linguistic:paraphrasing
Conservationist

Olmsted was an important early leader of the conservation movement in the United States. An expert on California, he was likely one of the gentlemen "of fortune, of taste and of refinement" who proposed, through Senator John Conness, that Congress designate Yosemite Valley and Mariposa Big Tree Grove as public reserves. This was the first land set aside by Congress for public use. Olmsted served a one-year appointment on the Board of Commissioner of the state reserve, and his 1865 report to Congress on the board's recommendations laid an ethical framework for the government to reserve public lands, to protect their "value to posterity". He described the "sublime" and "stately" landscape, emphasizing that the value of the landscape was not in any one individual waterfall, cliff, or tree, but in the "miles of scenery where cliffs of awful height and rocks of vast magnitude and of varied and exquisite coloring, are banked and fringed and draped and shadowed by the tender foliage of noble and lovely trees and bushes, reflected from the most placid pools, and associated with the most tranquil meadows, the most playful streams, and every variety of soft and peaceful pastoral beauty".

In the 1880s, he was active in efforts to conserve the natural wonders of Niagara Falls, threatened with industrialization by the building of electrical power plants. At the same time, he campaigned to preserve the Adirondack region in upstate New York. He was one of the founders of the American Society of Landscape Architects in 1898.

Olmsted was also known to oppose park projects on conservationist grounds. In 1891, Olmsted refused to develop a plan for Presque Isle Park in Marquette, Michigan, saying that it "should not be marred by the intrusion of artificial objects".