188.8.131.52. Food and Fiber
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.
5.8.4. Adaptation Options for Wetlands
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.
5.8.5. Vulnerability of Functions and Key Services of Wetlands
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).