Media playback is unsupported on your device Media caption 'Ghost trees' are victims of rising sea levels; Video produced by the BBC's Bill McKenna

Dying wetland trees along Virginia's coastline are evidence that rising sea levels threaten nature and humans, scientists say - and show the limits of political action amid climate change scepticism.

Dead trees loom over the marsh like the bones of a whale beached long ago.

In the salt marshes along the banks of the York River in the US state of Virginia, pine and cedar trees and bushes of holly and wax myrtle occupy small islands, known as hummocks.

But as the salty estuary waters have risen in recent years, they have drowned the trees on the hummocks' lower edges. If - when - the sea level rises further, it will inundate and drown the remaining trees and shrubs, and eventually sink the entire marsh.

That threatens the entire surrounding ecosystem, because fish, oysters and crabs depend on the marsh grass for food.

Image caption Trees die as rising salt water soaks their roots, Watts says

"These are just the early warning signs of what's coming," says avian ecologist Bryan Watts, stepping carefully among the fallen pines.

The sea level in the Chesapeake Bay area and in south-eastern Virginia is predicted to rise by as much as 5.2ft (1.6m) by the end of the century.

Ancient geologic forces are causing the land literally to sink, while the amount of water in the oceans is increasing because of global warming, scientists say.

As a result, the low-lying coastal areas - and the towns in it - are at tremendous risk of flooding.

To address the problem, climate scientists, environmentalists and their political supporters say the US must dramatically reduce its fossil fuel emissions, while also taking steps to lessen the impact of coastal flooding and wetland erosion.

"There is time to turn the ship around," says Michael Mann, a former University of Virginia climate scientist, "but there is not a whole lot of time."

But in Virginia's state capital Richmond, as in Washington, many politicians remain sceptical about the extent to which humans are responsible for global warming.

They fear measures needed to curb climate change would hurt the economy, threaten private property, and harm commercial and industrial interests.

"Here in Virginia there is very little political will to address the mitigation side of things - reducing our carbon footprint, reducing greenhouse gas emissions," says Carl Hershner, who studies coastal resources management at the Virginia Institute of Marine Science.

"There is a high degree of scepticism in the political and the general public."

Virginia's attorney general, Republican Ken Cuccinelli, has waged an aggressive public battle against the Obama administration's efforts to rein in greenhouse gas emissions, which he said would drive up electricity costs and kill jobs in the state's coal industry.

A battle in the climate war In 2010, Virginia Attorney General Ken Cuccinelli demanded access to Michael Mann's grant applications and correspondence. Mann was a prominent former University of Virginia climate scientist. Cuccinelli said he was investigating whether Mann had committed fraud in grant applications when he had said data showed a rapid rise in the earth's temperature. "The use of manipulated data to apply for taxpayer-funded research grants in Virginia is potentially fraud," Cuccinelli said. "This is about rooting out possible fraud and not about infringing upon academic freedom." But Mann and his supporters called Cuccinelli's move a politically motivated attack on a high profile climate scientist. The University of Virginia refused to give up the documents and hired a lawyer. Ultimately, the Virginia Supreme Court rejected Cuccinelli's demand for the documents, saying he lacked authority.

While politicians in Washington and in Richmond, Virginia's state capital, have done little to address the problem, authorities along Virginia's coast have watched the waters rise and have been forced to take action.

The city government of Norfolk spends about $6m (£3.8m) a year to elevate roads, improve drainage, and help homeowners literally raise their houses to keep their ground floors dry, says Assistant City Manager Ron Williams.

About 5%-10% of the city's lowest-lying neighbourhoods are subject to heavy flooding during storms. City planners do not currently recommend any areas be abandoned to the tide, but "you have to have the conversation as you look 50 years out", Mr Williams says.

At Naval Station Norfolk, the world's largest naval base, the US Navy is spending hundreds of millions of dollars to replace aging piers with new ones better able to withstand the rising water.

"Sea level rise was having a measurable impact on the readiness of the ships," says retired Capt Joseph Bouchard, who was commander of the base from 2000-2003. "And that's unacceptable."

So the Navy decided to replace the old piers with double-decked piers - one for utilities, the other for the ship operations - with the upper deck 21ft above current sea level.

Image caption Dead trees ring the living ones as a hummock is slowly inundated

"Were it not for sea level rise caused by climate change, the Navy could have replaced those piers with single deck piers at much much less cost," he says.

Even a measure as ostensibly mild as funding for a flooding study was fraught with climate change politics.

Senator Ralph Northam, a Democrat, and Chris Stolle, a Republican member of the Virginia's lower House of Delegates, this year shepherded a resolution through the legislature spending $50,000 on a comprehensive study of the economic impact of coastal flooding on the Virginia and to investigate ways to adapt.

To pass the bill, at Stolle's suggestion Northam excised the words "relative sea level rise" from an initial draft of the bill , replacing them with "recurrent flooding" in the final version .

Stolle says the change was necessary to ensure the bill focused on the issues Virginia politicians can handle - flooding - and not those they cannot address - global warming. In any case, "the jury's still out" on mankind' s contribution to global warming, he says.

"Other folks can go argue about sea-level rise and global warming," Stolle says. "What matters is people's homes are getting destroyed, and that's what we want to focus on. To think that we are going to stop climate change is absolute hubris. The climate is going to change whether we're here or not."

Northam describes the change in language as pragmatic politics - necessary to win support from conservatives sceptical of climate change science.

"If you mention climate change to them, it's like a big red flag," he says. "A barrier goes up. That's the way it is here in the Virginia."