Regional Highlights of Climate Change
Climatic extremes, ecological disturbance, and their interactions are expected to have major effects on ecosystems and social systems in most regions of the United States in the coming decades. In Alaska, where the largest temperature increases have occurred, permafrost is melting, carbon is being released, and fire regimes are changing, leading to a transition from conifers to hardwoods in some forests. In Hawaii and the U.S.-affiliated Pacific islands, an altered climate and sea level rise are changing hydrology and fire regimes, affecting both forest ecosystems and human communities. In the Northwest, insect outbreaks (already prominent) and increased area burned, in combination with declining snowpack, are expected to have a major effect on dry, interior forests. In the Southwest, recent large wildfires and forest dieback in pinyon pine exemplify the kinds of changes that may occur in arid and semi-arid forests if droughts become more common in the future. In the Great Plains, where trees currently occupy only a small portion of the landscape, warmer temperature and non-native insects could reduce the amount of forested area and alter species distribution. In the Midwest, warmer temperature is expected to affect the distribution and abundance of many tree species, associated habitat, and human use of forests in a region where private lands are mixed with public lands. In the Northeast, warmer temperature is expected to affect the distribution and abundance of many tree species, although the productivity of hardwood species may increase significantly. In the Southeast, biodiversity and productivity may be affected by a combination of warmer climate, altered fire regimes, and invasive plants and insects.