Excerpted from The Spine of the Continent: The Most Ambitious Wildlife Conservation Project Ever Undertaken, by Mary Ellen Hannibal. Copyright © 2012, by Lyons Press, an imprint of Globe Pequot Press. Reprinted by permission.

One five-star general in the campaign to save nature is Dr. Mary O’Brien, and she has a thing for beaver, the championing of which she has completely converted me to. In the first place, the quest for beaver has arguably had more impact on American history than the pursuit of any other single natural resource, its influence lasting well over 200 years. Sixty million or so beaver populated North America before 1600, and had a huge effect on the hydrology of the landscape – beaver dams stored water, slowed its flow and rate of evaporation, slowed erosion and supported a wealth of fish and bird species.  In fact, the extermination of beaver from North America arguably marks the point at which our landscapes began to buckle and slide down the ruinous course we find them on now. Especially in the West, where water has always been an enormous issue and will become more important as climate change affects it, there is a real imperative to put beaver back on the waterways.

As Utah Forests project manager for the Grand Canyon Trust, O’Brien directs the Three Forests Coalition, which puts her in charge of stewardship issues around the Dixie, the Fishlake, and the Manti–La Sal National Forests of southern Utah. These forests are at the core of the magnificent Colorado Plateau. The Trust would like to restore the area with native plants and thereby restabilize the soil; provide sage grouse with the cover of tall grasses and provide pollinators with flowers; protect cottonwood, aspen, and willow from overbrowsing by cattle, elk, and deer; and restore beaver to the waterways.

In October 2010 I joined O’Brien and a cadre of volunteers to assess various swaths of the Fishlake, to measure the presence and health of aspen and willow trees alongside several creeks that run through it. “These locations all had active beaver sites on them, so we want to see what kinds of conditions they’re dealing with—where they’re choosing to go. We’re measuring how close aspen is, how dense it is, how many old remnants are extant. Same with willow.” (There is not much cottonwood in the area.) “I want to go where there is beaver, because if that habitat is similar, it’s pretty clear you can reintroduce them to those other sites and have success.”

The twelve or so volunteers for this trip, who have come from all over the country, convene in a little town called Loa, from where we caravan to the spot where we will camp for five nights. O’Brien has us all pull over to observe a forest of aspen that stretches as far as the eye can see. “This is the Pando Clone,” O’Brien says. “It may be the largest living organism in the world, though a giant fungus in eastern Oregon might be bigger.” Pando is Latin for “I spread,” and a declarative statement has rarely been so emphatically evidenced. Not all aspen grow this way, but the Pando has extended its girth by sending underground shoots out from one original seed, which have sprouted to become over 40,000 genetically identical stems that we see as trees.  “Look at the size and height of Pando’s trunks,” she says. “They’re all about the same. It’s like you’ve walked into a village where there are only very old people, nobody middle-aged, nobody young.” She points out signs of stress on nearby trunks, splotches of disease, bark splitting into ugly cankers. “Pando is dying,” she says. The aspen are all the same age here because rampant deer, elk and cattle chew the new sprouts to the ground before they can mature.

What we are not seeing in the Fishlake National Forest or indeed nearly anywhere in the entire lower forty-eight is what the country looked like 200 years ago.  Before John Deere and Webcor began to alter the landscape, our friend the beaver was doing the job. As O’Brien says, “Restoration of the beaver is a restoration of a landscape to which we don’t have a cultural connection.”

O’Brien’s question, the one the gang of us have convened here in Fishlake National Forest to help her ask, is: Can beavers coexist with cattle grazing, and if so, how? Beaver will eat a lot of things but prefer willow, cottonwood, and aspen. Cattle will eat even more things and they will keep on eating and eating until . . . In Utah and on much of the vast western lands grazed by cattle, the cows never go home. Or hardly ever.

Everything is different when beaver are around. Here’s what happens: Beaver move into an area along a stream or a creek, part of the freshwater system that ultimately connects over the continent in a vast network like human veins and arteries.  In that they affect whole cascades of other interaction, beavers are known as a “keystone” species, though some scientists prefer the term “highly interactive species.” They function as multiconnectors. Beavers not only rejigger the ecosystem, but also affect the lay of the land itself. Cutting down trees on the edge of the streams opens up the area, creating new ponds, swamps, and meadows. They actually store a supply of water that can be released in the event of drought. This slowing, spreading, and layering of water is precisely what makes them pests in some areas—you may not want your backyard flooded, for example. But there is no downside to letting beaver help the miles and miles of wild land creeks in a place like Fishlake National Forest attain better resilience, especially confronting climate change.

O’Brien has led volunteer trips to measure willow and aspen browse in these forests since 2008, providing the data to the Forest Service. “I’m showing them where the cattle or elk are making it inhospitable to beaver,” she says, “and they agree with me that beaver should be back on the land.” Despite the fact that everybody can see it with their own eyes, you can’t just say, “Too many cattle spend too much time here,” and expect anything to be done about it. You have to measure the stuff growing out of the caked dirt at the water’s edge, spiky little remnants of . . . well, to figure that out, you have to look closely. We set out to document and measure two types of willow that grow here on Tasha Creek: Salix boothii (Booth’s willow) and Salix geyeriana (Geyer’s willow). You can tell the difference by the glaucous coating on the Geyer’s branches, underneath which the plant has a purplish hue. As with Pando’s younger sprouts, most of the willow we measure has been browsed below the leader, which means the plant cannot grow tall enough to produce catkins, by which it reproduces. Some of the plants are in fact mature, perhaps even ten years old, but have on them not a single leaf. At the outset of every measured transect a photograph and a GPS record is made: proof of where we were and what we did. In pairs of two we measure, call out to each other, and take note. Then we move on, 2 feet at a time. Yup, folks, this is the life of a field biologist, part of the time, anyway.

O’Brien coordinates with other NGO and agency efforts to quantify the value of beaver on the landscape. We live in a dollar-and-cents world, after all, and money is our arbiter. With funds from the Walton Foundation (an NGO branch of the family operations that bring us Walmart), O’Brien contracted a consulting firm to analyze the flow, storage, and transformation of materials and energy within the Escalante Basin, which covers about 2,000 miles, with and without beaver on it. In sum, the report says that if beaver were restored along the 400 miles of creeks and streams that form and feed the Escalante River, their dams could change the flow patterns of up to 500,000 acre-feet a year and recharge (or replenish) the aquifers. (An acre-foot of water is the amount required to cover one acre to a depth of one foot.) Stored water would be valued at $1.4 million to $4.2 million a year. Add to that the value of increased riparian habitat and that’s an additional $175 million to $470 million per year. Then there’s the avoided cost of having to restore the waterways to reduce water temperatures, a metric enforced by state regulations. The beaver would throw this in as part of their deal and save up to $411,000 per square mile. Mark Buckley, the senior economist and lead author of the paper, tells me all these estimates are extremely conservative and don’t include the voluminous benefits provided by a healthy ecosystem, including carbon sequestration and cleaner air. “I’m putting this document in front of as many eyes as I can,” O’Brien says. “People have just got to get it.”