In parts 1 and 2 of this series, we discussed the importance of forests in the hinterlands of Nova Scotia and elsewhere. This month, let us take to the streets to look at trees in the cityscape.
Forests make cities better
The first documented cases of humans maintaining street trees goes back over a thousand years to the early Tang Dynasty in China (618 – 907 AD). In the United States, ‘arboriculture’ (the care of urban trees) began in the late 1700s and took off in 20th century, highlighted by then-president Theodore Roosevelt in 1907: “To exist as a nation, to prosper as a state, and to live as a people, we must have trees.”
Urban parks were the starting point in Canada, with Stanley Park (Vancouver), High Park (Toronto), and Point Pleasant Park (Halifax) all created in the late 1800s. Nowadays, street trees are managed by municipalities who recognize that, in addition to many ecosystem services, urban forests can beautify a city, draw tourists, and elevate property values. Most cities in Canada have targets to cover 20 – 40% of their urban areas with tree canopy.
Benefits that urban forests provide are numerous, including increased water absorption, air filtration, wildlife habitat, carbon storage, space for recreation, shade, well-being, safety, and even food. A couple of well-supported facts about urban forests are: (1) trees are incredibly effective at cooling cities, and (2) benefits from street trees are not distributed equally, but are instead often linked to socioeconomic status or race. On that second point – continue reading to learn about a city attempting to tackle that problem.
Life in the streets
Trees in a city benefit many people. However, living around humans comes with a price – the street is a harsh environment for a tree. There are a few key arboriculture decisions that can determine if a newly planted tree will live a long life in the streetscape or if it will perish rather quickly.
Taxa (e.g., species) is one of the first decisions, where a diversity of planted species is often preferred. The City of Winnipeg historically chose to shade their streets with an abundance of American elm trees but has since lost of thousands of them per year to Dutch elm disease, a fungus that was accidentally introduced to Canada in the 1940s. The size/age of tree being planted is also a consideration. Small-ish mature trees (a few metres tall) suffer lower mortality rates but are more expensive to plant than seedlings, which need consistent tender love and care and will typically die otherwise.
Where a tree gets planted is a critical choice. How will nearby buildings influence sun exposure? Too much shade will be detrimental to some species, but intense light – reflection from glass or light-coloured surfaces – could overheat others. Space is also a precious commodity in cities. How much space is available between neighbouring trees? Between the street and the sidewalk? Between the planting site and other street infrastructure (e.g., power poles, street lights)? These are just a small fraction of the questions that get asked.
A well-placed resilient street tree can live for hundreds of years and will encounter a gauntlet of potential stressors as the city changes around it. Heat, drought, road salt, poor soil, street construction, vandalism, limb pruning, damage from grass mowing, windstorms, snow and ice storms, fires, diseases, insects, and burrowing animals are among the many interacting factors that may end a street tree’s existence.
Despite all of this, forests will thrive in streetscapes managed using evidence-based urban planning strategies that prioritize the health of trees and people. Now let’s turn our attention to a city that has largely succeeded on that front.
Halifax: A city of trees
The turn of the century saw an uptake of Canadian cities developing urban forest management plans, starting with Regina (2000), Spruce Grove (2004), Montréal (2005), and St. John’s (2006). Halifax’s city council committed to developing a plan in 2006 and its foremost Urban Forest ‘Master Plan’ was officially released in 2013. Researchers from Dalhousie University – Dr. Peter Duinker and his students in particular – were heavily involved with developing the plan and continue to work with the municipality on urban forest research and management.
Today, Halifax is known as a city of trees. An updated Halifax urban forest management plan is set to be finalized in 2025, with a draft target to bolster the regional municipality’s current 43% canopy cover with the planting of 1,000 new trees every year for the next 25 years. The target uses a ‘net’ accounting system, meaning newly planted trees (i.e., gains) must be on top any tree losses that occur (e.g., if 300 street trees are removed to re-route a road, then 1,300 new trees should be planted).
Mapping of trees and demographics in Halifax identified regions with relatively low tree canopy and high concentrations of equity-deserving individuals (e.g., visible minorities, low-income households). Through consultation, these communities expressed a desire for better access to green spaces and treed areas. As a result, certain Halifax neighbourhoods will be prioritized for street tree planting and creation of new green spaces in the coming years.
Climate change and extreme weather, invasive tree diseases and pests, competing interests for space, and urban population growth continue to pose a challenge in Halifax and other cities around the world attempting to sustainably manage urban forests. However, the immense value of street trees is not debatable. Cities are here to stay… so the trees should be too.
Photo by Jan Budomo on Unsplash
