The Amazon, a vast tropical forest stretching across South America, is so large that is virtually impossible to study the evolving landscapes within the basin without the use of satellites. Scientists have used satellite imagery of the Amazon for more than 30 years to seek answers about this diverse ecosystem and the patterns and processes of land cover change. This technology continues to advance and a new study shows that NASA satellite images can allow scientists to more quickly and accurately assess deforestation in the Amazon.
Researchers from the University of Maryland-College Park, Brazil’s National Institute for Space Research (INPE) of Sao Jose dos Campos, Brazil, and South Dakota State University, Brookings, S.D., compared multiple years of data from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra and Aqua satellites to data collected from the high-resolution Landsat satellite. They found that MODIS images can rapidly and reliably detect changes in Amazon land cover.
Unlike MODIS data, analyses of high spatial resolution data demand extensive storage and processing requirements. And, in tropical forest regions, image quality is often reduced by cloud cover and infrequent coverage of high-resolution images. But MODIS obtains images of the Amazon up to four times per day and evaluations of the quality of data are provided with the image, clearly marking areas of clouds, water, or high aerosols. These impacts are further minimized with daily composites created through the combination of individual images.
Deforestation rates in tropical Africa, Southeast Asia, and South America have remained constant or have increased over the past two decades, altering global carbon emissions and climate while elevating the need for frequent and accurate assessment of forest loss. In the Brazilian Amazon alone, where the growth of cattle ranching and cropland agriculture are the primary causes of forest clearing, about 7,700 square miles of forest are clear-cut and burned each year, or roughly the area of New Jersey.
This study found a marked trend of larger and more extensive deforestation events between 2001 and 2004 in Mato Grosso State, Brazil, which was later confirmed on the ground. Information like this is so valuable to scientists because the Amazon literally drives weather systems around the world. Building on the results of this study, Brazil’s INPE has developed a near or almost real time monitoring application for deforestation detection known as the Real Time Deforestation Monitoring System (DETER) system.
While this study highlights the challenges of monitoring deforestation and the use of MODIS data in the Amazon, it also shows that similar MODIS analyses could form the basis for a wide array of regional studies in a highly-automated fashion, with both scientific and decision-making utility.