Mangroves in the Gulf of California increase fishery yields
Year Published:
Study Number:
2
Country:
Author:

O. Aburto-Oropeza, E. Ezcurra, G. Danemann, V. Valdez, J. Murray & E. Sala

Abstract:

Mangroves are disappearing rapidly worldwide despite their well documented biodiversity and the ecosystem services they provide. Failure to link ecological processes and their societal benefits has favored highly destructive aquaculture and tourism developments that threaten mangroves and result in costly ‘‘externalities.’’ Specifically, the potentially irreparable damage to fisheries because of mangrove loss has been belittled and is greatly underestimated. Here, we show that, in the Gulf of California, fisheries landings are positively related to the local abundance of mangroves and, in particular, to the productive area in the mangrove–water fringe that is used as nursery and/or feeding grounds by many commercial species. Mangrove-related fish and crab species account for 32% of the small-scale fisheries landings in the region. The annual economic median value of these fisheries is US $37,500 per hectare of mangrove fringe, falling within the higher end of values previously calculated worldwide for all mangrove services together. The ten-year discounted value of one hectare of fringe is >300 times the official cost set by the Mexican government. The destruction of mangroves has a strong economic impact on local fishing communities and on food production in the region. Our valuation of the services provided by mangroves may prove useful in making appropriate decisions for a more efficient and sustainable use of wetlands.

Main Results and Conclusions:
  • This article focuses on fishery yields as the primary ecosystem service provided by mangrove forests:  “These coastal forests…strongly influence the structure of neighboring marine communities by increasing the biomass of commercially important fish and invertebrates that spend part of their life cycles in the mangrove environment (Mumby et al., 2004; Dorenbosch et al., 2004), (Nagelkerken et al., 2002; Rönnbäck 1999)” (10456).
  • Anthropogenic sources of mangrove degradation in the Gulf of California are as follows:
  • Aquaculture: “Although human density is low in the Gulf of California, there is an increasing pressure to transform mangroves into shrimp farms and tourism coastal developments (Glenn 2006), (Paez-Osuna et al., 1999; Paez-Osuna et al., 2003)” (10456).
  • Coastal Development: “…modification of water flows through construction of marinas and channels is also an important threat for these ecosystems; for example, coastal areas near La Paz alone lost 23% of the mangrove forests between 1973 and 1981 because of development (Mendoza 1984)” (10456).
  • Deforestation: “Today, mangroves are disappearing at a regional rate of 2% annually because of sedimentation, eutrophication, and deforestation (Instituto Nacional de Ecología 2005)” (10456).
  • The value of mangroves is often linked to the value of the fisheries. In this study, the consequences of mangrove forest deforestation and extinction on fishery yields are discussed by studying the correlation between range of the mangrove forest and size of 13 fisheries landings.
  • “The yearly landings between 2001 and 2005 for fish and blue crab in the Gulf of California averaged 11,600 tons. This production generated an average annual income of US$ 19 million for fishermen in the 13 fishing regions” (10457).
  • “Areas with smaller mangrove ecosystems, mostly located in the Baja California peninsula, showed more landings of high-priced resources like snappers and snooks” (10457).
  • “Thus, one kilometer of mangrove fringe contains 0.5–1.0 hectare (ha) of suitable habitat for marine organisms, and, on a per hectare basis, the annual productivity of the mangrove fringe alone is approximately US$ 25,000 to US$ 50,000 with a median value of US$ 37,500” (10457).
  • The study concludes by showing that mangrove forests are related to fishery yields. Another way of stating this conclusion is that strong fisheries can reinforce the value of mangroves locally.
  •  “…although we considered other explanatory environmental variables for fisheries landings, the analysis showed that only the mangrove area is significantly related to the amount of landings produced every year” (10458).
  • “…in the Mexican government administration time frame (6 years), the fisheries-based long-term value of one hectare of fringe mangrove is 200 times higher than the standard value of US$ 1,020 ha-1 established by the Mexican National Forest Commission (Secretaría de Medio Ambiente y Recursos Naturales, 2006)” (10458).
  • “Our analysis is based on data for a single time period, and changes in the price of fish and blue crab, or in the harvestable volume of the fisheries, can potentially modify our results. However, considering the price elasticity of demand for fish protein in Mexico (Golan, Perloff JM, and Shen EZ, 2001) and the country’s annual population growth of >1%, it seems unlikely that demand for fish will decline significantly in the future. Furthermore, with >60% of the world’s fisheries declining (FAO, 2007), it also seems unlikely that there will be dramatic increases in the supply of fish in the near future. Thus, significant decreases in the future value of the fishery services provided by mangroves are improbable”(10458).
Works Cited:

Dorenbosch M, van Riel MC, Nagelkerken I, van der Velde G (2004) The relationship of reef fish densities to the proximity of mangrove and seagrass nurseries. Estuar Coast Shelf Sci 60:37–48.

FAO Fisheries and Aquaculture Department (2007) The State of World Fisheries and Aquaculture 2006 (Food and Agriculture Organization of the United Nations, Rome, Italy).

Glenn EP, Nagler PL, Brusca RC, Hinojosa-Huerta O (2006) Coastal wetlands of the northern Gulf of California: inventory and conservation status. Aquat Conserv 16:5–28.

Golan A, Perloff JM, Shen EZ (2001) Estimating a demand system with nonnegativity constraints: Mexican meat demand. Rev Econ Statist 83:541–550.

Instituto Nacional de Ecología (2005) Evaluación preliminar de las tasas de pérdida de la superficie de manglar en México (Instituto Nacional de Ecología, SEMARNAT. Mexico, D.F.)

Mendoza R, Amador E, Llinas J, Bustillos J (1984) Memoria de la primera reunión sobre ciencia y sociedad, presente y futuro de la ensenada de La Paz (Gobierno del Estado de Baja California Sur, La Paz, Mexico).

Mumby PJ, et al. (2004) Mangroves enhance the biomass of coral reef fish communities in the Caribbean. Nature 427:533–536.

Nagelkerken I, et al. (2002) How important are mangroves and seagrass beds for coral-reef fish? The nursery hypothesis tested on an island scale. Mar Ecol Prog Ser 244:299–305.

Paez-Osuna F, Guerrero-Galvan SR, Ruiz-Fernandez AC (1999) Discharge of nutrients from shrimp farming to coastal waters of the Gulf of California. Mar Pollution Bulletin 38:585–592.

Paez-Osuna F, et al. (2003) Shrimp aquaculture development and the environment in the Gulf of California ecoregion. Mar Pollut Bull 46:806–815.

Rönnbäck P (1999) The ecological basis for economic value of seafood production supported by mangrove ecosystems. Ecol Econ 29:235–252.

Secretaría de Medio Ambiente y Recursos Naturales (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 metodología para su estimación (Diario Oficial de la Federación DCXXXI-8:11–15).