Native Oak Tree Ranges in the U.S.
Oaks are principally temperate zone trees or shrubs, estimating about 600 species globally. Oaks have remained on the non-glaciated territories of North America following the Cretaceous Period.
According to the U.S. Forest Service, 50 oak species are represented in 2/3 of the eastern North American wood cover types and dominate 68% of hardwood forests (77 million hectares or 191 million acres).
Oaks of the United States
The invasion of urbanization, agriculture, and hydrologic projects continue to affect oak forest types negatively. Such influences may require the establishment of preservation areas for vulnerable species.
In the southern U.S., forest management methods prefer conifers displacing hardwood forests in rich bottomlands. A new cause of concern includes the threat of displacement of native oaks by different exotic species. Moreover, forest types are placed at risk by introducing not only non-native plants but insects and diseases.
In 1997, a fungal pathogen (Phytophthora ramorum) was known as the cause of the Sudden Oak Death in California. Searching for potential hosts has found some sensitive species of eastern red oaks. Additional susceptible hosts include commercial nursery stock, which enhances the chance of the Sudden Oak Death expanding to eastern North America.