By Stephen Chittenden
BBC Five Live, Newtok, Alaska
Stanley Tom clambers down the crumbling bank of the Ninglik River to inspect the latest damage.
Some fear Newtok will disappear within a few years
It's a windy day, and cold even for him, the Yup'ik Eskimo tribal leader in the village of Newtok in the US state of Alaska.
He looks across the water. "South wind. Bad news. We could have flooding," he says.
Alaska is at the vanguard of climate change. The state's northern parts have seen an average temperature rise of three degrees celsius in recent decades
Now the permafrost - the frozen ground that previously kept the Ninglik stable, as well as providing a solid base for the village's scattered houses - is melting.
As its northern bank melts and slides into the tidal water, the body of the river moves steadily towards Newtok.
It is a village of fewer than 400 people, in the waterlogged tundra of the Yukon Delta. The only way in or out is by the tiny plane that flies daily from Bethel, 100 miles (160km) to the west.
Local pilot Chad Smith explains how planes link scattered populations
Flood defences have been tried, and have failed. The river encroaches by around 130ft (40m) each spring and summer, and it might swallow Newtok within a few years. So the villagers have decided to move on.
Stanley turns his back to the village and points across the water to snow-covered hills nine miles away.
"We're moving across there," he says. "That's really solid ground, we'll be safe from the erosion and flooding."
He has already arranged for three houses to be built at the new site. Next year, the US defence department plans to build a barge landing, road and evacuation centre, for use if there is a catastrophic flood in Newtok.
A report to the US Congress found that 181 Alaskan villages may be threatened by erosion.
Fifteen villages are a priority, of which three are urgent, including Newtok. The other two are the coastal communities of Shishmaref and Kivalina, which are vulnerable through a loss of protective sea ice during the stormy autumns.
Alaska's Governor Sarah Palin has set up special "immediate action" committees to deal with both the causes and consequences of global warming. She appointed environmental lawyer Larry Hartig as her commissioner for the environment.
He accepts there is a massive challenge ahead.
"Climate change is an immediate and serious problem for people all around this state," he says.
"It's hitting us in a variety of ways right now. It's particularly hitting rural Alaska, with flooding and erosion.
"It's also changing patterns of our fish and game around the state, which is impacting people's ability to get the subsistence foods they've relied on for hundreds of years."
The University of Alaska Institute for Social and Economic Reform carried out a study into the costs of climate change, based on predictive climate models. It estimated the bills could run into billions of dollars.
Race against time
The US Army Corps of Engineers is responsible for sea defences and flood protection.
Its chief engineer in Alaska, Trish Opheen, believes climate change could cause damage not just at the coast, but to runways, roads and structures right across the state.
"Climate change is going to affect the infrastructure, especially in the Arctic," she says.
These children are set to grow up away from Newtok
"It's jeopardised by the phase change of permafrost to thawing ground."
The state of Alaska has already funded some work to help the people of Newtok move, but the overall bill could run into hundreds of millions of dollars.
For Stanley Tom and the people of Newtok, it's a race against time. Now the riverbank is frozen until spring. But when the sun returns, the river will once again start eating into Newtok.
"It'll start melting as soon as the sun comes, it'll start dripping and just erode away," he says.
"All summer long it just keeps coming in. We've got maybe two, three more years. But there's no way of stopping the erosion."
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