Under Florida's swamps, forests and cane fields lie crucial materials for the construction of roads, bridges, houses and shopping centers. And a fight has begun in the state Legislature over how -- and whether -- to extract them.

Hoping to tap vast underground deposits of limestone and sand, state legislators have proposed bills that would overturn Palm Beach County's moratorium on new limestone mines and set up a commission to find ways to extract more of these construction materials from other parts of the state.

Any expansion of mining is likely to be controversial. Environmentalists have sued to halt the spread of mines along Florida's Turnpike in western Miami-Dade County, which supply about half the state's limestone.

Homeowners in southwestern Broward County blame blasting at the mines for cracking floors and foundations.

Supporting the bills are Associated Industries of Florida, which is the state's main business lobby, the sugar industry and the Florida Department of Transportation. It says the state could face a construction-materials crisis if a judge shuts down the Miami-Dade County mines.

"We've had issues with shortages over the past few years," said Ananth Prasad, chief engineer for the Transportation Department.

"We have to develop a long-term strategy to make sure there are adequate materials to sustain the growth we're going to see. We have to protect the environment. We have to protect the quality of life. But the reality is, if we don't have good quality raw materials in Florida, the costs are going to go up."

Opposed are environmentalists and officials from Palm Beach County and other county and city governments.

"It's another way you lose habitat," said Eric Draper, lobbyist for Audubon of Florida. "You can't regrow trees. The mining pits they leave behind aren't very environmentally friendly."

In a preliminary survey, the state Transportation Department identified a major untapped deposit of limestone on the Lake Wales Ridge, an area known for rare plants and animals, such as the Florida scrub-jay.

"It's a very environmentally sensitive part of the state," Draper said.

Like oil, another environmentally problematic substance that undergirds the economy, limestone consists of the remains of living things.

Formed during the 20 million years that Florida spent under water, it is made up of marine creatures' skeletons, corals and dissolved calcium carbonate, packed and mashed together to form rock.

Miners extract it with dynamite and backhoes, leaving behind holes up to 80 feet deep and becoming milky lakes.

The limestone goes toward making building materials such as concrete and asphalt.

Legislative committees last week approved bills that would preempt local laws on mining, invaliding the Palm Beach County Commission's vote in November to block new mining until its staff could research the impact on homeowners and the environment.

The bills would create a commission to evaluate the state's limestone needs, identify major limestone deposits and make recommendations to the governor on how to ensure a steady supply.

The most controversial part of the legislation, written more strongly in the House version, would overturn local restrictions on mining, a provision widely believed to be aimed at Palm Beach County.

Rep. Thad Altman, R-Melbourne, who voted for the bill, called the use of moratoriums "an extremely serious act."

"They should only be exercised if there's an imminent health or safety issue because you're basically quashing the private property rights of anyone in the area."

The sugar industry wants the moratorium lifted immediately. With new mines not allowed, the value of cane fields deflates, making it more difficult to obtain bank loans, said David Goodlett, lobbyist for the Sugar Cane Growers Cooperative of Florida, which represents about 50 farms along Lake Okeechobee. And it closes off options for farmers worried about the impact of international trade treaties on their business, he said.

"The mining moratorium diminishes the value of our properties for their highest and best use," he said. "You can't have residential, you can't do commercial. What do you do with your property?"

But Palm Beach County Commissioner Karen Marcus said the county has a responsibility to take the time to protect the Everglades and county residents. And to do this, it has to do a serious study of the impact of mining before allowing more to go into operation.

"We're not saying we're not going to issue any more mining permits," she said. "But we're in a unique area. Before you start putting holes in the ground, you have to look at the impacts."

David Fleshler can be reached at dfleshler@sun-sentinel.com or 954-356-4535.