Course 2: Increase Food Production without Expanding Agricultural Land (Synthesis)

Demand for milk and meat from grazing ruminants is likely to grow even more than demand for crops. Because pasture makes up two-thirds of all agricultural land, the productivity of livestock will critically affect future land use and emissions. Large productivity improvements for pork and poultry are unlikely in developed countries because of biological limits.³³ In developing countries, because traditional backyard systems make use of waste and scavenging, shifts to modern systems increase output but do not reduce land-use demands and emissions.

By contrast, ruminant systems have greater potential to improve, as suggested by the wide range in productivities across countries. The GHG emissions that result from producing each kilogram of beef—a good proxy for all aspects of productivity—are far higher in some countries than in others (Figure 10). Land-use requirements can be 100 times greater,³⁴ and the quantity of feed 20 times greater.³⁵

Higher ruminant productivity can be achieved by increasing output per animal through improved food quality, breeding, and health care; and by increasing feed output per hectare. Neither requires a shift to feedlots. On pastures with good rainfall, productivity can be increased by proper fertilization, growing legumes, rotational grazing, and adding supplemental feeds in dry seasons and during the last few months of “finishing.” In the “cut and carry” systems that predominate in Africa and Asia, farmers can grow a wide variety of improved forage grasses and shrubs with high protein leaves.

The real challenge lies in the scale of improvement required. Because much grazing land is too dry or too sloped to support large feed improvements, almost every hectare of wetter, accessible, and environmentally appropriate land would need to achieve close to its maximum productive potential to meet expected global demand without the need for further land conversion.

• Most ruminant farmers need to shift from low-management operations, which take advantage of cheap land, toward careful, intensive grazing and forage management using more labor and inputs.
• Governments in developing countries, which are home to the great majority of ruminants, should establish livestock productivity targets and support them with greater financial and technical assistance.
• Implementation of systems to analyze improvement potential and track changes in different areas and on different types of farms would help guide these investments and monitor their effects.

Figure 10

Inefficient beef production systems result in far higher greenhouse gas emissions per unit of meat output

Source

Herrero et al. (2013).

Breeding of improved crops is generally credited for half of all historical yield gains. Breeding can both increase the potential yield of crops under ideal conditions and help farmers come closer to those potential yields by better coping with environmental constraints. Countries that have invested more in recent years in crop breeding, such as Brazil and China, have seen vast improvements in their yields.

“Incremental” crop breeding has been the primary driver of yield gains through assessment and selection of the best performing existing crops, followed by purification, rebreeding, production, and distribution. In the United States, improved maize varieties are released every three years. Speeding new crop cycles would boost yield growth in many countries such as Kenya and India, where new grain varieties are released typically every 13 to 23 years.³⁶

Much debate has focused on genetically modified organisms (GMOs), which involve insertion of genes from one plant into another. The debate has centered overwhelmingly on two types of traits that assist pest control through glyphosate resistance and expression of Bt (Bacillus thuringiensis), a biological pesticide. Some bona fide debate is appropriate about whether the ease of use and relatively lower toxicity provided by these traits in the short term, and their potential value to small farmers without access to pesticides, justifies the longer-term risks of building resistance in weeds, worms, and insects—potentially leading to more pesticide use in the future. There is no evidence that GMOs have directly harmed human health.³⁷

Gene editing has far greater potential. Sometimes new genes can provide the only viable mechanisms for crops to survive new diseases. New genes may also play a major role in combating environmental challenges by making crops more efficient at absorbing nitrogen or suppressing methane or nitrous oxide emissions.

The CRISPR-Cas9³⁸ revolution since 2013 dramatically increases opportunities to improve breeding through genetic manipulation. CRISPR enables researchers to alter genetic codes cheaply and quickly in precise locations, insert new genes, move existing genes around, and control expression of existing genes. CRISPR follows a related genomics revolution, which makes it cheap to map the entire genetic code of plants, test whether new plants have the desired DNA without fully growing them, and purify crop strains more rapidly.

According to the most recent assessments, global public agricultural research is roughly $30 billion per year for all purposes, and private crop-breeding research is around $4 billion, which we consider modest. The vast opportunities created by new technologies warrant large and stable increases in crop-breeding budgets.

Revitalizing degraded soils, which may affect one-quarter of the world’s cropland,³⁹ provides another opportunity to boost crop yields. Degradation is particularly severe in drylands, which cover much of Africa and where low soil fertility is a direct threat to food security. Loss of organic matter is a special concern because soils then hold less water and are less responsive to fertilizers, making fertilizer use less profitable.

Agencies in recent years have encouraged African farmers to adopt “conservation agriculture,” which relies on no or reduced tillage (plowing) of soils and preserving crop residues^.40 These practices can limit soil erosion and may help boost yields modestly in particularly dry areas, but farmers are often reluctant to avoid tillage because of the increased need for weeding or herbicides, and because they often need to use crop residues for livestock feed.⁴¹

Some of the more promising approaches involve agroforestry, often using nitrogen-fixing trees. Farmers have helped regenerate trees in farm fields across 5 Mha in the Sahel, boosting yields.⁴² Commitments to agroforestry made by many African governments would benefit from more systematic evaluation of which systems work economically, and where. Microdosing crops with small quantities of fertilizer and trapping water on farms through various blocking systems also shows promise in drylands.⁴³

Strategies to improve soils will need to address the real obstacles facing farmers. Rebuilding soil carbon may require diversion of land, labor, or residues needed for food production and will therefore need financial support.⁴⁴ Efforts to grow more legumes to fix nitrogen in African soils must overcome high rates of disease, which requires breeding plants with improved disease resistance. Enhancing soil carbon also requires that farmers add or fix enough nitrogen to meet crop needs and those of soil-building microbes, so cheaper fertilizers must be available.

• In drylands like the Sahel, governments and international aid agencies should increase support for rainwater harvesting, agroforestry, farmer-to-farmer education, and reform of tree-ownership laws that can impede farmers’ adoption of agroforestry.
• Elsewhere, governments and aid agencies need to explore new models for regenerating soils. One option may be to provide financial help to farmers to work incrementally on their farms, improving one small piece of land at a time. If one small area can be improved quickly to the point where it generates large yield gains, the economic return may come soon enough to motivate farmer efforts.

FAO data indicate that more than 400 Mha of cropland go unharvested each year, suggesting that this amount of land is left fallow.⁴⁵ FAO data also indicate that farmers plant roughly 150 Mha twice or more each year (double cropping).⁴⁶ The ratio of harvests each year (harvested area) to quantity of cropland is known as the “cropping intensity,” a ratio that FAO currently estimates at 82 percent. Planting and harvesting existing cropland more frequently, either by reducing fallow land or by increasing double cropping, could in theory boost food production without requiring new cropland.

Some analysts have interpreted FAO data to suggest a large recent increase in cropping intensity, but these claims are mostly undercut by local satellite studies. Using relatively crude criteria, other studies have suggested a substantial theoretical potential to increase double cropping on rainfed lands. But roughly half of double-cropped land today is irrigated, and farmers probably plant two crops a year on only 6 percent of rainfed area. Practically and economically, the prospects for expanding double cropping on rainfed lands must therefore be limited, as is expanding double cropping on irrigated land because of water constraints.

In addition, there are significant environmental costs in some regions to planting fallow croplands more frequently because some fallow lands are either in very long-term rotations or are in the early stages of abandonment. Typically, they will revert to forest or grassland and help store carbon and provide other ecosystem services. Planting them more frequently sacrifices these benefits.

Despite difficulties, there are opportunities for progress. Raising cropping intensity is a promising option, particularly in Latin America, where double cropping has been growing. Our baseline assumes a 5 percent increase in cropping intensity to 87 percent. If cropping intensity were to increase another 5 percent, the land gap would shrink by 81 Mha, or 14 percent.

Strategies to encourage higher cropping intensity require scientists to conduct more detailed and spatially explicit analyses to determine realistic potential increases in cropping intensity. Studies should account for limitations on irrigation water availability and build in at least some basic economics. Governments and researchers will then be better able to determine which improvements in infrastructure or crop varieties can contribute to economically viable increases in cropping intensity

The global impacts of climate change on agriculture are sufficiently uncertain that we did not attempt to model them in our 2050 baseline. Although earlier analyses suggested that effects on crop yields by 2050 might even be beneficial, by the time of the 2014 IPCC report, models projected on average that, without adaptation, global crop yields were “more likely than not” to decline by at least 5 percent by 2050—with even steeper declines by 2100.⁴⁷

Many estimates are even larger, and uncertainty should be a cause for greater concern because “medium” impacts are not more likely.⁴⁸ We modeled one plausible estimate of a 10 percent decline in crop yields due to climate change without adaptation. Cropland would need to expand overall by 457 Mha (increasing the total land gap by 45 percent).

Climate change will benefit some crops, at least in the short term, as higher concentrations of carbon dioxide increase the efficiency of photosynthesis. Warmer temperatures will extend the growing season in colder countries and regional shifts in rainfall patterns will make some locations wetter.⁴⁹ But some areas will also become drier and hotter. Higher temperatures will harm crops by drying soils, accelerating water loss, and increasing pest damage.⁵⁰ Extreme heat events will harm maize, wheat, coffee, and many other crops by interfering with reproduction.⁵¹ Growing seasons in parts of sub-Saharan Africa could become too short or too irregular to support crops (Figure 11), contributing to major food security concerns.⁵²

The evidence from crop models indicates significant but uncertain capacity to adapt using tailored crop varieties. Uncertainties about local climate change suggest broad “no regrets” strategies, many of them already included in our other menu items. For example, closing yield gaps in Africa and India would increase incomes and provide a buffer against adverse climate impacts, forest protection could increase resilience through improved local hydrology, while safety net programs for the rural poor will better equip small farmers to deal with future variability.

Some climate effects, however, are sufficiently clear to emphasize the need for new measures or expanded effort on other menu items:

• Farmers need effective regional crop-breeding systems that enable them to select alternative crop varieties specifically adapted to local conditions.
• Small-scale irrigation and water conservation systems will help farmers cope with rainfall variability.
• Research organizations and companies must breed new traits to overcome highly likely big climate challenges such as high temperature effects on maize, wheat, rice, and coffee.
• Governments must help fund adaptation to those major physical changes that are clearly predictable, such as altering production systems in areas that will be affected by sea level rise.

Figure 11

Climate change could shorten growing seasons in much of sub-Saharan Africa by more than 20 percent by 2100 

Source

Verhage et al. (2018) using methods from Jones and Thornton (2015).

The menu items in Course 2 are needed first merely to achieve our baseline. As Figure 9 and Table 2 show, the productivity gains assumed in our baseline projection close more than 80 percent of the land gap (and approximately two-thirds of the GHG mitigation gap) that would result if agricultural efficiency did not improve at all after 2010. We also modeled more optimistic scenarios to 2050, where, relative to the baseline projection, we assume a 25 percent faster rate in ruminant livestock productivity gains, 20 and 50 percent faster rates of growth in crop yield gains, and a 5 percent additional increase in cropping intensity.

Even these additional improvements leave significant land and GHG mitigation gaps (Table 2). This is why closing the land gap completely will require demand-side measures (Course 1) and action to protect and restore natural ecosystems (Course 3), and why closing the GHG mitigation gap completely will require action across all courses.

Table 2

Higher crop and livestock productivity could reduce agricultural land area and greenhouse gas emissions in 2050

Notes

“Cropland” includes cropland and aquaculture ponds. Numbers not summed correctly are due to rounding.

Source

GlobAgri-WRR model.