There are people who say you can't unwind time. Their attitude is that humankind must just learn to live with environmental mistakes caused in the past. 

And then there are others who refuse to accept such fatalism. They live for achieving gains.  When given a chance, scientists say, the Earth has an incredible capacity for healing. 

Something that few people dispute is that our oceans are in trouble.  And oceans are shaped, in large measure, by what drains into them.

Once upon a time, the Pacific Northwest in the U.S. and Canada was a wonderland for wild salmon runs.  Ecological richness gave people a reason to want to live there.  The five major salmon species (chinook, coho, chum, pink and sockeye) as well as anadromous steelhead, cutthroat and bull trout would migrate up major rivers and tributaries, sometimes hundreds of miles, to spawn in the freshwater and then die.  The recycling of nutrients affected everything, from the size of trees to the health of bears, eagles, seals, orcas and life up and down the food chain.

But during the 20th century, water buffaloes wanting to control flows and harness hydropower, erected gauntlets of dams dooming most of the greatest salmon runs.  In turn, the plummet in fish numbers has had huge negative biological consequences.

One such water project was the Elwha Dam in Washington State.  The Elwha is the largest watershed in Olympic National Park.  Historically, fishery biologists say, some 400,000 adult salmon returned to their birthplace to spawn in the river before there were dams;  in the wake of dams obstructing flows, just 4,000 did and the numbers were dwindling.  As a result of legislation passed in 1992, engineers this fall finally began deconstructing the Elwha Dam a few miles upstream from where the Elwha River empires into the Strait of Juan de Fuca.  It's the first step toward restoring the natural fish passageway and includes the razing of Glines Canyon Dam.  The process will take three years and it represents the largest dam removal project in U.S. history.

For the Lower Elwha Klallam Tribe, it means be given an opportunity to recover species that resided at the center of its ancient culture.  The tribe's language in many ways revolved around the way that people interacted with salmon.

Of course, no choices are simple ones.  Generations that became accustomed to the dams—and the lack of salmon—are resistant to change.  It is uncertain how big the dividends might be for salmon and anglers and recreationists and the ecosystem. The irony is that the clean power produced by the dam will need to be replaced by another source.  Is the tradeoff of paying a few cents more for electricity each month worth it to have wild salmon back in the stream?

What does it look like to begin liberating a river?  Peruse the footage above using a time-lapse camera and posted on YouTube recently by environmental policy expert Alan Durning of the Sightline Institute.  You are watching history in the making as the clock turns back.  The National Park Service has created a site that offers great background  on dam removal if you want to learn more.  And for ongoing coverage, visit National Parks Traveler.