The familiar forests of oak, hickory and maple that cover the eastern half of the Unites States are referred to as temperate deciduous forests because their leaves change color and drop as winter approaches. The health of temperate deciduous forests is important for many other plants, animals, and aquatic ecosystems that forest ecosystems support. The forests are also important for humans because they play an essential role in the economies of agriculture and lumber supply as well as pollution reduction and soil fertility; which is why it is important to understand the ongoing environmental problems that threaten these ecosystems.

Invasive Insects

The introduction of insects such as the hemlock wooly adelgid or emerald ash borer have had a devastating effect on temperate deciduous forests in North America. According to the U.S. Park Service, the hemlock wooly adelgid was accidentally introduced to temperate deciduous forests in North America in the 1920s and the U.S. Forest Service estimates that hemlocks are being killed at a rate of 8-15 square kilometers per year. The emerald ash borer is another invasive insect that was brought to the U.S. in the 1990s and has killed tens of millions of ash trees in North America, according to the U.S. Forest Service. As these invasive insects kill tress in the temperate deciduous forests

Deforestation and Fragmentation

Temperate deciduous forests are also affected by the creation of small patches of forest that are commonly fragmented by property development, roads, towns and railways. Deforestation refers to the clear cutting of forests for the construction of properties such as housing communities or business campuses in which nearly all of the existing forest and species within are destroyed. Related to this is the issue of forest fragmentation, which occurs when only small patches of forest are left which cannon maintain species diversity. Diversity is important for all species to remain healthy and resilient toward disease. The EPA estimates that more than 19 percent of all forests in the U.S. consist of smaller patches rather than a "core forest" in which biodiversity can occur.

Animal Overgrazing

The reduction of hunting for large grazing animals, such as deer, has led to the destruction of temperate deciduous forests. Grazing animals like deer eat the leafy shoots of newly forming trees and lower canopy shrubs. When the population of grazing animals spikes from lack of predation, the result can be the overgrazing and destruction of forests. The Nature Conservancy reports on a New York state study which showed that nearly one third of deciduous forests in the state were being destroyed by overgrazing from animals like deer.

Invasive Plants

Many forests face the challenge of being outcompeted by species that are not native to the habitat. The Black Locust, for instance, is an invasive plant from the Ozark mountain region of the U.S. that was introduced to the upper midwest states such as Wisconsin in the early 1900s. Because of the tree's rapid growth it has begun taking over grassland areas where new deciduous forests would have developed. The result is a reduction in the total area where new oak and maple trees can expand. Another common invasive plant threat to deciduous forest is the Tree of Heaven, which is a plant native to China that spreads quickly into forest edges and prevents forest growth.