A canopy is the vegetation cover formed by trees over a given territory. For the purposes of the index, the ground area covered by a tree’s crown is calculated relative to the total surface area of the land under study.
The canopy index for the Montréal Urban Agglomeration was 20.3% in 2007 and 20.8% in 2015. However, these two indicators cannot be compared because they were generated using different methods. Eight years separate the two surveys, and the technology used to evaluate the canopy index is changing and becoming more sophisticated over time. It was also determined that the method used in 2007 led to an overstatement in the index, whereas the more accurate, automated method adopted in 2015 leaves less room for interpretation.
Care must be taken when canopy indexes are being analyzed, as they take into account only vegetation measuring 3 metres or more. They therefore do not factor in recent planting efforts. In addition, Montréal is having to contend with the emerald ash borer. The insect attacks all ash species and can devastate a tree within a few years. In Montréal, 20% of public trees on streets or in parks are ash trees.
Public property is estimated to occupy just onethird of the City of Montréal’s territory but accounts for more than 50% of the current canopy. If the canopy index is to increase from 20% (2007 level) to 25% by 2025, collective action is necessary. All cities in the Urban Agglomeration, including the City of Montréal and its 19 boroughs, must play a part in this. It is also crucial for industries, institutions, businesses and homeowners, big and small, to engage in this collective effort.
- Increase the canopy cover from 20 to 25% by 2025 (Sustainable Montréal 2016-2020).
- Plant as many trees as possible on public and private property within the Montréal Urban Agglomeration by 2025, with a focus on sustainability (Sustainable Montréal 2016-2020).