Copper, it turns out, is a big problem in the Puget Sound region. As people brake their cars, fine copper dust is emitted and washes into streams. In some streams, 90 percent of coho salmon returning to spawn have been wiped out, in part because of high copper levels from brakes and other sources; the copper can harm a salmon’s sense of smell, interfering with its ability to navigate back to natal streams or detect predators. But, says Licht, copper is an essential nutrient for trees, whose roots and hummus can absorb large quantities of the element.
The largest green roof in the world is the 10.4-acre Ford Dearborn Truck Assembly Plant in Michigan, a living rooftop prairie with seven species of grass and flowers that attract butterflies and hummingbirds. Ford officials say the roof, part of a 600-acre green storm water treatment system at the facility, cost $15 million and eliminated the need for a $50 million water treatment facility. The roof also reduces heat and cooling needs by 5 percent.
Another green infrastructure tool is permeable pavement, which is made of materials that allow water to soak through into the ground instead of running off. In Chicago the city is modifying its urban alleys with permeable pavement and with “cool” pavement that reduces temperatures. One limitation is that permeable pavement can’t be used for regular streets because plowing and sanding damage it.