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Color-coded radar maps reveal a mosaic of forest fire destruction in California


Every year in California, thousands of fires ravage hundreds of thousands of acres of land. Deciphering how well large chunks of vegetation recover over time can be difficult from the ground up. New radar maps now reveal the mosaic of plant destruction and regrowth after more than a decade of fires in the Los Angeles National Forest and other areas near Los Angeles.

A NASA research aircraft equipped with radar instruments, known as UAVSAR, flew over Southern California several times between 2010 and 2020 to produce a detailed map of the terrain below. By sending microwave pulses to the Earth’s surface and measuring the bouncing signals, the instruments can detect changes a few millimeters in height. They’re also sensitive to moisture, says Yunling Lou, a radar engineer at NASA’s Jet Propulsion Laboratory in Pasadena, California. The resulting maps can distinguish areas with chapparal trees and shrubs from the uncovered land.

Lou and his colleagues are developing an approach to color-coding maps each year to track large-scale changes in vegetation and monitor the recovery of forests and scrub after destructive forest fires. Areas with vegetation appear red in 2010, green in 2017, and blue in 2020. When the three maps are placed on top of each other, they tell a story of loss and regrowth. For example, the 2016 Fish Fire destroyed the vegetation that was present in 2010 and did not grow back until 2017 or 2020, so it still appears red on a composite map. The area affected by the 2020 Bobcat fire appears yellow: vegetation was present in 2010 and 2017 (red and green combine to turn yellow) but not 2020.

A multicolored approach combines vegetation maps of 2010 (red), 2017 (green) and 2020 (blue). A closer look at the Los Angeles National Forest and other areas near Los Angeles shows how the specific fires of the last decade have shaped forests and scrub. For example, the area affected by the 2020 Bobcat fire is yellow because vegetation was present in 2010 and 2017 (red and green combine to turn yellow) but not 2020.Joshua Stevens / NASA Earth Observatory

map of vegetation changes near Los Angeles in 2010, 2017 and 2020A multicolored approach combines vegetation maps of 2010 (red), 2017 (green) and 2020 (blue). A closer look at the Los Angeles National Forest and other areas near Los Angeles shows how the specific fires of the last decade have shaped forests and scrub. For example, the area affected by the 2020 Bobcat fire is yellow because vegetation was present in 2010 and 2017 (red and green combine to turn yellow) but not 2020.Joshua Stevens / NASA Earth Observatory

“Much of the Los Angeles National Forest has been affected by the fire at some point and has patches that are in different stages of regeneration,” says Naiara Pinto, JPL landscape ecologist. The color-coding method could allow researchers to identify factors, such as vegetation and soil types, that affect them regenerating different areas at different speeds. These maps could also be used to identify burned regions without vegetation and at risk of landslides.

The team continues to develop additional ways to use the data collected by UAVSAR. Radar can also penetrate smoke or clouds, potentially allowing it to track forest fires in real time to help firefighters actively fight the flames.



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