High

Shorter-term fluctuations in the variability of ocean dynamics, atmospheric shifts, and ice mass loss from Greenland and Antarctica have been connected to recent accelerations in the sea level rise rate in this region. Sea levels have risen over the past century, and all global climate models agree that sea level will rise over the next century. Worst-case and lowest-probability scenarios project that sea levels in the region could rise upwards of 11 feet (3 m) on average by the end of the century.

Heavy precipitation events have increased substantially in number and severity in the across the Northeast over the last century, and many models agree that this trend will continue over the next century. Extreme precipitation events could lead to more frequent or severe flooding and an increase in soil erosion. Monthly precipitation in the Northeast is projected to be about 1 inch greater for December through April by end of century (2070–2100) under a high emissions scenario.

All global climate models agree that there will be changes in precipitation patterns across the assessment area, but there is large variability among projections of future precipitation. Most climate models project increases in annual precipitation. Seasonally, winter and spring are also generally projected to have increases in precipitation during the next century. Projections of summer and fall precipitation for this region vary, with many models projecting decreased precipitation or only very slight increases.

Evidence at both global and local scales indicates that growing seasons have been getting longer, and this trend is projected to become even more pronounced over the next century. Warmer temperatures will result in fewer days with minimum temperatures below 32°F and a shorter freeze-free season.

All global climate models project that temperatures in New England and northern New York will increase over the next century as a result of continued increases in atmospheric greenhouse gas concentrations.

Habitat fragmentation can hinder the ability of species to migrate to more suitable habitat on the landscape, especially if the surrounding area is nonforested. Modeling results in this assessment and elsewhere indicate that trees would need to migrate at rates of hundreds of feet to several miles per year to keep pace with the changes in climate that are projected to occur over the next century. Species in community types that tend to be more rare and fragmented may be at a particular disadvantage.

Species-rich communities have exhibited greater resilience to extreme environmental conditions and greater potential to recover from disturbance. Conversely, ecosystems that have low species diversity or low functional diversity (where multiple species occupy the same niche) may be less resilient to climate change, its associated stressors, or both. Genetic diversity within species is also critical for the ability of populations to adapt to climate change, because species with high genetic variation tend to have more individuals that can withstand a wide range of environmental stressors

Model results suggest an increase in suitable habitat for many species at or near the northern extent of their current range, including shortleaf pine, post oak, and blackjack oak. In addition, habitat may become favorable to species not currently found in the assessment area, such as loblolly pine. However, habitat fragmentation and the limited dispersal ability of seeds are expected to hinder the northward movement of the more southerly species despite the increase in habitat suitability. Most species can be expected to migrate more slowly than their habitats will shift.

Results from climate impact models suggest a decline in suitable habitat for northern species such as sugar maple, white ash, and American beech when compared with habitat suitability under current climates. These northern species may be able to persist in some southern portions of their range if potential new competitors from farther south are unable to colonize these areas, although they are expected to have reduced vigor and be under greater stress.

A warming climate is allowing some invasive plant species, insect pests, and pathogens to survive farther north than they had previously. One particular emerging threat to the region is the southern pine beetle, which attacks shortleaf and other pines. Oak decline, a disease complex brought about by droughtand other stressors, is expected to become a larger problem in the red oak group as droughts become longer and more widespread. Some drought- and fire-tolerant invasive plants, such as sericea lespedeza, may also benefit from projected climate changes.