Urban Forest Health

The uncertainty of future precipitation patterns makes it difficult to determine whether conditions may become dry enough to increase moisture stress for plants in the Northeast. Forests that are affected by moisture deficits and drought are more likely to experience reduced tree vigor or increased mortality, both of which can affect forest composition and structure. Further, warmer temperatures can drive or enhance drought-induced mortality by disrupting plant physiology . This “hotter drought” can also interact with other forest stressors to cause tree death and forest die-off .

The loss of a traditionally cold climate and short growing season in the region may allow some insect pests and pathogens to expand their ranges northward such as hemlock woolly adelgid and southern pine beetle. Forest impacts from insect pests and pathogens are generally more severe in ecosystems that are stressed by drought and other stressors. Basic information is often lacking on the climatic thresholds that trigger increased populations of many forest pests, and our ability to predict the mechanisms of infection, dispersal, and transmission for disease agents remains low.

The uncertainty of future precipitation patterns makes it difficult to determine whether conditions may become dry enough to increase moisture stress for plants in the Northeast. Forests that are affected by moisture deficits and drought are more likely to experience reduced tree vigor or increased mortality, both of which can affect forest composition and structure. Further, warmer temperatures can drive or enhance drought-induced mortality by disrupting plant physiology . This “hotter drought” can also interact with other forest stressors to cause tree death and forest die-off.

Across the central U.S., very heavy (greater than three inches per day) and extreme (greater than six inches per day) precipitation events increased in the period from 1979 to 2009 compared to the 1948 to 1978 period. Model projections for the central U.S. suggest a potential increase in these events, especially during winter months. Other future climate projections indicate that the Midwest may experience two to four more days of extreme precipitation by the end of the century.