Damage and Decay

Latest Score:


in 2019

Weight: 8%
score trend is flat over time

Trees can become damaged for a variety of reasons such as lightning strikes, neighboring treefall, logging damage, poor growing conditions, insects, or genetics. Physical damage to trees can reduce their life span by allowing diseases and fungi to infiltrate the wood, leading to rot and decay. While damaged and decaying trees have a vital role in the forest ecosystem through providing habitat and food for a variety of organisms from fungi to insects, an increase in the proportion of our trees that are classified as damaged or decaying can impact the value of our forests and suggest that trees are being negatively impacted by stressors. Here, damage and decay is a measure of the proportion of Vermont’s trees that are considered “non-growing stock". Non-growing stock trees are classified from a timber perspective as trees with deformities, damage, or rot. We computed the ratio of these non-growing stock trees to all live trees on Forest Inventory and Analysis plots1. A higher score results from stable amounts of damage and decay over time.

-- Expert interpretation for Damage and Decay is not available--

The score is calculated using a target value and the historical range of the the entire long-term dataset. The higher the score, the closer this year's value is to the target.

Once the score is computed for each year, the trend in scores over time is calculated. If the trend is significantly positive or negative, the long-term trend is marked as increasing or decreasing respectively.

Component Description
Scored as

Distance between the minimum and maximum (scaled 1-5)

Target value

Long-term mean

Directionality of scores

No change from the long-term mean is better

Minimum value used in scoring

Data minimum - 10% of the range

Maximum value used in scoring

Data maximum + 10% of the range

Data on tree damage and decay were extracted from the USFS Forest Inventory and Analysis (FIA) Program EVALIDator1. We used an FIA-established query to retrieve the number of live trees (“0004 Number of live trees (at least 1 inch d.b.h./d.r.c.), in trees, on forest land”) filtered by trees ≥5 inch DBH (“and DIA>=5”). We computed tree damage and decay as any living tree ≥5 inch DBH with a recorded damage agent (“and DAMAGE_AGENT_CD1>0)2. We set the target for this dataset as the long-term mean. The current year is scored for where it falls between the target and the upper scoring bounds (maximum value in the dataset plus 10% of the range) or the lower scoring bounds (minimum value in the dataset minus 10% of the range), scaled to be between 1 and 5.

1 USDA Forest Service. 2019. FIA EVALIDator. Available at:
2 USDA Forest Service. 2018. Forest Inventory and Analysis Glossary. Available at: