PARENT SESSION
Oral Session #34: Forests: Models of function and structure. Presiding: M. Lechowicz.
Tuesday, August 7, 2001. 1:00 PM to 3:45 PM. Hall of Ideas F.
Using MODIS data to assess regional forest degradation from human activity.
DEFRIES, R.1,2, HANSEN, M.1, 1 2
ABSTRACT- Coarse-scale satellite data have been used in previous research to characterize the proportional coverage of woody vegetation within each pixel at a global scale. In contrast to traditional classification schemes, the "continuous fields" characterize mixtures and gradients across the landscape. Prototypes have been derived from AVHRR data at 1km resolution and global data sets based on MODIS data at 250 and 500m are currently under development. Sharp distinctions between administrative units and boundaries of protected areas are clearly visible in the percent tree cover estimates. Assuming relatively homogeneous characteristics of climate, soil, and "natural" vegetation within ecoregions, the "continuous fields" can be used to assess the degree of forest degradation within administrative units by comparing percent tree cover within and outside of the protected areas. Areal statistics cataloging forest cover and forest cover fragmentation measure degradation from human activity across regions. An example from the Western Interior Atlantic Forest Mixed Forest ecoregion in South America illustrates the distinctly different stages in forest clearing of the three countries with territory in the ecoregion (Brazil, Paraguay, and Argentina). Such information compiled for forested ecoregions around the world will contribute to the Millennium Ecosystem Assessment as one measure of the health of the world's forested ecosystems.
KEY WORDS: remote sensing, forest degradation, MODIS