Rapid Population Growth in California: A Threat to Land and Food Production

David & Marcia Pimentel. June 2, 2008. Rapid Population Growth in California: A Threat to Land and Food Production. Cornell University, College of Agriculture and Life Sciences

Are Californians —who are now coping with overcrowded cities, jammed highways, and a damaged environment— prepared for future population growth? Consider that by 2035, California’s population will approximately double to 64 million (39 million now), if current population growth continues. This projection is based on the state’s current 2% annual growth rate —a rate that is greater than the national growth rate of 1.1% and is generated primarily by the high immigration rate, both legal and illegal.

All human activities, economical enterprises, environmental preservation and food production systems will suffer when human numbers exceed the basic resources that support human life. If the population continues to climb, food security —the potential to produce enough food so that people in California can lead healthy and productive lives— will be significantly stressed. The future status of agricultural production is especially critical, as vital resources like arable land, clean water, adequate energy, and abundant biodiversity are rapidly depleted throughout California and the world.

Land Availability

Of the 2.3 billion acres of land in the United States, only 460 million acres, or 20%, are considered suitable for agricultural production. California has a fair amount of that fertile land, and ranks first in agricultural production in the U.S. However, a loss of agricultural land, and subsequent decrease in production, is imminent if current population trends continue. Essentially, the U.S. population, including California’s, is increasing geometrically while arable land per capita is simultaneously decreasing (Figure 1). This fertile land is lost to urbanization and industrial spread, transportation systems, and wind and water erosion.

At present, about 8% of the 100 million acres in California —8 million acres— are devoted to crops. Yet each year about 122,000 acres —1.5%— are lost from production when swallowed by urban and industrial spread. As the population grows, more and more people need a place to live and work, placing increasing demands on limited land areas. In general, each person added to the population requires approximately 1 acre of land for urbanization and highways. When the California population doubles to 64 million, as projected for 2035, about 32 million of California’s 100 million acres will need to be used for the housing, employment, and transportation of those 32 million additional people. Does California have that much land to spare even today?

Arable soil consists of only about the top 6 inches of soil; this fertile soil is easily lost by wind and water erosion. Stated simply, erosion occurs when the soil is exposed to energy from wind or water, like rainfall or running water. Poor farming tactics, such as the failure to practice crop rotation or to use wind blocks, can increase rates of erosion. Agricultural land in the United States typically erodes at a rate of about 6t/ha/year (2.47 acres = 1 hectare) for pasture land to 13t/ha/year for cropland, so a significant portion of California’s current 8 million acres of agricultural land are lost each year to erosion. Finally, salinization and/or waterlogging of soil from irrigation can further diminish the productivity of the land. And when crop production is curtailed, food prices will increase and the economic health of the state will suffer.

Agricultural production in California totals $20 billion each year, contributing a significant amount to the state’s income. The major agricultural counties in California are Fresno, Tulare, and Monterey, with annual sales of $2.1, $1.4, and $1.2 billion per year respectively. Much of this income could easily be lost unless California’s agricultural land base is protected from further population growth.

It is projected that in about 60 years, per capita agricultural land will be reduced to approximately half of what it is today. With a decreased supply and increased demand for food, food prices are expected to increase by 3-to-5 times current prices. So, even if the total dollar value of sales doesn’t decline as a direct result of the increased demand for diminished supply, the land area devoted to farms —and the number of farms— may be half what it is today. This change in the farming system will have a major impact on the economy of California and its people.

All told, California stands to lose a substantial amount of available farm land, at a substantial economic loss, if the population continues to grow. In fact, if the current rate of land loss continues, in less than 33 years approximately half of California’s cropland will no longer be available for production. In addition, the growing numbers of humans stress other natural resources, including water, energy, and the environment, that are also vitally important to agricultural production.

Water Resources

California, like many western U.S. states, is considered an arid state, with rainfall levels between 200 and 500 mm per year. The average American uses about 1,450 gallons/day/capita of water to meet all his/her needs, including agricultural production. Unfortunately, to provide the ever-increasing amounts of water necessary for a steadily increasing population, overdraft is already occurring from surface and ground water resources. For example, by the time the Colorado River enters the Gulf of California, it is literally a small trickle. The seven adjacent states —among them California, Nevada, Colorado, and Arizona— remove enormous amounts of water to meet their local needs, but return little or no water to the rapidly diminishing supply. Americans, especially those in arid states like California, are going to have to conserve and reduce their water use sooner rather than later, as the amount of available water per capita rapidly diminishes.

California agriculture consumes 80% of the pumped water in the state. For decades, providing water for agricultural, industrial, and home use has required massive efforts to channel water from afar to where it was needed in urban and agricultural areas. For instance, about 250 gallons of water are needed to produce 1 pound of grain. To irrigate an acre of corn requires nearly 1 million gallons of water during the 3 to 4 month growing season. Nearly all of California’s cropland, plus large percentages of forage and pasture land, are irrigated. The total land area currently irrigated in California is about 7.6 million acres.

At present, much of the irrigation water is being applied to low value crops like forage alfalfa and rice. This practice is possible only because the federal government provides generous subsidies —estimated at approximately $1.5 billion annually— to pay for the irrigation. This situation will change in the future when California agricultural requirements compete more intensely with the needs of a rapidly growing human population and industry. At present, irrigation water is cheap for the farmer, but since the water supply is limited and cannot be increased very much, available water will have to be shared, and at a higher price than at present. And as quality cropland is lost to urbanization and erosion, poor quality marginal land will probably need to be used for growing crops —land will surely require irrigation, further stressing the limited water supplies and increasing irrigation costs.

Energy Resources

People depend on a variety of sources of energy —wind, hydropower, solar energy, fossil fuels, and even energy from animals and people— to meet their basic needs. In most developed areas, including California, the primary source of energy is fossil energy from oil, gas, and coal. Like most U.S. farmers, California farmers use large amounts of fossil fuels to run their farm machinery and irrigation systems; about 17% of U.S. fossil energy expenditure supports our food system. Energy is also used to manufacture the fertilizers and pesticides needed by farmers as well as to power food processing and food transport systems.

Fossils fuels are a finite resource; once gone, their supplies cannot be replenished. Numerous studies indicate that the U.S. has only about 20 years of oil reserves and about 30 years of natural gas reserves left, given current levels of use. A steadily increasing population will place even greater demands on these limited supplies, requiring more and more oil to be imported from other countries. According to the U.S. Department of Energy, about 60% of our oil supply is currently being imported; nearly 100% will be imported by 2015.

In most of our lifetimes, and certainly in our children’s, we will witness the essential depletion of our U.S. oil reserves. As domestic oil supplies grow increasingly scarce, the price of gasoline and associated products will eventually rise. Then, both the high cost and limited availability of oil and other fossil fuels will restrict all human activities, including the expansion of modern intensive agriculture. Californians will need to produce even more food to feed the growing population, but will lack the energy resources to expand the agriculture systems.


In the late 1800’s, when California’s population reached 1 million, significant damage to the natural environment already was apparent. With each additional human added to the state’s current population of 32 million, the impact on California’s environment is intensified.

Californians are well aware of the air pollution in their cities and towns. For example, the ozone levels in Los Angeles, which has the highest density of automobiles per person in the world, well exceeds the EPA standard. The average exposure to carcinogens there is as much as 5000 times above the acceptable EPA level. Beyond harm to human health, air pollutants are also hazardous to crops and cause several million dollars worth of lost crops each year. As it becomes more and more difficult to feed increasing numbers of people, we cannot afford to lose any crops to pollution.

To date, about 91% of California’s wetlands have been drained and/or altered to provide more room for human activities. Loss of wetlands has significantly reduced the natural biodiversity in the state. Biodiversity is another finite resource; when a species is lost, it cannot be replaced. Maintaining biodiversity in plants, animals, and microbes is essential for the productivity of agriculture and forestry systems, the development of pharmaceutical products, the protection of the evolutionary processes that stabilize ecosystems, and for sustaining a quality environment for present and future generations.

In addition to the ongoing soil erosion and salinization associated with agriculture, water resources are being contaminated with sediments, pesticides, fertilizers, and salts. Livestock wastes, which are increasing in some areas, are a public nuisance and also seriously pollute waterways. As the population continues to grow, and as more livestock and food crops are required to feed the increasing numbers of humans, these environmental problems are expected to increase.

All these problems, from pollution to loss of biodiversity, will continue and intensify as long as the human population and its diverse activities continue to expand in California.


For the following reasons, California agriculture will be limited in the future, based on anticipated population growth and available resources: (1) substantial amounts of fertile agricultural land are lost each year to urbanization and erosion; (2) the water supply available for irrigation and other human uses is already severely stressed —current levels of use cannot be sustained much longer; (3) domestic fossil energy stores, the major source of power for agricultural production, are close to depletion; and (4) environmental damage in the form of polluted land, air, and water and lost biodiversity will limit the future development of crops and livestock.

As the human population in California, and throughout the world, continues to climb, the finite resources necessary for successful agricultural production will continue to be depleted; as these resources grow increasingly scarce, food production will be more limited and more expensive. As it becomes harder to feed the growing numbers of humans, our quality of life, even in developed countries like the United States, will decline. Our diet will change as food choices becomes more limited, depending less on animal protein and more on grain, legumes, and fruits and vegetables. As food becomes more expensive, Americans will need to spend more and more of their income —30 to 50% as compared to the current 15%— on food. With less money available to spend and less land available for recreation and other activities, our lifestyles may be significantly modified.

Many people propose that technological advances will save us, that we will figure out ways to cope with our increasing population and diminishing resources. While technology has produced many positive benefits for humankind, it cannot increase the supply of our basic resources; technology cannot increase the land area of California or produce fresh water, fertile soil, or fossil fuels. In fact, realizing the potential of technology rests of the continued availability of our basic land, water, energy, and biotic resources.

Conserving remaining natural resources is a necessary starting point for preserving our health and quality of life. However, conservation measures alone will not be sufficient to ensure food security for future generations unless population growth is curtailed. Private citizens and public leaders in California need to work together to stabilize their population. Their aim should be to insure that future generations have a secure food supply and a life style they can enjoy. As the basic per capita resources decrease and the quality of the natural environment declines, personal freedom to have adequate, healthy food, to earn a satisfactory living and to enjoy nature no longer will be an option. The lives and livelihood of future Californians depend on what action present generations are willing to take to reduce population numbers. Otherwise, the harsh realities of nature will impose a drastic solution for us.

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