There”s a land rush of sorts going on across the nation”s most productive farming region, but these buyers don”t want to grow crops. They want to plant solar farms.

With California mandating that 33 percent of electricity be generated from renewables by the end of the decade, there are 227 proposed solar projects in the pipeline statewide. Coupled with wind and other renewables they would generate enough electricity to meet 100 percent of California”s power needs on an average summer day, the California Independent System Operator says.

And new applications for projects keep arriving. But the trend of covering over prime farmland with solar arrays is a worrier for some officials, including at least one Yolo County supervisor.

“I”m very much in favor of building solar panels on buildings,” said Supervisor Duane Chamberlain during a Nov. 13 board of supervisors meeting. “But when you cover raw land like this, you take the land, it”s useless for anything else.”

Chamberlain, a farmer himself, was referring to a county project to install panels on two county-owned sites, including on 41 acres of undeveloped land at Grasslands Regional Park. Altogether the panels will generate an estimated 5.8 megawatts of electricity and eliminate Yolo County”s electric bill, according to staff.

On a much larger scale, developers are flocking to flat farmland near power transmission lines all along the Central Valley. The movement has agriculture interests, environmental groups and even the state concerned that there is no official accounting of how much of this important agricultural region”s farmland is being taken out of production.

“We”ve been trying to get a handle on the extent of this for quite a while now,” said Ed Thompson of American Farmland Trust, which monitors how much of the nation”s farmland is absorbed by development.

No statewide plan or policy exists to direct projects to areas where land is marginal for farming and power transmission lines exist or can be easily routed – though groups as diverse as the Defenders of Wildlife and the independent state oversight agency Little Hoover Commission have issued studies calling for one.

Projects are approved by elected county boards of supervisors, or – if larger than 50 megawatts – the California Energy Commission. The largest solar facility operating so far covers 500 acres 60 miles northwest of Bakersfield and produces enough electricity for 36,000 homes.

“There”s no consistent approach” county to county in deciding what gets approved on farmland, said Kate Kelly, a planning consultant who is studying the environmental impact of valley projects for Defenders of Wildlife.

The California Department of Conservation, which is supposed to track development on privately held farmland, has been unable to do so because of staff and funding reductions, officials say.

“I”d love to say we have all of that information, but we really don”t,” said Molly Penberth, manager of the land resource protection division. “We”re going to play catch up getting that information, particularly in the San Joaquin Valley.”

Planning department records in four of the valley”s biggest farming counties show about 100 solar generation plants already proposed on roughly 40,000 acres, or about the equivalent of 470 Disneyland theme parks. Planners in Fresno County say their applications for solar outnumber the ones they received for housing developments during the boom days.

Solar developers have focused on the southern San Joaquin Valley over the past three years for the same reason as farmers: flat expanses of land and an abundance of sunshine. Land that has been tilled most often has fewer issues with endangered species than places such as the Mojave Desert, where an endangered tortoise slowed solar development on federal land.

Much of the solar development is proposed for Kern, Tulare, Fresno and Kings counties, which are home to more than 400 crops that pump $30 billion into the economy and help sustain U.S. food security.

In January, the farmland trust released a report projecting that by 2050 more than 570,000 acres across the region could be lost to development as the Central California population explodes. Farmland losses due to housing, solar development, a warming climate, cyclical drought and ongoing farm water rationing to protect endangered fish, plus the state”s signature transportation project – the High Speed Rail – are all issues the trust is trying to monitor.

“These are things that don”t make headlines, but come under the category that you don”t know what you”ve got until it”s gone,” Thompson said.

While one of the nation”s leading solar trade groups has not taken an official position on conversion of farmland to solar, Katherine Gensler of the Solar Energy Industries Association says more thought must go into location.

Just three weeks into 2013, five valley farmers have told the Department of Conservation that they want to cancel low agriculture tax rate contracts to develop solar on their property. None takes advantage of a year-old law making it easier to cancel on marginal land, Penberth said.

County boards of supervisors are attracted to the promise of clean energy construction jobs. Some of the projects are on prime land as small as 20 acres, some on habitat shared by threatened or endangered species such as the kit fox, Swainson”s hawk and blunt nose lizard. The 9,000-acre Maricopa Sun project in western Kern County is on prime land that the county says lacks a reliable water supply.

Almost always developers chose sites because there”s a willing seller in the vicinity of existing transmission lines, experts say.

Transmission is the biggest reason for the holdup of a massive project that energy planners, agriculture interests and environmentalists agree is perfectly situated – the Westlands Solar Park in remote Kings and Fresno counties. It”s planned for 47 square miles of farmland fallowed because of high levels selenium in the soil.

Developers say the project ultimately could provide 2.7 gigawatts of electricity – enough for 2.7 million homes. But the wait for approval from the California Independent System Operator to tap into transmission lines for a large project proved too long so they got out. For now. “We realized it would be a seven-to-10 year process,” said Joshua Martin, the solar company”s chief financial officer. “We could easily have spent $7 million in fees to stay in line, but it doesn”t make good business sense. It”s a messy market right now and things need to calm down.”

Ten years might be wishful thinking. An email the ISO sent to stakeholders on Jan. 18 said that it could be 12 years or longer before the needed upgrades in transmission infrastructure could be complete for solar projects currently waiting for transmission hookups in the Fresno area.

Westlands Solar Park is betting that environmental obstacles and connection costs will force many of the projects in the pipeline statewide to be abandoned. But what they”re hoping in the meantime is that state regulators eventually will direct solar development away from prime farmland.

Next month the California Energy Commission is set to make a move in that direction with adoption of a report that will recommend a coordinated approach placing solar in “zones with minimal environmental or habitat value,” near existing or planned electric system infrastructure. The agency would also collaborate with the Department of Conservation to identify areas of the state with marginal land.

Martin says the move likely is too late to help the projects that are stalled and in danger of missing out on federal tax incentives that expire in 2016.

“Someone needs to take a role and say what lines should be built and which aren”t in the state”s best interest,” said Martin. “So far we have been underwhelmed.”