Editor’s note: When MPA habitats become severely degraded, active rehabilitation by management may be desirable – or necessary, in some cases – to restore ecological functions formerly provided. Such rehabilitation can be controversial, however, when artificial technologies are applied. The concept of “naturalness”, which management normally strives to protect with an MPA, becomes somewhat blurred.
Mark Erdmann is USAID’s marine protected areas advisor for the 890-km2 Bunaken National Park, located in North Sulawesi, Indonesia. (USAID is the US Agency for International Development.) In the following piece, he proposes that the use of artificial habitats for rehabilitation is sometimes appropriate, and that Bunaken National Park provides a good example of such a case. Readers are invited to respond with their insights.
By Mark Erdmann, Bunaken National Park (Indonesia)
Over the past few years, a range of coral reef rehabilitation techniques has been developed, many involving the placement of three-dimensional hard substrate forms (including cement, rock and ceramic) in areas of degraded reef. Although the science of reef restoration ecology is truly in its infancy (and hence a steep learning curve is to be expected), these methodologies have tended to draw a negative response from reef ecologists, who often compare them to the many ill-conceived artificial reef projects of the past – including dumping of used tires to create “reefs” that aggregate fishes. These skeptics maintain that reef rehabilitation is expensive and drains resources that would be more prudently dedicated to better management of intact reefs, and that it is best to allow natural reef recovery processes to run their course in degraded areas.
While these criticisms certainly have merit and should be carefully considered by MPA managers on a case-by-case basis, I strongly believe that there are situations where reef rehabilitation (defined herein as efforts to enhance natural reef recovery processes in areas that have suffered severe degradation, with the end goal of returning the reef to its natural condition prior to damage) is an appropriate intervention. In particular, rehabilitation should be considered in those situations where an MPA’s reefs:
- Have suffered large-scale, physical damage and show no signs of natural recovery on an economically meaningful decadal time scale;
- Are currently well-managed, with major threats to the reefs under control;
- Have sufficiently good water quality and larval availability to support vigorous reef growth; and
- Can attract dedicated funding for reef rehabilitation (e.g., from the private tourism sector) that would not otherwise be available for general reef management.
I would like to focus on one specific example of this: that of legacy blast-fishing damage in MPAs in the “Coral Triangle”. Across Southeast Asia, hundreds of thousands of hectares of once-productive coral reefs have been decimated by blast fishing, leaving vast rubble fields in their place. Despite generally excellent water quality and abundant coral larval availability, these rubble fields often show no signs of natural recovery on a decadal scale. This is because corals recruiting to unconsolidated rubble are quickly smothered when the rubble invariably moves as a result of currents or waves. This “alternate stable state” is particularly frustrating to those MPA managers who have instituted effective management but are forced to live with legacy bomb damage; to them, reef rehabilitation is an enticing option.
One case study is Bunaken National Park in Indonesia, where blast fishing has been largely brought under control but large areas of rubble field remain (many blasted nearly 20 years ago). Two stakeholder groups have shown strong interest in rehabilitating these rubble fields to increase productive reef area: village fishers eager for enhanced fisheries yields and dive operators hoping to spread effort among more dive sites and thus raise the diver carrying capacity of the park.
In response to this interest, the Seacology Foundation (http://www.seacology.org) provided a grant to the park village of Manado Tua to purchase 600 ceramic “EcoReef” modules to rehabilitate a nearly 1-hectare rubble field in return for the villagers’ commitment to set aside this area as a no-take zone. While this rehabilitation effort is focused upon fisheries enhancement (the area is off-limits to divers), local dive operators donated nearly 300 hours of dive time to install the EcoReef modules to help determine if this methodology is one in which they might invest to restore other degraded sites.
Completed in mid-January 2004, the results to date have already been impressive. The ceramic “snowflakes”, designed to mimic a branching coral thicket, immediately attracted large numbers of both schooling and sedentary fishes to the previously barren and lifeless rubble field. Benthic recruitment to the modules has been rapid, with coralline algae, bryozoans, vermetid worms, tunicates, and hard coral recruits now covering the modules. Perhaps most encouragingly, over one hundred coral fragments transplanted to the EcoReef modules (by simply wedging between the ceramic spines) have shown 100% survival, with nearly two-thirds of the fragments cementing to the modules and laying down new tissue over the ceramic in the first two months. Additional transplantation is scheduled for May 2004.
To be sure, the verdict on the success of this reef rehabilitation project will not be clear for 3-5 years. A grant from the Packard Foundation will permit us to monitor the biological and socioeconomic impacts of the project for the next three years to gauge cost-effectiveness of this technique. Villagers, dive operators and park management are pleased with the results to date and hopeful that within five years’ time, the ceramic modules will no longer be visible – overgrown by a thriving reef with high fisheries productivity. The potential for such a result certainly seems worth the effort.
Photos and video of the Manado Tua installation are viewable at http://www.ecoreefs.com.
For more information: Mark Erdmann, NRM III, Jl. Stadiun Klabat Selatan, Manado 95115, Indonesia. Tel: +62 431 827524; Email: erdmann@nrm.or.id