Landsat shows us the home planet, warts and all.
- By Linda Shiner
- Air & Space magazine, April 2013
(Page 3 of 4)
The team has used the satellite imagery to identify corridors joining several wildlife preserves where the loss of forest would endanger the bonobos and other animals. With this information, the team works with the surrounding communities on plans to protect the corridors. “In exchange, our partners help the farmers increase their yields by teaching them about crop rotation and practices to prevent soil erosion,” says Nackoney.
The satellite images (opposite) are also used to monitor deforestation and serve as the basis for maps showing land cover (left). In the Landsat images, darker greens indicate primary forests and swamp forests, where the canopy is intact; agricultural fields are light green; and pink spots show areas that have been newly cleared.
Wildfires destroyed more than nine million acres of forest in the United States last year, a jump over the 10-year average of 6.5 million acres. Most Americans are aware that the U.S. Forest Service works to contain wildfires and protect nearby homes and businesses. But few know that after the fires are out, another kind of firefighting begins.
For the past decade, the USGS and Department of Interior have used Landsat data to show forest service workers where fire damage threatens adjacent developments. If emergency response teams take action quickly, post-fire flooding, mudslides, and erosion can all be prevented.
Light reflected from severely burned soil differs from that reflected by areas where there are still plants and ground cover. Remote-sensing experts have learned that Landsat’s two mid-infrared bands are more sensitive to fire-caused changes in soil than other bands. With Landsat imaging, the forest service is able to generate maps showing four levels of damage, from unburned to severely burned—areas where all the organics like pine needles and duff have burned away and ash predominates. In those areas, fire response teams spread ryegrass seeds, place straw mulch on hillsides, or take some other action to prevent runoff and erosion.
Before 2001, says USGS geographer Randy McKinley, fire perimeters were sketched by teams on the ground or overflying the area in a helicopter; both methods were time-consuming and expensive. “Landsat supplanted the traditional ways that Burned Area Emergency Response teams get information,” says McKinley. With Landsat images, firefighters generate preliminary maps that are usually adjusted with data gathered in the field. But even the preliminary maps provide accurate locations for the perimeters of fires and also show within the perimeters unburned islands that don’t need treatment.
The Landsat archive also provides an atlas of old fires that were never mapped; scientists and environmental groups can study them to determine, for example, whether a fire has made the land more susceptible to invasive plant species.