Investing in Perennial Crops to Sustainably Feed the World: The Dramatic Increases in Yields of Annual Crops Are Approaching Their Limits. but Similar Advances Are Possible in Hundreds of Underused Perennial Species
Kahn, Peter C., Molnar, Thomas, Zhang, Gengyun G., Funk, C. Reed, Issues in Science and Technology
The world's food supply is insecure and inadequate and growing more so. But that gloomy prospect could be altered dramatically if the world adopted a novel but simple strategy: supplement the annual food crops that will soon be unequal to the task of sustaining us with improved perennial plants such as food-bearing and bioenergy-producing trees, shrubs, forbs, and grasses. Making this shift will not be easy and will require significant additional research. But we believe it is a practical and relatively inexpensive approach that will not only increase food and energy security, but will also improve soil quality, protect water resources, reduce floods, harvest carbon dioxide (C[O.sub.2]), and provide jobs for millions of people.
During the past half-century, the world's population has doubled, increasing by more than three billion people. Fortunately, grain production has more than doubled during that time. Availability of nutritious food at the lowest cost in history underlies whatever peace, prosperity, and progress human society has enjoyed.
In the next half-century, however, the planet is scheduled to add another three billion people. We will once again need to increase food production by an equivalent amount just to stay in place. But staying even will not be enough. Today there are millions of people who don't have enough to eat and millions more who yearn to move away from mainly plant-based diets. The recent push to produce crops for energy use complicates the situation.
Increases in the yields of the annual crops on which we now rely are certainly possible and should be pursued vigorously. However, these efforts are unlikely to provide a complete and sustainable solution to the growing scarcity of food and energy. Much of the land on which we depend is losing productivity because of deforestation, development, overgrazing, and poor agricultural practices. Erosion, pollution, and the expansion of deserts are among the consequences.
Water tables are falling as aquifers are pumped at rates exceeding their ability to recharge. Even the water in deep-fossil aquifers, laid down millions of years ago and which can't be recharged, is being depleted. Nearly 90% of all fresh water used by humans goes for irrigation. According to the United Nations Food and Agriculture Organization (FAO), just 16% of the world's cropland is irrigated, but this 16% produces 36% of the global harvest.
The stripping of forest and grassland and the cultivation of sloping land have led to rapid runoff of rainwater that normally would help recharge near-surface aquifers. In many regions, inadequate drainage has increased the salt content of the soil, leading to a loss of productivity and sometimes abandonment of agriculture altogether. The once-fertile crescent of the Middle East is a striking example, and similar salinization is accelerating in the United States, China, and elsewhere. It is certainly possible and imperative to increase the efficiency of agricultural water use, but it is not clear whether this will fully compensate for water losses or increase yields of annual crops enough.
Dust bowls and desertification are serious in many parts of the world. Depletion of the fossil aquifer under the North China plain, for example, has led to huge dust storms that choke South Koreans every year. Increasingly frequent storms from Africa routinely drop irreplaceable soil into the Caribbean, endangering the coral and thus the ecosystem there while depleting African lands.
Worldwide cereal crop production appears to have leveled off during the past few years, and per capita cereal crop production has been declining since the 1980s. One result of this decline has been steadily increasing pressure to convert environmentally sensitive land to annual crop production. A vicious cycle of burgeoning population and diminishing soil productivity has led to farming marginal land.
In addition, tropical forests are being cut for timber and burned to create grassland for cattle and farmland for soybeans and other annual crops. …