This chapter is concerned with two closely related but geographically different environments. The oceans—which cover more than 70% of the Earth's surface—are open, expansive, and spatially continuous. By contrast, coastal zones are long, narrow, and discontinuous. As a result, climate change impacts on marine ecosystems may be accommodated more readily in the open ocean (e.g., by migration) than in coastal regions, where mobility is restricted, there are more environmental constraints, and human impacts may be more severe.

Figure 6-2: The role of natural and human adaptive capacity and resilience on the socioeconomic impacts of climate change following climate forcing, sea-level rise, and nonclimate forcing. The equity arrow in the bottom box indicates that impacts will not be uniform and that there will be wide inequalities, depending on socioeconomic conditions.

The potential biological and physical impacts of climate change and sea-level rise vary considerably between the oceans and coastal regions. The least vulnerable coastal and marine ecosystems have low exposure or high resilience to the impacts. Similarly, coastal communities and marine-based economic sectors that have low exposure or high adaptive capacity will be least affected. Countries, communities, and individuals in the higher range of economic well-being have access to technology, insurance, construction capital, transportation, communication, social support systems, and other assets that enhance their adaptive capacity. Those that do not have access have limited adaptive capacity. Unequal access to adaptation options, therefore unequal vulnerability, are attributable largely to different socioeconomic conditions. Poor adaptation or "maladaptation" also may lead to increased impacts and vulnerability in the future, with implications for intergenerational equity. These concepts are summarized in Figure 6-2.

Whereas the estimated costs of sea-level rise and other climate-related impacts in developed countries typically are limited to property losses, the reported outcomes of coastal floods in developing countries often include disease and loss of life. Vulnerability assessments in the developing world often do not consider the costs of business interruptions and failures, social disruption and dislocation, health care, evacuation, or relocation. A full accounting of the economic costs associated with lost, diminished, or disrupted lives would require estimates of the economic productivity losses they represent. Because this level of cost accounting is rare in developing countries, inequities may be significantly underestimated.

Turner et al. (1996) note that coastal zones are under increasing stress because of an interrelated set of planning failures, including information, economic market, and policy intervention failures. Moreover, moves toward integrated coastal management are urgently required to guide the co-evolution of natural and human systems. Acknowledging that forecasts of sea-level rise have been scaled down, they note that (1) much uncertainty remains over, for example, combined storm-surge and other events; and (2) within the socioeconomic analyses of the problem, resource valuations have been only partial at best and have failed to incorporate sensitivity analysis in terms of the discount rates utilized. They suggest that these factors would indicate an underestimation of potential damage costs and conclude that a precautionary approach is justified, based on the need to act ahead of adequate information acquisition and use economically efficient resource pricing and proactive coastal planning.

More recently, Turner et al. (1998) have aimed to elicit the main forces influencing the development of coastal areas and the means available to assess present use and manage future exploitation of the coastal zone. Their way of analyzing coastal change and resource management is through the pressure-state-impact-responses (P-S-I-R) conceptual framework. They analyze a variety of pressures and trends (including climate change, population changes, port development, marine aggregate extraction, and pollution). In the P-S-I-R framework, all of these factors are examined in the context of sustainable use of coastal resources and on the basis of an interdisciplinary ecological economics approach.

Several changes that might be expected to accelerate with global warming in the future already are detected in some regions and systems. Examples include global sea-level rise, increases in SST, and regional decreases in sea-ice cover. Impacts associated with these changes have included shoreline erosion, wetland loss, seawater intrusion into freshwater lenses, and some impacts on coral reefs. These impacts provide contemporary analogs for potential impacts in the future, recognizing that future changes and impacts may be of greater magnitude than those experienced so far and that changes and impacts may become more geographically widespread, including expansion into new areas that have not experienced such conditions previously. The contemporary environment gives us some insights into potential ecosystem impacts, some idea of costs, and some experience with potentially useful adaptation strategies.

We have found very few studies that indicate benefits of climate change and sea-level rise in coastal and marine systems. Recent studies, however, point to possible economic benefits from adaptation measures. Such benefits are likely to be restricted, particularly in the areas most at risk—including a large number of developing countries. Furthermore, the extent of impacts in those regions and the range of potentially effective adaptation measures remain poorly defined. Although there is growing acceptance of the need for integrated management strategies, progress has been slow in implementing these concepts in many jurisdictions. Part of the reason is limited development of understanding and tools for integrated assessment and management needs, involving various levels and aspects of integration, each of which may be difficult to implement. For instance, integration between the different disciplines involved in coastal and marine impact and adaptation analysis has been identified as a key issue by Capobianco et al. (1999). This and other integration needs are summarized in Box 6-7.

Some progress has been made since the SAR in developing and refining methodologies for assessing impacts of sea-level rise. Environments under particular threat include deltas, low coastal plains, coastal barriers, heavily utilized seas, tropical reefs and mangroves, and high-latitude coasts where impacts from warming may occur sooner or more rapidly.

Some topic areas rarely have been addressed, however. For instance, only a few case studies attempt to integrate potential impacts of sea-level rise and increased precipitation and runoff in coastal watersheds in assessing coastal vulnerability. Techniques for similar integration between biophysical and socioeconomic impacts are developing slowly, while human development and population growth in many regions have increased socioeconomic vulnerability and decreased the resilience of coastal ecosystems. Few studies provide details or any quantitative measures. We believe that integrated assessment and management of open marine and coastal ecosystems and a better understanding of their interaction with human development could lead to improvements in the quality of sustainable development strategies.

Global climate change will affect the biogeophysical characteristics of the oceans and coasts, modifying their ecological structure and affecting their ability to sustain coastal residents and communities. Impacts in the coastal zone will reflect local geological, ecological, and socioeconomic conditions within a broader regional or global context. Shorelines are inherently dynamic, responding to short- and long-term variability and trends in sea level, wave energy, sediment supply, and other forcing. Coastal communities—particularly on low-lying deltas, atolls, and reef islands—face threats of inundation, increased flooding, and saltwater intrusion, with impacts on health and safety, water supply, artisanal fisheries, agriculture, aquaculture, property, transportation links, and other infrastructure. In some coastal areas, particularly in developed nations, a shift in emphasis toward managed retreat appears to have gained momentum. Enhancement of biophysical and socioeconomic resilience in coastal regions increasingly is regarded as a cost-effective and desirable adaptive strategy. Growing recognition of the role of the climate-ocean system in the management of fish stocks is leading to new adaptive strategies that are based on determination of accepable removable percentages in relation to climate change and stock resilience.

Vulnerability to climate change and sea-level rise has been documented for a variety of coastal settings via common methodologies developed in the early 1990s; these assessments have confirmed the spatial and temporal variability of coastal vulnerability at national and regional levels. New conceptual frameworks include biophysical and socioeconomic impacts and highlight adaptation and resilience as components of vulnerability. Recent advances include models to evaluate economic costs and benefits that incorporate market and nonmarket values. Sustainable approaches to integrated coastal management can now include new financial accounting approaches that include ecological services and traditional cultural values. Nevertheless, adaptive choices will be conditioned by policy criteria and development objectives, requiring researchers and policymakers to work toward a commonly acceptable framework for adaptation.

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