Green Infrastructure: Development of a Multi-Scale Strategy Based on Complexity and Resilience in Urban Settings

Climate change is increasingly threatening the green infrastructures of our cities, particularly trees, which are affected by increased environmental stresses and the arrival of exotic insects and diseases. Yet, these trees have been providing, directly and indirectly, and through the urban ecosystem, ecological services from which we derive many benefits for our survival and well-being.

These services comprise support, provisioning, regulation and cultural services. If trees become affected by climate change, these services may be significantly reduced, such as the regulation of the local climate, the control of runoff, the reduction of the heat island effect, or benefits of an aesthetic and recreational order.

• Conduct a review of the current status of trees and urban forests in terms of specific, functional and phylogenetic diversities and the spatial distribution on the territory of Montreal and other Quebec cities;

• Conduct a review of the scientific and gray literature as well as an expert consultation to determine the future threats to trees and urban forests and their diversity, resilience and quantity and quality of services provided;

• Propose a management strategy for the urban forest in a context of climate change adaptation.

• Quantification of ecosystem services provided by urban forests;

• Economic analysis based on willingness-to-pay and the cost of droughts (water stress);

• Production of reforestation scenarios from data of the urban forest heritage and from spatially explicit data on the diversity of trees based on functional and horticultural traits of species;

• Estimation of sensitivity indices based on data on the threats and tolerances of species and the biodiversity effect;

• Measuring the response of trees to water stress using several indicators.

Ecological networks and corridors and ecosystem services in the greater Montreal area (Dr. Gonzalez).

The project’s research framework was expanded to consider ecosystem services when prioritizing natural infrastructures for conservation in the Montreal Metropolitan Community. Quantification of the ecosystem services provided by urban forest cover (400,000 street trees in Montreal), including carbon storage, pollination, flood prevention, and heat island mitigation, was carried out.

For example, Figure 1 shows the results of a spatial prioritization analysis ranking the area’s infrastructures according to the magnitude of their contribution to the ecosystem services analyzed.

Figure 1. Conservation prioritization map using a strategy promoting flood risk reduction, biodiversity conservation and heat island mitigation (Maure et al. 2018).

Economic analysis using the willingness-to-pay method shows that the urban canopy saves more than CAD$4.3 million per year in ecological services. A spatial analysis under three land use change scenarios and four climate change scenarios was also carried out. Ecological services mapping was used to identify priority areas for urban canopy enhancement.

A review of the scientific and grey literature and consultation with experts led to the identification of the main future threats to the area’s trees and forests, the impact of diversity on their resilience, and the quantity of services provided. This was done in order to propose a tree planting strategy to maximize complexity, resilience and consequently the services that urban trees and forests provide.

Issues and risks for urban trees; replanting strategy for resilience (Drs. Messier and Paquette).

A new approach was developed and applied to more than 300 tree species in several Québec cities to analyze tree diversity based on biological characteristics (i.e. functional traits) (Paquette and Messier, several reports). This approach was simplified by grouping the trees present in Québec cities into 10 broad functional groups (Figure 2).

In addition, the effect of functional diversity on tree drought tolerance was analyzed using thermal analysis and growth response following a drought period. However, this effect could not be analyzed since there were no significant drought periods during the study period.

Figure 2. Biological and ecological characteristics of the functional groups and sub-groups formed with the approximately 300 tree species present in Québec cities (Paquette 2016)