|Working Group II: Impacts, Adaptation and Vulnerability|
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13.3. Adaptation Potential
In this section, our analysis is restricted to adaptation in the major primary sectors (water, soils, ecosystems, agriculture) and in coastal regions. These are the main sectors where adaptation will be needed.13.3.1. Water
There are, broadly, two different approaches to adaptation in the water sector: “supply side” (change the water supply) and “demand side” (alter exposure to stress). Table 13-6 summarizes some supply-side and demand-side techniques that are available to cope with adverse impacts in the water sector and may be appropriate in the face of climate change. “Supply-side” techniques to address water resources and risks are most widely known and used at present. In terms of water supply, these strategies include building new supply and distribution infrastructure and managing existing sources more efficiently. There is an increasing tendency toward conjunctive use of different sources within a region. Supply-side techniques in flood management are termed structural adjustments; they involve actions to lessen flood peaks and keep floodwaters away from at-risk property. Demand-side techniques historically have been less well used but are the focus of increasing attention. In terms of water supply, the most obvious demand-side approach is to reduce the demand (or slow the increase in demand) for the water resource through a range of measures, including differential pricing, public awareness campaigns, or statutory requirements for WUE (e.g., for domestic appliances).
Attention to date has been concentrated on supply-side options; demand-side techniques are less well-known and the subject of considerable technological advance. Although there is a good deal of awareness of broad options, there has been less research into applying these options in an uncertain future: How, for example, can a water distribution network be designed so that it can be incrementally updated as more information on climate change appears, rather than built to a single fixed standard?
An adaptation in one aspect of the water environment or in one area might have a severe effect on another aspect or area. For example, increased use of a river to maintain supplies may impact the instream environment. Increased storage of water in a reservoir over the winter might reduce its ability to prevent flooding. Finally, the time scales over which adaptation can occur vary. Some adaptive strategies can be implemented with little warning and can be easily amended. Others take longer to implement and, once completed, are harder to change. For example, it typically takes decades for a reservoir to move from the planning stage to completion. Urban storm drainage has a relatively short lead time but a very long design life. An ideal adaptive strategy is one that can be altered as more information becomes available. However, the adaptive response by a water management agency to climate change will depend on procedures for considering strategies, as well as adaptive capacity.13.3.2. Soils
The use of land management techniques in adaptation to climate change will seek to maintain soil functions. A summary of appropriate techniques and their relationships to the soil functions and properties discussed earlier in this chapter is given in Table 13-18.104.22.168. Ecosystems
Tundra areas have practically no adaptive options available. The only possible response is to better protect areas with particular value (e.g., for bird life) from other stresses such as land exploitation and tourism. In boreal regions, many effects of climate change and CO2 increase, as noted above, are positive in terms of productivity. Areas that are under threat (e.g., low-productivity mountain forests) have no adaptive options available. If changing water tables present a significant problem, boreal wetlands could receive technical measures for controlling water level, but such measures are unlikely to be technically and economically feasible in many areas. Other approaches to adaptation can include establishment of buffer areas around wetlands, promotion of sustainable uses of wetlands to minimize additional stresses brought on by climate change, and restoration of already destroyed wetland habitats (Hartig et al., 1997).
Water shortage in parts of the temperate zone may be compensated to some extent by additional irrigation or river management. To achieve any large-scale effect, however, such measures would have to be applied in economically infeasible dimensions. Most other areas will have positive effects and therefore no adaptive problems.
In the Mediterranean, many landscapes face an acute management problem already without climate change because bush encroachment in earlier agricultural areas is affecting many ecosystems with respect to species richness and susceptibility to fire. Climate change may aggravate these developments in some areas. It is not likely that there are direct ways to adapt to these trends.
With regard to forests, the central problem is that any potential adaptation requires long-term planning. Essentially, adaptation to climate would require planting trees today that will be suitable for such a future climate. However, given our uncertainties in the prediction of future climate and the formulation of models that are used to assess its ecological impacts, it is unlikely that adaptation measures will be put into practice in a timely manner.
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