeting particular ‘hotspots’ of low efficiency, measured as the disproportionate use of water and nutrient inputs relative to production, could significantly reduce the environmental problems of intensive agriculture. Furthermore, agroecological innovations in crop and soil management show great promise for improving the resource efficiency of agriculture, maintaining the benefits of intensive agriculture while greatly reducing harm to the environment.While improving crop yields and reducing agriculture’s environmental impacts will be instrumental in meeting future needs, it is also important to remember that more food can be delivered by changing our agricultural and dietary preferences. Simply put, we can increase food availability by shifting crop production away from livestock feed, bio-energy crops and other non-food applications. In Supplementary Fig. 7, we compare intrinsic food production and delivered food production for 16 staple crops. By subtracting these two figures, we estimate the potential to increase food supplies by closing the ‘diet gap’: shifting 16 major crops to 100% human food could add over a billion tonnes to global food production , or the equivalent of 33 1015 food kilocalories . Of course, the current allocation of crops has many economic and social benefits, and this mixed use is not likely to change completely. But even small changes in diet and bio-energy policy could enhance food availability and reduce the environmental impacts of agriculture. A large volume of food is never consumed but is instead discarded, degraded or consumed by pests along the supply chain. A recent FAO stud suggests that about one-third of food is never consumed; others have suggested that as much as half of all food grown is lost; and some perishable commodities have post-harvest losses of up to 100% . Developing countries lose more than 40% of food post-harvest or during processing because of storage and transport conditions. Industrialized countries have lower producer losses, but at the retail or consumer level more than 40% of food may be wasted. In short, reducing food waste and rethinking dietary, bio-energy and other agricultural choices could substantially improve the delivery of calories and nutrition with no accompanying environmental harm. While wholesale conversions of the human diet and the elimination of food waste are not realistic goals, even incremental steps could be extremely beneficial. Furthermore, targeted efforts—such as reducing waste in our most resource-intensive foods, especially meat and dairy—could be designed for optimal impact.Today, humans are farming more of the planet than ever, with higher resource intensity and staggering environmental impacts, while diverting an increasing fraction of crops to animals, bio-fuels and other nonfood uses. Meanwhile, almost a billion people are chronically hungry. This must not continue: the requirements of current and future generations demand that we transform agriculture to meet the twin challenges of food security and environmental sustainability.