Mangrove ecosystem services and the potential for carbon revenue programmes in Solomon Islands
K. Warren-Rhodes, A.M. Schwarz, L. NG Boyle, J. Albert, S. S. Agalo, R. Warren, A. Bana, C. Paul, R. Kodosiku, W. Bosma, D. Yee, P. Ronnback, B. Crona and N. Duke
Mangroves are an imperilled biome whose protection and restoration through payments for ecosystem services (PES) can contribute to improved livelihoods, climate mitigation and adaptation. Interviews with resource users in three Solomon Islands villages suggest a strong reliance upon mangrove goods for subsistence and cash, particularly for firewood, food and building materials. Village-derived economic data indicates a minimum annual subsistence value from mangroves of US$ 345–1501 per household. Fish and nursery habitat and storm protection were widely recognized and highly valued mangrove ecosystem services. All villagers agreed that mangroves were under threat, with firewood over-harvesting considered the primary cause. Multivariate analyses revealed village affiliation and religious denomination as the most important factors determining the use and importance of mangrove goods. These factors, together with gender, affected users' awareness of ecosystem services. The importance placed on mangrove services did not differ significantly by village, religious denomination, gender, age, income, education or occupation. Mangrove ecosystem surveys are useful as tools for raising community awareness and input prior to design of PES systems. Land tenure and marine property rights, and how this complexity may both complicate and facilitate potential carbon credit programmes (Climate Change) in the Pacific, are discussed.
"In Solomon Islands, both terrestrial and mangrove forests are key sources of rural goods and income and harbour high biodiversity, but are under considerable threat from commercial and subsistence activities. PES and carbon credit projects may prove a viable option for mitigating both rural poverty and climate change, yet the specific effects on local subsistence populations from altering the use of these ecosystems remain unknown"(486).
Residents of Solomon island communities value the ecosystem services provided by mangrove habitat: Among the 30 types of mangrove goods identified (Table 2), nearly 75% were classified as important or very important (≥20% of users), including B. gymnorhiza propagules ('fruit') for food, mangrove sticks for husking coconuts, building materials, firewood and fish (Figs 2 and 3a)"(489).
There is a major economic incentive to preserve mangroves for natural ecosystem goods and services: "Although marked differences among villages were found, in general users identified firewood, food (propagules) and building materials as the most important direct benefits from mangroves. Initial economic data suggested a minimum annual subsistence value from these goods of SBD$ 2500–10 718 household−1 yr−1, which represented 38–160% of annual cash incomes. Mangrove-derived fish and invertebrates added SBD$ 5500–12 100 household−1 yr−1 in household subsistence and cash income"(492).
Key threats: "Local users perceived the key threats to mangrove forests as overharvesting for firewood and timber, and damage from natural disasters"(493).
Awareness of villagers regarding the importance of mangroves is extensive: "Our study results also confirmed that local ecological knowledge (Aswani & Hamilton 2004; Crona 2006) of mangroves and their function exists in Solomon Islands. Over 90% of users were aware of fish habitat/nursery and protection services, while 80% recognized the complex linkages between mangrove fisheries and coral reefs (Larsson et al. 1994; Ogden 1997). About 60% of villagers understood mangroves' central role in water quality and biodiversity, and over 50% mentioned other services relating to air quality and local climate"(493).
Recommendations for sustainable mangrove resource use is as follows: "Sustainable harvesting, effective traditional management and protection were measures recommended by villagers as necessary to ensure the availability of mangrove goods and services for future generations"(493).
Communities can provide insight into ecosystem management planning: "Our study results demonstrated the utility of conducting mangrove ecosystem surveys prior to the design of PES and carbon systems and as a first step in formal communication and consultation processes with communities"(494).
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