Growing ... Growing ... Gone

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Since 1998, world grain production per person has fallen 5 percent, suggesting the ranks of the hungry are now expanding. This demonstrates a widespread deterioration in the human condition.

TWO NEW CHALLENGES

As we exceed the Earth's natural capacities, we create new problems. For example, farmers are now facing two new challenges: falling water tables and rising temperatures. Farmers today are the first to face widespread aquifer depletion and the loss of irrigation water. They also face higher temperatures than any generation since agriculture began 11,000 years ago.

The global average temperature has risen in each of the last three decades. The 16 warmest years since recordkeeping began in 1880 have all occurred since 1980.

With the three warmest years on record — 1998, 2001 and 2002 — coming in the last five years, crops are facing heat stresses that are without precedent.

Higher temperatures reduce crop yields through their effect on photosynthesis, moisture balance and fertilization. As the temperature rises above 94 degrees, photosynthesis slows and then ceases for many crops when it reaches 100 degrees. When temperatures in the U.S. Corn Belt are 100 degrees or higher, corn plants suffer from thermal shock and dehydration, and each such day shrinks the harvest.

In addition to decreasing photosynthesis and dehydrating plants, high temperatures impede the fertilization needed for seed formation. Recent findings indi cate harvests could drop 11 percent by 2020 and 46 percent by 2050.

The second challenge facing farmers, falling water tables, also is recent. With traditional animal- or human-powered water-lifting devices it was almost impossible in the past to deplete aquifers. With the global spread of powerful diesel and electric pumps, however, overpumping has become commonplace. As the world demand for water has climbed, water ta bles have fallen in scores of countries, including China, India and the United States, which together produce nearly half of the world's grain.

In the United States, the third major grain producer, water tables are falling under the southern Great Plains and in California, the country's fruit and vegetable basket. As California's population expands from 34 million to a projected 48 million by 2030, increasing urban water demands will siphon water from agriculture.

In addition to falling exponentially, water tables also are falling simultaneously in many countries. This means cutbacks in grain harvests will occur in many countries at more or less the same time. And they will occur at a time when the world's population is growing by more than 70 million a year. Many countries are overpumping their aquifers: Pakistan, Iran and Mexico are some of the more populous ones.

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