By BBC Environment Correspondent Robert Piggott 

                 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. 


                                            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. 


                                   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. 


                                            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. 


                                            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. 

                 As it thaws this once changeless icy wilderness is being steadily
                 destroyed.