Services that involve artificial drainage might even benefit from climatic warming and additionally lowered water levels. Moya et al. (1998) report that rice biomass and seed yield is increased by CO2 concentrations of 200 and 300 ppm above ambient, but these increases are diminished or reversed when air temperature is elevated by 4°C. In the northern latitudes of Scandinavia, forest production in drained peatlands clearly is favored by higher temperatures (Keltikangas et al., 1986) and lower water-table levels.
Most wetland processes are dependent on catchment-level hydrology, which is being changed by land-use changes at fairly large scales. Thus, it may be very difficult if not impossible to adapt to the consequences of projeted climate change. For key habitats, small-scale restoration may be possible if sufficient water is available. In cases where wetlands are used for arable agriculture, the impact on the carbon balance could be controlled by the choice of cropping method, including alternative crops and depth of drainage.
The types of inland wetlands that are most vulnerable to global change (i.e., experience the largest changes) are difficult to ascertain. As concluded in the SAR, arctic and subarctic ombrotrophic bog communities on permafrost would change drastically after thawing of the frost layer and might be considered prime candidates in the vulnerability assessment, together with more southern depressional wetlands with small catchment areas. The increasing speed of peatland conversion and drainage in southeast Asia will place these areas at a greatly increased risk of fire. This will be one of the principal factors in determining the viability of tropical systems.
Global change impacts on wetlands would cause changes in many of the ecosystem services of wetlands. Especially vulnerable are functions that depend on a high degree of water availability. Services that involve artificial drainage might even benefit from climatic warming and additionally lowered water levels. For instance, in northern latitudes of Scandinavia, forest production in drained peatlands clearly is favored by higher temperatures (Keltikangas et al., 1986).
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