Pests and Diseases
Many non-native diseases and pests have infiltrated temperate forests in the U.S., one of the density-dependent factor. While some pests and diseases are native and indigenous to temperate forests in the US, others, such as the hemlock and balsam woolly adelgids, are non-native invasive species that are threatening the hemlock and spruce-fir forests along the east coast. Another example of a non-native disease includes the Chestnut Blight, which has killed off the entire mature American Chestnut population. According to Invasive, over 400 species of exotic insects have been naturalized into the US forested ecosystems, causing "serious ecological and economic consequences."