OVERVIEW
Every plant is keyed to a habitat, an important part of which is temperature tolerance. Soil and precipitation also are vital. Given the restraints of habitat, those who propose that we cope with a warming world simply by moving North America’s breadbasket to the Yukon and Northwest Territories are displaying an unusual amount of hubris—even for human beings. What, one may ask, about the suitability of soils scraped clear by millennia of glaciation? Such proposals rank with those who tell polar bears to turn brown, scavenge human garbage dumps, and get with the program.
Adaptation to a climate that changes more swiftly, and in malign ways, has become increasingly important for those who grow our food. As an editorial in Nature phrased agriculture’s challenge (“Prepare Farms” 2015): “Farmers must prepare for, and adapt to, a changed climate that is likely to feature more erratic rainfall, temperature extremes, drought, soil erosion, invasive weeds and durable pests. . . . But if adaptation is to work, climate scientists, agricultural researchers, farmers and government officials must work closely together.”
This section contains two types of entries. One describes what rising greenhouse gas emissions have done and will do to the agricultural activities that provide the food we eat. Those who believe that rising levels of carbon dioxide in the air will be beneficial for domesticated plants tend to downplay the damage that heat inflicts and dwell on the obvious, if rather simplistically analyzed, biological fact that plants breathe carbon dioxide and expel oxygen. More carbon dioxide, it is assumed by nonreaders of agricultural science journals, will deliver bigger, greener, and more robust harvests.
A body of evidence indicates that although “enhanced” levels of carbon dioxide may indeed accelerate the growth of some plants, these are not usually the types we will eat unless we become extremely hungry. Weeds tend to flourish under elevated levels of CO², whereas edible plants suffer damage from both exceptional heat and added greenhouse gases. In some cases, foliage increases, but seeds and fruits do not.
Hartwell Allen, a researcher with the University of Florida and the U.S. Department of Agriculture, has been growing rice, soybeans, and peanuts under controlled conditions, including varying temperatures, humidity, and carbon dioxide levels. Allen and his colleagues have found that although higher temperatures (to a point) and CO² levels stimulate lusher and faster growth, they are deadly during flowering and pollinating stages. At temperatures above 36°C during pollination, peanut yields dropped 6 percent per degree C of temperature. John Sheehy of the International Rice Research Institute in Manila found that damage to the world’s major grain crops begins during flowering at approximately 30°C. Around 40°C, yields for these crops essentially fall to zero. Crops grown under elevated levels of carbon dioxide also may be deficient in vital nutrients such as zinc and iron, which already pose a substantial public health problem around the world.
Even modest temperature increases that are anticipated by some climate models could be enough to reduce rice yields significantly over the next century. Researchers at the University of Florida tested several varieties of rice, growing them in chambers that simulated various temperature-change situations. They found that although the rice plants flourished no matter what the temperature, yields of grains declined precipitously as temperatures increased. The more modest temperature increases, the researchers say, could reduce rice yields by 20 percent to 40 percent by 2100, whereas the larger increases predicted by more dire forecasts could cut rice production entirely.
Climate-Ready Crops
n some quarters, adaptation has become a hot ticket. Agriculture contributes approximately 20 percent of human greenhouse gas emissions. Agricultural research is underway to reduce this figure, including such projects as breeding low-flatulence cattle (beef animals are a surprisingly large source of atmospheric methane, as is rice farming). Low-till or zero-till farming can help keep carbon in the soil, and more selective use of nitrogen fertilizer may inhibit emission of nitrous oxide, a greenhouse
gas 310 times more potent than the main greenhouse gas carbon dioxide. In 2008, the National Farmers Union paid farmers in the United States $5.8 million to adopt environmentally constructive practices in a “carbon credit” program, many of which (such as no-till farming and rotational grazing) capture carbon dioxide. Agencies that aid farmers already are developing new varieties of corn, wheat, rice, and sorghum as well as programs to encourage more efficient use of water and soil resources and to develop new practices to reduce greenhouse gas emissions from farming.
Large multinationals already have been racing to dominate so-called climate-ready crops. By 2008, three companies—Germany’s BASF, the Chinese multinational Syngenta, and U.S. agribusiness giant Monsanto—had filed applications that would allow them to control two-thirds of gene families in worldwide patent office filings, according to ETC Group of Ottawa, Canada, which advocates causes that benefit subsistence farmers. These new crops are being bred to resist not only heat and drought but also saltwater inundation, flooding, and increasing ultraviolet radiation (associated with depletion of stratospheric ozone).
Farming with an eye to carbon sequestration utilizes soil restoration and woodland regeneration, no-till farming, cover crops, nutrient management, manuring and sludge application, improved grazing, water conservation, efficient irrigation, agroforestry practices, and the growth of energy crops on spare lands.
In the meantime, people are being encouraged to eat with an eye toward reducing carbon dioxide and methane emissions—more vegetables and less meat. Local production reduces use of fossil fuels in transport. Food production in the United States today requires an average of six calories of energy to produce one calorie of food. Much of this energy is consumed in transport and in energy-intensive cultivation of factory farms, often because of a popular preference for energy-intensive types of food such as meats (most notably beef ).
FUTURE OF AGRICULTURE
Agriculture contributes approximately 20 percent of human greenhouse gas emissions. Low-till or zero-till farming can help keep carbon in the soil, and more selective use of nitrogen fertilizer may inhibit emission of nitrous oxide, a greenhouse gas 310 times more potent than the main greenhouse gas, carbon dioxide. In 2008, the National Farmers Union paid farmers in the United States $5.8 million to adopt environmentally constructive practices in a “carbon credit” program, many of which—such as no-till farming and rotational grazing—capture carbon dioxide. Agencies that aid farmers already are developing new varieties of corn, wheat, rice, and sorghum as well as programs to encourage more efficient use of water and soil resources and to develop new practices to reduce greenhouse gas emissions from farming.
Climate-Ready Crops
Large multinationals have been racing to dominate so-called climate-ready crops. By 2008, three companies—Germany’s BASF, the Chinese multinational Syngenta, and U.S. agribusiness giant Monsanto—by 2008 had filed applications that would allow them to control two-thirds of gene families in worldwide patent office filings, according to ETC Group of Ottawa, Canada, which advocates causes that benefit subsistence farmers. These new crops are being bred to resist not only heat and drought but also saltwater inundation, flooding, and increasing ultraviolet radiation (associated with depletion of stratospheric ozone).
Although the ETC Group maintains that the companies are engaged in “an intellectual-property grab,” the companies assert that “gene-altered plants will be crucial to solving world hunger but will never be developed without patent protections” (Weiss 2008). Patenting genes will prevent farmers in poor countries from saving seeds for future harvests and require them to purchase new seeds from the companies. The rush to patent new seeds also may prevent distribution by public-sector agencies affiliated with the United Nations and the World Bank. “When a market is dominated by a handful of large multinational companies, the research agenda gets biased toward proprietary products,” said Hope Shand, ETC’s research director. “Monopoly control of plant genes is a bad idea under any circumstance. During a global food crisis, it is unacceptable and has to be challenged” (Weiss 2008).
Speaking for Monsanto, Ranjana Smetacek said these companies should be appreciated for developing crops that will survive adverse environmental conditions. “I think everyone recognizes that the old traditional ways just aren’t able to address these new challenges. The problems in Africa are pretty severe” (Weiss 2008). Monsanto maintains that not all of its work is profit oriented. It has joined with BASF, for example, to support the Bill and Melinda Gates Foundation’s development of drought-resistant corn free of royalties to farmers in four southern African countries. “We aim to be at once generous and also cognizant of our obligation to shareholders who have paid for our research,” Smetacek said (Weiss 2008). The patents may be applied to a wide variety of crops, including “maize, wheat, rye, oat, triticale, rice, barley, soybean, peanut, cotton, rapeseed, canola, pepper, sunflowers, potato, tobacco, eggplant, tomato, peas, alfalfa, coffee, cacao, tea, Salix, oil palm, coconut, perennial grass, and forage crop plants” (Weiss 2008).
Fog and Fruit Trees
One side effect of intense and enduring drought that affects California agriculture has been a notable reduction in coastal and valley fog. This “Tule fog,” as it is called locally, decreased 46 percent between 1981 and 2013, according to reports from the NASA Earth Observatory. In 2014, the observatory called the decrease “bad news for California’s fruit and nut farmers” (“Winter Fog” 2014).
University of California–Berkeley scientists Dennis Baldocchi and Eric Waller used satellite photography to compile a record of “fog days.” They explained via the NASA Earth Observatory:
"Fog forms on cold winter nights after rain, when the air near the ground is moist with water evaporating out of the soil. When temperatures dip low enough, the moist air condenses into fog. Fewer fog days occur when temperatures are warmer or conditions are drier. The fog is important to California’s crops because fruit and nut trees, like people, need sufficient rest before they can be their most productive. They get that rest in the winter when cold temperatures—between [0 and 7°C (32 and 45°F)]—bring on a dormant period. Fewer fog days corresponds with fewer cold days. . . . The trees are now being exposed to hundreds fewer cold hours compared to 1982. The fog also shields the trees from direct sunlight during the winter. Direct sunlight can warm the buds even when surrounding air temperatures are cool. The warming decreases the number of cold-rest hours the tree gets during the winter, which decreases its productivity. (“Winter Fog” 2014; Baldocchi and Waller 2014)"
Reduction of cool winters required by fruit and nut trees in California already is imperiling some crops, according to a joint study by the University of California–Davis (UC Davis) and the University of Washington. “Depending on the pace of winter chill decline, the consequences for California’s fruit and nut industries could be devastating,” said Minghua Zhang, a professor of environmental and resource science at UC Davis (“Warming Climate Jeopardizes” 2009). By 2000, winter temperatures already were too high in most of California’s Central Valley to sustain apples, cherries, and pears. By 2100, the same area may no longer sustain walnuts, pistachios, peaches, apricots, and plums. Lack of cold weather affects the plants’ flowering time. “Our findings suggest that California’s fruit and nut industry will need to develop new tree cultivars with reduced chilling requirements and new management strategies for breaking dormancy in years of insufficient winter chill,” said Eike Luedeling, a postdoctoral fellow in UC Davis’ department of plant sciences (“Warming Climate Jeopardizes” 2009).
Twenty-First Century Projections
Temperatures by the end of the 21st century will rise to such a level that Europe’s extreme heat of August 2003 (which killed 30,000 people) will become common and devastate world agriculture and provoke a “perpetual food crisis,” including crop failures in many regions. That was the conclusion reached in a study published in Science January 9, 2009, that had been conducted by scientists at the University of Washington and Stanford University. Yields of staples such as wheat, corn, and rice may be reduced 20 percent to 40 percent. The study’s lead author, University of Washington climate researcher David Battisti, said that effects will be most intense in the tropics and subtropics were many people already live at the margin of survival (Mittelstaedt 2009). The scientists used data from 23 global climate models to show a high probability that more than 90 percent of growing-season temperatures in the tropics and subtropics by the end of the 21st century will exceed the most extreme seasonal temperatures recorded from 1900 to 2006 (Battisti and Naylor 2009, 240).
How will agriculture fare in a warmer world? The MINK Study (an acronym for Missouri, Iowa, Nebraska, Kansas) surveyed potential climate change in the central United States, North America’s agricultural heartland. Under certain circumstances, the authors found, higher levels of carbon dioxide might enhance the growth of some crops, but as a whole the productivity of the region’s agriculture would be significantly diminished. Agriculture in current farming regions will be severely affected not only by heat stress but also by reduced surface-water supplies because most global climate models predict that the interiors of continents will become not only hotter but also drier, especially during the growing season, as the atmosphere warms. An additional problem facing farmers in Nebraska and Kansas is depletion and salinization of aquifers that already support a large part of agricultural production in both states, especially their drier western areas.
Earth’s population by 2050 is expected to increase by nearly half, or 3.5 billion people. Roughly 75 percent of poor people still will depend on agriculture. Hotter, drier weather combined with explosive bursts of precipitation may shorten growing seasons and threaten production in some areas (notably in Africa and India) where agricultural production is limited by availability of water rather than the onset of cold weather. Hundreds of millions of people who already live at the margin may find their survival threatened.
Various modes of adaptation such as breeding crops that can resist more heat, flood, drought, or insect infestations may provide some help in the short range, but their ability to mitigate the destructive nature of warming will probably decline as temperatures rise. Accelerating climate change will provide farmers with an ever-changing environment that is bereft of old environmental benchmarks. A research report by the Consultative Group on International Agricultural Research (CGIAR) in Washington, D.C., a worldwide network of agricultural research centers, is already developing new crop strains that can withstand rising temperatures, drier climates, and increasing soil salinity. CGIAR also researches measures to reduce the carbon footprint of farming (Zeller 2006).
In the National Climate Assessment, which was published in January 2013, major agricultural areas in the middle of the United States were warned to anticipate more heavy spring rains of intensities that will ruin planting seasons and fewer summer rains that help relieve drought and replenish corn and other crops. Loss of topsoil from occasional but extremely heavy rains in a “drought or deluge” scenario is also anticipated. Higher nighttime temperatures will interfere with the pollination of many crops, which will suffer heat damage as weeds, plant diseases, and pests flourish during warmer growing seasons. Runoff from wide swings in snowpacks will become more erratic in irrigated areas as hotter weather strains general resources. Wider swings in both temperatures and rainfall also will play havoc with agriculture (Gaarder 2013, D1).
Warming and Canadian Grain Production
Climate-change skeptics often advance a simplistic solution to agricultural problems caused by warming temperatures and a more explosive hydrological cycle: move it all northward. Following their climatic logic, one can almost imagine corn sprouting along the shores of Hudson Bay. This assumes, however, that the soils will be right for growing crops. Even today, wheat, soy and canola are grown almost to the 60th parallel in the Peace River valley in Northern Alberta and British Columbia. Some varieties of grain, rye, flax, and canola mature in 120 days. Given enough rain (a problem in some northern latitudes) warmer weather could benefit Canadian agriculture. Grain-growing areas in Russia also may move northward in areas where soil is suitable.
The northern areas of Alberta and Saskatchewan are already producing hardy varieties of wheat. In northern Ontario and part of western Quebec, the clay belts are currently being farmed. Many of the Canadian Shield’s soils do not support agriculture, mainly because the soil is poor, although some areas are fertile. Warmer temperatures, especially in August and September, would allow for increased farming in Canada. The fertile eastern townships of Quebec in the St. Lawrence Lowlands have been farmed since at least the early 1700s. Most of these areas are former lake or sea bottoms and have deep, rich soils. The limiting factor has been the growing season. The boreal forests of northern Canada include tens of millions of acres with abundant water, in which trees have grown, died, rotted, and regrown for millennia. Add warmth and some of these areas might become productive farmlands.
Eastern Canada north of the Great Lakes and the St. Lawrence River valley is not generally suitable for grain. The western plains from western Lake Superior to the Rocky Mountains contain excellent grain-growing soils, however. Grain from Manitoba, Saskatchewan, and Alberta fed Great Britain from 1939 to 1941 during the early days of World War II.
Global-Scale Issues
Temperature increases and shifts in rainfall patterns probably will reduce growing periods in sub-Saharan Africa by more than 20 percent, with some of the world’s poorest nations in eastern and central Africa at greatest risk. A warming climate probably will reduce wheat production in India’s breadbasket. Production may decline by around 50 percent by 2050, a decrease that could put as many as 200 million people at greater risk of chronic hunger.
Although some studies anticipate rising food production in some areas during the early stages of global warming, others anticipate “negative surprises” in world agriculture, especially during the last half of the 21st century. Poor (i.e., “developing”) nations may lose 334 million acres of prime farmland during the next half century as temperatures rise and storms intensify, according to three studies in the December 11, 2007, edition of the Proceedings of the National Academy of Sciences: Tubiello et al., Howden et al., and Schmidhuber and Tubiello. By the last half of the 21st century, even cooler regions that may benefit from earlier temperature rises could experience declines in productivity. The authors of these studies argue that extremes of heat will join with other factors such as the spread of weeds and diseases to compound agricultural problems. These problems will inhibit increases in food production necessary to feed rising populations. These studies project that as many as 170 million people may be “at risk of hunger” by 2080 (Schmidhuber and Tubiello 2007, 19703).
“Many people assume that we will never have a problem with food production on a global scale. But there is a strong potential for negative surprises,” said Francesco Tubiello, a physicist and agricultural expert at NASA’s Goddard Institute for Space Studies, who coauthored the three PNAS reports published. The PNAS study authors said that much previous research work is oversimplified; as a consequence, the potential for bigger and more rapid problems remains unexplored. Heat waves and extreme storms could have their greatest effects on crops at crucial critical germination or flowering times. Tubiello says this is already happening on smaller scales.
Redrawing the Maps
During 2008, the U.S. Department of Agriculture issued a revised climatic-zone map for gardeners. This map assigns zones to various plants for winter survival. In the 18 years since the map had been revised in 1990, growing zones for many plants have moved northward. Southern magnolias, for example, once restricted to coastal Virginia southward, now thrive into Pennsylvania. In 1990, kiwis died north of Oklahoma. In 2008, they fruited in St. Louis, Missouri.
The Arbor Day Foundation has made similar adjustments in its maps, which were last revised in 2005. New drafts of U.S. Department of Agriculture maps may be difficult to find because they were delayed by political bickering within the agency between climate scientists and skeptics, as well as between owners of nurseries. Nursery owners feared losing money if they sold plants with money-back guarantees and the plants died in the new zones, but other sellers want to expand their marketing northward (Weise 2008).
Written by Bruce E. Johansen in "Climate Change - An Encyclopedia of Science, Society, and Solutions", ABC-CLIO, LLC, USA, 2017, vol. I, pp.1-9. Digitized, adapted and illustrated to be posted by Leopoldo Costa.