As Alaska's climate changes, its landscape is being transformed.

The Columbia Glacier, big enough to dwarf the mountains through which it flows, is melting.

Warmer weather made the glacier lose its footing on a ridge in Prince William Sound 16 years ago, and since then it has retreated eight miles, leaving a litter of floating ice behind it.

Scientists say that since the mid 1970s glaciers have been melting faster than ever. On average they're losing 15% of their length every decade.

Freezing rain locks away food from Caribou that cannot dig

The changes indicate a more dramatic world impact says Gunter Weller of the Geophysical Institute at the University of Alaska:

"We're looking at dramatic changes, that have implications for the rest of the world.

"These changes are unprecedented...the recession of glaciers, the disappearance of sea ice, the thawing of the permafrost, they all indicate major impacts."

Thawing after 125,000 years

The most far reaching effects are taking place beneath the surface.

Robert Piggott: the Alaskan wilderness is slowly being destroyed

The permanently frozen ground which covers most of Alaska is thawing for the first time for 125,000 years. If these higher temperatures persist, tens of millions of acres of forest will be turned into swamps.

Trees lean drunkenly as the ground beneath them gives way, and die in the water logged soil.

As the vegetation in these drowning forests rots, the methane and carbon dioxide it gives off could speed climate change significantly.

Trees lose hold in the waterlogged ground

Where blocks of ice lie buried, holes several metres deep are opening up in the ground.

The telegraph poles linking the widely scattered human population have to be tethered to stop them falling over.

Warmer winters have brought not drought but heavy snow, which breaks the branches of trees.

Warm, dry summers have weakened them further, and led to an explosion in the population of predatory insects.

Wildlife threatened

Beetles eat the tissue between the bark and wood - starving the tree by interrupting the flow of nutrients on which it depends.

Studies of Alaska's wild animals confirm profound changes in climate.

Beetles eat away tree flesh

The caribou population is declining. It's possible that freezing rain is sealing their food out of reach under a layer of ice.

Fires, like one which destroyed this forest in 1983, also threaten wildlife.

After summer drought fires are more intense, scorching the soil and releasing tonnes of carbon dioxide.

Winter has again come late to Alaska this year.

The Nenana River should be frozen by now. Much of Alaska's frosty earth is now only one or two degrees below freezing.