Despite their heterogeneity, small island states share some common characteristics that help to define their high vulnerability and low adaptation potential to climate change effects (Nurse et al., 1998; see also Section 17.1.2). Vulnerability assessment typically seeks to achieve three main goals: to identify the degree of future risks induced by climate change and sea-level rise; to identify the key vulnerable sectors and areas within a country; and to provide a sound basis for designing adaptation strategies and their implementation.
The IPCC Common Methodology was the first method to be widely applied to assess the vulnerability of countries to sea-level rise (IPCC, 1992). However, the methodology lacks the flexibility to consider factors of critical significance for small islands (e.g., so-called nonmarket goods and services) and requires certain quantitative data that often are not easily available in many small island states. An index-based method was developed for use in the south Pacific (Yamada et al., 1995, based on Kay and Hay, 1993). In addition, alternative assessment methodologies were developed in conjunction with the various country study programs (e.g., Leatherman, 1996; Klein and Nicholls, 1998). What is significant, however, is that all available assessments confirm the high vulnerability of small island states to climate change, independent of the methodology applied. As already noted, global assessments come to the same conclusions (Nicholls et al., 1999). This is therefore a robust finding, which must be of considerable concern to these countries.
Most vulnerability indices developed to date have focused on economic and social systems, although studies by Ehrlich and Ehrlich (1991) and Atkins et al. (1998) focus on environmental vulnerability. The economic vulnerability indices include those developed by Briguglio (1995, 1997), the Commonwealth Secretariat (Wells, 1996, 1997; Atkins et al., 1998), Pantin (1997), and the Caribbean Development Bank (Crowards, 1999). Another index, the Environmental Vulnerability Index, has been developed recently for small island states, particularly countries for which data availability is limited. It incorporates climate, nonclimate, and human stresses on the environment and seeks to reflect relative vulnerability as a function of these combined factors (Kaly et al., 1999). All vulnerability indices consistently identify small statessometimes more specifically small island statesas being more economically vulnerable than larger states.
Most existing studies have fulfilled the first two of the three aforementioned goals of vulnerability assessment, although information on socioeconomic impacts of climate change often is limited. The third goalto provide a basis to guide possible adaptationusually is met only in general terms. Effective planning and design of adaptation strategies requires more detailed information on crucial vulnerable sectors and areas. Such information may be partly derived from analysis at an integrated level (see Box 17-2)as suggested, for instance, by Klein and Nicholls (1999).
Box 17-2. Tools for Vulnerability Assessment and Adaptation Policy Development
The numerous and well-developed interactions between the natural and human systems of island countries underscore the relevance of integrated assessment as a meaningful analytical tool for designing adaptation strategies. One such tool that has proven particularly beneficial is VANDACLIM, an integrated assessment model developed by the International Global Change Institute (University of Waikato, New Zealand), in collaboration with the South Pacific Regional Environment Programme (SPREP) and United Nations Institute for Training and Research (UNITAR) (Warrick et al., 1999). Enhanced and country-specific versions of VANDACLIM currently are being developed.
Development of VANDACLIM involved linking a regional scenario generator with selected impact models for four key sectors: agriculture, coastal zones, human health, and water resources. The user has considerable flexibility in generating scenarios; the user can choose among a large range of projections from GHG emission scenarios; the low, mid, or high cases from each projection (which encompasses the range of uncertainty in model parameter values); several GCM patterns; and the year of interest (in 5-year increments from 1990 to 2100).
VANDACLIM integrates a variant of the "Bruun rule" with a simple inundation model that is suitable for flat, low-lying deltaic coastal plains. Health impacts projections are derived from a biophysical index that estimates potential incidence of malaria and a simple threshold index for estimating change in the risk of cholera outbreaks related to extreme flooding events. For water resources, three models are included: an atmospheric water balance model for assessing the overall water resource situation for the country; a water balance-river discharge model for estimating monthly mean discharge for estimating wet and dry season river flow; and a discharge-flood area model for defining the areal extent of flooding. For agriculture, various crop models and indices are integrated, including degree-day models, rainfall (soil moisture), a land suitability index, and temperature for a variety of tropical crops.
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