For the past eight months at his home in the Summit County hills, John Fielder spent most every morning and afternoon sifting through photographs tucked away for decades.

They were transparencies from his years of hauling heavy film equipment deep into Colorado’s backcountry. The transparencies needed paring down – duplicates in which the exposure and/or contrast wasn’t quite right. Fielder estimated copies to number around 150,000, with another 50,000 or so from his digital days after 2008.

The countless hours spent sifting, editing and scanning were “enough to whack me,” said Fielder, 72.

It was all for the sake of others.

The state’s most famous nature photographer has arranged the gift of a lifetime: his lifetime of work.

History Colorado, the nonprofit agency preserving and promoting the past, announced Monday that Fielder had donated a massive portfolio spanning the peaks and plains of the state’s nearly 105,000 square miles, compiled from an illustrious career spanning the better part of 50 years.

Many have been seen – Rocky Mountain majesty gracing walls, calendars and coffee table books everywhere – and many have been unseen. All of them, more than 5,000 selected from that batch of about 200,000, will be free for personal and commercial use upon History Colorado completing its online hub later this spring.

An exhibit celebrating Fielder’s collection is expected this summer at the History Colorado Center in downtown Denver, added Monday’s announcement.

“The magnitude of John’s donation to the people of Colorado is as breathtaking as the landscapes he captures,” History Colorado Executive Director Dawn DiPrince said in a news release.

The donation was made, she said, “so that future generations might be both inspired in their stewardship and informed of how humanity has impacted these lands we call home.”

Fielder likes the idea of people searching for photos of remote, hard-to-reach places they’ve only ever heard about. Even more, he likes the idea of scientists using the repository “to have a baseline for judging climate change,” he said, “and the impact of global warming in the decades to come.”

Fielder previously collaborated with History Colorado on a seminal work, “Colorado 1870-2000.” The book offered a side-by-side comparison of the new century’s scenery with that captured by William Henry Jackson from the dusty Frontier (and simultaneously showcased the preeminent photographer of the day and the one of now).

Just as the book cemented Fielder’s legacy in 2000, it proclaimed the newer mission of his career: to somehow protect the grandeur he saw being compromised by man-made climate change.

“The deaths of millions of acres of trees because of global warming,” he said. “The proliferation and fecundity of insects that would normally freeze to death in the bark, but now have been able to propagate beyond what they normally would because of global warming.”

And glaciers. “Even though we’re not known for massive glaciers, we still have them. St. Vrain Glacier in the Indian Peaks Wilderness, that thing is almost completely gone. In Rocky Mountain National Park – gone.”

Population growth and development have also obscured the view. In a prior interview with The Gazette, Fielder expressed guilt for his images that had been reaching the masses since starting his career in the 1970s. He realized he was branding and marketing the state’s beauty in a way similar to today’s social media.

“All of those books and calendars did not slow people down” from moving and visiting, Fielder said. “I realized that I was part of the problem.”

He sought to be part of the solution.

Beauty, pain shape life of John Fielder, Colorado’s famous nature photographer

Photography would be his livelihood, yes, but it would also be his way of helping fund and promote causes dear to him, such as clean air and water. Or causes such as the initiative approved by voters in 1992 that created Great Outdoors Colorado, which has used lottery revenues to set aside more than a million acres. In 1993, the Colorado Wilderness Act created 36 federally protected landscapes – landscapes that Fielder spent days, weeks and months exploring to provide inspirational photos to lawmakers.

Fielder has prided himself on hiking, llama-packing, skiing and rafting every nook and cranny of Colorado in search of new sights, better angles and ideal lighting. His daughter, Ashley, has referred to him as “the bionic man” for his tenacity and titanium in his knees and hip.

It was all for the sake of these photos now granted to the public domain.

While people have been a problem, Fielder maintains hope that they can help. “I have come to know that photographs can influence human action,” he said.

And however laborious those countless hours spent sifting, editing and scanning, there was a personal benefit.

“I revisited all these places that define my life, the most sublime places in Colorado,” he said. “That was an incredible treat, living life all over again.”