Forest

All global climate models agree that sea level will rise. Sea levels have increased over the past century, and this trend is expected to continue. At the current rate of increase, sea levels could rise nearly 6 inches by the end of the century across the Northeast, which is a conservative estimate. Additional warming is expected to increase sea levels in the Northeast by 7 to 23 inches by the end of the century.

The lower Chesapeake Bay is especially at risk due to high rates of sinking land (known as subsidence) Climate change and sea level rise are also likely to cause a number of ecological impacts, including declining water quality and clarity, increases in harmful algae and low oxygen (hypoxia) events, decreases in a number of species including eelgrass and seagrass beds, and changing interactions among trophic levels (positions in the food chain) leading to an increase in subtropical fish and shellfish species in the bay.

The intensity, frequency, and duration of North Atlantic hurricanes, as well as the frequency of the strongest (Category 4 and 5) hurricanes, have all increased since the early 1980s. Hurricane-associated storm intensity and rainfall rates are projected to increase as the climate continues to warm.

Changes in climate may allow some nonnative plant species, insect pests, and pathogens to expand their ranges farther north as the climate warms and the region loses some of the protection offered by a traditionally cold climate and short growing season. The abundance and distribution of some nonnative plant species may be able to increase directly in response to a warmer climate and also indirectly through increased invasion of stressed or disturbed forests.

Peer reviewed multi-decadal studies have documented an advance in springtime phenological events of species in response to climate warming. Evidence suggests that insect emergence from overwintering may become out of sync with pollen sources, and that the beginning of bird and fish migrations are also shifting.

Model projections and other evidence support modest productivity increases for forests across the northeast under climate change, although there is uncertainty about the effects of carbon dioxide (CO2) fertilization. Warmer temperatures are expected to speed nutrient cycling and increase photosynthetic rates for most tree species in the Northeast. Longer growing seasons could also result in greater growth and productivity of trees and other vegetation, but only if sufficient water and nutrients are available.

Impact models agree that many temperate species will experience increasing suitable habitat and biomass across the Northeast, and that longer growing seasons and warmer temperatures will lead to productivity increases for temperate forest types. For the Northeast, models predict a decrease in suitable habitat for spruce-fir forest, moderate decline in suitable habitat for the maple-birch-beech forest, and expansion of suitable habitat for oak-dominated forest by the end of the century.

Some species and forest types are confined to particular habitats on the landscape, whether through requirements for hydrologic regimes, soil types, or other reasons. Similar to species occurring in fragmented landscapes, isolated species and systems face additional barriers to migration. Widespread species may also have particular habitat requirements. For example, sugar maple is often limited to soils that are rich in nutrients like calcium, so this species may actually have less available suitable habitat than might be projected solely from temperature and precipitation patterns.

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 by mid-century, increasing by 3-4 weeks in most areas, trending towards an earlier onset of spring.