More about heat islands and trees

Stuart Gaffin is a research scientist with the Earth Institute at Columbia University. He was part of a group that studied the "urban heat island" in New York City and presented solutions for mitigating heat. You can read a full article on NASA's website, but here are some key passages that present compelling arguments for preserving the Ridgewood Reservoir:

"On a hot, sunny afternoon, walk outside and find a parking lot bordered by grass. Put one hand on the asphalt and the other on the grass. The same surfaces of asphalt, stone, brick, and cement that keep weeds and water out of our way can sizzle in the sunlight and raise local temperatures. To make room for all these buildings and roads, cities squeeze out vegetation that would otherwise cool its surroundings by evaporating water. Added to the mix are car motors, hot air from air conditioners and clothes dryers, earth-moving machines, even smokestacks. All of these heat sources work together to raise temperatures. According to the U.S. Environmental Protection Agency, an urban area can see air temperatures up to 6 degrees Celsius (10 degrees Fahrenheit) hotter than the nearby suburban and rural areas."

"An especially effective mitigation strategy involved planting trees. Each tree could not only cool its immediate area, it could also cast shade onto nearby buildings. Gaffin and his colleagues estimated that 17 percent of the city’s surface could be planted with trees. They also estimated, however, that the biggest temperature reductions could be achieved by addressing New York City’s dark, impervious surfaces such as roads and roofs. Their assessment of the city indicated that 64 percent of the city area consisted of such surfaces."

"As he researched mitigation options for the urban heat island, he became aware of another issue that causes some cities as much hardship: stormwater runoff. “The purpose of asphalt is to create an impervious surface,” he explains, to keep out water. Unfortunately, the water that can’t be absorbed by roofs and roads has to go somewhere else." "To deal with runoff from heavy rains, cities have storm sewers, but many cities use the same systems to handle both the overflow from rainstorms and the water flushed out of toilets. Heavy rains can overwhelm these systems (called combined sewer overflows), pushing raw sewage into waterways. “It’s the major source of pathogens in the New York Harbor. It’s a major problem in Europe. This is one of the impediments to ever reclaiming the recreational and other values of our urban water systems,” he says. He has coined a term for this problem, as a parallel to the urban heat island. He calls it “the urban runoff island.”

"Gaffin and his colleagues used Landsat data to assess New York City’s summer heat. The top map shows temperature, with cooler temperatures appearing in blue and hotter temperatures appearing in yellow. The bottom image shows vegetation, with beige indicating sparse vegetation and dark green indicating dense vegetation. The maps show a correlation between dense vegetation and cool temperatures, and between sparse vegetation and high temperatures. NASA’s Landsat satellite captured these images of New York City on August 14, 2002, at 10:30 a.m. (Maps by Robert Simmon, using data from the Landsat Program.) Gaffin and his colleagues used Landsat data to assess New York City’s summer heat. The top map shows temperature, with cooler temperatures appearing in blue and hotter temperatures appearing in yellow. The bottom image shows vegetation, with beige indicating sparse vegetation and dark green indicating dense vegetation. The maps show a correlation between dense vegetation and cool temperatures, and between sparse vegetation and high temperatures. NASA’s Landsat satellite captured these images of New York City on August 14, 2002, at 10:30 a.m. (Maps by Robert Simmon, using data from the Landsat Program.)"

In addition to the heat mitigating value of the forests of the Ridgewood Reservoir is its use to control storm water. A comprehensive management report for the "Jamaica Bay Watershed Protection Plan" was released this month. On the New York City Department of Environment Protection website is a summary of the report. The Department of Parks and Recreation wants to replace forest and vegetation with artificial turf and asphalt at the Ridgewood Reservoir. I guess they didn't get this memo:

"Most notably, the plan builds on the Mayor’s PlaNYC, recommending a series of Best Management Practices for storm water management."

I didn't read any recommendations for cutting down 23 acres of forest. Read the entire news release here.

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