THIS makes for a depressing game of spot the difference. These two images of Rondônia, a state in western Brazil, show the impact of deforestation on this part of the Amazon rainforest since 1975, when the picture on the left was taken. Human activity in the area began with the construction of a main highway (orange line in left-hand image), which cut deep into the rainforest. As settlers and farmers moved in, secondary roads were built at right angles to the initial road, resulting in the distinctive fishbone pattern visible in the right-hand image, taken in 2012.
The entire process was captured by NASA’s Landsat satellites, which have been continuously monitoring Earth’s surface for the past 40 years. The stunning images generated by these eyes in the sky have allowed for a dramatically improved understanding of the way our planet works.
Some of those images were used by Compton Tucker, a biologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and his colleague David Skole of Michigan State University in East Lansing, in a landmark study of Amazon deforestation published in 1993 (Science, doi.org/bgb6zs).
Their discoveries at first seemed paradoxical. While the rate of deforestation in Rondônia was lower than anticipated, the impact on biodiversity was greater. Somehow, the fishbone technique was living up to its ominous name.
Skole and Tucker concluded that the spatial pattern of deforestation is as important as the size of the area affected. This was especially true in Rondônia, where the extensive branching of roads increasingly fragmentated the rainforest, cutting organisms off from shelter and leaving them more exposed to human activity.
These images are part of a series released by NASA’s Earth Observatory to mark the 40th anniversary of the Landsat programme.