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The Terrestial
Ecosystem Or Ecosystems
The future for terriestial ecosystems |
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Predicting changes over the next 50-100
years is difficult! It is not only the changes in the balance of
production and decomposition within the system that have to be considered.
It is also the rate of spread of vegetation following the gradual
changes in climate. This is where the computer models come into
play. The most recent model summarises the climatic factors driving
change, and the responses of plant growth and soil organic matter.
It is expected that the mean annual temperature of the region will
rise by about 4°C this century, more in the High Arctic, less
in the subArctic and Boreal forest. Snow and rain will change
much less, probably increasing by only a few centimetres each decade.
Based on these assumptions, the model is then run from 1850 to 2100,
covering the circumpolar region from 50o Northwards. It predicts
that: |
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- Coniferous forest will expand at the expense of tundra.
- The present tundra area will be halved by 2100.
- The increased growth of forest will exceed increased decomposition
so that the region will continue to be a carbon 'sink' throughout
this Century.
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Many factors have to be taken into
account and such models are always tentative. Changes will not be
smooth and regular. There will be periods and places where the trend
is briefly (decades) reversed because of local conditions and variations
in the climate. Short-term changes will be difficult to detect,
partly because the biological response will lag behind the climate
trend - but the system will change, that is sure. |
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