Pillar of Sand, by Sandra Postel, is spellbinding book about everyone’s favorite subject, irrigation. It discusses the history of irrigation, the numerous serious problems, and the theoretical solutions — many of which seem to be economically or politically impossible. The general health of irrigated agriculture is worrisome, and so is its future. Feeding ten billion a few decades from now is not going to be a piece of cake.
The benefits of irrigation enabled the development of many civilizations, and the drawbacks of irrigation then destroyed many of them. Today, 17 percent of the world’s cropland is irrigated, and it produces 40 percent of our food. This amazing productivity has thrown gasoline on the flames of human reproduction, resulting in explosive population growth, which is never a good thing.
From the very beginning, irrigation seemed to be a fountain of bad karma. From the flooded fields sprouted a bumper crop of mighty emperors, vast palaces, powerful armies, multitudes of slaves, contagious diseases, the loss of freedom, and a pitiable way of life, isolated from wild nature. It was a high-powered form of agriculture, but the magic was mixed with serious defects. Sudden shifts in precipitation or temperature could make an entire civilization vulnerable to famine. The levees, canals, and dams required continuous maintenance by large numbers of hard-working grunts. The infrastructure also provided excellent targets for malevolent invaders, and vengeful enemies.
Over time, irrigation often led to the buildup of salt in the soil — salinization, which eventually transformed excellent cropland into infertile wasteland. Irrigation was a primary reason why the once lush gardens and orchards of the Cradle of Civilization are now bleak deserts decorated with ancient ruins.
Today, salinization is increasing on 20 percent of irrigated land, causing productivity losses over vast areas. Farmers can slow this destruction by installing a combination of drainage systems and high-efficiency drip irrigation. Unfortunately, this is very expensive, few farmers do it, and the salt continues to accumulate. Postel writes, “Salt remains one of the gravest threats to irrigated agriculture and food security in a world that will be striving to feed 8 to 9 billion people within 50 years.”
In the last 200 years, irrigated land has increased 30 times in area. We went on a dam-building binge. In the last 50 years, there has also been an explosion in the number of powerful electric and diesel pumps. They allowed irrigation to expand into many new regions. It is no coincidence that our population also skyrocketed — more food, more mouths, more problems.
It is no coincidence that we are discovering limits to the supply of fresh water. In many places the water table is falling, because water is being pumped from underground aquifers faster than the ecosystem replaces it. This groundwater mining is a widespread threat in primary food-producing regions of Pakistan, the Middle East, North Africa, the Arabian Peninsula, India, northern China, and the western United States.
The problem is well understood, but little effort is being made to address it, because over-pumping generates lots of food and money. Eventually, the wells will go dry, and the golden goose will drop dead. About a tenth of global grain production currently depends on aquifer mining. Postel warns us: “Groundwater over-pumping may now be the single biggest threat to irrigated agriculture, exceeding even the buildup of salts in the soil.”
Irrigation is also draining major rivers. In 1997, sections of the Yellow River in China had no flow for 226 days. The dry stretches are often 600 kilometers long, and this takes a big toll on farm production. Other threatened rivers include the Ganges, Indus, Nile, Amu Darya, Syr Darya, Chao Phraya, and Colorado. In these basins, irrigation can no longer be expanded. Growing cities and industries are consuming more and more water too, and they can produce more money with a gallon of water than a farmer can. The proverbial wisdom says that water flows uphill toward money.
Meanwhile, the catastrophic population explosion continues, and another two or three billion are expected to come to dinner in 2050. How will we feed them? Oceanic fisheries are past peak and declining. Ranching isn’t able to dramatically expand, neither is rain-fed agriculture. The Green Revolution is over, and there are no new plant-breeding miracles on the horizon.
This leaves irrigated agriculture holding the bag, and it looks like a wobbly bloody boxer after 18 rounds in the ring with a hard-punching opponent. Conflicts over water are on the rise. Numerous aquifers are being depleted. Major rivers are being pumped dry. Salinization continues to destroy more cropland. Climate change could introduce serious additional problems, because our systems are designed to function in the current climate scenario.
The ideal sites for dams are already taken, and an anti-dam movement is growing. Existing dam reservoirs are continuously accumulating silt. On average, the capacity of the world’s reservoirs is diminishing by one percent annually. For this reason, all dams have an expiration date, because removing the silt is very expensive. “Like salinization and groundwater depletion, the silting up of reservoirs is a quiet, creeping threat that is building to massive proportions.”
Governments are running low on funds for the costly maintenance of water systems, and they are losing interest in building costly new water systems. Many farmers do not feel obligated to obey the water use rules (if any), and enforcement of these rules is minimal. Few farmers can afford to install state-of-the-art irrigation technology. Cheap subsidized water discourages farmers from investing in efficiency improvements. Few if any farmers could afford to pay the full cost for their water. Few are interested in investing big money today to avert a problem that may not become serious until 20 or 30 years from now, especially if they don’t own the land, or have big money.
Despite all of these challenges, the strategic global goal is to double the productivity of irrigated lands. In theory, Postel believes that this is possible. In reality, important changes are being made far too slowly. The subtitle of this book is “Can the Irrigation Miracle Last?” From what Postel tells us, I wouldn’t bet on it. Was the invention of irrigation really a “miracle?” It unleashed major changes in history, and it’s not hard to argue that the costs far exceeded the benefits.
On the last two pages, Postel mentions population. Population growth tends to magnify all problems, while solving none. Therefore, major efforts to further increase food production are not perfumed with the intoxicating aroma of wisdom. As long as we’re dreaming for miracles, it would be far more intelligent to sharply reduce population, and thereby diminish many problems simultaneously. But the current generation seems to be firmly against this — breed now, pay later.
Postel, Sandra, Pillar of Sand — Can the Irrigation Miracle Last?, W. W. Norton & Company, New York, 1999.