National parks and reserves Law and legislation 96 Management 70 History 50 Historic sites 42 Public lands 33 Government policy 27 espandi ... Nature conservation 27 Fees 20 Wilderness areas 20 Conservation of natural resources 15 Environmental conditions 15 Social aspects 14 Appropriations and expenditures 12 Natural resources 11 Boundaries 10 Environmental aspects 10 User charges 10 Description and travel 9 Ecology 9 Forest reserves 9 Environmental policy 8 Recreation areas 8 Recreational use 8 Environmental protection 7 Historic preservation 7 Indians of North America 7 Land titles 7 Multiple use 7 Parks 7 riduci ...