ForWarn II

Satellite-Based Change Recognition and Tracking

Disturbance Events

Browse some of the verified and potential forest disturbance events captured by the ForWarn tracking system.

Explore in interactive map
i.e. Gypsy Moth
Title: Iowa Derecho
Title: Drought in CA
Title: Drought in OR
Title: Drought in CA
Title: San Isabel NF
Title: Craig Co., VA
Title: Rutland, VT
Title: Unitas NF, UT
Title: Kingsport, TN
Title: KY Plateau
Title: Adams Co., OH
Title: WI-MN border
Title: MD Cankerworm
Title: Port Wing, WI
Title: Reston, VA
Title: Roanoke River
Title: central MN
Title: n. WI
Title: ne OR
Title: Rhode Island
Title: Georgia SPB
Title: La Sal NF, UT
Title: Carson NF, CO
Title: Santa Fe, NM
Title: eastern PA
Title: Creed, CO
Title: Maryland
Title: Los Padres NF
Title: central NY
Title: MI
Title: Utah, eastern
Title: Helena NF, MT
Title: White Mtn, NH
Title: upper NH-MA
Title: Scranton, PA
Title: nne NY
Title: Mobile, AL
Title: LA Delta
Title: Roanoke River


Hurricane Michael damage to coastal forests

The destructive impacts of Category 4 Hurricane Michael on the forests of northwest Florida were captured by ForWarn II's routinely produced Early Detect product one week after the event.

Hail storm damage to corn and soybeans from Sentinel 2

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.

Hurricane Florence moves toward landfall in North Carolina

Hurricane impacts to forests can vary greatly depending on the qualities of the storm.

Defoliation on the Boise

ForWarn’s ability to accurately map defoliation comes from the high temporal frequency of the source imagery (MODIS).

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

Remote sensing technologies provide an increasingly efficient way to monitor large tracts of forest canopy conditions in near-real-time and seasonally.

Gypsy Moth defoliation was extensive in 2015 in northeastern Pennsylvania

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.

Forest Tent Caterpillar defoliation along Conoho Creek

The Forest Tent Caterpillar (Malacosoma disstria) is a widespread native defoliator of deciduous forests in the Eastern US.

Pandora Moths on the Kaibab National Forest

The Pandora Moth (Coloradia pandora) is a native defoliator of ponderosa, Jeffrey and lodgepole pine trees of the Western US. During most years, populations and defoliation is minor, but periodic outbreaks cause widespread defoliation (Speer and others 2001).

The start of greenup for a mixed urban-agricultural Minnesota landscape

Urban areas are renowned for their admixture of species and vegetation types that can change from one parcel to the next. Yards and woodland parks intermix with road medians--all of which may be dominated by an irregular mix of native and exotic trees, shrubs, herbs and grasses.

ForWarn's start of green-up for croplands

Understanding the normal start of greenup for croplands is important because it provides a baseline to compare year to year conditions.

ForWarn's median date of start of greenup

The start of the annual growing season is among the most important climate-sensitive measures that Land Surface Phenology (LSP) products like ForWarn can provide.

September 2014 hail storm streaks through northern Wisconsin

It can be challenging to detect disturbances during seasonal periods of transition such as Fall or Spring in the eastern deciduous forest.

North Carolina coastal tree mortality associated with 2011 Hurricane Irene Dare County, NC ForWarn EFETAC

Coastal forests and shrublands can be vulnerable to climate-associated disturbances such as the strong winds and storm surges associated with hurricanes.

Hail devastates corn and soybean fields in Nebraska and Iowa during June of 2014 ForWarn EFETAC Steve Norman

During the first week of June 2014, hail caused significant damage to corn and soybean fields in eastern Nebraska and western Iowa.

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.

True color shows snowpack in the Sierra Nevada

ForWarn's true color product is produced every 8 days at 1km resolution to provide a quality control for ForWarn's disturbance maps. Clouds and snow cover that persists for the entire 24-day MODIS collection window can create the appearance of vegetation disturbance, when it is not.

Year to year variation in climate has been extreme in California's Sierra Nevada. In particular, low winter snowpack raises concerns about municipal water supplies as reservoirs are fed by spring meltwater. However, low winter snow cover has implications for the region's forests as well.

Sudden Oak Death (SOD) is a disease caused by the new pathogen Phytophthora ramorum (Frankel and others, 2013). This spore-producing water mold was first observed when tanoak trees began dying during the mid 1990s in California’s Marin and Santa Cruz Counties.

Since 2004, southwestern Colorado's Englemann spruce forests have experienced a severe outbreak of spruce beetles (Dendroctonus rufipennis). Such outbreaks occur episodically, multiple times per century (Anderson et al. 2010).

The 2013 Rim Fire burned over a quarter million acres of California's Sierra Nevada, including a portion of the Stanislaus National Forest and Yosemite National Park. It started in mid-August as an illegal campfire after an unusually dry winter and spring.

In early September of 2013, unusually heavy rain resulted in catastrophic flooding across Colorado’s Front Range and downstream along the South Platte River. Rainfall exceeded 20 inches northwest of Denver, which is close to the average rainfall for that area during an entire year.

By late 2012, forest health monitors in western New York and Pennsylvania knew that they were about to experience a severe outbreak of the non-native Gypsy Moth.

Effects of a severe hailstorm in Massachusetts and Connecticut

ForWarn's standard calculation of the current state of vegetation is based on the maximum NDVI value observed for each 24 day period. This standardized window is needed to minimize the chance that clouds or other atmospheric effects will cause misleading results in the change product.

Land managers in the West seek to efficiently monitor their forests and rangelands, particularly after wildfire. ForWarn's high frequency record of the Normalized Difference Vegetation Index (NDVI) provides a coarse filter means to accomplish this using two measures.

Relative effects of Hurricane Sandy to forests of the Northeast

Hurricane Sandy, one of the most damaging hurricanes to strike the United States, tested the monitoring ability of the ForWarn system. Detecting any disturbance is difficult during the spring and fall because vegetation is actively changing due to normal seasonal dynamics.

Los Alamos NM

ForWarn's MODIS satellite-based products go back to 2000, and this allows us to observe the effects of wildfire and recovery since early in the decade.

Hail defoliates the City of Asheville, NC watershed

The spring of 2012 was exceptional across much of the eastern US because it occurred weeks earlier than normal. Yet some forests also experienced strong spring hail storms that left leaves in tatters and set spring growth back.

ForWarn's ability to capture short and long-term change is shown by this animated image pair that provides two different temporal contexts for the same date in May of 2012. The "all year" baseline shows change since 2000.

Mountain Pine Beetles have killed hundreds of trees around Harney Peak in the Black Hills of South Dakota.

Over the last 15 years, Mountain Pine Beetles have killed large tracks of ponderosa pine across the Black Hills of South Dakota. Beetles thrive with continuous stands of dense trees, and decades of fire exclusion have led to that landscape and stand-level condition.

Regional drought in the Southeast hit Texas and Oklahama hard.

Across Texas, 2011 will long be remembered as the year that the trees died.

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

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.

The effects of heavy snowpack after the 2009-10 winter on the Tug Hill Plateau, New York. Image: Steve Norman, USFS

This late April 2010 image shows a large anomaly just east of Lake Ontario on the Tug Hill Plateau of New York. A less severe area of departure from the prior year’s condition occurs to the east.

Outbreaks of the defoliating pine butterfly are rare. In eastern Oregon, outbreaks occurred in 1908-11, 1940-43, 1982 and from 2008 to 2011. Sometimes defoliations can lead to mass mortality of ponderosa pine—the primary host, but not always.

Floodwaters drown vegetation along the Gulf Coast; Image credit: Steve Norman, USFS

The Atchafalaya basin's forests thrive with seasonal flooding, yet high water is normally a spring phenomenon there. During the past month, unusually high water levels have inundated wetlands and forests along and near the Mississippi River basin.

Dead pines from drought in Houston; Photo credit: Ron Billings, Texas Forest Service

The forests of Texas continue to suffer through one of the most extreme droughts on record and a large number of trees have already died. The photo shows mortality in Memorial Park, Houston (Ron Billings, Texas Forest Service).

A Fall Webworm defoliation in the Allegheny National Forest, Pennsylvania; Image Credit: Steve Norman, USFS

This fall 2011 webworm outbreak in the Hickory Creek Wilderness Area of the Allegheny National Forest, Pennsylvania stands out against the near normal (blue) background that dominated the state in early fall.

Fire and frost strike the Upper Midwest during late 2011. Image credit:Steve Norman, USFS

In September of 2011, the Pagami Creek Fire burned over 92,000 acres in the Boundary Waters Canoe Area Wilderness (BWCAW) of the Superior National Forest, Minnesota Much of this burned at high severity, as indicated on the October forest change image.

Cumulative effects of insect defoliation in the Wenatchee National Forest, Washington. Image: Steve Norman, USFS

A sizable portion of the Wenatchee National Forest, Washington shows less vegetational vigor than it did at its peak of the last decade.

Deforestation for urban development near Raleigh, NC

Substantial forest area has fallen to development in the periphery of many urban areas over the last decade. The image below shows deforestation in the periphery of Raleigh, NC as yellow to red anomalies. Blue areas have not changed during the last decade.

The 2010 Yazoo City tornado. Image: Steve Norman, USFS

On April 24, 2010, a lethal F4 tornado struck the forests east of Yazoo City, Mississippi. Within a few weeks the path of the storm and patterns of severity are clearly shown with this comparison of conditions relative to the same time in 2010--the year before the event (top image).

Defoliation in the Wasatch Range, Utah. Image: Steve Norman, USFS

This image shows forest change anomalies on the north slope of the Wasatch Range of Utah on September 13, 2011 compared to the prior year. The high elevation zone above treeline is shown as an uncolored area under the words “Wasatch Range”.

Deforestation near a strip mine in western Virginia. Image: Steve Norman, USFS.

Deforestation for strip mining is common practice in the coal regions of eastern Kentucky, Virginia and West Virginia. The image below shows areas where forests have been removed for mining over the last decade (left).

Hurricane Irene moves up the eastern seaboard. Photo credit: NASA

This before-after image pair shows changes associated with Hurricane Irene. Its path is shown by the bold blue line. In the pre-Irene image (left) shades of green and yellow show the effects of drought on vegetation and dark red spots are recent wildfires.

A low severity burn during the 2011 Wallow Fire. Photo credit: AZ IMT

In June, the Wallow Fire burned over half a million acres in east-central Arizona, much of it on the Apache-Sitgreaves National Forests. A substantial portion of the burn area was of high severity, killing millions of trees outright.

The 2011-12 Honey Prairie Fire near the Georgia-Florida line. Image credit: Steve Norman, USFS.

Georgia’s Okefenokee Swamp National Wildlife Refuge near the Georgia-Florida line burned in 2007 and again in 2011. This rapid recovery of fuels reflects the importance of sprouting vegetation. In the map sequence from the summer of 2011, this resilience is clear.

The Pains Bay Fire. Image credit: USFWS

The Pains Bay Fire was started by lightning on May 4, 2011 in the peaty soils of North Carolina’s coastal plain. By the end of June, the fire was contained, but the deep soils continued to smolder for weeks. The white line marks this 45,000 acre fire’s final perimeter.

The 2011 Springfield tornado. Image credit: Steve Norman, USFS

A severe tornado touched down near Springfield, Massachusetts on June 1, 2011, then carved a path through nearly 30 miles of state and private forest. The streak in red show an extreme reduction in growth compared to the prior year’s condition as of mid-June.

According to climate data, coastal North and South Carolina were having a mild drought in mid May of 2011.

The April 27, 2011 tornado that hit Great Smoky Mountains National Park in eastern Tennessee was a powerful EF4 storm (its direction is indicated by the black arrow).

An ephemeral wind or hail disturbance in northeastern Tennesssee. Image: Steve Norman, USFS.

Full-fledged tornadoes are typically well documented, but the massive outbreak of April 2011 also had localized short-term effects that are easily overlooked.

Forests across northern Mississippi, Alabama and Georgia were hard hit by tornadoes in April, 2011. Tree mortality was often severe for areas in the direct path of these storms as shown in this photo from near Lake Burton in the Chattahoochee National Forest, Georgia (top).

Other Disturbances Assessed

Likely weather based event

Moderate to severe NDVI decline for parts of Pierce, Wayne, Stanton Counties of NE - mostly areas north of Norfolk, NE

Likely weather based event

Hail streak showing up in the upper mid-western US in 3 counties of SD (Edmunds, Brown, and Days counties going west to east). According to on-line news accounts, the storm occurred on 8-28-21.

Likely weather based event

weather event date 07/26/2021

Likely insect based event

Congaree and Wateree Rivers, SC

Likely weather based event

event date 04/20/2021

Likely weather based event

80-mile, EF-3, 150mph, max width 2,300yds

Likely weather based event

3yr NDVI change, 09/20/2020 -

Likely weather based event
Likely insect based event

Forest canopy greenness decline in portions of Montmorency, Alpena, Alcona, and Oscoda counties of Michigan