(Aquaculture au Salvador : trop cher payé)
01 / 1998
Shrimp aquaculture is considered a growth industry yielding high returns and earning much-needed foreign exchange. However, its development is also known to lead to environmental degradation and social conflicts. In El Salvador it has led to the loss of rich and diverse ecosystems, such as mangroves. A little over 4,000 hectares of the total remaining area of mangrove forest is estimated to be prime land for aquaculture. Many private investors eagerly await the opportunity to convert this into ponds and tanks for shrimp cultivation. The ecosystemic value of mangroves for supporting flora and fauna, for fisheries, for providing fuelwood and fodder, for stabilising the coastline, and so on, is well known. Approximately 112,000 Salvadoran families depend directly on the 26,700 hectares of mangrove and brackish forests for their living. The conversion of mangroves to aquaculture ponds displaces the livelihoods of these families and denies them traditional access to the environmental goods and services that the mangroves provide.
While there are several analyses of the profits generated by shrimp culture, the true environmental costs of conversion have not been fully explored. This calls for not a mere calculation of costs and benefits, but an examination of the value society places on the environment. It is important to consider how the costs and benefits are distributed: asking who wins and who loses highlights the concentration of power and the exercise of choice. A group of economists, socio-biologists and artisanal fishers decided to explore whether benefits from shrimp culture outweigh the costs. A site in western El Salvador in the Department of La Union in the Gulf of Fonseca was chosen.
The idea was simple-to calculate the value of the forest assuming that it is deforested at current rates, and the value of all the benefits that it would secure if it were to remain the same size and not converted. These values would be compared with those in which all the land potentially available for conversion to aquaculture was excavated to form shrimp ponds.
These three different scenarios were labelled: the current management strategy; the partial conversion strategy; and the sustainable management strategy. It was decided to account for all the costs and benefits, the loss of fuelwood and timber, the loss of fish in the estuaries and at sea, and compare these to the benefits generated by selling a high value-added product which earns foreign exchange.
A household survey to develop estimates of the demand for timber and fuelwood and the use of other forest products, and a fishing survey to estimate the returns from marine and estuarine fishing activities, was undertaken.
These data were added to Ministry of Agriculture’s data on industrial and artisanal fisheries. Shrimp farms were surveyed and data on yields, shrimp larvae production, costs of operation and profits collected. All this information was combined to develop a measure of the value of the mangroves over time, taking account of their different growth and regeneration rates. A group of local community members, fishers, NGOs and forestry service employees helped design the hypothetical sustainable management option.
Since costs and benefits occur over time, they were discounted to reflect a single value that has meaning at one point in time. After all costs and benefits were accounted for, both for the conversion option and for the sustainable management option, it was possible to compare the net benefits (benefits minus costs)and answer the question: do the final benefits from aquaculture outweigh the costs?
It was possible to conclude that the net present value of the sustainable management strategy exceeds that of the other two management options. The net present value of benefits reaped under sustainable management exceeds that generated under partial mangrove conversion by US $73,120,115.
If the period for which these benefits were calculated was longer, say 100 years instead of 56, the benefits from the sustainable management option would far exceed those from other proposed management strategies.
It is evident that conversion of mangroves for shrimp cultivation is an unsustainable option from a long-term perspective. Despite this shrimp culture continues to grow rapidly in many parts of the developing world. The true environmental costs are substantial. In addition, many of the costs of shrimp culture are borne by communities living adjacent to shrimp culture areas. Were such costs to be internalised by investors and developers, it is unlikely that the economic rationale for shrimp cultivation would exist at all.
The conversion of mangrove areas to aquaculture farms needs to be reconsidered. Other alternatives for the design and operation of aquaculture ponds that do not degrade the environment, displace artisanal fishers and cause the irrevocable loss of biodiversity, need to be explored. Concerns about environmenal justice and sustainability should guide our choices about all decisions to transform, degrade or utilise natural environments.
Articles et dossiers
GAMMAGE, Sarah, Too great a cost in. Samudra Report, 1997/07, 18