Working Together to Prevent Decline of Coastal Ecosystems
31 Jan, 2008 04:32 pm
Recent scientific studies have documented the alarming decline in coastal ecosystems and habitats worldwide.
To arrest coastal habitat decline, concerned international organizations and scientists are calling for a new approach - “ecosystem-based management” (EBM) - as a way of reconciling the decline in vital coastal ecosystem services with continuing human development pressures.
While endorsing the general need for coastal EBM, our paper argues that such a strategy is likely to fail unless economists and ecologists work together to improve current methods of assessing coastal ecosystem benefits. Too often, poor ecological data lead to inaccurate valuation of these benefits, resulting frequently yields in an “all or none” choice of either preserving or converting all coastal habitats to human use. This “all or none” outcome is at odds with EBM strategies, which are trying to find acceptable compromises between conservation and development.
To illustrate the importance of this dilemma, we focus on the key ecosystem service of coastal wetlands acting as “natural barriers” to the economic deamages caused by frequent coastal storm events. In recent years, this critical “storm prevention” service of coastal habits – such mangroves and marshlands – has received considerable attention due to the massive damages inflicted by the December 2004 Indian Ocean Tsunami, the August 2005 Hurricane Katrina along the US Gulf Coast, and the 15 November 2007 Cyclone Sidr in coastal Bangladesh.
From field studies of mangroves, salt marshes, seagrass beds, nearshore coral reefs, and sand dunes, we show that the ability of these critical habitat to “attenuate”, or break-up, incoming storm surges and waves declines considerably as more and more habitat is lost. We illustrate the coastal management implications of this relationship with the example of valuing the coastal protection benefit of mangroves in Thailand. We show that, by valuing correctly this “natural barrier” service, the best land use is neither complete conversion of the mangroves to an alternative use, such as commercial shrimp aquaculture, nor preservation of all the mangrove forest. Instead, the best coastal management policy is a mix of these development and conservation options. In fact, the outcome from our Thailand mangrove valuation example corresponds to “best practice” guidelines for mangrove management in Asia, which recommend that ideal mangrove:pond ratios should not exceed 20% of the habitat area converted to ponds.
In sum, as the case study of Thailand mangroves illustrates, the way in which ecological and economic analysis is combined to estimate the values of various ecosystem services can have a large impact on coastal EBM outcome. Rearchers need to be aware how incorrect assumptions underlying ecological and economic analysis might inadvertantly force EBM decision-making into a simple “all or none” choice. If the analysis is done correctly, however, then the right balance between development and conservation objectives can be achieved in the world’s heavily used coastal areas.
Edward B. Barbier et al., “Coastal ecosystem-based management with non-linear ecological functions and values," Science 319, no. 5861, 18 January 2008. Abstract available here.