For the past few weeks I have noticed a horse trailer and several goats in the abandoned lot on SE 11th and Belmont. Any idea what they are doing there? Besides the obvious eating and pooping? Are they being used for weed control? —Kvineyard

In a word, yes. In 250 words, the Great Goat Invasion of 2010 is the brainchild of Brett Milligan, a landscape architect and self-described urbanist whose Free Association Design website is full of phrases like "negotiated space" and "the nature/culture dichotomy."

A few months ago, Milligan was minding his own business, documenting emergent urban forests, when he had an idea: Why not localize the entire consumptive process inherent in the already existing mowing regime? (For you slower kids, that means "use goats instead of mowers.")

This turns out to be a brilliant idea in any number of ways. Most prominently, the small gas engines that run things like lawnmowers produce a disproportionate amount of pollution, disgorging 100 to 1,000 times more hydrocarbons and nitrogen oxide than a car. Lawnmowers also tend to disperse weed seeds, while the goats digest them.

One benefit Milligan didn't fully anticipate is the goats' value as a public amenity: "People love goats," he says. "They bring their kids." In fact, people love goats so much that they go to the grocery store and bring the goats vegetables to eat, which tends to compromise the mission, but whatever.

What is perhaps most striking about all of this is that Milligan didn't own the property, nor did he own any goats. He just had the idea, and managed to talk the property owner into a relationship with Portland's leading goat-provider, Goat Rental NW. "If you call some people, you can make something happen," he observes.