On Sept. 3, America's Wilderness Act will turn 50. For half a century the idea has endured, and thrived, that some selected places — owned by all Americans as public land — are best left alone. That doesn't mean we don't use, enjoy, or benefit from them. They are open to hikers, campers, hunters, anglers, horseback riders and others who leave their motorized equipment — including bulldozers, strip-mine drag-lines and chainsaws — at the gate.

Throughout the West, designated wilderness protects water supplies used by the majority of cities, homes, farms and ranches — 85 percent by some estimates. These remote, wild places remain essential wildlife habitat for big game, for plants and animals going extinct elsewhere but serving as cogs in the greater wheels of life, and for salmon that spawn in headwaters whose undisturbed quality underpins whole industries of sport and commercial fishing.

Here in southern Oregon, the Kalmiopsis Wilderness was among the first in America, designated with the original passage of that act in 1964. Nearly 77,000 acres were included with recognition by the Forest Service, local people and Congress that this stunningly rugged terrain was one of a kind. Named for a rare but elegantly flowering shrub, Kalmiopsis leachiana, the remote uplift of once-undersea lava had been mostly bypassed by roads, settlers and loggers. While Oregon's greater coastal mountains have been 98 percent clearcut, and while 400,000 miles of roads crisscross national forests nationwide, the Kalmiopsis remains a rare refuge of wildland — scarce and irreplaceable.

Part of the reason the Kalmiopsis was bypassed by the American mainstream is that it burns frequently, as we saw in 2002, but in spite of that, and in part because of that, this wilderness nurtures plant life found nowhere else on earth. It's part of the world's most varied conifer forest, designated by the World Conservation Union as one of only seven Areas of Global Botanical Significance in North America. Perhaps most important, the Kalmiopsis supplies headwaters to three rivers that run to the core of what makes our region special: the Chetco in its secret plunge across big mountains to the coast, the Illinois coursing its canyon corridor and feeding requisite cold water and wild salmon to the legendary fishery of the Rogue, and the North Fork Smith — the most pristine river in all of California and vital to that state's greatest salmon stronghold. Recognizing all that, Congress added an additional 102,000 acres to Kalmiopsis in 1978. But that was only half of what was proposed, and not enough to protect our rivers and fish.

Edging the designated wilderness are equally steep mountainsides, equally sculpted canyons and equally transparent streams — just as wild but outside the boundaries of protection. These havens are vulnerable to the kinds of strip mines we see proposed today at the Illinois' headwaters of Rough and Ready Creek, and for the source of the celebrated Smith. For a window to alternative possibilities for these places, just look at the Mount Polley Mine disaster in British Columbia, a Niagara of toxic mud on Aug. 4 turning 6-foot-wide Hazeltine Creek into a 160-foot-wide "wasteland." No need to go to Canada; check out the hazardous waste of the Formosa mine, right here near Riddle. Lessons of the past say our rivers will remain in jeopardy if a greater Kalmiopsis lacks permanent protection.

Some will say enough is enough, but consider the numbers. Only 4 percent of Oregon is designated as wilderness. One acre in 25 is not much as a reservoir of nature, a guarantee of clean water, a refuge for wildlife and an escape for people who want to leave the drone, the hassle and the crowds of our civilization behind, perhaps just for a day. Even so, that 4 percent is one of the features that makes life here better than in, say, Illinois or Oklahoma.

The nature of the Kalmiopsis Wilderness is among the qualities that make Southern Oregon a place that people enjoy, love and depend upon. Our children deserve the same prize we've inherited from those who had foresight before us. Fifty years has proven that a little bit of wilderness is good for us. A little bit more would be better yet.

Tim Palmer is the author of "Field Guide to Oregon Rivers," "Rivers of America," "Pacific High," and other books. See www.timpalmer.org