Three broad response strategies are distinguished (Klein et al., 2000):
These strategies have been termed "protect," "retreat," and "accommodate," respectively. Protection usually is associated with coastal squeeze and hence a decline in natural functions and values, although soft protection approaches may not raise this problem.
The actual strategy chosen will depend on local and national circumstances, including the economic and ecological importance of the coastline, technical and financial capabilities, and the legislative and political structure of the countries concerned. Although optimum response strategies have yet to be developed, it is likely that a range of responses will be the norm within any country (Bijlsma et al., 1996). Turner et al. (1995) analyzed protection in East Anglia, England. At the aggregated scale of East Anglia, protection can be justified for the entire coast given a 50-cm rise in sea level by 2050. However, this is not the scale at which coastal management decisions are made. When the 113 individual flood compartments are evaluated independently, 20% optimally would be abandoned even for present rates of relative sea-level rise (10-cm rise in sea level by 2050). This analysis assumes that there is no interaction between flood compartments-which may not always be the case. However, it reinforces the conclusion that a range of responses will be appropriate.
Some national estimates of protection costs are given in Table 13-5, primarily for a 1-m rise in sea level. In terms of relative costs, Poland appears to be more vulnerable than Germany and The Netherlands. The absolute costs for Germany are larger than for The Netherlands, reflecting the much longer German coastline.
Adapting successfully to climate change requires more than a list of options. Klein et al. (1999) argue that successful adaptation must consider several issues, including recognizing the need for adaptation, planning, implementation, and evaluation. Although there is increasing recognition of the need for adaptation in some countries, this is not uniform across Europe (e.g., Nicholls and Hoozemans, 1996). It also is clear that coastal adaptation to climate change must happen in the broader context of coastal management.
Response options may be hindered by resource constraints. In Cyprus, the coast is no longer receiving new supplies of sand as a result of catchment regulation and management (Nicholls and Hoozemans, 1996). Erosion is expected in response to sea-level rise, but there are no ready sources of sand available for beach nourishment. Yet maintaining the beach is critical to the tourist industry. Although this problem has not been analyzed in detail, external (and hence costly) sources of sand may be required for beach nourishment. Many other Mediterranean islands appear to have similar problems, including those in Greece, Italy, France, and Spain. Some adaptation that anticipates climate change already is being implemented, and this seems to be raising important questions about long-term coastal management (Klein et al., 1999). The Netherlands is highly threatened by sea-level rise (see Table 13-5): About 60% of the country (23,600 km2) is in the potential impact zone (Baarse et al., 1994). A new national law "outlaws" erosion and mandates maintenance of the present shoreline position via ongoing beach nourishment (Koster and Hillen, 1995). However, a debate about the optimum response continues; some people advocate a more dynamic response, including a mixture of holding the line, allowing some retreat, and coastal advancement in areas where more land is required (de Ruig, 1998; Klein et al., 1998). The debate includes explicit consideration of maintaining and enhancing coastal resilience.
In Britain, coastal cells have become the basis of shoreline management; about 40 shoreline management plans that cover the entire coastline of England and Wales are finished or nearing completion (UK Ministry of Agriculture, Fisheries, and Food, 1995; Leafe et al., 1998). Managed realignment of sea defenses in estuaries also is attracting increasing attention, including some trial experiments (Klein et al., 1999). Low-grade agricultural land is given up to the sea as flood defenses are abandoned or relocated inland. If managed realignment is practiced at a large scale, it will help to maintain natural values as well as the flood protection benefits of coastal wetlands under a rising sea level. However, there will be a corresponding net loss of freshwater ecosystems in the protected areas (Lee, 1998). About 100 ha yr-1 of land would need to be released just to counter present rates of salt marsh loss resulting from sea-level rise. Although the economic analysis of Turner et al. (1995) would suggest that there are many suitable sites available, this requires strategic planning to be put in place as part of shoreline management planning (UK Ministry of Agriculture, Fisheries, and Food, 1995; Leafe et al., 1998). Political acceptance of managed retreat remains to be assessed.
Around the Mediterranean, models of deltaic response to sea-level rise and frameworks to analyze vulnerability and sustainability are being developed (e.g., Sanchez-Arcilla et al., 1998). This raises the prospect of a dynamic management approach that harnesses natural inputs and processes within deltas to counter global and local (as a result of subsidence) sea-level rise, rather than a move to hard defenses.
One pertinent issue is cross-border transport of sediment, which has costs within the country of origin but reduces the vulnerability of the receiving country to sea-level rise. For instance, coastal erosion on the east coast of England provides mud that helps to sustain the Wadden Sea in The Netherlands and Germany under rising sea level (Dyer and Moffat, 1998; Nicholls and Mimura, 1998). This suggests a need for a regional perspective on the coastal impacts of sea-level rise.
In conclusion, a common problem across Europe is developing strategic management approaches that allow both continued human utilization of the coastal zone and preservation of coastal ecosystems, given sea-level rise (Nicholls, 2000). Slow but steady degradation of the coastal fringe in much of Europe has gone largely unnoticed until recently, and this will continue and accelerate with sea-level rise. Developing methods to balance protection of people and the economy against the costs of degradation of the coastal environment will require multidisciplinary research.
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