Insects cause extensive damage in western U.S. forests each year, often affecting an area similar to that burned by wildfire. The Forest Service monitors insect-caused tree damage annually using aerial surveys, in which surveyors map tree damage from airplanes. However, COVID-19 is expected to reduce 2020 aerial survey efforts, which occur beginning in late summer.
Remotely sensed satellite data can also be an effective tool for detecting and mapping tree mortality caused by forest insect outbreaks. Building on past work, RMRS scientists recently developed a methodology for mapping tree mortality severity across large areas using satellite imagery. Using the Landsat Thematic Mapper satellite imagery archive that began in 1984 and cloud computing within Google Earth Engine, the method detects areas of forest change and relates this change to percent tree mortality. It can produce maps of tree mortality that are comparable to aerial survey data across large areas for multiple types of insects.
This approach was tested across three study areas in the western United States. It is now being applied to National Forest lands in FS Regions 1 and 4 to map 2020 tree mortality, helping monitor and understand insect outbreaks even as the COVID-19 pandemic complicates survey efforts.
Meddens, A.J.H.; Hicke, J.A. 2014. Spatial and temporal patterns of Landsat-based detection of tree mortality caused by a mountain pine beetle outbreak in Colorado, USA. For. Ecol. Manage. 322, 78–88. DOI: 10.1016/j.foreco.2014.02.037