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Between the northern edge of the boreal forest, where trees actively
regenerate, and the treeless tundra is a dynamic transition zone known
as 'forest-tundra'. This zone can range from a few kilometres in North
America to more than 200 kilometres in Europe (Stonehouse 1989). It is
naturally fragmented and contains patches of relatively heavy forest cover
punctuated by areas of lichen-heath as well as areas of very sparse tree
growth. It supports more species than either the boreal or the tundra
systems since it contains species from both systems (CAFF 2001). The trees
of the forest-tundra are often poorly formed and stunted, and regeneration
is slow. Traditionally, this has made commercial exploitation of timber
impractical although the ecosystem has provided indigenous peoples over
the centuries with wood for fuel and construction (CAFF 2001). As world
pressure on resources escalates, however, the tundra-forest could become
a larger commodity producer. In fact logging operations in Fennoscandia
and northwest Russia crept close to the forest-tundra in the 1960s and
1990s (CAFF 2001).
In winter, the forest-tundra provides important habitat for some populations
of North American caribou and for European reindeer, in turn supporting
the traditional reindeer husbandry activities of indigenous peoples such
as the Saami of Scandinavia. The zone also supports sheep farming, fishing
and harvesting of non-timber products. Important physical functions of
the forest-tundra system are to stabilize and protect fragile soils and
nutrients, to prevent erosion, to conserve water resources and watershed
capability, to filter pollutants, to act as an indicator of climate change
and, together with the boreal forest proper, to act as a carbon store
(see box).
| Arctic forests and climate change |
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Any significant change in the area of boreal forests could have
a considerable effect on the level of CO2 in the atmosphere.
With 26 per cent of total carbon stocks, boreal forests account
for more carbon than any other terrestrial ecosystem - 323 gigatonnes
(Gt, 109 tonnes) in the Russian Federation, 223 Gt in
Canada and 13 Gt in Alaska (Dixon and others 1994).
Conversely, it has been calculated that boreal forests will experience
greater temperature increases from climate change than any other
forest type. The warming, which is expected to be greater in winter
than in summer, will shift climate zones north by as much as 5 km
a year. Boreal forests will advance northwards while their southern
edges will experience die back or replacement by temperate species.
During summer, soils will be drier, and fires and drought more frequent.
Local species loss may be significant although few tree species
are expected to become extinct (UNEP-WCMC 2002).
Models used to predict the long-term changes in vegetation distribution
have not conclusively shown whether the overall area of boreal forest
will expand or decrease. However, one of the most comprehensive
models of climate change forecasts that the northward expansion
of forest will reduce the area of tundra by about 50 per cent by
2100 (White, Cannell and Friend 2000).
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