In the context of climate change and coastal management, vulnerability is now a familiar concept. On the other hand, the concept of coastal resilience is less well known but has become much more important in recent years (Box 6-5). Coastal resilience has ecological, morphological, and socioeconomic components, each of which represents another aspect of the coastal system's adaptive capacity to external disturbances. We have identified several natural features that contribute to resilience of the shore-zone by providing ecological buffers, including coral reefs, salt marsh, and mangrove forest and morphological protection in the form of sand and gravel beaches, barriers, and coastal dunes.

Socioeconomic resilience is the capability of a society to prevent or cope with the impacts of climate change and sea-level rise, including technical, institutional, economic, and cultural ability (as indicated in Box 6-5). Enhancing this resilience is equivalent to reducing the risk of the impacts on society. This resilience can be strengthened mainly by decreasing the probability of occurrence of hazard (managed retreat or protection); avoiding or reducing its potential effects (accommodation or protection), and facilitating recovery from the damages when impacts occur. Among these options, managed retreat has gained some prominence in the past 2 decades (see Box 6-6); Clark (1998) has argued that flood insurance is an appropriate management strategy to enhance coastal resilience in the UK.

Technological capacity is a component of social and economic resilience, although adaptation strategies may involve more than engineering measures. Technological options can be implemented efficiently only in an appropriate economic, institutional, legal, and sociocultural context. A list of technologies that could be effective for adaptation appears in Klein et al. (2000). Indigenous (traditional) technologies should be considered as an option to increase resilience and, to be effective, must fit in with traditional social structures (Veitayaki, 1998; Nunn et al., 1999).

Enhancing coastal resilience in these ways increasingly is regarded as an appropriate way to prepare for uncertain future changes, while maintaining opportunities for coastal development (although some tradeoffs are involved, and the political discourse is challenging). In short, enhancing resilience is a potentially powerful adaptive measure.

Figure 6-1: The role of adaptation in reducing potential impacts in the coastal zone from global temperature increase and sea-level rise to the year 2100. The bottom panel is a schematic that shows the increasing cost or loss to an economic sector, ecosytem, or country. The area shown by cross-hatch indicates the range of possible impacts and how net impact can be reduced with adaptation. Stipple within the cross-hatched areas indicates the importance of sector, ecosystem, or country resilience as a component of net impact.

The purpose of adaptation is to reduce the net cost of climate change and sea-level rise, whether those costs apply to an economic sector, an ecosystem, or a country. A simple schematic of the objective of adaptation appears in Figure 6-1.

Adaptation within natural systems has been considered a possibility only recently; it results in part from considerations of coastal resilience. An example is provided by coral reefs. Applying the two types of adaptation discussed in Box 6-5, Pittock (1999) suggests that "autonomous adaptation" is what reefs would do by themselves, whereas "planned adaptation" involves conscious human interference to assist in the persistence of some desirable characteristics of the coral reef system. The first type of adaptation may involve more rapid growth of coral, changes in species composition, or evolution of particular species in response to changed temperatures or other conditions. Planned adaptation might involve "seeding" of particular reefs with species adapted to higher temperatures or attempts to limit increased sediment, pollutant, or freshwater flow onto reefs. For reef communities that presently are under stress and are likely to be particularly vulnerable to climate change, the design of managed (or planned) adaptation should involve an evaluation of the extent of autonomous adaptation that can be expected given the current and probable future status of the reef system.

Some adaptation measures handle uncertainty better than others. For example, beach nourishment can be implemented as relative sea level rises and therefore is more flexible than a dike or seawall; expansion of the latter may require removal or addition of structures. Any move from "hard" (e.g., seawall) to "soft" (e.g., beach nourishment) shore protection measures must be accompanied, however, by a much better understanding of coastal processes that prevail in the area (Leafe et al., 1998). Rolling easements are more robust than setbacks (Titus, 1998) but may be impractical for market or cultural reasons. Maddrell (1996) found that over time scales of 35 and 100 years, managed coastal retreat is the most cost-effective adaptation option in reducing flood risks and protection costs for nuclear power facilities on the shingle foreland at Dungeness, UK. Flood insurance can discourage a flexible response if rates are kept artificially low or fixed at the time of initial construction, as they are in the United States (Crowell et al., 1999).

Reevaluations of the efficacy of hard shore protection schemes as a long-term response to climate change and sea-level rise are increasingly being undertaken. Chao and Hobbs (1997) have considered the role of decision analysis of shore protection under climate change uncertainty; Pope (1997) has suggested several ways of responding to coastal erosion and flooding that have relevance in the context of climate change. Documented changes in tidal characteristics as a result of the construction of sea dikes and seawalls also have implications for shore protection in the face of rising sea level. Several alternatives to seawalls have been suggested as adaptation measures to reduce coastal erosion and saltwater intrusion from rising sea levels in Shanghai, including improving drainage quality and channel capacity, increasing pumping facilities to reduce the water table, constructing a barrier across the mouth of the river, and developing new crops that are tolerant of a higher groundwater table (Chen and Zong, 1999).

It also should be noted, however, that Doornkamp (1998) has argued that in some situations past management decisions about human activities in the coastal zone (including flood defenses, occupance of flood-prone lands, extraction of groundwater and natural gas) have had an impact on relative land and sea levels and have done more to increase the risk of coastal flooding than damage that can be assigned to global warming to date.

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