Since the IPCC First Assessment Report (1990) and its supplement (1992), the interrelationships between the impacts of climate change and human activities have become better understood. Although the potential impacts of climate change by itself may not always be the largest threat to natural coastal systems, in conjunction with other stresses they can become a serious issue for coastal societies, particularly in those places where the resilience of natural coastal systems has been reduced. Taking into account the potential impacts of climate change and associated sea-level rise can assist in making future development more sustainable. A proactive approach to enhance resilience and reduce vulnerability would be beneficial to coastal zones and small islands both from an environmental and from an economic perspective. It is also in line with the recommendations of the UN Conference on Environment and Development (UNCED) Agenda 21. Failure to act expeditiously could increase future costs, reduce future options, and lead to irreversible changes.

Since 1990, there has been a large increase in research effort directed at understanding the biogeophysical effects of climate change and particularly sea-level rise on coastal zones and small islands. Studies have confirmed that low-lying deltaic and barrier coasts and low-elevation reef islands and coral atolls are especially sensitive to a rising sea level, as well as changes in rainfall, storm frequency, and intensity. Impacts could include inundation, flooding, erosion, and saline intrusion. However, it has also been shown that such responses will be highly variable among and within these areas; impacts are likely to be greatest where local environments are already under stress as a result of human activities.

Studies of natural systems have demonstrated, among other things, that:

The coast is not a passive system but will respond dynamically to sea-level and climate changes (High Confidence).

A range of coastal responses can be expected, depending on local circumstances and climatic conditions (High Confidence).

In the past, estuaries and coastal wetlands could often cope with sea-level rise, although usually by migration landward. Human infrastructure, however, has diminished this possibility in many places (High Confidence).

Survival of salt marshes and mangroves appears likely where the rate of sedimentation will approximate the rate of local sea-level rise (High Confidence). Generally, coral reefs have the capacity to keep pace with projected sea-level rise but may suffer from increases in seawater temperature (Medium Confidence).

The assessment of the latest scientific information regarding socioeconomic impacts of climate change on coastal zones and small islands is derived primarily from vulnerability assessments based on the IPCC Common Methodology. Since 1990, many national case studies have been completed, embracing examples of small islands, deltas, and continental shorelines from around the world. These studies mainly utilize a scenario

of a 1-m rise in sea level and generally assume the present socioeconomic situation, with little or no consideration of coastal dynamics. There is concern that these studies understate nonmarket values and stress a protection-orientated response perspective. Despite these limitations, these studies provide some important insights into the socioeconomic implications of sea-level rise, including:

Sea-level rise would have negative impacts on a number of sectors, including tourism, freshwater supply and quality, fisheries and aquaculture, agriculture, human settlements, financial services, and human health (High Confidence).

Based on first-order estimates of population distribution, storm-surge probabilities, and existing levels of protection, more than 40 million people are estimated to experience flooding due to storm surge in an average year under present climate and sea-level conditions. Most of these people reside in the developing world. Ignoring possible adaptation and likely population growth, these numbers could roughly double or triple due to sea-level rise in the next century (Medium Confidence).

Protection of many low-lying island states (e.g., the Marshall Islands, the Maldives) and nations with large deltaic areas (e.g.. Bangladesh, Nigeria, Egypt. China) is likely to be very costly (High Confidence). Adaptation to sea-level rise and climate change will involve important tradeoffs, which could include environmental, economic, social, and cultural values (High Confidence).

Until recently, the assessment of possible response strategies focused mainly on protection. There is a need to identify better the full range of options within the adaptive response strategies: protect, accommodate, and (planned) retreat. Identifying

the most appropriate options and their relative costs, and implementing these options while taking into account contemporary conditions as well as future problems such as climate change and sea-level rise, will be a great challenge in both developing and industrialized countries. It is envisaged that the most suitable range of options will vary among and within countries. An appropriate mechanism for coastal planning under these varying conditions is integrated coastal zone management. There is no single recipe for integrated coastal zone management; rather, it constitutes a portfolio of sociocultural dimensions and structural, legal, financial, economic, and institutional measures.

Continued exchange of information and experience on the inclusion of climate change and sea-level rise within integrated coastal zone management at local, regional, and international levels would help to overcome some of these constraints. In addition, more research is required on the process of integrated coastal zone management to improve the understanding and modeling capability of the implications of climate change and sea-level rise on coastal zones and small islands, including biogeophysical effects, the local interaction of sea-level rise with other aspects of climate change, and more complete assessment of socioeconomic and cultural impacts.

Coastal zones and small islands contain some of the world's most diverse and productive resources. They include extensive areas of complex and specialized ecosystems, such as mangroves, coral reefs, and seagrasses, which are highly sensitive to human intervention. These ecosystems are the source of a significant proportion of global food production. Moreover, they support a variety of economic activities, including fisheries and aquaculture, tourism, recreation, and transportation. In recent decades, many coastal areas have been heavily modified and intensively developed, which has significantly increased their vulnerability to natural coastal dynamics and the anticipated impacts of global climate change.

Many attempts have been made to define the "coastal zone" and its land and seaward boundaries. Some definitions are based on physiographic characteristics, such as the extent of tidal influence on the land or the geomorphology of the continental shelf; others simply use a fixed distance from the shoreline. In the case of small islands, the coastal zone could include the entire island. While the boundaries of the coastal zone may or may not coincide with political or administrative boundaries, they rarely coincide with those of areas from which demands on the resources of the coastal area are derived (Ehler, 1993).

The global importance of coastal zones and small islands in terms of both ecological and socioeconomic values is widely recognized. Many international organizations, including IPCC, have called for action to implement strategies toward better planning and management of coastal areas and resources to prevent them from being degraded and becoming progressively more vulnerable to the potential impacts of climate change and associated sea-level rise. The World Coast Conference, partly held under the auspices of IPCC, has supported the Framework Convention on Climate Change (UNCED, 1992a) and Agenda 21, Chapter 17 (UNCED, 1992b), requiring action on coastal zone management planning, among many other initiatives, by all signatories (WCC'93, 1993).

This chapter presents an assessment of the latest scientific

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and small islands and on strategies that countries may wish to apply in response to these impacts. It builds on the previous IPCC assessments carried out in 1990 and 1992 and on the work of the former Coastal Zone Management Subgroup (CZMS) of IPCC. The chapter concentrates on the scientific work completed since 1990, although earlier work is acknowledged where appropriate.

The structure of this chapter is schematically depicted in Figure 9-1. This figure also shows how this chapter relates to other chapters and Working Group reports of this IPCC Second Assessment Report. In Section 9.2, the functions and values of coastal zones and small islands are discussed. Special emphasis is put on the importance of maintaining the proper functioning of coastal systems with regard to sustainable development and their resilience to climate change. Section 9.3 then discusses the likely consequences of climate change on sea-level rise, sea-surface temperatures, and tropical cyclones in the context of coastal zones and small islands. On this basis, Section 9.4 addresses the effects of climate change on biogeophysical systems, and Section 9.5 examines the socioeconomic impacts. Section 9.6 considers response strategies to climate change and the need to integrate them with other coastal management activities. Finally, Section 9.7 identifies needs and opportunities for future research and monitoring that would help nations to respond more appropriately to the likely impacts of climate change on coastal zones and small islands.