In the United States limited game laws were passed in various states in the late 17th cent., but it was not until after the mid-19th cent. that legislation dealt with the depletion of wildlife. By that time, the populations of many birds and mammals had been alarmingly reduced, and some species had become extinct, chiefly because of the indiscriminate slaughter of animals for feathers and hides, for food, for sport, and also because of the destruction of habitat by the draining of swamps and leveling of forests for farming and human settlement. Modern wildlife conservation policy began with a conference of state governors and other officials called by President Theodore Roosevelt in 1908 to inventory the nation's natural resources; its immediate outcome was the appointment of a national conservation commission, followed shortly by the establishment of similar commissions in most of the states (see conservation of natural resources).
Milestones in early legislation designed to preserve wildlife in the United States were the Lacey Act (1900), regulating imports of and interstate commerce in birds and mammals, and a similar supplementary act for black bass (1926); the establishment (1916) of the National Park Service, which forbids hunting within its parks; international treaties for the protection of migratory birds made by the United States with Canada (1918) and with Mexico (1937); the Norbeck-Andresen Migratory-Bird Conservation Act (1929), which provided for the development of a system of refuges; and an act (1934) requiring hunters of migratory fowl to purchase a stamp and a similar act (1937) establishing a tax on arms and ammunition, the funds raised in both cases to be used for wildlife preservation programs. More recent legislation to protect wildlife has included the National Environmental Policy Act of 1970. other antipollution legislation, and the Endangered Species Acts of 1966, 1969, 1973, 1978, 1982, and 1988 (see endangered species).
In 1948 an international conference established the International Union for the Conservation of Nature and Natural Resources. The first international organization devoted solely to wildlife conservation and environmental protection, the union by 1999 had a membership of 146 countries. The group was instrumental in convening the 1973 meeting in Washington, D.C., that drafted the Convention on International Trade in Endangered Species of Wild Fauna and Flora. In connection with the convention more than 350 biosphere reserves have been established in more than 80 countries.