We developed benthic habitat maps for shallow (<30 meters) areas around the main islands of the Republic of Palau to help local managers and researchers develop reef fish management strategies, optimize biological monitoring sampling design, and develop place-based action strategies to address key issues and remedy specific threats to coral reefs.
Why We Care
The Republic of Palau is an exceptional example of a vibrant coral reef ecosystem, due in part to its geographic isolation, but also the proactive management measures put in place. However, the construction of the Compact Road circumnavigating Babeldoab caused sedimentary run-off which had an immediate negative impact on nearshore coral reef habitats. Of greatest concern are the long-term impacts of increased accessibility to the full extent of Babeldoab for the thousands of tourists that visit Palau to dive and snorkel these reefs. The sheer number of visitors (68,000 visitors in 2009) and the infrastructure associated with supporting their visit (e.g., hotels, restaurants, sewage treatment) risks coral degradation.
Palau’s management and research community have been very active in minimizing the impacts of tourism. For instance, Palau has designated 31 marine protected areas covering nearly 40% of Palau’s nearshore marine area. Locating these marine protected areas, as well as evaluating their management success, is predicated on having benthic habitat maps to evaluate habitat changes. Furthermore, the addition of future marine protected areas, as encouraged under the Micronesian Challenge, requires identifying ecological hotspots made possible by the benthic habitat map products.
What We Did
We mapped 1,500 km2 of shallow-water habitats around the Republic of Palau, supported by funding from NOAA’s Coral Reef Conservation Program. Maps were produced from Anguar north to Ngaruangel Atoll (Velasco Reef), but did not include Helen Reef to the south. Thirty-two distinct benthic habitat types (i.e., 4 major and 14 detailed geomorphological structure classes; 8 major and 3 detailed biological cover types) were mapped by visually interpreting of commercial satellite imagery (i.e., GeoEye IKONOS).
What We Found
The geomorphological structure in Palau is dominated by “unconsolidated sediment/sand” (39.6% of the total area, 517 km2), but “pavement” and “aggregate patch reef hard bottom structure,” which are conducive for soft and hard coral, are also present in significant quantities (20.9% of the total area, 310 km2; 20.2% of the total area, 299 km2). In general, “low (10% – <50%) density coral” and “uncolonized” are the dominate cover types of Palau (26.1 % of the total area, 386 km2; 24.5% of the total area, 362 km2).
The maps were also reviewed and edited by local experts prior to being published. The final deliverables for this project included the benthic habitat maps, source imagery and georeferenced underwater videos and photos.