"California's population is approaching 40 million people. Population growth in and of itself is one of the most significant forces in the quest to develop land for interests other than agricultural production and open space," said John Lowrie of the California Department of Conservation at the July meeting of the California State Board of Food and Agriculture in Sacramento.

While California is the nation's most populous state, because of its geographic size its overall population density is fairly low, he said, but because population is concentrated in a few areas, those locations feel the effects of urban growth more than other regions.

"One of the more alarming developments, at least to me, is the increasing density in the San Joaquin Valley, which is one of the major agricultural areas of the state," Lowrie said. "The conversion of agricultural land to urban uses starts slowly; it doesn't happen overnight. It can be driven by a number of forces and factors, many of which began as very localized and then expanded over time."

Edward Thompson Jr. of American Farmland Trust told the board that 30 percent of the developed land in California was originally prime farmland. In the Central Valley, the percentage is even higher - more than 60 percent.

"Since most of the cities are  located in the vicinity of the best farmland, if we are going to save farmland while cities continue to grow and accommodate more people and jobs, we need to think in terms of yield per acre the same way that farmers look at crops," he said.

Statewide, there are just under 10 people for every developed acre of land and in the San Joaquin Valley it is about eight people per developed acre. This includes residential and commercial areas, such as shopping malls and parking lots, Thompson said.

"We are likely to lose another 2 million acres of prime agricultural land by mid-century," he said. "While Southern California bears an enormous amount of that growth, again it is the San Joaquin Valley that is responsible for 60 percent of our agricultural production that is going to bear an equal amount of that growth."

Thompson cited projections of population growth that would indicate an acceleration in the loss of prime farmland in the San Joaquin Valley. At the present time, there are about 11 acres of prime land in the valley for every developed acre, but if the current pace of development continues, by 2050 there will be fewer than five acres of prime farmland for every developed acre.

"That is a pretty dramatic difference and we really don't have all that much productive farmland," he said. "In the San Joaquin Valley, there are about 6 million acres of productive farmland and if we develop another half million acres - which is the projection - we are really tipping the scales away from agriculture and towards urban development."

Thompson also expressed concern about the amount of agricultural land that has been lost to what he termed "hobby farms": five-, 10- or 20-acre ranchettes. He suggested that construction of a high-speed rail system through the valley would add to the problem.

"I find it highly unlikely that someone who is commuting to Los Angeles (via high-speed rail) is going to want to live in downtown Fresno. It is more likely that they will want to live in one of these ranchettes," he said. "No one has really taken stock of the potential impact of solar development as well as high-speed rail. This is a sleeping giant and I don't think anybody knows exactly how big it is at this point."

John Gamper, taxation and land use director for the California Farm Bureau Federation, also expressed concern about the potential ramifications of both high-speed rail and solar development.

"If high-speed rail is ever completed, it will certainly change the face of the Central Valley as it becomes a bedroom community to Los Angeles," he said.

Of even more concern is what Gamper termed a 21st century land rush, as utility companies and independent solar developers seek sites for photovoltaic projects, many of which are proposed on prime farmland.

"Just at a time when there is a lull in development because of the recession and the lack of housing starts, here comes this industrial land use that is jumping out into agricultural preserves," he said. "These solar developments could potentially cause the loss of hundreds of thousands of acres of prime agricultural land, simply because prime farmland is adjacent to substations or other interconnection sites."

"The Farm Bureau is adamant that California farmland protection laws must not be sacrificed in a rush to expedite the development of utility-scale renewable energy projects," Gamper said. "With opposition from the environmental community for solar development in the desert, the bull's-eye is really on prime farmland, primarily in the Central Valley."

Gamper added he hopes that counties will encourage solar developments on marginal or non-productive land.

"There are hundreds of thousands of acres, if not a million acres, of non-productive or physically impaired land in the Central Valley," he said.

Lowrie recalled that while growing up in California, he often heard it described as "vast" and "abundant."

"I have come to the conclusion that good land and good water here in California are neither vast nor abundant at this point in time and will become increasingly more scarce over time unless something is done," he said.