South Coast Botanic Garden, Palos Verdes Peninsula, Calif. (Leave It Better Than You Found It).

In one sense, all botanical gardens are living laboratories. South Coast Botanic Garden offers an additional challenge to its caretakers--solving horticultural problems at one of the world's first botanical gardens developed on a completed sanitary landfill. The site of the garden was an open pit mine from 1929 until 1956; then it became a sanitary landfill, and remained in operation as such until 1965. In 1967, at the urging of private citizens and horticulture groups, the Los Angeles County Board of Supervisors approved converting the site into a botanical garden.

Today, the garden is home to more than 150,000 plants, with approximately 140 families, 700 genera and 2,000 species represented. The garden is particularly rich in plants from Australia and South Africa; those areas' similar climate to southern California's makes the garden ideally suited for plant-introduction programs. More than 110,000 visitors tour the gardens each year, and numerous horticultural groups use the garden's facilities for meetings and workshops. Departmental educational programs offer lectures, walks and horticulture classes for the public. A stream and lake on the site have drawn more than 300 species of birds. Because almost no plant or animal life existed at the site before landfill operations began, the diversity of animal life offers important ecological lessons in land-use planning.