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Climate Change Vulnerability Assessment and Adaptation Planning ...

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1.0 Mangroves: Values, Status <strong>and</strong> ThreatsType Attributes River-dominated Tide-dominated Wave-dominatedGeomorphic settingSediment sourceDeltaicdistributariesEstuarine withelongated isl<strong>and</strong>sBarrier isl<strong>and</strong>s/spits <strong>and</strong> lagoonsRiver- <strong>and</strong> wavedominatedDistributaries <strong>and</strong>lagoonsLow isl<strong>and</strong>Marine-dominatedAllochthonous Allochthonous Autochthonous Allochthonous AutochthonousTidal range Low High Any Any LowMangrove locationsDominant processExamplesSpecific vulnerabilitySeaward edge <strong>and</strong>distributariesFreshwaterdischargeMississippi;Ganges-Brahmaputra;Rufiji, Tanzania<strong>Change</strong> indischarge <strong>and</strong>sediment supplyTidal creeks <strong>and</strong>isl<strong>and</strong>sInside lagoonsLow-energydistributaries <strong>and</strong>lagoonsTidal currents Wave energy Wave energy<strong>and</strong> freshwaterdischargeOrd, Australia;Fly, Papua NewGuinea; Klang,MalaysiaIncreased tidalaction; change insediment budgetsEl Salvador;Mono, Benin;Laguna deTerminos, MexicoIncreased waveaction; change insediment budgetsGrijalva, Mexico;Burdekin, Australia;Sanaga, CameroonReduction insediment supplyFringing or basinSea levelTongatapu;Kiribati; Gr<strong>and</strong>Cayman;Jaluit, MarshallIsl<strong>and</strong>sLowsedimentationratesTable 2. Mangrove geomorphic settings <strong>and</strong> their controlling attributes (adapted from Thom, 1982; <strong>and</strong> Ellison, 2009a).The response of mangrove habitats in differentcoastal locations to climate change will depend on anumber of factors of coastal behavior, including tidalrange, sedimentology, salinity regime, communitycomposition <strong>and</strong> shore profile. Although they areintertidal, mangroves occur in a range of settings thatmay have different vulnerabilities to climate changeimpacts (Table 2).Allochthonous means that there are external sources ofsediment for the mangroves, particularly from rivers.This sediment tends to be inorganic, <strong>and</strong> mangrovesystems that have such sediment supply have highersedimentation rates, making them less vulnerable tosea level rise.Tidal range <strong>and</strong> relative sea level change are keyexposure factors relating to the vulnerability ofmangroves to sea level rise. For example, sea levelrise will have a greater impact on intertidal systems inmicrotidal areas than in macrotidal areas because thetidal zone relocation will be more complete (Figure 3).Global sea level rise will also have a greater impact onareas that already suffer from relative sea level rise dueto deltaic subsidence. Identification <strong>and</strong> interpretationof such vulnerabilities are the objectives of Sections 3<strong>and</strong> 4 of this manual.Autochthonous means that sediment sourcesare primarily organic <strong>and</strong> from in situ mangroveproduction, resulting in peaty sediment. Mangroveswith such sediment supply tend to have lowersedimentation rates, making them more vulnerable tosea level rise. These factors are incorporated into thevulnerability ranking in Section 4.<strong>Climate</strong> <strong>Change</strong> <strong>Vulnerability</strong> <strong>Assessment</strong> <strong>and</strong> <strong>Adaptation</strong> <strong>Planning</strong> for Mangrove Systems | 5

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