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NASA'S LANDSAT PATHFINDER HUMID TROPICAL FOREST PROJECT 
William Salas 
Institute for the Study of Earth, Oceans, and Space 
University of New Hampshire, Durham, NH, USA 
Dave Skole and Walter Chomentowski 
Basic Science and Remote Sensing Initiative 
Michigan State University, East Lansing. MI, USA 
John Townshend and Vivre Bell 
Department of Geography 
University of Maryland, College Park, MD, USA 
Chris Justice 
Department of Environmental Sciences 
University of Virginia, Charlottesville, VA, USA 
and 
C. 4. Tucker 
Biospheric Science Branch 
NASA Goddard Space Flight Center, Greenbelt, MD, USA 
KEY WORDS: Remote Sensing. Deforestation, Carbon Cycle, Landsat Pathfinder Program, Tropical Forest Monitoring. 
ABSTRACT 
Carbon dioxide concentration in the atmosphere has increased by more than 2596 over the last two centuries. Up to a third of this 
increase is thought to have come from deforestation. Until recently, estimates of the rate and extent of deforestation have varied 
tremendously. The recent use of high resolution (20-100m) satellite based remote sensing has begun to resolve these 
discrepancies by quantifying the temporal and spatial variations in deforestation in the tropics. NASA's Landsat Pathfinder Humid 
Tropical Forest (HTF) project has demonstrated that satellite-based techniques, relying on high resolution data within a GIS can be 
applied on a regional to global scale to map deforestation at a decadel time step. These data can then be used to reduce the 
aforementioned uncertainty in deforestation rates and thereby provide vastly improved forcing functions for global carbon 
models. 
The NASA Landsat Pathfinder Humid Tropical Forest (HTF) Project is a collaborative effort between the University of New 
Hampshire's Institute for the Study of Earth, Oceans and Space, Michigan State's Department of Geography, University of 
Maryland's Geography Department, University of Virginia's Department of Environmental Sciences, and NASA's Goddard Space 
Flight Center. The project has focused on the three regions where most of the tropical deforestation in the world has occurred: (1) 
the Amazon Basin, (2) Central Africa, and (3) Southeast Asia. These three regions account for the majority of deforestation 
activities in closed tropical forests worldwide. This paper presents an overview of the project with a detailed discussion of the 
methods employed for analyzing the thousands of Landsat images in the HTF archive covering the tropical forests from 1973 to 
1993. 
third of the observed increase was thought to be due to land use 
change in the tropics. In fact, before 1920 emissions of 
carbon from deforestation were greater than from fossil fuel 
combustion, and over the last two hundred years the total 
release from deforestation has been approximately equal to 
that from fossil fuels. 
1. SCIENCE RATIONALE AND JUSTIFICATION 
1.1 Landuse and the Global Carbon Cycle 
Concentration of carbon dioxide in the atmosphere has While the tropics may provide a net source of carbon to the 
increased by over 25%, from 275 ppm in the eighteenth 
century to more than 350 ppm in 1989. Combustion of fossil 
fuels was the major source of this increase, however, upto a 
Intemational Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998 
atmosphere, research points to the mid to high latitudes as a 
sink. Although this places new importance on the role of 
temperate zone ecosystems, nevertheless, it is important to 
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