Conservationists often say that all their victories are temporary and all their losses permanent. Over the years, I may have dismissed that statement as the understandable hyperbole of passionate advocates.

As I consider what looms over the future of the Boundary Waters, I am no longer quite so sure. One scheme in particular, the proposed Twin Metals mines, could cost us the soul of this splendid place that we have thought well-protected.

Arizona has its Grand Canyon, Wyoming its Yellowstone, California its Yosemite. These wonders come to mind unbidden as images of a place when those states are named. The Boundary Waters is such an image for Minnesota. It is also our responsibility.

That our wilderness is intact and safe today is no accident. Rather, it is the result of an enduring struggle. In 1926, the U.S. secretary of agriculture directed that over 600,000 acres of the area be managed as wilderness. Every generation of Minnesotans since has been called to the area’s defense. Today’s threat dwarfs them all.

A Chilean mining company, Antofagasta, now holds the only two federal leases on the Superior National Forest. The leases, first issued in 1966, have expired, and now the Bureau of Land Management (BLM) is weighing an application for their renewal. Renewal would free Antofagasta to pursue its plans for the Twin Metals mines, a massive sulfide-ore copper project along the Kawishiwi River upstream from the Boundary Waters.

Some history here is useful. The leases were issued 50 years ago — two years after the Wilderness Act of 1964 became law and four years before passage of the National Environmental Policy Act (NEPA). NEPA posited the then-novel notion that we really ought to know what we are about before taking major federal actions.

In the intervening time, we have learned much about the catastrophic consequences of sulfide-ore mining. Above all else, we have learned that sulfide-ore mining has never — never — been undertaken without serious environmental consequences. Sulfide-ore mining is dangerous everywhere and most dangerous in wet environments. And the Boundary Waters is nothing if not wet.

The consequences of such mining are perpetual. They will surely outlive all of us and will just as surely outlive the mining company’s pledges, promises and sureties.

Ideally, the BLM and its parent, the Interior Department, will move to withdraw from its mineral leasing program all federally managed minerals in the Boundary Waters watershed. That would permanently protect the Boundary Waters from sulfide-ore mining. But so long as the Twin Metals leases are extant, that step would have only partial results. The agency has ample authority to do both those things — deny the leases and withdraw the minerals. Our job is to see that it finds the will to do so.

We must do what Minnesotans before us have done: defend the wilderness. Vice President Hubert Humphrey and I were deeply committed to protection of the Boundary Waters and its precious waters. Although we were mindful of the need for jobs, we knew that it was imperative to protect the magnificence of the Boundary Waters. The Twin Metals mining proposal lacks this balance. That means that today I join Minnesota’s Gov. Mark Dayton and urge the federal land management agencies to continue the work of nearly 100 years and to ensure that the Boundary Waters wilderness remains the place it is today.

They were titans, the people who forged the Wilderness Act of 1964 and fought for inclusion of the Boundary Waters and a hundred other matchless places in the National Wilderness Preservation System. Among them were Ely’s Sigurd Olson and his friends the Muries — Olaus (another Minnesota native) and his wife, Mardy. In 1964, Mardy testified at a congressional hearing on the Alaska Lands Act. Though Alaska was the immediate subject, Mardy’s message was universal:

“I hope the United States of America is not so rich that she can afford to let these wildernesses pass by … or so poor that she cannot afford to keep them.”

That fairly describes the question before us: Are we generous enough, secure enough, mature enough to refuse short-term gain in order to avert long-term calamity? Our children’s legacy depends on the answer.

Walter Mondale is former vice president of the United States.