Vancouver, known all over the world for its natural beauty, is losing trees to developers seeking to maximize square footage on residential lots. Tree canopy has declined to 18% cover in 2013, down from 22.5% in 1995. The loss is almost entirely due to trees being cut down on private property. Recent changes to regulations have saved more than 2,500 trees since it was implemented.
To fight climate change, and add ecosystems services, Vancouver’s Urban Forestry Plan calls for halting canopy cover decline and to regrow canopy to 22% by 2050. To accomplish the goal will require 150,000 trees planted by 2020.
In a presentation to the Green Cities Conference by Bill Steohen, Urban Forester at City of Vancouver, said the city will pursue multiple channels to accomplish the goals: 1) Regulatory protection for trees; 2) Expanded public and private planting programs, including an innovative Street Tree Cooling Network; and 3) Tree management through soil volume standards, tree care plans and data systems to monitor operations.
Vancouver’s Street Tree Cooling Networks have a goal to cool streets and walkways by partnering with private business and the residential community. They’re beginning with a map of the hottest areas of town and targeting those for tree planting efforts. They’ve overlain data of vulnerable populations with the urban heat island to further prioritize their efforts.
Part of the Vancouver’s tree canopy strategy is to replace low-growing, understory trees with larger growing canopy trees that will provide more shade. “Replacing small underperforming trees and bring big results,” Bill said. The city is also selecting species to plant that are resilient to climate change and disease/pests.
While more than 100 genera (500 species) are planted throughout the city, two genera dominate Vancouver’s urban canopy: Acer (24.3%) and Prunus (ornamental cherry/plum, 21.7%). Kwanzan cherries alone are 7.4% of all trees planted. While ch
erries take away from diversity, they do spur tourism and are the reason for community festivals/tours during flowering season.
Many of the city’s current canopy trees were planted in the 1980s and 1990s and are growing well, Bill said. “In 20 years, 2.2% of the city will have the canopy that it does not have now because of growth of the trees we have in the ground now.” The city’s tree pricing pays a premium for non-grafted trees on their own roots. “Grafting takes 30 to 40 years off the life of a tree,” Bill said.
Working with consultants, Vancouver has built a database of existing tree inventory and indexed it to the number of tree failures of that species, how large the tree was at failure and other management information. These are also indexed to a number of resilience metrics, like how easily the tree breaks in a windstorm, drought tolerance, flammability, and whether or not it’s native and attractive to insects and birds.
Most recently the city is migrating away from a DOS-based program where they tracked 300,000 work activities on 144,000 street trees for 25 years to a more modern system that integrates with the city’s utilities departments. Everyone will be able to see what’s happening spatially. “In the past we’ve all thought in terms of our individual entities [departments].” Now engineers, utility maintenance and others will be able to see the location of trees too, Bill said.
NewTerrain April 16, 2016.