Climate Change Vulnerability Assessment and Adaptation Planning ...

3.0 Conducting a Vulnerability AssessmentHow to interpret vulnerabilityAlthough higher temperatures are not a vulnerabilityfactor for mangroves, adjacent coral reef systems arevulnerable to temperature increases (see subsection 3.7).Changes in rainfall patterns and downscaled rainfallprojections may show rainfall trends, as well asdemonstrate changes in seasonality of rainfall (whichmight affect phenology). Changes in frequency of dryspells can affect mangroves separately from the longertermtrends.More severe or more frequent freshwater floodingevents are excluded from the vulnerability assessmenteven though they cause mortality as mentionedearlier. This is because site-specific storm impacts areimpossible to predict, and overall sea level inundationvulnerability is covered in subsection 3.5.Drier conditions may increase the vulnerabilityof mangroves, such as through reduced diversity,photosynthesis and productivity, as well as groundlevelsubsidence (Table 1). However, as demonstratedin the case study below, rainfall projections currentlytend to be highly uncertain and hence difficult toquantify. This will improve as rainfall modelingbecomes more sophisticated.Rank vulnerability on the scale below. Record the scorein the final column (S = score).Strengths/weaknessesData on changes in ground level and forest diversityand condition are collected in the forest assessment,elevation and sedimentation components of thevulnerability assessment already described. From thesebaseline surveys, such changes can be monitored in thefuture and the results interpreted relative to rainfallchanges. Rainfall projections within downscaledclimate modeling may eventually improve in their levelof certainty, which would make them more useful formangrove vulnerability assessment.Rank 1 2 3 4 5 SExposure factorsPrecipitation change Becomes wetter Rainfall unchanged Somewhat drier Moderately drier Significantly drierCase studyFollowing traditional approaches in climate changevulnerability assessment, the WWF project initiallyinvestigated climate models for the pilot sites andfound very uncertain results for the exposure factor ofprecipitation change (Table 22), in that it was predictedto either get wetter or drier.In Fiji, downscaled modeling was undertaken to try toreduce this uncertainty. The results were inconclusive,with 7 of 12 models showing a future (2080–99) withhigher annual rainfall than at present (1980–99).These results implied that it would be wise forenvironmental planners, when reviewing adaptationoptions, to consider both negative and positiverainfall projections for the 21st century. Hence, themodeling was of little help to the overall vulnerabilityassessment.Regions 2010-2039 2040-2069 2070-2099Mediterranean -35.6 to +55.1 -52.6 to +38.3 -61.0 to +6.2Caribbean -14.2 to +13.7 -36.3 to +34.2 -49.3 to +28.9Indian Ocean -5.4 to +6.0 -6.9 to +12.4 -9.8 to +14.7NorthernPacificSouthernPacific-6.3 to +9.1 -19.2 to +21.3 -2.7 to +25.8-3.9 to +3.4 -8.23 to +6.7 -14.0 to +14.6Table 22. Projected change in precipitation over smallislands, by region (percentage). The ranges are derivedfrom seven atmosphere-ocean general circulationmodels (GCMs) run under the key SRES emissionsscenarios (from IPCC, 2007c).Climate Change Vulnerability Assessment and Adaptation Planning for Mangrove Systems | 73