was
underlain by permafrost. About 42 per cent of this permafrost
has been affected by thermokarst development
within the last 100 to 200 years. The thaw depths are
typically 1–2 m, with some values as high as 6 m. On
the Yamal Peninsula of north-west Siberia, land-use and
climatic changes since the 1960s, when supergiant natural
gas fields were discovered, have led to changes in
the tundra landscape (Forbes 1999). Extensive exploration
meant that large areas were given over to the
construction of roads and buildings.