Forest Ecosystem Monitoring Cooperative

FEMC: Tracking Shifts in Disturbance Regimes

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Native Pests

All ecosystems have natural pest/pathogen dynamics that evolve alongisde host species over time. Under ideal conditions, native pests have a controlled and cyclical survivorship with their hosts and maintain an equilibrium in their community. However, as abiotic conditions shift due to global climate change, native invasive pests and pathogens may become a more severe disturbance. Changes in temperature and percipitation, among other factors, can alter the phenological timing of native pests and increase detrimental impacts to trees and forest systems. Monitoring trends in the extent and severity of native pest and pathogen defoliation patterns can help anticipate impacts to forests under changing climate conditions. Native pests of concern include: Eastern Spruce Budworm and Forest Tent Caterpillar.

Frequency (number of years observed) and maximum area damaged in single extent by agent, with the size of the circle indicating total damage caused to date. Click and drag to zoom into chart.
Forest Tent Caterpillar

Forest tent caterpillar (FTC) is a pest native to the northeast, with oubreaks happening roughly every 10-15 years and generally lasting 2-4 years. FTC is a defoliator- it eats the leaves off of trees—so rarely does it directly cause tree mortality. It does place trees under stress, making them more susceptible to other stressors. Using the 100 years of data provided by the FEMC Northeastern Forest Health Atlas – a standardized collection of Aerial Survey Data – we extracted records of damage by forest tent caterpillar across the region and assessed outbreak events using annual forest health reports.

Analysis

STATE:
Frequency is represented by three metrics, 1) the number of years since the last outbreak started (outbreaks determined from state and federal forest health and pest reports), 2) the total acres damaged during the duration of the outbreak, and 3) the annual acres damaged.
Severity is represented by two metrics, 1) the number of acres of damage categoriezed as mortality and 2) the percent of total acres damaged categorized as mortality
Extent is calculated as the total area (acres) damaged by the selected pest
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Disturbance Trend Summary

There are too few outbreak events in the historical record to analyze long-term trends, however the number of years between outbreaks has been decreasing over time.

While the total acres damaged by FTC is decreasing over time the percent of those total acres categorized as mortality is increasing significantly.

Highlights

  • The most recent outbreak started in 2004 in Vermont, expanding to New Hampshire in 2005 and 2006. In 2007 populations crashed in VT and NH but soared in New York while also appearing in CT and RI. The outbreak continued in New York through 2010. This demonstrates that the extent and location of outbreaks can shift over time.
  • Forest tent caterpillar outbreaks typically last 3 years in an area (but may last 2-9) and tend to happen roughly every 10 years. The extensive duration of the most recent outbreak is due to the migration of the pest across the region, with 2-3 year outbreak cycles moving from east to west.1
  • The decrease in total acres damaged and the increase in the percent of damage categorized as mortality indicates that forest tent caterpillar damage is less extensive and more severe, possibly caused by compounding with other stress agents.1 2

Additional Resources

Data Program Years Org Data Products
Spruce Budworrm

Spruce budworm is a native pest that infests spruce-fir forests. It periodically outbreaks usually every 30-40 years, and usually last several years. Using the 100 years of data provided by the FEMC Northeastern Forest Health Atlas – we extracted records of damage by spruce budworm across the region and assessed outbreak events using annual forest health reports.

Analysis

STATE:
Frequency is represented by three metrics, 1) the number of years since the last outbreak started (outbreaks determined from state and federal forest health and pest reports), 2) the total acres damaged during the duration of the outbreak, and 3) the annual acres damaged.
Severity is represented by two metrics, 1) the number of acres of damage categoriezed as mortality and 2) the percent of total acres damaged categorized as mortality
Extent is calculated as the total area (acres) damaged by the selected pest
legend for chart
legend for chart
legend for chart
Use SHIFT+Scroll to zoom

Disturbance Trend Summary

There are too few outbreaks in the historical record to analyze long-term trends, however, the number of years between outbreaks has increased over time indicating that outbreaks are happening less often.

The overall trend in the total acres damaged by spruce budworm is decreasing over time and this decrease is statistically significant.

No spruce budworm damage has been recorded as mortality.

Highlights

  • Spruce budworm has primarily impacted Maine where a large proportion of forests are spruce/fir. The only other state that has recorded presence of spruce budworm is New Hampshire in the 70s and 80s but the acres damaged were minimal.
  • There has not been a large scale spruce budworm outbreak since the 1980s and it has not been recorded in the annual aerial detection surveys since 2000. However it continues to be a pest of concern in northern Maine.
  • All spruce budworm damage has been recorded as defoliation. This is likely due to a combination of the variability of the mapping methods prior to 1997 when the forest service established more rigorous criteria for mapping and reporting pest and disease disturbance, and spruce budworm being primarily a defoliator, with mortality only showing up in later years of an outbreak.

Additional Resources

Data Program Years Org Data Products