New Study Leads the Way to Detailed Mapping of Tropical Rain Forest Types
A new study shows that widely available satellite imagery can be used to map tropical rain forests with much more detail than was previously thought possible. Although satellite imagery is commonly used to map tropical forests across large areas, only a few forest types are usually identified. This study, however, showed that if many dates of imagery are available, as in newly available satellite image archives, clues to distinguishing among forest patches containing different groups of tree species could be found.
Tropical countries need to produce detailed forest maps for a financial mechanism that gives countries incentives for Reducing Carbon Emissions from Deforestation and Degradation (REDD+) and for managing forests to sustain biodiversity and enhance carbon stocks. Detailed maps of forest types, including maps that distinguish groups of tree species, are essential, but until now, scientists have assumed that tropical forest tree communities appear too similar to each other in most satellite imagery to be mapped.
Working in the Republic of Trinidad and Tobago, the study authors searched through the recently opened archives of Landsat satellite imagery and through the very high-resolution satellite images that are viewable using Google Earth. They discovered that the spatial distributions of many tree communities, thought to be indistinguishable in satellite imagery, can in fact be revealed, but only in imagery from unique times, such as that collected during periods of severe drought, or when a particular tree species is flowering.
Other forest types were distinct in very high-resolution imagery because of unique canopy structure. These maps are the first for an entire tropical country that show the distributions of communities of tropical forest tree species. The study also produced a new set of topographic maps for the country at two scales that depict reserve areas, town, roads, rivers, and other landscape features in addition to forest type.
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