Terrestrial Environments

Knowing how landscape has changed over time provides valuable information for conservation land managers and for guiding community development and restoration efforts.

Babeldaob Island contains the largest area of intact native lowland forest in the Pacific. The forests of Babeldaob are the most diverse forests in Micronesia and are vital to maintain Babeldaob’s watersheds, near shore environment, and forest resources. To understand where and how much forests and vegetation have changed over time on Babeldaob, a collaborative group from the Palau Coral Reef Research Foundation, the USDA Forest Service, and Palau Forestry analyzed historical aerial photos and satellite imagery over a 60 year time period of 4 land cover categories: forest, mangrove, non-forest vegetation (savanna), and non-vegetation (i.e., roads, buildings). This method allows us to understand how the landscape of Babeldaob has changed over time.

Manual classification was used to classify aerial photos from 1947, 1976, and 1992 and automated classification was used to classify satellite imagery from 2001 and 2005. Maps of Babeldaob Island land cover over time and detailed images from Melekeok state showing specific areas of forest cover increase and areas where forest had been cleared between mapped periods. Babeldaob has a moderately fragmented landscape with relatively stable forest interiors and dynamic forest and savanna edges. Forest cover has been increasing, despite some forest edge clearance and increases of non-vegetation from road construction and other urban development.

In addition to monitoring landscape change via the large scale image analyses, the USDA Forest Service and collaborators have also implemented an upland forest monitoring protocol within a permanent plot in Palau. This detailed study of a single diverse area will help meet the terrestrial monitoring objectives of the Micronesian Challenge and provides detailed information on the growth, survivorship and mortality of individual plants. An autonomous weather station on site provides detailed data on the conditions affecting the plot. The Ngardok Nature Reserve, part of the Melekeok Conservation Network, was selected as the site for the first permanent forest dynamic plot in Palau and uses the methodology of the Smithsonian’s Center for Tropical Forest Science (CTFS) Permanent Plot Network. This very high resolution measurement program gives baseline information on forest changes and allows for detection of sensitivities of recruitment, growth and death to stressors like climate warming and drought.

Knowing about Palau’s forests is important for many reasons, including the ecosystem services (supply of freshwater, control of flooding and erosion, forest products, wildlife habitats, recreational activities) provided. This knowledge allows the comparison of ecological properties of Palauan forests with those of forest plots in tropical and temperate forests around the world. The Palau plot (NNR) contains a similar density of tree stems per hectare as other tropical forests in the CTFS network, but contains three times the number of tree species as Hawaii’s permanent plots, highlighting Palau’s high biodiversity for a pacific island.