Going Green

New York City is a maze of buildings and paved streets. But on top of a giant building in Manhattan, you can find nature: a 7-acre garden that’s home to birds, bats, and bees. The rooftop garden—or green roof—is one of the largest in the U.S.

I recently visited the Javits Center’s rooftop garden and learned about how green roofs can help the environment. It’s no surprise that they’re sprouting all over the world.

New York City is a maze of skyscrapers and streets. But you can find nature on top of a giant building there. There’s a 7-acre garden on its rooftop. It’s home to birds, bats, and bees. The garden is called a green roof. It’s one of the largest in the U.S.

I recently visited the rooftop garden. It’s atop the Javits Center. I learned how green roofs can help the environment. It’s no surprise they’re sprouting all over the world. 

Green roofs come in all shapes and sizes. But there’s one thing every green roof needs: plants! The Javits Center’s roof is covered in sedum, a hardy plant that can survive scorching summers and freezing winters.

These plants do a lot of good. For one, they absorb stormwater, water that falls as rain or snow during a storm. Normally, when water hits a paved surface, it flows into the city’s sewer system, carrying pollutants to streams and lakes. The Javits Center’s rooftop garden can keep up to 7 million gallons of stormwater from flowing off the roof each year!

Green roofs come in all shapes and sizes. But there’s one thing every green roof needs. It’s plants! The Javits Center’s roof is covered in sedum. That’s a hardy plant. It can survive scorching summers and freezing winters.

These plants do a lot of good. For one, they absorb stormwater. This water falls as rain or snow during a storm. Normally, rainwater hits a paved surface. Then it flows into the city’s sewer. It carries pollutants to streams and lakes. But the Javits Center’s garden soaks up stormwater. It keeps up to 7 million gallons from flowing off the roof each year!

Green roofs also help keep cities cool (see Natural Coolers). Typical roofs absorb the sun’s energy and release it as heat into the air around them. That makes cities several degrees hotter than rural areas. Extreme heat can be dangerous for people.

On green roofs, plants use the sun’s energy to make food. The sun’s heat causes water contained in the soil and plants to evaporate, or turn from a liquid into a gas. That process cools the air. “More vegetation means cooler cities,” says Franco Montalto, an environmental engineer at Drexel University.

Green roofs also insulate buildings. They help keep the indoor air temperature cooler in summer and warmer in winter. That means buildings have to use less energy for heat and air-conditioning.

Green roofs help keep cities cool (see Natural Coolers). Regular roofs soak up the sun’s energy. Then they release the energy into the air as heat. That makes cities hotter than the countryside. That extra heat can be bad for people.

Plants use the sun’s energy to grow. The sun’s heat causes water in soil and in plants to evaporate. That means it turns from a liquid into a gas. That helps cool the air. “More vegetation means cooler cities,” says Franco Montalto. He’s an environmental engineer. He works at Drexel University.

Green roofs also insulate buildings. They help keep the indoor temperature cooler in the summer. They also help keep buildings warmer in the winter. That cuts down the need for heating and air-conditioning. As a result, buildings with green roofs use less energy.

The plants on green roofs aren’t alone. Animals live there too! The Javits Center’s roof is used by more than 20 species of birds. Last year, about 300 bird eggs were found in nests there. The green roof also hosts bats, honeybees, and other insects.

Because of their many benefits, green roofs are being built in cities around the world. “It’s a big trend,” says Montalto. “Why should roofs be off-limits to people, plants, bugs, and birds?”

The plants on green roofs aren’t alone. Animals live there too! More than 20 species of birds use the Javits Center’s roof. Nests found there last year had about 300 bird eggs. The garden also hosts bats, honeybees, and other insects.

Green roofs have many benefits. That’s why they’re being built in cities around the world. “It’s a big trend,” says Montalto. “Why should roofs be off-limits to people, plants, bugs, and birds?”