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13.3.5. Coastal Regions
Three broad response strategies are distinguished (Klein et al., 2000):
- Reduce the risk of the event by decreasing its probability of occurrence
- Reduce the risk of the event by limiting its potential effects
- Increase society’s ability to cope with the effects of the event.
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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