Provided by Steven Victor, The Nature Conservancy, Palau
The Republic of Palau, a small nation comprised of over 400 islands in the western Pacific Ocean, is surrounded by approximately 525 sq km of barrier, fringing, and atoll reefs, with patch reefs scattered throughout numerous coral lagoons. As part of the 1994 Compact of Free Association between Palau and the United States, the U. S. agreed to fund the construction of an 85-km road around Palau’s largest island, Babeldaob, as a means of improving access and promoting economic growth. However, construction for the road, which was completed in 2007, led to widespread clearing of forest and mangroves, causing soils to erode into rivers and coastal waterways that impacted seagrass beds and coral reefs. The new road also prompted further development for houses and additional access roadways. At the same time, Palauans started noticing declining coral reef health and fish stocks, and degraded quality of freshwater resources. Compounding this threat from land-based sediments, the 1998 worldwide coral bleaching event also caused widespread coral mortality across Palau, reducing coral cover below 5% in most areas by 2001.1
Due to Palauans’ affinity for the ocean, conservation efforts in Palau have traditionally focused almost exclusively on the marine environment, with much less attention on protecting the land. In 2003, the Palau International Coral Reef Center (PICRC) conducted studies aimed at improving understanding of the connectivity between marine and terrestrial environments by quantifying sediment input to coastal waters and documenting the condition of coral reefs. The results revealed that the degradation of reefs was a direct result of land-based sediments, which cause reduced coral cover, lower coral recruitment, and excessive growth of algae.2 Reefs in Airai Bay, a lagoon on the southeastern end of Babeldaob, were particularly impacted by sediment.3
PICRC scientists presented these findings to communities in Babeldaob as evidence of the importance of terrestrial ecosystems in protecting coastal water quality and coral reef health. In response, community members lobbied the governing body of Airai state, the second-most populated state in Palau, to ban the clearing of mangroves, which act as important buffers between the marine environment and terrestrial runoff. The greater awareness of ecosystem connectivity has also shifted the focus of conservation efforts in Palau to entire watershed areas, transcending political boundaries between neighboring States.
The creation of the Babeldaob Watershed Alliance (BWA) is representative of this shift, successfully merging the interests of communities, government agencies, conservation practitioners, and traditional leaders to protect entire watershed areas. A major success of the BWA was the signing of ‘Master Cooperative Agreements’ between several states on Babeldaob, which identify collective conservation goals and incentives for progress toward these goals. Other major outcomes include the establishment of four new terrestrial protected areas and completion of several community-level land management plans. The BWA has also improved communication between local communities and government agencies and conservation organizations such as the U.S. Fish and Wildlife Service and the Micronesia Conservation Trust (MCT), allowing for better coordination and streamlined assistance to meet local priorities. To date, nine of the ten Babeldaob states now participate in the BWA and optimism for the future ecological health of coastal areas is on the rise.
PICRC also found that in the ten years since the bleaching event, Palau’s coral reefs have recovered in areas not impacted by heavy sedimentation, with an average of 30 to 40% coral cover by 2005 in sediment-free areas. Scientists have attributed the recovery to key ecological processes that were still intact following the 1998 bleaching event, such as presence of remnant coral population1 and a healthy herbivorous fish population, which controls algal overgrowth on reefs to facilitate coral recruitment.4 Both of these key factors are limited where heavy sedimentation occurs. Therefore, preservation of mangroves and seagrasses as natural sediment traps—accompanied by improved watershed management—are vital to promoting reef resilience.
Golbuu, Y. et al. Palau’s Coral Reefs Show Differential Habitat Recovery Following the 1998-Bleaching Event. Coral Reefs 26, 319-332 (2007). ↩
Victor, S., Y. Golbuu, E. Wolanski and R. H. Richmond. Fine Sediment Trapping in Two Mangrove-Fringed Estuaries Exposed to Contrasting Land Use Intensity, Palau, Micronesia. Wetland Ecology and Mangement 12, 277-283 (2004); Fabricius, K. Effects of Terrestrial Runoff on the Ecology of Corals and Coral Reefs: Review and Synthesis. Marine Pollution Bulletin 50, 125-146 (2005). ↩
Golbuu, Y. Trapping of Fine Sediment in a Semi-Enclosed Bay, Palau, Micronesia. Estuarine, Coastal and Shelf Science 57, 941-949 (2003). ↩
Mumby, P. J. et al. Fishing, Trophic Cascades, and the Process of Grazing on Coral Reefs. Science 311, 98-101 (2006). ↩