➔ Courtney Humphries, “The city is an ecosystem, pipes and all” — “Cities may strike us as the opposite of “the environment”: As we pave streets and erect buildings, nature comes to feel like the thing you find somewhere else. But scientists working in the growing field of urban ecology argue that we’re missing something. A city’s soil collects pollutants, but it also supports a vast system of microscopic life. Water courses beneath roads and buildings, often in long-buried streams and constructed pipes. And city ecosystems aren’t static; they change over time as populations grow, infrastructure ages, and different political structures and social values shape them. Seen this way, the city is a distinct form of “environment,” and an important one.”