Last Ditch Effort

But preservation has been a mixed blessing, at best. The creation of recreational trails became a selling point for even more suburban development along the canal; in some stretches, what Pyle calls "enthusiastic grooming" of the trails has damaged mature vegetation along the canal's banks. Since 1960, as Aurora expanded from a city of 40,000 to one of more than a quarter-million, 40 percent of the butterfly species Pyle has studied along the canal have declined greatly in number or have simply disappeared; as he notes in The Thunder Tree, that's a greater rate of loss than that of Los Angeles or San Francisco.

"Every time I come back to Denver, I see parts of the canal that have been further degraded," Pyle says. "It seems ironical to me that folks move to those kinds of places and then want to get rid of the cottonwoods because of the seeds or get rid of coyotes because they eat their cats. If you move into that kind of place, you acquire a responsibility to help protect the values that drew you there.

"But what excites me now is the sheer number and variety of people using the canal--not just the bicyclists and joggers. I see a lot of people out walking, young people just nosing around. And biological diversity still present in proximity to human dwellings--that's a rare thing."

Yet every new road or housing project brings with it the threat of what Pyle calls "the extinction of experience"--a kind of alienation from nature that occurs when children don't have even a decent ditch in which to encounter an ungroomed, untamed, living world.

"The extinction of experience takes place in bits and pieces," Pyle explains. "It doesn't occur only in inner cities or jampacked suburbs. It also takes place in affluent areas like Highlands Ranch. If, on a piecemeal basis, we continue to chip away at the natural heritage in this manner, then we dismantle diversity--and each neighborhood experiences its own extinction of experience.