The overlooked role of New York City urban yards in mitigating and adapting to climate change

Abstract

There is a dearth of research focusing on the role that urban residential open space plays in climate change adaptation, despite evidence suggesting that environmental benefits accrue when even small pockets of open space are made permeable and vegetated. In densely built New York City, there are 21,448 ha (53,000 acres) of such land. One city block with adjoining contiguous open space was investigated to quantify its existing environmental value and also its potential to provide enhanced services through redesign. The study block's open space was found to be 35% permeable and planted with 96 trees, storing 45,359 kg (100,000 lb) of carbon. Simulations conducted using the United States Environmental Protection Agency Stormwater Management Model contrasting normal, light, and heavy precipitation years suggested that increases in annual precipitation could be fully mitigated by reducing impervious surface cover by 25%. The preservation of the existing vegetated residential urban open space and the conversion of paved surfaces to a pervious condition both appear to be effective strategies for enhancing the city's ability to adapt to and mitigate for climate change.

Keywords:

• sustainability
• climate change adaptation
• land cover change
• green infrastructure
• storm water management

Notes

1. The NYC Green Infrastructure Plan (2010) defines grey infrastructure as traditional constructed infrastructure, such as pipes, underground storage tanks, and treatment plants. Green infrastructure encompasses strategies such as green roofs, bio-swales, and rain gardens.

2. However, hundreds of city trees are lost annually due to storm damage, development, high mortality rates of young, newly planted trees, and tree ageing.

3. While researchers could view 100% of the yards, the type of surface cover was not always evident from a distance.

4. While urban soil is considered relatively compact (National Resources Conservation Group, USDA 1966), the soil infiltration rates measured in three study block yard spaces exceeded 10.2 cm (4 in.) of rain/hour; these filtration rates were twice the rate associated with many permeable pavement options.

5. See Peper et al. (2007), Nowak and Crane (2003), and the i-Tree Streets Users Manual (2009) for more information with regard to the rationale, functioning, strengths, and limitations of the software modelling program.

6. A privacy agreement was signed in which the team pledged not to reveal the location or release photographs with addresses.

7. Remnants of two formal English gardens remaining from the early part of the twentieth century bore witness to perhaps the first New York City “garden movement” that oriented townhouses towards backyard spaces, once they were no longer needed for domestic purposes (Dolkart 2009).

8. This model does not account for the additional value of soil and vegetation other than trees that is found in the block inner courtyard – a comparison that is not applicable to the street tree modelling.

9. Indeed an advertisement for an apartment in the very building in our study features an online picture of the introduced seating areas and large planters in the previously unused alley-yard behind the building.

10. Many US cities, such as Philadelphia and Seattle adjust storm water fees based on the surface cover, but these measures do not extend to small, private residential urban lots.