ForWarn II

Satellite-Based Change Recognition and Tracking

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Welcome to ForWarn II!

ForWarn II has enhanced sensitivity, now showing even slight disturbances earlier than ever before, and now covers a larger geographic area.


ForWarn II is mostly the same system with which you're already familiar, but now has a totally new production system that offers some exciting new capabilities, including some new products designed for specialized purposes. For example, disturbances within grasses, shrubs and other shallow-rooted vegetation can sometimes dominate the disturbance signal seen in ForWarn maps, particularly in the Western United States. Almost every ForWarn II disturbance map now has a "Muted Grass/Shrub" companion product that concentrates on the disturbance responses of trees, reserving more of the dynamic range in the maps for showing forest impacts.


Most new ForWarn II products are already available for the entire MODIS period starting in 2003 to present. Most of the data viewer features, like the Share-This-Map, the NDVI graphing tool, and the PestProximity tools, will still work just as always. Documentation is still being developed, so please pardon our virtual dust as we continue to carry these improvements throughout the entire Forest Change Assessment Viewer 2 and the ForWarn II website. Enjoy the new features, and we welcome your feedback!

Hemlock death transforms Appalachian forests

Across the Southern Appalachians, Eastern Hemlock has long created an important ecological niche. As these trees are evergreen, they provide year-long cover for wildlife and they cool riparian areas where they tend to grow. Since the mid 2000s, these forests have been... read more »

Gypsy Moth defoliation affected a large part of Rhode Island in 2016

Monitoring the state of Rhode Island's forests

Remote sensing technologies provide an increasingly efficient way to monitor large tracts of forest canopy conditions in near-real-time and seasonally. Observational systems, such as ForWarn's MODIS-based product line, provide a continuous weekly stream of observational... read more »

Gypsy Moth defoliation was extensive in 2015 in northeastern Pennsylvania

Tracking Gypsy Moth emergence and severity with magnitude and duration

Remote sensing is adept at identifying and qualifying many forest disturbances, but there remains a substantial need to further quantify actual impacts in many cases. Traditionally, vegetation change-detection approaches, such as that used by ForWarn, identify and... read more »

Hail storm damage to corn and soybeans from Sentinel 2

ForWarn II maps hail damage to Midwestern crops

ForWarn's all-lands approach to monitoring provides valuable insights into crop damage caused by summer storms. In July and August of 2018, hail storms struck eastern Nebraska causing severe damage to corn and soy.

Remote sensing provides an invaluable way to... read more »

Hurricane Florence moves toward landfall in North Carolina

Hurricane Florence soaks the South

Hurricane Florence brought extreme flooding to the Carolinas. ForWarn's near real time capabilities capture the storm's effects in the weeks after they unfold.

Monday, Sept. 24 update: ForWarn II's Early Detect product suggests a reduction in NDVI in bottomlands,... read more »

Spring defoliations emerge like measles during 2010; Image: Steve Norman, USFS.

Defoliation on the bayou

Spring often brings defoliating insects to the forests of Louisiana. In this image from early May 2010, defoliations from forest tent caterpillars and baldcypress leafrollers create an erupting "measles-like" pattern. Note the subtle differences in severity outward from... read more »

Defoliation on the Boise

Assessing defoliation in the Boise National Forest

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... read more »

Get Started

ForWarn provides near-real-time tracking of vegetation changes across landscapes in the United States. Useful for both monitoring disturbance events as well as year-to-year variability, derived products can also be used to develop insights into seasonal and inter-annual dynamics.

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Forest Change Assessment Viewer

The Forest Change Assessment Viewer provides a vegetation change recognition and tracking system for ForWarn that uses high-frequency, moderate resolution satellite data.

Recent News

05/14/2017 - 09:17
ForWarn has always allowed users to view historical 8-day NDVI data, and this capability provides important long-term context for understanding disturbance impacts, recovery, inherent differences...
11/16/2016 - 11:03
Sap-sucking insects called hemlock woolly adelgids are draining the life from a common evergreen tree in the eastern United States. Once the non-native bugs become well-established, the consequences...
09/22/2016 - 09:47
Some disturbances come and go, leaving forests no worse for the wear. Hailstorms, insect defoliations, and light prescribed fires, for example, commonly occur early in the growing season, but,...