The Heat Is Online

Higher Temperatures Drive Crop Yields Down for Four Years

Wheat and Rice Prices Moving Up

By Lester R. Brown

Earth Policy Institute, Sept. 2003

This year's world grain harvest is falling short of consumption by 93 million tons, dropping world grain stocks to the lowest level in 30 years. As rising temperatures and falling water tables hamstring farmers' efforts to expand production, prices of wheat and rice are turning upward.

For the first time, the grain harvest has fallen short of consumption four years in a row. In 2000, the shortfall was a modest 16 million tons; in 2001 it was 27 million tons; and in 2002 a record-smashing 96 million tons. In its September 11 crop report, the U.S. Department of Agriculture (USDA) reported that this year's shrunken harvest of only 1,818 million tons is falling short of estimated consumption of 1,911 million tons by a near-record 93 million tons.

Agricultural leaders are now looking to next year's crop with fingers crossed. If 2004 brings another large shortfall comparable to this year or last year, there could be chaos in world grain markets by this time next year as more than 100 grain-importing countries scramble for scarce exportable supplies.

Higher temperatures are thwarting farmers' efforts to expand food production. The earth's average temperature has been rising since the late 1970s, with the three warmest years on record coming in the last five years. As temperatures continue to rise, crop yields start to fall.

Last year India and the United States suffered sharp harvest reductions because of record temperatures and drought. This year Europe bore the brunt of higher temperatures. Record heat in late summer scorched harvests from the United Kingdom and France in the west through Ukraine in the east. Bread prices are rising in several countries in the region.

After several years of seeing crops withered by heat, scientists are now beginning to focus on the precise effect of temperature on crop yields. New research from crop ecologists at the International Rice Research Institute and the USDA's Agriculture Research Service shows an emerging consensus that a 1-degree Celsius rise in temperature (1.8 degrees Fahrenheit) above the optimum during the growing season leads to a 10-percent decline in grain yields.

How much will the earth's temperature rise? The Intergovernmental Panel on Climate Change (IPCC)with some 1,500 of the world's leading climate scientistsis projecting a rise of 1.4-5.8 degrees Celsius (2.5-10.4 degrees Fahrenheit) during this century if carbon emissions continue to increase. Farmers on the land now are facing the prospect of higher temperatures than those faced by any generation of farmers since agriculture began.

Although the IPCC projections are presented as global averages, the rise in temperature will be geographically uneven. Temperature rise is projected to be much greater over land than over the sea, in higher latitudes than in equatorial regions, and in the interior of continents than in coastal regions. The higher latitudes and continental interiors where the projected temperature rise is to be greatest neatly defines the North American breadbasketthe wheat-growing Great Plains of the United States and Canada and the U.S. Corn Belt.

This generation of farmers is also the first to face widespread aquifer depletion due in part to the use of powerful diesel and electric pumps that have become widely available only in the last few decades. Prospects for the big three grain producersChina, India, and the United States, which account for nearly half of the world's grain harvestshow the potential consequences of future water shortages.

Under the North China Plain, which produces half of China's wheat and a third of its corn, water tables are falling up to 3 meters per year. A World Bank assessment of China's water situation says, "Anecdotal evidence suggests that deep wells [drilled] around Beijing now have to reach 1,000 meters [more than half a mile] to tap fresh water, adding dramatically to the cost of supply." In unusually strong language for a Bank report, it foresees "catastrophic consequences for future generations" unless water use and supply can quickly be brought back into balance.

In India, water tables are falling throughout most of the country. As a result, thousands of wells are going dry each year. The USDA reports that water tables have dropped by more than 100 feet (30 meters) in parts of Texas, Oklahoma, and Kansas. Water supplies are even tighter in California.

Overpumping for irrigation is a way of satisfying the growing demand for food today that almost guarantees a future drop in food production when the aquifer is depleted. For a few countries, the day of reckoning with aquifer depletion is already here. For many others it is drawing near.

Over the last four years the world's farmers have fallen further and further behind the growth in grain demand. We must now at least ask the question: Are the positive influences on production, such as advances in technology and investment in land improvement, largely being offset by negative influences, such as soil erosion, aquifer depletion, and rising temperature?

Since there has not been any growth in world grain production in eight years, the answer to that question may be yes. If so, we will need to move quickly to stabilize population, raise water productivity, and stabilize climate. If future grain shortages lead to dramatic price rises, they could destabilize governments in low-income grain-importing countries, disrupting global economic progress. Food security could quickly become the overriding security issue.

With most of the nearly 3 billion people who are due to be added to world population by 2050 coming in countries where wells are already going dry, there is an urgent need to stabilize population size as soon as possible. Some 34 countries have already stabilized their population. It is time for the remaining 150 countries to do so.

With water shortages spreading, we need a concerted global effort to raise water productivity, one patterned on the highly successful effort to raise land productivity that was launched a half century ago and that has nearly tripled world grain yields since then.

With rising temperature now shrinking harvests, we need to get serious about stabilizing climate, going far beyond the global goal set in the Kyoto Protocol of a 5-percent cut in carbon emissions by 2012. Reducing fossil fuel use is the key to stabilizing climate. It is perhaps a commentary on the complexity of our time that decisions made in ministries of energy may have a greater effect on food security than those made in ministries of agriculture.

Future food security may depend not only on stabilizing population, raising water productivity, and stabilizing climate, but on doing all these things at wartime speed.

© 2003 Earth Policy Institute