How long is forever?

I read on a plaque at Mount Rushmore that the granite that forms the heads of the four presidents erodes at the rate of one inch per 10,000 years. Since then I have been stuck with a mental image of an earth long after our present civilization has disappeared and maybe our species too. Whoever or whatever succeeds us will come along a million years from now and look at those heads and wonder what kind of beings created them.

How long will the changes we humans make in our surroundings last? I confess to a pet peeve regarding subtitles of history books that include a version of the phrase “changed the world forever." I understand the desire of authors and publishers to claim the greatest plausible importance for the stories their books are relating. But no one in the here and now can know if change will last forever.

Some readers will be aware of a story which I have been following because it relates to the part of the world where I grew up. Starting in the early twentieth century, planners and engineers began building dams on many of the rivers of the American West. The function of the dams was often threefold: controlling floods, irrigating farm fields, and generating electrical power. Hundreds of dams were built on rivers small and large. The biggest dams, Grand Coulee on the Columbia and Hoover on the Colorado, were among the most gigantic works humans ever constructed.

And they seemed to change their portions of the landscape forever. They certainly changed the rivers, and in doing so disrupted the lives of many of the species living along and in them. Pacific salmon grow from eggs laid in shallow gravel beds in the mountain headwaters of western rivers and drift and swim downstream to the ocean, where they grow and mature for years before returning to their birth streams to spawn and die. The dams blocked their travel in both directions. Whole populations of the salmon vanished.

Species that consumed the salmon suffered too. Bear and eagle populations declined. Even some of the flora in the streams of the spawning grounds fell on hard times. The rotting carcasses of the salmon that spawned fertilized the mountain watersheds, transferring nutrients from the ocean far inland. The dams terminated this transfer.

Certain human populations were among the victims of the dams. The salmon fishery of the Columbia River had supported perhaps the wealthiest indigenous economy in what became the United States. Indians at Celilo Falls on the Columbia annually caught and dried thousands of tons of salmon, which found its way through a trade network radiating outward for hundreds of miles. Archaeological evidence suggests that one tribe or another had lived at Celilo Falls for more than 10,000 years, making it one of the oldest continuous habitations in North America.

But in the 1950s, the U.S. Army Corps of Engineers built The Dalles Dam, which ended the habitation by submerging the falls and the land around it. If anyone could claim that their world had been changed forever, it was the people of the tribes at Celilo.

The Dalles Dam remains in place. But some other dams have been dismantled. To date, these are very few in number. Yet that number is growing. Several months ago the last of four dams on the lower Klamath River near where it crosses from southern Oregon into northern California was removed. The dams had converted a free-flowing river into a stair-step of lakes. Upon the removal of the dams, the Klamath flowed freely again.

And just this month, the first salmon in more than a century have been spotted in this part of the river. They will spawn, and their offspring will float and swim to the sea, to return in due course and complete their link in the chain of the life of their species.

Conservationists are delighted. So are fishing guides and outfitters. But to no group is the return of the salmon of greater importance than to the Indian tribes that had historically relied on the salmon. Their members had opposed the building of the dams in the first place. But at that time their voices were ignored in the halls of power. They never stopped opposing the dams, yet only after decades did other voices join the chorus, sufficient in number and influence to effect the dams’ removal.

Of necessity, during the last century the tribes diversified economically. The salmon won't become as important to members’ physical sustenance as they were to that of their great-grandparents. But symbolically the salmon connect the members to their heritage.

Sometimes a part of the world seems to change forever. But sometimes forever proves to be just a few generations. A lifetime is forever for an individual, but it can be a blip for a species or a people.