American cities have become laboratories for novel policies to reduce climate change, reverse environmental degradation and support alternative energy. Because of the nature of the U.S. federal system, cities’ policies are often adopted at the state or national level, putting cities at the center of the environmental movement.

Joggers on a path through Central Park (Batchelder/Alamy)

Bright lights, green city

The five boroughs that make up New York City are home to one of the most environmentally friendly transportation systems in North America. More than half of the city’s bus fleet runs on alternative fuel. New subway trains have brakes that feed energy that would otherwise be lost as heat when a train stops back into the electric third rail.

The city has improved its air quality by replacing heavily polluting heating oils with cleaner fuels. Its carbon-dioxide emissions per capita are lower than those in other U.S. cities.

New York soon will welcome recreational boaters. (© AP Images)

New York’s environmental land-use effort also stands out. By redeveloping postindustrial sites and vacant lots, New York  expands its green spaces, with the goal of ensuring that all New Yorkers live within a 10-minute walk of a park. As of 2014, 44 hectares of new parkland had been added.

The MillionTreesNYC program planted its millionth seedling in 2015. The city planted 70 percent of the trees along streets, in parks and in other public spaces. The other 30 percent was planted by homeowners, business owners and nonprofit organizations on their own properties.

The city is restoring its shorelines for recreational use through improved water quality and waterfront access. It plans to open 90 percent of its shoreline to residents by 2030.

Want to know what the world is doing to fight climate change? Follow the November 7–18 global climate summit, called COP22, @US_Center, and use the hashtags #ActOnClimate and #AskUSCenter.