Forest monitoring in the Amazon basin is vital to map forest cover and identify areas of deforestation. Moreover, forest biomass measurement is a necessary step to identify total forest carbon stocks and establish baselines for carbon finance mechanisms such as REDD+. In the Amazon, researchers use remote sensing and satellite techniques to measure and monitor forests.
Forest inventory has traditionally been conducted by field plot measurements. H.H. Chapman and others at the Yale School of Forestry were some of the first foresters to develop forest mensuration methodology in the United States. Today, allometric equations are then used to extrapolate total biomass and carbon content over a large scale. However, these biomass estimates vary between sites, and field plot measurements are costly and time consuming to replicate over a large area. Satellite data can be used to estimate forest cover across a large area at resolution of 30 square meters for Landsat and 250 square meters for MODIS. A recent mapping project between the University of Maryland and Google created a detailed global map of forest cover change. The research, using Landsat images, confirms the slowdown in Amazon deforestation in Brazil, although shows increased deforestation in dry forest area of the Cerrado and Chaco forest, in southern Brazil, Bolivia and Paraguay. Other studies using MODIS images show the annual change in forest cover in South America. They find continued forest loss in the arc of deforestation extending from Para, Brazil, south to Mato Grosso, and west into Acre, while finding forest recovery in steep areas of the Andes, the Atlantic Forest of Brazil, and the dry Caatinga of northeast coastal Brazil.
Higher resolution tools such as LiDAR have the potential to provide detailed forest inventory mapping at the large scale of the Amazon Basin. Researchers at the Carnegie Institution at Stanford University use a LiDAR quipped airplane to map total forest biomass and carbon stocks for large areas such as the Peruvian Amazon. LiDAR systems shoot lasers from airplanes and measure the height and distribution of ground vegetation based on the signal that returns to the airplane. Enhanced aerial observation can use LiDAR in addition to other sensors to measure plant pigments, water content, structure, and other nutrients, all of which can be used to detect forest health conditions and even distinguish individual species. Read an overview of these techniques in a Nature news feature and at Yale E360.
Combined, these satellite monitoring methods provide accurate monitoring of forest conditions and deforestation. Forest monitoring from Brazil’s space institute, INPE, has been influential in reducing the country’s deforestation rate. Tools such as the Global Forest Watch of World Resources Institute use near real-time satellite data to provide current information about deforestation threats around the world.
Aide, T. M., Clark, M. L., Grau, H. R., López‐Carr, D., Levy, M. A., Redo, D., … & Muñiz, M. (2013). Deforestation and reforestation of Latin America and the Caribbean (2001–2010). Biotropica, 45(2), 262-271
Asner, G. P., Powell, G. V., Mascaro, J., Knapp, D. E., Clark, J. K., Jacobson, J., … & Hughes, R. F. (2010). High-resolution forest carbon stocks and emissions in the Amazon. Proceedings of the National Academy of Sciences, 107(38), 16738-16742.
Hansen, M. C., Potapov, P. V., Moore, R., Hancher, M., Turubanova, S. A., Tyukavina, A., … & Townshend, J. R. G. (2013). High-resolution global maps of 21st-century forest cover change. Science, 342(6160), 850-853.
Nepstad, D., Soares-Filho, B. S., Merry, F., Lima, A., Moutinho, P., Carter, J., … & Stella, O. (2009). The end of deforestation in the Brazilian Amazon. Science, 326(5958), 1350-1351.