New York's "urban heat island" effect is a byproduct of several factors, including the black, tarred rooftops made of asphalt and concrete that trap sunlight and heat, raising the temperature in the city by as much as 10 degrees. There has to be a better solution, and over at Gotham Gazette, Sam Williams examines two alternatives - the white roof and the green roof. A "white roof" is simply a roof that has been treated with a basic coating of light-colored water sealant, while a "green roof" is a roof that includes a garden (usually, plants or trees atop a layer of soil).

According to the executive director of Manhattan-based EarthPledge, “Roof tops are an enormous wasted resource" in New York. What's more, as Williams explains, there are a number of environmental benefits to green roofs - they tend to limit storm water runoff and they have the ability to filter pollutants and to remove carbon dioxide via photosynthesis.

Be sure to check out the stunning array of "green roofs" from Greening Gotham. There are examples of Japanese gardens, Miami Beach-style roof terraces and stunning views of the city.