The United States Forest Service is an agency of the United States Department of Agriculture that administers the nation's 154 national forests and 20 national grasslands, which encompass 193 million acres (780,000 km2). Major divisions of the agency include the National Forest System, State and Private Forestry, and the Research and Development branch. The mission of the Forest Service is "To sustain the health, diversity, and productivity of the Nation’s forests and grasslands to meet the needs of present and future generations." Its motto is "Caring for the land and serving people." As the lead Federal agency in natural resource conservation, the US Forest Service provides leadership in the protection, management, and use of the Nation’s forest, rangeland, and aquatic ecosystems. The agency's ecosystem approach to management integrates ecological, economic, and social factors to maintain and enhance the quality of the environment to meet current and future needs. Through implementation of land and resource management plans, the agency ensures sustainable ecosystems by restoring and maintaining species diversity and ecological productivity that helps provide recreation, water, timber, minerals, fish, wildlife, wilderness, and aesthetic values for current and future generations of people.