A Yearly Health Checkup for U.S. Forests

Annual report monitors conditions across all 50 states

The USDA Forest Service Forest Health Monitoring program tracks forest health across the U.S. and summarizes it in an annual report. USFS image.

Every year, the USDA Forest Service Forest Health Monitoring (FHM) program tracks changing forest conditions, including national assessments as well as focused regional analysis. The resulting report is the only national summary of forest health undertaken on an annual basis.

Forests constantly change as a result of tree growth and mortality, weather events and climate trends, and disturbances from stressors including fire, insects, and diseases. The goal of the 2019 FHM report is to identify ecological resources whose condition is deteriorating, potentially in subtle ways, across large regions.

This requires consistent long-term monitoring of forest health indicators, which is not possible without the participation of multiple federal, state, academic, and private partners.

Scientists from across the Forest Service as well as university researchers, state partners, and many other experts contributed to the 2019 report, which is available as a General Technical Report titled Forest Health Monitoring: National Status, Trends, and Analysis 2019.

Kevin Potter, a North Carolina State University scientist supported by the Southern Research Station, edited the 2019 report with fellow NCSU scientist Barbara Conkling. Each year, data from the previous year are used to inform the current year’s report.

“A lot of effort goes into collecting forest health data each year across the country, by people in field crews and in airplanes, and by satellite sensors,” says Frank Koch, who represents Forest Service Research on the FHM Management Team. “The job of the FHM reports is to make sense of these data. That’s a challenge, but an important one because it helps inform decisions about how to manage our forests.”

Individual report chapters are available for download, along with the full series of FHM annual reports since 2001. Users can search reports and chapters by year or topic. Highlights and additional resources are also included.

Notable highlights from the 2019 FHM report include:

  • In 2018, 56 different mortality-causing insects and diseases were detected on nearly 5.3 million acres across the lower 48 states, and 56 defoliation-causing insects and diseases were detected on 10.6 million acres. Emerald ash borer was the most commonly detected cause of mortality in the East, while a variety of bark beetle species, especially fir engraver, were the main causes in the West. There was a large outbreak of several defoliators in the Northern Rockies, including western spruce budworm, pandora moth, and Douglas-fir tussock moth, along with a major infestation of baldcypress leafroller in Louisiana.
  • Drought conditions in the eastern U.S. were largely confined to northern New England and southern Florida. From the Rocky Mountains westward, most forest areas experienced at least mild drought in 2018, but contiguous areas of severe to extreme drought were limited in number and geographic extent.
  • A new measure of forest disturbance, using data collected by satellite, combines the magnitude and duration of change in forest greenness to pinpoint locations with sustained disturbance impacts across the conterminous U.S.
  • An assessment of insect and disease data collected over 20 years found mortality to be relatively consistent over time, with insects being more widespread agents of mortality than diseases. Nonnative insects and diseases had the largest relative impact on forests of the North.
  • Overall, the number of satellite-detected forest fire occurrences in 2018 was very close to the average for the previous 17 years of data collection. Areas in northern California, southern Oregon, northeastern Nevada, and north-central Washington had the highest density of forest fire occurrences.
  • Analysis of Forest Inventory and Analysis (FIA) data from the West showed that mortality was very high as a percent of live tree volume in northern and central parts of the Interior West. Several West Coast areas had high mortality levels relative to growth. These are all areas that have experienced insect outbreaks, fire, severe drought, or some combination.
The most recent FHM report includes a new, satellite-based measure of forest disturbance. Strong and sustained decline in vegetation greenness during 2018 is shown here in darker reds—drought impacts can be seen in the Southwest. USFS image.

In addition to these findings, the 2019 report presents results from two FHM-funded studies of undesirable changes in forest health in sub-regional areas. Those chapters focus on the health of black walnut (Juglans nigra) trees in Ohio and Indiana with symptoms of thousand cankers disease and on woodborer insect activity in Sierra Nevada forests that have experienced forest fires.

“It’s always interesting to see such stark differences between the East and the West in the issues that are affecting forests,” says Tom Eager, FHM national program manager. “The forests in the two regions are very different, of course, so it’s not a surprise they have different forest pests. At the same time, there was a dramatic difference in precipitation, with almost all of the West in drought and almost all of the East in moisture surplus in 2018.”

Potter, Conkling, and other authors have completed a draft of the next FHM report in the series, the 2020 report, and expect to publish it by the summer of 2021.

Read the full text of the report.

For more information, email Kevin Potter at kevin.potter@usda.gov.

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