Greg Gordon is a professor of environmental studies at Gonzaga University. He is the author of When Money Grew on Trees: A. B. Hammond and the Age of the Timber Baron and The Landscape of Desire: Identity and Nature in Utah’s Canyon Country. His latest book Rewilding the Urban Frontier: River Conservation in the Anthropocene (Nebraska, 2024) was published this month.

In both my personal and professional life, I’ve long focused my interests and activities around big wilderness and landscape-level conservation, but when I moved to Spokane, Washington, I found myself ensconced in an urban environment. Nonetheless, on my walks around town, I was amazed at the abundance of wildlife: not just deer and quail, but moose and turkey, coyotes and bobcats, eagles and herons—all seeming to thrive amidst highways, buildings, and lawns. Not surprisingly, the greatest concentration of both plants and animals was along the city’s creeks and rivers.

In 2015, I attended a conference on landscape ecology and, drawn to sessions on urban ecology, discovered there was an emerging field dedicated to “novel ecosystems.” The concept of novel ecosystems, in which exotic and native species co-exist to create a functional system heavily influenced but no longer dominated by humans, upended my entire conservation paradigm.

Certainly, there are still intact, wild ecosystems across the planet, but as I dug into the scientific literature on novel ecosystems, I began to wonder if there was something we’d missed in the traditional conservation approach. Could wild nature and human artifice be reconciled into something functional that could foster both biodiversity and human needs?

A number of factors seem to be converging in the twenty-first century: the twin crisis of a rapidly changing climate and the catastrophic loss of biodiversity, the emergence of the Anthropocene as a catch-all concept for human impacts on planetary systems, the replacement of the natural with the virtual and subsequent loss of the former in the human experience, and ever-increasing urbanization and spread of human landforms across the globe.

As I wandered along the vacant spaces of the city, along the waterways where broken slabs of concrete constrained the river, but also provided habitat for marmots, where Siberian elm and Japanese knotweed mixed with cottonwoods and ponderosa pine and housed porcupine and raccoons, where red-tailed hawks and osprey rode the thermals, I began to wonder if maybe the Anthropocene might provide its own antidote.

If wild nature (and by “wild,” I mean, self-willed, self-perpetuating) kept inserting itself into “our” urban environments, instead of keeping it out or controlling it in the form of city parks and manicured landscaping, could we instead provide opportunities for nature to flourish alongside human infrastructure? What if we did this in an intentional way that provides migration corridors through our cities to link larger habitats? And what better place than along the most degraded, neglected, and “wild” spaces—our urban creeks and rivers?

I began to explore cities that contained rivers, many severely degraded, to examine how cities were attempting to recover their urban waterways, which, by nearly every criterion, met the definition of a novel ecosystem.

In Colorado, upon hearing of my interest, John Davenport with Trout Unlimited invited me to go fly fishing on the South Platte River in downtown Denver. I pulled into the park and ride where John suggested we meet. Early on Sunday morning, the lot was mostly empty save an old beige van piled high inside and out with its inhabitant’s belongings. Someone else was sleeping inside an old sedan. I spied John across the lot pulling two long flyrods out of his Prius.

“Ready to go fishing,” he said with a grin, noticing my obvious skepticism.

We picked our way through the willows and abandoned homeless camps to a wide, shallow, brown stretch of water. Hard-pressed to call this a river, much less a trout stream, I headed downstream, casting my fly among beer cans, pop bottles, plastic bags, and swirling golf balls. Between casts, I gazed up at the streamside roller-coaster of Elitch Garden’s amusement park standing silent in the October sun like the skeleton of some post-apocalyptic infrastructure. Elitch’s was recently purchased by a developer, and the old roller coaster will come down, along with the tilt-a-whirl and arcade games. In their places will rise high-end condos, riverbank restaurants, boutique shops, and a greenway along the river—the new urbanism. The South Platte, once an industrial sewer, is becoming a valued amenity. To enhance this amenity, the developer released rainbow trout along this stretch of river.

Unsuccessful in our fishing, we opted for lunch at a nearby eatery. Eyeing our waders, a man at the next table leaned over and asked where we were fishing, and when John replied, the South Platte, he looked startled, “for carp?” he asked.

“No, trout, rainbow trout.” John explained that last year witnessed two trout introductions, just below the confluence and those fish are now 18 and 21 inches long.  When we stood to leave, another man approached us and we proceeded through the same conversation.

Afterward, John said, “See?  Interactions. I can raise awareness about the river just by walking around in waders.” He added that he fishes the Platte to bring awareness to the river so more people start to think about the river’s health. If people think of the river as a trout stream rather than a drainage canal it will lead to improved ecological health. Trout, unlike carp for example, need cold, highly oxygenated water, which requires pools and riffles, rocks and logs in the river, and shading along the banks. All of which contribute to greater structural complexity and, in turn, higher biodiversity.

Rainbow trout, however, are not native to the South Platte watershed. On the other hand, instead of the historic intermittent summer flows, the upstream dams now allow for continual flow. With its altered hydrology, channelization, and introduced species, the South Platte is the definition of a novel ecosystem. Does that make it any less important, less worthy, or even less wild?

As I continued to investigate urban rivers and met with people working to restore, revitalize, and rewild these waterways, I realized that these local experts knew their rivers much more than I did and deeply cared about these places. So instead of writing a book myself, I enlisted their help. Rewilding the Urban Frontier is the result.