Why green yards are important

From the Wall Street Journal:

New York City, in the public imagination, is a land without yards. The relative scarcity of private residential green spaces is one of the many ways home life in the densely-packed city is thought to differ from the spacious suburbs.

So it’s something of a shock to learn that residential yards make up 27% percent of the city’s total area — and that’s not counting parks or the greenery found adjacent to sidewalks or on street medians. That finding comes from the work of a group called Sustainable Yards, whose founder, Evan Mason, used satellite images to tally the yard space in all five boroughs.

Mason describes her research, conducted with help from the City University of New York, in an interview with science blogger Emily Anthes. The discussion hits on the importance of these yard spaces, including ways they can help the city save money. Green yards, which absorb rain and moisture, are better than concrete from an economic view, Mason explains:

Very simply said: Soil is good. It costs $127 a gallon to treat water in our water treatment system. So what we’ve done is actually gone into as many backyards as we can in one particular block. With CUNY, we’re actually measuring the square footage, how much is permeable, how much is impermeable. So if a whole set of backyards, is, say, 90 percent permeable, then you can start making a calculation of how many gallons are diverted from the water treatment system and how much money that saves the city.

This is technically not true. Homeowners must, by law, maintain storm water runoff on their own property. By obeying the law, they aren't "saving" the City a dime. People who pave over their yards are in effect breaking the law, are the ones who are overburdening the sewer system, costing the City money and should be fined accordingly.