A new way of studying and visualizing Earth science data from a NASA and U.S. Geological Survey satellite program is resulting in, for the first time, the ability to tease out the small events that can cause big changes in an ecosystem.
Called LandTrendr, this computer program is able to find patterns previously buried within vast amounts of scientific data. Still in development, it’s already led to seeing for the first time in satellite imagery an obscured, slow-moving decline and recovery of trees in Pacific Northwest forests. Comparing satellite data to ground data, scientists uncovered the cause. “It was, as it turns out, bugs,” says Robert Kennedy, a remote sensing specialist at Boston University, who consulted with U.S. Forest Service experts to confirm his observations.
The unexpected disturbance pattern showed a long slow decline of tree health over years followed by slow regrowth. It emerged in several areas, particularly near Mount Hood in the 1980s, peaking in 1992 when regrowth began, and near Mount Rainier where the insect outbreak lasted ten years from its onset in 1994 till the insects killed all the trees and moved on in 2004.
Kennedy created the LandTrendr program specifically to work with data from the NASA and U.S. Geological Survey (USGS) Landsat program. Kennedy’s new way of viewing Landsat imagery has already changed how the Forest Service in the Pacific Northwest operates its yearly forest monitoring program that uses ground stations, satellite imagery and statistics to evaluate current conditions.
Kennedy says that LandTrendr works because of the unique nature of Landsat data. The data embedded in images are a scientific record of the Earth’s surface that goes back 40 years. Each image, or scene, covers an area 115 miles by 112 miles (185 kilometers by 180 kilometers) and provides data for wavelengths of light reflected or emitted from the Earth’s surface, which scientists use to see, for example, forest conditions not apparent in visible light. With the four-decade record, they can compare images between years and see how the land changes with time.
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