Arctic coastlines are crumbling away and retreating at the rate of two metres or more a year due to the effects of climate change, it has been claimed.
In some locations, up to 30 metres of the shore has been vanishing every year.
The rapid rate of coastal erosion poses a major threat to local communities and ecosystems, according to a new report by more than 30 scientists from ten countries.
Two-thirds of Arctic coasts consist of frozen soil, or permafrost, rather than rock, and are highly sensitive to erosion by wind and waves. Rising temperatures are melting protective sea ice fringing the coastlines and leaving them more exposed to the elements, say the experts.
The report, "State of the Arctic Coast 2010", says ten-year average rates of coastal retreat are "typically in the one to two metres per year range, but vary up to 10 to 30 metres per year in some locations". Worst-hit areas include the Beaufort Sea, the East Siberian Sea and the Laptev Sea.
The study, led by scientists from the Helmholtz Association of German Research Centres and the International Arctic Science Committee (IASC), is published online and in the journal Estuaries and Coasts.
Information on more than 100,000 kilometres of Arctic coastline - around a quarter of the total - was collected for the report.
The scientists stressed that Arctic coastal habitats were the "prime lifeline" for Arctic communities, supporting a large population of fish, birds and mammals, including an estimated 500 million seabirds.
They wrote: "It is evident that the coast is a critical component of the Arctic system requiring explicit attention. As a focus of human activity with attendant hazards, the circumpolar Arctic coast is clearly a priority for monitoring and detection to support pro-active adaptation and sustainable development."
They hoped the report would help to close information gaps and "mobilise the resulting knowledge in an effective way for the betterment of Arctic coastal ecosystems, the peoples of the north and the global community".