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New method helps monitor forest insect outbreaks

Date: July 27, 2020

Satellite imagery can be used to map trees killed by insects, supporting aerial surveys.

An aerial view of a forest with large areas of dead trees killed by mountain pine beetles.
A large-scale mountain pine beetle outbreak in the Gospel Hump Wilderness of central Idaho. Photo by Chad Nelson, USDA Forest Service.
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.

A map showing tree mortality percentage from low (blue) to high (red).
Tree mortality map created from Landsat imagery for an area near Stanley, Idaho that experienced a mountain pine beetle and western spruce budworm outbreak in recent years. Image by Ben Bright, USDA Forest Service.

Key Findings

  • Landsat time series analysis can detect and predict tree mortality severity with 61-80% accuracy.
  • Landsat-derived maps are comparable to aerial survey data in terms of spatial patterns of mortality and annual estimates of total mortality area. However, low-level tree mortality was not always detected.
  • This method has the potential to generate timely estimates of tree mortality across large areas.
  • Research identifying which insect is causing damage using satellite imagery and complimentary geospatial data is ongoing.

Other Publications

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

Featured Publications

Bright, Benjamin C. ; Hudak, Andrew T. ; Meddens, Arjan J. H. ; Egan, Joel M. ; Jorgensen, Carl L. , 2020
Meddens, Arjan J. H. ; Hicke, Jeffrey A. ; Vierling, Lee A. ; Hudak, Andrew T. , 2013

Principal Investigators: 
Principal Investigators - External: 
Arjan J.H. Meddens - Washington State University
Forest Service Partners: 
Joel M. Egan, Cooperator, Forest Health Protection
Ryan P. Hanavan, Cooperator, Forest Health Protection
Carl L. Jorgensen, Cooperator, Forest Health Protection