Land, Public and Private

Human land use invariably alters the environment.
Environmental scientists use three concepts to understand land use:
- Tragedy of the Commons: Shared resources tend to be depleted if unregulated.
- Externalities: Costs or benefits not included in the price of a good or service.
- Maximum Sustainable Yield (MSY): The maximum amount of a renewable resource that can be harvested without compromising future availability.
- $MSY$ is difficult to calculate and verify.

Approximately 42% of U.S. land is publicly owned; 25% is owned by the federal government.
Resource conservation ethic: Maximize resource use for the greatest good.
Multiple-use lands: Used for recreation, grazing, timber harvesting, and mineral extraction.
Federal agencies managing public lands:
- Bureau of Land Management (BLM): grazing, mining, timber, recreation.
- U.S. Forest Service (USFS): timber, grazing, recreation.
- National Park Service (NPS): recreation, conservation.
- Fish and Wildlife Service (FWS): conservation, hunting, recreation.

Management varies for rangelands, forests, and parks.
Rangelands: Dry grasslands used for grazing; overgrazing leads to erosion.
Forests: Dominated by trees, used for commercial logging.
- Clear-cutting: Removing all trees in an area.
- Selective cutting: Removing single or small groups of trees.
- Ecologically sustainable forestry: Maintains plants and animals in a natural state.
Tree Plantations: Areas planted with single, rapidly growing species.
Fire Management
- Prescribed burns: Controlled fires to reduce dead biomass and prevent uncontrolled fires.
National Parks: Managed for science, education, aesthetics, and recreation; can be harmed by overuse.
National Wildlife Refuges: Protect wildlife.
National Wilderness Areas: Preserve intact ecosystems.

National Environmental Policy Act (NEPA): Requires environmental assessments for projects with federal money or permits.
- Environmental Impact Statement (EIS): Outlines project scope, environmental context, alternatives, and impacts.
- Environmental mitigation plan: Addresses environmental concerns.
Endangered Species Act: Protects species from extinction.

Suburb: Low-density area surrounding a city.
Exurb: Similar to a suburb but not connected to a city.
Urban sprawl: Urban areas spreading into rural areas.
- Caused by automobiles, living costs, urban blight, and government policies.
- Urban blight: Degradation of urban environments accelerating suburban migration.
Highway Trust Fund: Funds road construction, contributing to sprawl.
Induced demand: Increased supply causes demand to grow.
Zoning: Separates industry from residential areas.
Multi-use zoning: Allows retail and residential to coexist.