PUERTO LOBOS, SONORA — What goes around comes around, whether in a healthy natural community or a balanced human economy — or with a well-trued bicycle wheel. In the human ecosystem that makes up Puerto Lobos, Sonora, there are plenty of detritivores, mechanics with a genius for patching mangy cast-offs from north of the border through another season of sand roads and salt air. But Elson Miles occupies a different niche. Since 1989, when he sold his bike shop in Arizona and began spending increasing amounts of time on this desert coast, he’s been the manual-powered detritivore who keeps the place rolling — on two wheels.

Miles, who is tall, genial, and slightly scruffy, has a finely honed scavenging instinct and a messianic view of bikes. His yard in Flagstaff is chock-full of his raw materials: frames, wheels, chains. You can often find him there, piecing together polished new machines out of the myriad discards he finds in an era when a bicycle, to many an owner, is simply another artifact of planned obsolescence.

He sells some, on the cheap, to those who need them locally: college students, poor Hispanic kids who need to get to an after-school job. But every time he heads south he takes along a half-dozen or so — as many as he can get through the border without raising too many questions. And then, in Puerto Lobos, he converts what was once discarded into useful transportation, and into a sort of social glue. The kids come by his place on their way to school in the morning: their tires are low. They come back in the afternoon: another goathead seed has caused a flat. That’s no cause for lament; it’s a reason to stop by. Only a dull ecosystem, after all, lacks frequent interactions between its components.

After some years of this, Puerto Lobos, among Mexican fishing villages, now has an inordinate number of bikes. And Miles has become part of the town. He’s not just any gringo anymore. His place has become el taller, the bike workshop.

Knowing something of economic imbalances between north and south, he used to give them away, only to find that a freebie seldom prompts the sort of caring that paid ownership does. And so he sells each re-cycled bike now, even if for only a peso, to a fisherman’s young son or daughter.

“A bike needs an owner, a responsible caretaker,” he says. He loves to see that someone ride off — a pleasing image, no matter how often repeated, that fills what he calls his “feel-good niche.” He knows that owner, no matter how responsible, will be back before too long: for air in the tires, for a tweaking of the brake cables, a greasing of the chain, a shooting of the salt breeze.