When governments discuss measures to address dramatic biodiversity loss at COP15, the protection of large land and marine areas and sustainable practices in forestry, fisheries and agriculture are at the heart of the discussions.
However, the underlying causes of biodiversity loss lie largely in our current patterns of production and consumption and in the overexploitation of nature by a population that today numbers more than eight billion people. And more than half of these eight billion people already live in cities…
City dwellers directly and indirectly determine the future of biodiversity on our planet. Directly, because cities continue to expand. Indirectly, because the increasing use of resources by city dwellers is changing land use elsewhere, whether for infrastructure or industrial-type agricultural and energy production, and all of this is reducing natural habitat.
Over the past 20 years, Canada’s nine largest metropolitan areas have grown by 1,700 square kilometres, or 3.5 times the size of the island of Montreal. This corresponds to an increase in urban sprawl of 34%, while the population has only increased by 26%. Each Canadian now uses 336 m2 of urbanized territory, i.e. 6% more than in 2001.
An article written by colleagues from the Weizmann Institute appeared in the journal Nature in 2020 impressively shows that man-made mass has now exceeded all living biomass on our planet. Buildings and infrastructure dominate with 1100 gigatons and have a mass greater than that of all the trees and shrubs combined, which is 900 gigatons. Plastics, at eight gigatons, are twice the weight (four gigatons) of all animal species. At the beginning of the XXe century, man-made products accounted for only 3% of the total biomass. This shows us that we are truly in the Anthropocene!
The contribution of cities to biodiversity therefore requires a dual strategy: on their own territory, urban sprawl must be stopped and biodiverse green spaces must multiply again; In terms of resource use, cities need to embrace circular economy concepts by minimizing resource inflows and resulting waste, while residents need access to sustainably produced food. All of these measures contribute directly to mitigating climate change, since energy and resources are used more efficiently in these green, compact and livable cities, where it is easier to walk around than in sprawling suburbs.
There is much talk today about nature-based solutions and the related concept of ecosystem services: food or water provisioning services; regulating services improving air quality, lowering temperatures or managing rainwater; habitat services providing living spaces for organisms; and cultural services promoting recreation and providing psychological benefits. These discussions reveal a very anthropocentric vision of what nature can do for us, especially since these “services” are generally inexpensive. No wonder they are attractive…
But if we are to quantify ecosystem services within the paradigm of our society where money reigns supreme, let us do it and place a high value on the accessibility of parks, green spaces, green backyards and urban farms.
In this vein, the City of Montreal’s Climate Plan promises half a million additional trees on the island by 2030 as part of a $1.8 billion greening project. These trees should be planted in the right neighborhoods because there is a clear correlation between neighborhood wealth and access to green spaces. The spatial distribution of vegetation in Montreal shows that low-income populations have less access to vegetation and trees on public land than in their private backyards. Across the island of Montreal, the wealthier neighborhood of Mount Royal, with its median income of $110,000, has 40% tree cover, while in Hochelaga-Maisonneuve, where the median income is amounts to $40,000, it is only 11%.
Last but not least, a neighborhood’s walkability increases if it is green and compact, with amenities within walking distance. Greening is not always synonymous with a park, as it can also mean street greening, an urban farm or community gardens. Even diehard city dwellers would love to hear the birds chirping around town. Thus, if cities and their inhabitants are today responsible for the loss of biodiversity, they can also be the drivers of the shift towards a sustainable future.