WATERVILLE — Robert Adams’ plaintive and poignant photographs of the Pacific Northwest signal a cry for help. He looks for hope in the forests traversed by Lewis and Clark, but comes away finding mostly the scars of clear-cutting and land spoiled by the intrusion of man.

“Robert Adams: Turning Back” is an essay in black and white of the photographer’s quest to follow the trail of the explorers, from the Oregon coast inland. It is on view at Colby College through June 5 and coincides with Colby’s focus on nature during the academic year.

Adams, 78, lives in Astoria, Oregon, where Meriwether Lewis and William Clark made camp in November 1805 before building Fort Clatsop nearby. Commissioned by President Thomas Jefferson, Lewis and Clark set out along the Missouri River through what is now Missouri and Nebraska, and headed west to establish a transcontinental water route. They made contact with Indian tribes along the Missouri and recorded discoveries, observations and skirmishes in journals.

After camping on the Pacific Coast, they turned back east to report their findings to Jefferson and the world.

“Turning Back” is sad and solemn, and beautiful in its melancholy quietness. Adams takes photographs of hillsides stripped of all except stumps, and toppled trunks that rise up until they meet a narrow stand of trees. He shows us heavy machinery uprooting underbrush, and chain saws slicing through trees that have stood for generations. In one, a cross-section of a stump is so large it does not fit in Adams’ frame.

The beauty lies in the sensitivity of the artist, who finds bucolic hope amid the ruin: Apple trees bearing fruit, surviving; the majesty of an old-growth forest.

He is interested in what’s been lost and what remains.

A two-time Guggenheim fellow and MacArthur genius grant recipient, Adams has focused most of his work on the American West, both its beauty and its fragility. He’s an activist artist, and this body of work is among his most politically charged, said Gary Green, an associate professor of art at Colby, who arranged the exhibition.

“I wished I’d felt free to try just to make art, but standing in front of the wreckage, smelling the herbicide, listening for birds that weren’t there, sometimes got in the way of long-term understanding and acceptance,” Adams, who declined an interview for this story, told Green.

His statement is bleak: Where there is great beauty, there also is great tragedy. Of the exhibition, Adams once said, “The theme of this (work) is the glory of the natural world and the tragic nature of human beings. The West is gone. What did we do with it? What have we traded for this great forest? What did we get in exchange?”

The exhibition is dense, with 164 black-and-white photos in just two sizes. It spreads out between two floors of the Colby museum and is a lot to absorb.

Adams, 78, made these photos over several years, beginning in the late 1990s, and he timed the project to coincide with the Lewis & Clark bicentennial between 2004 and 2006. Adams turned east from the Oregon beach, hiking inland among ruined slopes and ugly landscapes.

These photos have been widely shown, but not often in their entirety. Green wanted to exhibit all 164 because Colby is focusing on the relationship between man and nature this academic year. The museum will host a conservation conference in April, “Sustaining Livelihoods and Landscapes.”

Adams came to Green’s attention after Green began taking pictures of open fields and abandoned industrial spaces. A friend suggested that Green’s work shared an aesthetic with Adams’ in their observation of the space around them and man’s destructive nature.

The two photographers met two years ago. Green sent Adams a photography book of his own work. Adams responded favorably, and the two began a cross-country correspondence in writing. When Green and his wife visited the West in 2014, Adams invited them to his home in Oregon.

Green described Adams as “a very serious person.”

“He is somebody who cares deeply about humanity, about decency and ethics,” Green said. “He is a lovely, lovely person, a tough-minded intellectual with a generous spirit.”

As a young boy, Adams moved with his family to Colorado from New Jersey, by way of Wisconsin. He fell in love with the outdoors after taking walks with his father in Colorado. He studied English in college and began teaching English in the 1960s. He maintained that career only until he discovered photography, which quickly took over his life. By 1970, New York’s Museum of Modern Art was buying his prints.

Early work that hinted at “Turning Back” came in the mid-1970s, when Adams began taking pictures of what he called the “man-altered landscape.” He had a mid-career retrospective at the Philadelphia Museum of Art in 1989, and several U.S., Canadian and European museums have exhibited a second retrospective, “The Place We Live.”

“Adams was a photographer who went out in the American landscape, and not necessarily the landscape of Yosemite or the Ansel Adams’ vision of the American landscape,” said Colby museum director Sharon Corwin. “Instead, he went into the suburbs of Denver and began to photograph these tract homes.”

He looks at the landscape not as a heroic notion of American greatness, but as a place of loss and shame. And, at times, hope.