July 30, 2014

Bringing nature back to the city

Almost three-quarters of southern Ontario wetlands are developed and home to many species at risk

Last spring, falcons nested on a ledge of the Harlequin building in North York

Last spring, falcons nested on a ledge of the Harlequin building in North York

Have you ever thought about the grass that grows in sidewalk cracks? These hardy plants are routinely trampled, savaged by extreme summer heat, washed out by rainfall and buried by winter snow. To survive these conditions is a testament to the plant’s resilience, but it rarely gets attention.

That’s why I’m intrigued with the work of Nova Scotia researcher Jeremy Lundholm and his team at Saint Mary’s University. Their research demonstrates something simple and surprising: hardy species found in these environments are similar to those occupying nature’s own inhospitable spaces — steep cliffs and barren rock slopes.

While the connection between pavement and cliff face isn’t immediately obvious, it makes sense. Plant species that succeed in sidewalk cracks have similar qualities to ones that have adapted to inhabit crevices in exposed, rocky, windswept places.

As Lundholm says, this sort of research demonstrates that rather than seeing our communities as entirely human-created, unnatural environments, we should recognize that urban spaces are in many ways “structurally and functionally equivalent” to natural ecosystems.

In a recent article for the Nature of Cities, ecologist Eric W. Sanderson suggests we try to “conceive of cities in their entirety as ecological spaces.” This vision includes all streets, buildings and parking lots interacting with soil, water, air and “everyone and everything that participates in the great congress of life on Earth.”

Within this ecosystem, species are constantly adapting. The Smithsonian Conservation Biology Institute’s Migratory Bird Center found their subjects often adapt to human environments. Some songbirds have learned to survive in noisy urban landscapes by changing melodies they use to communicate. They sing higher notes to trump ambient city noise, and deeper notes in areas with many buildings and hard surfaces. Nesting on the ledges of high-rises rather than cliff faces has even helped peregrine falcons adjust to city life and assisted their post-DDT comeback.

Yet, the speed and scale of urbanization in Canada has pushed many native species to the brink of extinction.

Ducks Unlimited found that over 72 per cent of the original wetlands in southern Ontario have been developed, and the region is now home to about one-third of the province’s species at risk.

While we need to show some love to the current occupants of nooks and crannies, we must also redouble our efforts to bring nature back to the city and enhance what assets remain.

Efforts like the Rona Urban Reforestation program are on the right track. The hardware retailer is helping to green urban spaces with its support for planting thousands of trees in Canada’s cities. This past summer it also started a pilot program aimed at promoting native shrubs and trees through in-store nurseries. Planting native species in our gardens and communities is increasingly important, because indigenous insects, birds and wildlife rely on them. Over thousands of years they have co-evolved to live in local climate and soil conditions.

Ultimately we need to recognize that while humans continue to build urban landscapes, we share these spaces with other species. 

David Suzuki is the host of the CBC’s The Nature of Things and author of more than 30 books on ecology.