Standing at the peak of Mount Mansfield in Vermont on a crisp October day, crimson reds, golden yellows, and brilliant greens form a blanket on the surrounding mountains and the valley floor, right up to the edge of Lake Champlain. The eastern forests and woodlands are known for this colorful fall display of leaves. Covering from Maine to Florida and west to the Mississippi River, these forests once stretched almost unbroken across the region, but now coexist with people in some of the most heavily populated areas of the world. The deciduous trees that make these forests famous include oaks, maples, beech, birches, and hickories. While evergreen conifers, such as spruce and firs, do live in the eastern forest, they are not as common or dominant as the deciduous trees except under particular types of local conditions.

The eastern forests ecoregion includes a range of landscapes from the rugged Adirondack Mountains in New York and the Appalachian Mountains that span the entire eastern seaboard, to rolling hills, valleys, and plains. Each of these landscapes has varying climates, soils, altitudes, and frequencies of fire, all of which play key roles in determining the composition of trees that make up forest stands.

In general, the eastern United States has cold winters and long warm summers. Possibly the most important feature in determining the makeup of the eastern forests is precipitation in the form of rain and snow. Total precipitation throughout the year is higher in the eastern forests than anywhere else in North America, except for the tropical and subtropical areas to the south and the temperate rain forest found along the Pacific Coast.

These deciduous forests are rich in species due to the abundance of food and shelter provided by the trees that produce fruits, nuts, and berries to eat, and multiple forest layers in which animals can live. Species include migratory birds on their journeys north and south, as well as year-round residents such as red northern cardinals, gray squirrels, black bears, white-tailed deer, raccoons, red foxes, and opossums.

All of these species depend on the trees to provide them with food and shelter. Changes in climate that affect the eastern forests will thus also affect the plants and animals that live in and use them.