August 2016.

Forest managers, at the regional, state, and national levels need mortality maps updated every 1-2 months, because the situation changes very rapidly in the Southern Sierra. However, currently there is no operational tool to map forest disturbance in the region so frequently — and at the same time — reliably and at low cost.

To address this gap of information, our partners in the US Forest Service Region 5 Remote Sensing Lab apply eDaRT (Ecosystem Disturbance and Recovery Tracker) to provide mortality map updates with higher frequency than the current standard 6-12 month step.  The eDaRT algorithm, unlike previous generation change detection systems, is designed to process all available images from Landsat, down to a 16-day time step. In this way,  forest health status can be monitored frequently and robustly with respect to vegetation seasonality that interferes with disturbance detection. To provide continuous mapping of tree mortality, the current eDaRT version 2.5 requires additional input from a GIS specialist-operator.  The fully automated, near real-time,  continuous monitoring is planned in a future version, currently in development.

Please slide blue handle to compare the overlay with the high-resolution image below.

An example of recent tree mortality mapping by eDaRT. The 30 x 30 meter cells show forests affected by water stress and  mortality events in 2015 (yellow cells) and early 2016 (light-gray cells). The mortality map is portrayed over the National Agriculture Imagery Program (NAIP) high-resolution aerial imagery acquired in July 2016.  The generic polygons shown in yellow border and hatched interior represent a previously available mortality map for 2015.

Please slide blue handle to see newly dead trees (brown patches) in the high-resolution satellite images below.

To verify mortality detections and improve eDaRT algorithms, analysts routinely use bi-temporal high-resolution airborne and satellite imagery. Here is an example of an image pair from Word View satellite showing change in these forests between 2014 and 2015.

More Details:

Koltunov, A.,  C. Ramirez, and S. Ustin (2016), “Rapid assessment of forest disturbance and mortality in California using the eDaRT”, In: 43rd Natural Areas Conference, Davis CA, October 2016