“There’s a lot of potential there,” Wilson said. “The oak and madrona savannah is a pretty rare habitat, and there aren’t many places in the metro area to do something on this scale.” The city’s posted signs sum up the project’s ambition by describing a “desired future condition”: a loose tree canopy that towers over native grasses and shrubs, and that someday could become the site of educational field trips for schoolchildren.

My God—it almost sounds like a nice place for a walk. Behold the Portland ethic in action: Where other cities might see a weedy bandit’s lair, we see a chance to strike a blow for ecological rectitude. As Jeremy and I head toward the white-noise roar of N Greeley Avenue, I try to imagine our current path transformed into an Eden. Of course it would be a good thing. As a right-thinking liberal, I could only applaud the enlightened city in action. (Think what a luxury it is, in human historical terms, to have a local government that worries about native plant restoration. Beats the Borgias.)

Yet after we leave the tree house and the other fortifications installed in these unwelcoming woods by parties unknown, for reasons unknown, I feel a pang of pre-emptive nostalgia for the gone-to-seed vigor of the escarpment as it is. I can think of few other places where this riotous profusion of greenery (not quite the kind most Portlanders approve of, of course) could exist just beyond the pale of settlement. In a well-ordered, progressive city, a place like the escarpment represents a messier kind of freedom—where danger intermingles with the possibility that, within a mile of my espresso bar of choice, I could choose to disappear into terra incognita, go live among the Tree-House Tribe. It also provides a healthy reminder that any city—even green-friendly, sustainability-mad Portland—exists at the edge of nature, not vice versa; there’s always an implacable wave of undergrowth waiting to take back any available space.

Beyond the broken glass, Jeremy and I discovered that the escarpment is not without beauty. We saw wildflowers. We saw a red-tailed hawk. We saw a hipster couple who’d ridden their bikes out to the cliff’s edge and brought a sleeping bag to cuddle in. We even saw a few tough old oak and madrona trees—stubborn survivors, right at home.