While certainly too small to see from space, the gypsy moth caterpillar (Lymantria dispar) can cause enough change in a forest to be seen with Landsat’s 30-m resolution. A mere 1/16 inch long when they hatch in May, the caterpillar can reach 3 inches long by late June when they pupate. In that short time span, the pest feeds on the leaves of deciduous trees. Beginning in 2016, they caused noticeable change in the Northeastern United States.
While Landsat has not typically been used to monitor insect outbreaks in near-real time, new analytical tools combined with the open access to Landsat data make it possible to quantify insect damage over a large area at a level of detail not possible with aerial surveys alone.
The 2016 and 2017 images show the widespread defoliation of the trees in orange-brown, with a large area of heavy defoliation to the west of Providence, Rhode Island, and additional patches in eastern Connecticut. In 2018, defoliation was much less widespread and severe; however, continued defoliation is now mixed with mortality as individual trees succumb to multiple years of defoliation and other stressors including drought.
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