Efforts to build urban housing, bike and bus lanes, and sewage systems have been loudly criticized for displacing trees. Such criticisms follow a common formula:
1. [Developers, planners, city engineers, the mayor] are ruining our city by cutting down beloved trees to build an unnecessary [building, bike path, sewage line].
2. Urban trees are essential for [air quality, sequestering carbon, mental health, wildlife habitat].
3. Our city is becoming a concrete jungle.
4. We need stronger tree-protection laws.
I certainly appreciate the intent. Trees are beautiful and enhance our environment. We should support urban forests. However, not every tree deserves preservation. Tree removals are often justified to achieve other sustainable-development goals, such as increasing housing, improving efficient travel options or building sewage-treatment facilities.
Tree-preservation advocates generally ignore the greatest threat to our forests: Sprawled development, which significantly increases the impervious surface (building and pavement) footprint of buildings, roads and parking facilities, and increases pollution emissions. Recent studies have measured these impacts.
The graph compares the footprints of typical urban and suburban households. It assumes that the urban household lives in a three-storey townhouse and the suburban household has a one-storey home. The urban household has one car; the suburban household needs two. Because higher densities allow more shared parking, urban cars require just two parking spaces compared with six in suburban areas. Higher traffic densities and shorter average trip lengths reduce the road space required for urban cars compared with suburban vehicles.
In total, the suburban family requires about 5,000 more square feet of impervious surface, which displaces five to 12 trees and generates about three times the emissions as would occur in a walkable urban neighbourhood.
A good example is the two-acre Bellewood Park project under construction near downtown Victoria, which required removing 10 significant trees to build 83 housing units. Building that number of homes on quarter-acre suburban lots would disrupt 21 acres of open space, and displace about 415 to 996 trees with driveways, parking and roads.
Many residents are understandably uncomfortable with changes that are occurring in our community, resulting in sometimes heated NIMBY responses. Tree removals are tinder to this conflict. However, that does not justify attacks on public officials, or ignoring the community benefits provided by new houses, bike and bus lanes, and improved sewage treatment.
It is far better to manage change than simply oppose it. If we want a healthy urban forest, we must plant more trees than are lost each year, and do everything possible to minimize building, road and parking-facility footprints to free land for greenspace. Many cities are implementing pavement-busting policies such as the following:
• Improve space-efficient transport modes (walking, bicycling and public transit) so residents can reduce their driving and, therefore, the need for roads and parking.
• Encourage more compact housing types (secondary suites, townhouses and apartments).
• Reduce parking requirements, and efficiently manage parking so fewer spaces are needed.
• Reduce road widths, expand boulevards and plant more street trees.
• Improve parking-facility design with pervious surfaces, landscaping and shading.
• Expand neighbourhood parks.
• Encourage natural landscaping, rooftop gardens, planters and other creative greenspaces.
A healthy tree canopy benefits everybody, but it is important to see the entire forest, rather than individual trees, for sustainable community planning.
Todd Litman is an urban planning consultant and member of Cities for Everyone, a local organization that advocates for more affordable and inclusive communities.