Forest and woodland are estimated to cover some 13.1 million ha (35.6 million acres), or about 10.8% of the total land area. A total of six forest reserves cover 229,400 ha (566,900 acres). Mali's Water and Forests Service works to preserve and increase the amount and quality of general and classified forest domain and to assure reasonable exploitation. However, wood is Mali's primary energy source, and overcutting for fuel is a serious problem. Roundwood production in 2000 amounted to 5,143,000 cu m (181,550,000 cu ft), with 87% used for fuel.