When Maria Gunnoe started campaigning against open-cast mining on the mountains above her West Virginia home in 2003, she could not have imagined the ordeal that would follow.

Over the past five years, her car brake lights have been vandalised, sand has been poured into her petrol tank and two of her dogs have been shot dead.

The intimidation appeared aimed at silencing Ms Gunnoe's criticism of a controversial form of mining that involves blowing up mountaintops to reach coal.

More than 400 mountains in the Appalachian region have been disfigured by dynamite and dozens more are threatened as the industry strains to meet soaring demand.

Local communities are bitterly divided between supporters of mountaintop mining, who view it as a crucial economic lifeline for a struggling region, and opponents who say the practice wrecks lives by polluting water and causing floods.

"They are destroying the environment and they are destroying communities that have been here for generations," says Ms Gunnoe, whose home sits beneath a mountaintop mine near the tiny hamlet of Bob White in Boone County.

As energy issues rise towards the top of the presidential election agenda, the debate over mountaintop mining highlights the difficult choices facing the US as it pursues two often contradictory goals: energy independence and environmental protection.

All three main presidential candidates - John McCain, Barack Obama and Hillary Clinton - accept that coal has a big role to play in helping meet rising energy demand while reducing dependence on foreign oil and gas. America is known as the "Saudi Arabia of coal" because it has enough of the fossil fuel to last at least two more centuries.

Each candidate has promised heavy investment in so-called clean coal technology to find ways of reducing the greenhouse gas emissions that contribute to global warming.

But they have had less to say about the environmental costs involved in extracting coal from the ground.

Mr Obama and Mrs Clinton both walked a delicate line on the issue in the run-up to yesterday's Democratic primary election in West Virginia, expressing concern about mountaintop mining while acknowledging the economic benefits that stem from the practice. They are likely to continue the balancing act ahead of next Tuesday's primary in Kentucky, another Appalachian coal-producing state with large surface mines.

Mining supports about 47,000 direct jobs in West Virginia and 21,000 in Kentucky, making it one of the biggest employers in two of America's poorest states.

"Without mining, there wouldn't be anything going for this place," says Michael Brunty, a 24-year-old who earns $70,000 a year - more than twice the state average - at a mountaintop mine in Boone County.

Driving through the narrow, winding valleys of southern West Virginia, mountaintop mines are impossible to miss. Rolling hillsides have been stripped of trees and transformed into jagged moonscapes.

About a third of US coal comes from the Appalachian region and a third of that is from mountaintop seams. Energy companies prefer surface-mined coal because it is cheaper to extract and contains less sulphur, which causes acid rain, compared with deeper-laying deposits. It is also safer than underground mining - an important consideration in West Virginia, where 12 people died in the Sago mine disaster two years ago.

While mining companies reap a windfall from mountaintop mining, however, Ms Gunnoe sees only costs. Her valley-bottom home has suffered repeated flooding since blasting began eight years ago and she claims that tests have revealed carcinogens in her water supply, forcing her family to spend $250 (£130, €160) a month on bottled water. "When you chop off the top of a mountain, the rest of the mountain crumbles, too," she says.

"We're not tree huggers like the industry likes to portray us. We're citizens fighting for our rights to protect our property and our health."

Bill Raney, president of the West Virginia Coal Association, an industry lobby group, says there is no evidence that mountaintop operations have caused flooding or unsafe drinking water.

Magnum Coal, owner of the Callisto mine near Bob White, did not immediately return calls for comment.

Opinion polls show that a majority of people in West Virginia and Kentucky are opposed to mountaintop mining. Yet political leaders in both states are overwhelmingly supportive.

"The politics of coal in these states is straight out of the robber baron era," says Mary Anne Hitt, executive di­rector of Appalachian Voices, a conservation group.

"The coal industry and the political establishment are interconnected and the interests of industry are put ahead of ordinary people."

The industry also has powerful allies in the Bush administration, which loosened regulations to allow mountaintop mines to dump waste in streams.

"Big coal" is bracing itself for a tougher regulatory environment under the next president but, with electricity demand forecast to increase by a quarter over the next two decades, advocates say the US can ill afford to restrict access to the country's cheapest and most abundant source of energy.

"There is no way to get at this coal except through mountaintop mining," says Mr Raney. "If this country is to ever become energy independent, we cannot leave such rich deposits untapped."