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Published online 21 July 2008 | Nature | doi:10.1038/news.2008.966
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Mexican mangroves well worth saving
Fishing survey puts dollar value on endangered ecosystems.
A study of the fishing industry off the west coast of Mexico has measured the financial consequences of mangrove forest destruction.
The scientists behind the study say this is the first detailed research to put a dollar value on the potentially irreparable damage being done to these coastal ecosystems.
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The approach by which an unknown nature or biodiversity value is compared against the known financial-economical difference between alternatives was first introduced into the natural resource valuation literature 40+ years back (1). The slant, though not perfect, is rightful, and relies on the attributed value of a natural asset to justify its preservation, or use, on economic grounds. The relationship between mangrove loss and fisheries is difficult, and until now the best economic study was probably that of Barbier & Strand (2) where the loss in fisheries revenue due to yearly mangrove deforestation in Laguna de Términos –Mexico, was estimated in US$1400/ha. This amount is still <300 times the ten-year discounted annual economic median value of one hectare of mangrove fringe as published by Aburto et al in a recent issue of PNAS (3) using the same underlying principle, but close to the official land-use compensation cost of US$1020/ha set by the Mexican government from costs of labor and material inputs for wetland’s restoration (4) –which is still far from the US$3000 to 510000/ha restitution costs of damaged, routinely harvested or destroyed mangrove forests elsewhere (5). By leaving out these differences in rationale, the article has given enough ammunition to a lurid media coverage that has misled the public with unfair comparisons about the disparity of these valuation approaches –which rely on different grounds and serve different development objectives. We agree with most of the article, yet we feel these juxtapositions over-state the implications of different underlying methodological principles, and require some clarification and perspective in order to offset the green-press’ clear intention to heap scorn upon a policy that, incidentally, was repealed de jure by Presidential decree last year (6). Since the referred standard one-time payment value established by the Mexican National Forest Commission is not based on any environmental service provided by mangrove ecosystems, Aburto et al’s comparison is undue and should be tempered, instead, against the uncertainty of their own linear approach upon the highly variable –and nonlinear fisheries regime in each of their 13 regions (7,8). Overfishing, or not fishing at all, lowers mangroves’ economic value. So, for a proper valuation, the fisheries regime has to be taken into account since the crucial question is whether these fisheries are operating at bionomic equilibrium where costs equal revenue –hence probably the inconsistency with Barbier & Strand’s comparable estimates, and others’. Pricing mangrove ecosystems by considering the monetary revenues of the main economic activities they support –e.g., commercial fisheries, tourism infrastructure or aquaculture, leaves out the value of probably “less fruitful†but equally relevant activities –e.g., a value of US$5163/ha/yr draws from services provided to fisheries ≈57%, water quality maintenance ≈43%, and timber and firewood <0.1% (9). Since every valuation approach has limitations, a much more convincing case to preserve mangrove ecosystems can be made if social equity is included in the debate –adding to the article’s valuation accomplishment. Distribution of income is a central political issue, especially in nations like Mexico, where local, usually poor, artisanal fishers receive modest benefits from mangrove-dependent fisheries while the big benefits from tourism or shrimp ponds, due to their high investment costs, accrue to distant, rich investors. Conversion of mangroves to any of these options therefore results in an unfavorable change in income distribution not reflected in total value, and adds to the costs of public assistance programs needed to support affected local families that see their income terminated by the creation of areas no longer accessible for docking, fishing, transit, recreation, shipping, etc. Whatever the approach, valuation assumes also the possibility of substitution between human and natural capital thus creating serious difficulties once the irreversible loss of biodiversity is sensibly considered into the costs’ breakdown. Finally, our point has not been to justify that mangrove ecosystems could be callously converted into anything else, but valuation may not be the most appropriate weapon to prevent this as the deemed article’s last paragraph implicitly states. As of today, and until novel risk- or prevention-related public policies regarding ecosystems conversion prove themselves effective in taking care of imbalances or inconsistencies among societal stakeholders, or between these and the state, mangrove restoration accomplishments reached elsewhere (10) should be consciously acknowledged as workable alternatives. José M. Galindo Jaramillo§ Carlos Viesca Lobatónïº Luis G. López-Lemus¶†§Staff Counselor to the Secretary and ¶Division of Environmental Policy; Secretariat of the Environment and Natural Resources; México City, DF 14210, MEXICO. ïºChief Scientific Advisor; Grupo AbarMar; Monterrey, NL 66230, MEXICO. †To whom correspondence should be addressed. E-mail: luis.lemus@semarnat.gob.mx 1. Krutilla JV (1967) Conservation reconsidered. American Economics Review 57: 778-786. 2. Barbier EB, Strand I (1998) Valuing mangrove-fishery linkages: A case study of Campeche, Mexico. Environment, Resources and Economics 12: 151-166. 3. Aburto-Oropeza O, Ezcurra E, Danemann G, Valdez, V, Murray J, Sala E (2008) Mangroves in the Gulf of California increase fishery yields. Proceedings of the National Academy of Sciences 105: 10456–10459. 4. Comisión Nacional Forestal (2006) Acuerdo mediante el cual se expiden los costos de referencia para reforestación o restauración y su mantenimiento para compensación ambiental por cambio de uso de suelo en terrenos forestales y la metodologÃa para su estimación. Diario Oficial de la Federación, 1ra Sección (Abril 12, 2006): 11-15. 5. Spurgeon J (1998) The socio-economic costs and benefits of coastal habitat rehabilitation and creation. Marine Pollution Bulletin 37: 373-382. 6. SecretarÃa de Medio Ambiente y Recursos Naturales (2007) Decreto por el que se adiciona un artÃculo 60 TER; y se adiciona un segundo párrafo al artÃculo 99; todos ellos de la Ley General de Vida Silvestre. Diario Oficial de la Federación, 1ra Sección (Febrero 1, 2007): 82. 7. Barbier et al (2008) Coastal ecosystem-based management with nonlinear ecological functions and values. Science 319: 312-323. 8. Sala E, Aburto-Oropeza O, Paredes G, Reza M, López-Lemus LG (2004) Fishing down coastal food webs in the Gulf of California. Fisheries 29: 19- 25. 9. Lara-DomÃnguez AL, Yáñez-Arancibia A, Seijo JC (1998) in Economic Aspects of the Biodiversity of Mexico, eds BenÃtez DÃaz H, Vega López E, Peña Jiménez A, Ãvila Foucat, S (CONABIO-INE/SEMARNAP-WWF, México), pp 23-44. 10. Bosire JO et al (2008) Functionality of restored mangroves: A review. Aquatic Botany 89: 251-259.