As of 2000, over 33 percent of the United States' total surface area is made up of forests. The United States features approximately 750 million acres of forests, according to the U.S. Forest Service. The majority of forests in the United States are in the South, which includes states such as Mississippi, Louisiana, Alabama, Georgia, Tennessee and the Carolinas. The types of forest in the United States include coniferous -- pine, spruce, fir and hemlock -- and deciduous -- maple, birch, ash and oak. The Forest Service estimates approximately 300 million forest acres have been lost in the United States since the 18th century due to the timber industry and urbanization.
Texas A&M University estimates approximately one billion acres of grasslands were in the United States prior to the arrival of the European colonists in the 17th century. In 1990, it was estimated less than 400 million acres of grasslands still exist. The amount of grassland acreage may be contributed to urbanization and agricultural development. The majority of grasslands in the United States are in the Great Plains and Midwest regions, between the Rocky Mountains and Mississippi River.
The United States is home to the Great Lakes water system in the country's Upper Midwest region. With over 750 miles of shoreline, the Great Lakes comprise over 84 percent of the freshwater system in the United States and provides 21 percent of the world's water. All the bodies of water in the Great Lakes system -- Lakes Michigan, Ontario, Huron, Superior and Erie -- are natural lakes. Also, the world's third longest river, the Missouri River, runs through the Midwest and Great Plains regions of the United States. The Missouri River, a tributary of the Mississippi River, is approximately 2,540 miles long.
Wetland ecosystems differ from freshwater ecosystems since wetlands are bodies of water covering a surface area. Examples of wetlands include bogs, marshes and swamps. The River Basin Initiative estimates the United States has lost over 50 percent of its wetlands since the 18th century. As of May 2011, the United States has 247 million acres of wetlands. The primary causes of wetland loss is drainage for agricultural development and urbanization. One of the largest wetland regions in the United States is the Everglades National Park in south Florida; the majority of this park is swampland and covers over 1.5 million acres.