On average, New York City trees fall about 30% below the potential shade they could produce.

“Shade and access to shade is a citywide problem,” Kobald said.

In a comparison of three neighborhoods with similar building heights, street widths and tree counts – Pelham Gardens in the Bronx, Park Slope in Brooklyn and Ozone Park in Queens – the study found big disparities in shade and very different exposures for heat vulnerability.

In Park Slope and Pelham Gardens, the vegetation is very evenly distributed. The tree canopies are all very similar in size – and they’re very large and healthy compared to Ozone Park.

“Park Slope ends up with a lot of very beneficial shade that’s falling on streets and sidewalks during the hours that you would want that shade to be there,” Kobald said.

In contrast, Ozone Park had much smaller trees, and many of them were not healthy. The findings also revealed another major difference that was a factor in good shade – orientation. The trees in Ozone Park were often located on major thoroughfares with less foot traffic or on north-south oriented streets, which have less sun exposure.

“We do need to be mindful of which tree we put in which place because trees respond to and are affected by local conditions,” said Emily Maxwell, New York Cities Director at the Nature Conservancy.

Blocks of mid- to high-rise buildings can cast large shadows, nullifying the shade that trees can contribute on streetscapes.

“These north-south oriented streets don’t provide the same amount of shading benefit as if they had been on the east-west corridors that experienced a lot more sun during the hot summer afternoons” Kobald said.

But tall glass and concrete buildings come with the negative consequence of reflecting sunlight, which can cause excess heat in the vicinity. This phenomenon contributes to the urban heat island effect, or metropolitan areas are hotter than average due to the absence of greenspace. A climate report published in July found that New York City has the worst urban heat islands in the U.S. due to the number of people affected by the excess warmth.

“We can think a lot more expansively about how to use trees as an asset in the city,” Kobald said. “We should be much more creative about the solutions that we propose rather than this default of double lined street condition — trees on both sidewalks regardless of orientation and neighboring circumstances.”

Advocacy groups, such as Nature Conservancy, back the city council’s push for legislation to establish a citywide urban forest plan aimed at achieving the 30% canopy cover goal and require periodic LIDAR monitoring to track canopies. They also want trees and their canopies to be considered in the city’s long-term sustainability planning.

“Street trees provide a range of benefits,” Maxwell said. “They clean our air. They beautify our neighborhoods. They help filter stormwater, and being around trees has been shown to improve our health and wellbeing.”

Original article here.