Urban Forestry & Climate Change

Urban Foresters have big jobs.  They are responsible for the care, maintenance and protection of trees on our streets, in our parks, and in our natual areas.  They have to plant new trees, trim and cut trees that present a hazard to humans or property, protect our forests from invasive plants, protect our trees from new pests such as Long Horned Beetle, care for trees on city property, and develop policies to promote and protect trees on private property.  While we all appreciate the beauty that trees provide and the shade they offer, we seldom think about the care and maintenance they require, particularly in an urban environment.

Urban trees and forests provide many environmental benefits.  They can prevent run-off, act as a sink for greenhouse gases, support biological diversity, lower temperatures during the high heat of summer, provide shade, and reduce energy costs associated with air conditioning.

Urban trees and forests are also good for the health and well-being of people. Trees, bushes and other vegetation can promote physical activity by making walking and cycling routes aesthetically pleasing (Lee & Moudon, 2004). Forests encourage people to be physically active by providing a destination to walk or cycle to, and a place to be walk and cycle recreationally (Lee & Moudon, 2004). Trees and forests also provide residents contact with nature; something which may improve concentration, reduce stress, and enhance cognitive development and creativity (TPH, 2011). Trees also provide shade that can protect people, particularly children, from sunburns and skin cancer (TCPC, 2010).

Trees and forests can also reduce deaths related to heat waves particularly among low income populations.  Large urban centres get hotter, and stay hotter longer, during heat waves because the heat is absorbed and stored in hard surfaces such as concrete and pavement. Toronto Public Health and Environment Canada have estimated that heat contributes to about 120 deaths per year in Toronto alone.  These numbers are expected to increase with climate change (TPH 2011a).

Heat waves lead to illness and death particularly among vulnerable groups such as:

  • the elderly and the very young who are sensitve to heat;
  • low income populations who may not have access to air conditioning or cool respites; and
  • those who live in neighbourhoods with higher surface temperatures (CIHI, 2011).

Thermal imagery conducted by Landsat Thematic Mapper has demonstrated that temperatures in cities can vary significantly creating micro-urban heat islands. A study conducted by the Canadian Institute for Health Information (CIHI) has demonstrated that in Toronto and Montreal, these hotter areas are more likely to occur in low income neighbourhoods where populations are already more susceptible to the negative health impacts of heat waves (CIHI, 2011).

The thermal imagery has also demonstrated that neighbourhoods with a higher proportion of built and artificial surfaces were the hottest (CIHI, 2011).  Trees, green spaces and vegetation can lower the surface temperature in these urban environments, cool buildings, and provide cool respites for residents (CIHI, 2011).  By targeting heat vulnerable neighbourhoods with tree planting, Urban Foresters can mitigate the negative health impacts of heat waves particularly among low income populations and in heat-vulnerable neighbourhoods.