The purpose of the study published in the paper The Value of Green Infrastructure on Vacant and Residential Land in Roanoke, Virginia, is to show the value of vacant land in cities as a viable, available green infrastructure resource. Here I am summarizing the contribution of residential spaces in Roanoke. The actions we take in developing, redeveloping, planting and maintaining residential landscapes matter in how those spaces function in terms of ecosystems services.
It should be no surprise that trees on residential land are in better shape than vacant land, with 69.7% being rated as excellent compared to 9.5% on vacant land. The three most common species on Roanoke residential land are Alianthus altissima (10.8%), Cornus florida (10%) and Prunus serotina (9.3%). Nearly three quarters, 72%, of trees on residential land are native.
If you’re seeking to help maximize ecosystems services from the landscape, here are a couple of ideas from the study authors:
Plant the largest trees possible. If you want to boost ecosystems contributions of trees wherever they’re planted, select the largest growing species for the space. In general, ecosystems services are most associated with the amount of healthy leaf surface area. Large trees cast more shade, thus reducing temperatures. Large trees also intercept more stormwater. Canopy trees, such as oaks, allowed to grow to their full size provide significant services, especially for wildlife. It’s also smart to have trees across a range of ages to ensure continuity of services in the landscape over time.
Keep trees healthy. When trees die they release carbon back in to the atmosphere. Keep trees healthy to maximize their life and thus the ecosystems services benefits they deliver.
Annual Contributions of Roanoke’s Residential Trees
- 1,682,518 trees covering 22.3 sq. mi., about 96 trees/acre density
- Removed about 13,600 tons of carbon annually valued at $1.1 million; net CO2 sequestration is about 9,530 tons a year. Alianthus altissima sequestered the most CO2 on residential land at about 10.8%
- Removed about 211 tons of air pollutants per year valued at $5.55 million
- Reduced runoff by 89.2 million gallons annually valued at about $795,000
- Reduced energy costs by $497,000, avoided CO2 emissions by 814 tons valued at $63,899