ForWarn’s ability to accurately map defoliation comes from the high temporal frequency of the source imagery (MODIS). With any change detection, multiple disturbances are often at work in the same landscape at the same time, so careful assessment requires consideration of other stressors or disturbances.
In the Boise National Forest, defoliation from the spruce budworm and large wildfire have been recurring every year. Recently, a periodic eruption of the Douglas fir tussock moth has begun, and drought is episodic.
Emmett Ranger District
"Area was hit hard by gypsy moth caterpillar defoliation for the third year in a row. We mapped it during this years aerial survey and ground truthed the area last week to confirm gypsy moth as the primary defoliation agent".
There was no response received to initial email inquiry.
Areas east of Sault Ste. Marie, Ontario, Canada. Agent appears to be active eastward to New Brunswick to n. Maine.
Forest defoliation by baldcypress leafroller and forest tent caterpillar detected in these southern Louisiana counties: Ascension, St. James, Assumption, n. Lafourche, n. Terrebonne, St. Martin and e. Iberia County. Public lands affected appear to be the western district of Maurepas Swamp Wildlife Management Area.
ForWarn potentially indicates that an area in the Fremont National Forest, Oregon experienced a decline in green vegetation due to the Mountain Pine Beetle from 2004 through 2010 and still may not have recovered in terms of vegetation canopy greenness. The anomaly may also be associated with climate change initiating a shift in vegetation type in the area.
ForWarn has detected a slight decline in green vegetation within the Isle Royale National Park in Michigan in August 2016. The disturbance is likely caused by a severe storm or potential insect damage.