Structure Condition Services Stressors
Water is essential to a healthy forested ecosystem, but excess water can lead to flooding and disease outbreaks, while a deficiency can lead to drought1. For example, extreme rain events can cause flooding in low-lying areas, but even upland forests may experience “overland flow”. This occurs when rainfall is so heavy that it cannot be absorbed into the soil. Aquifers are not replenished and soil erosion may happen, exposing tree roots and washing away nutrients. Fluctuations in rainfall above or below the long-term mean will lead to stressful conditions for some forest species while creating ideal conditions for other species. Trees are adapted to the long-term conditions they have experienced, therefore deviations in precipitation from the long-term mean (both above and below) could be problematic to forests. Ideally, a healthy forest ecosystem has water availability that remains consistent. Total annual precipitation is the sum of all water (in the form of rain, snow, or ice) that fell within a calendar year for Vermont. A high score means that precipitation levels are near the long-term mean.
Annual precipitation is expected to slightly increase, but the largest change will be in the intensity and occurrence of extreme precipitation events. Extreme, flood producing, events are increasing, where a large amount of precipitation falls in a short amount of time. This can cause soils to wash out, and a large amount of runoff, with less water absorbed by the soil. Short-term summer and fall droughts are expected to increase. Lack of moisture during the growing season can harm the health of trees.
NOAA, Northeast Regional Climate Center at Cornell University (2020)
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.
Distance away from long-term mean (scaled 1-5)
|Directionality of scores||
No change from the long-term mean is better.
|Minimum value used in scoring||
Data minimum - 10% of range
|Maximum value used in scoring||
Data maximum + 10% of range
Data of annual total precipitation (inches) for Vermont were collected from NOAA National Centers for Environmental Information1. We set the target for the dataset as the total precipitation from 1961-1990 which is used as the baseline normal for climate comparisons by the Intergovernmental Panel on Climate Change (IPCC). The current year is scored for where it falls between the target and the upper scoring bounds (maximum value in the dataset) or the lower scoring bounds (minimum value in the dataset), scaled to be between 1 and 5.
Acid rain harms forests and other ecosystems by damaging leaves and leaching nutrients.
The length of the growing season varies from year to year, but large or persistent changes can be problematic to forests.
Ozone can cause many negative impacts to forests by reducing regeneration, productivity, and species diversity.
Mercury is a toxin that persists in the environment for long periods by cycling back and forth between the air, water, soil and organisms - resulting in long-term, negative effects to forest ecosystems.
Warmer winter minimum temperatures can allow for non-native species to proliferate, while at the same time stressing native forest trees.
Higher maximum summer temperatures can stress forests, reducing productivity and health.
Changes to precipitation can alter the water balance in Vermont’s forests, causing either drought or deluge.
Snow insulates the soil and tree roots from cold temperatures and provides water when it melts.
Climate change will continue to result in more extreme weather events, which can stress forests beyond what they are accustomed.
Lack of sufficient precipitation can cause both immediate and long-term stress to trees.
As native trees are not adapted to defending themselves from non-native, invasive insects and diseases, widespread damage and mortality can result.