Tall grasses glow in the afternoon sunlight. The last bees and butterflies of the season hover over goldenrod and asters. Silver orbs that look like alien spacecrafts shimmer nearby.

The wild-looking meadow is not in a rural outpost, but sandwiched between a sewage plant — the orbs are the tanks — and a parking lot packed with tractor- trailers . The plants perch atop the roof of a film production studio in the Greenpoint section of Brooklyn, beside a Superfund toxic-waste site .

As bird and insect populations plummet , sounding new alarms about the health of the natural world, one promising arena where humans can help is also a surprising one: cities. In New York, scientists and officials are calling for residents and companies to do their part, with projects as ambitious as the rooftop meadow and as simple as choosing native plants for home window boxes.

For some species , scientists say, cities can be more hospitable than rural and suburban areas, because fewer lawns and farms mean fewer pesticides. The green roof in Brooklyn, Kingsland Wildflowers at Broadway Stages, draws endangered monarch butterflies, a panoply of birds and wild bees that are native to New York City but threatened by what scientists have called an “insect apocalypse.”