Climate change set to disrupt urban wildlife, study finds

Animal populations living in North American cities are likely to undergo a significant shift as changes to the Earth’s climate intensify – and that, in turn, is likely to have an impact on us.

That is among the key findings of a University of Toronto study led by Alessandro Filazzola, who was recently a post-doctoral researcher in U of T Mississauga’s Centre for Urban Environments (CUE), a transdisciplinary research centre focused on promoting healthy urban environments.

Filazzola used computer modelling to project the impact of global warming on more than 2,000 terrestrial animal species in the 60 most populated cities in Canada and the United States. He made predictions according to three different scenarios of greenhouse gas emissions and urban land use. 

Published recently in the journal PLOS One, the study shows that across all three scenarios each of the 60 cities will experience both substantial gains and losses of urban species by the end of this century. In Toronto, for example, 40 to 195 species that currently live in Canada’s largest city are predicted to disappear, while 159 to 360 new species could emerge.

“Most Canadians live in cities, and the nature we interact with every day is in our backyard or local park,” says Filazzola, who has a PhD in biology and works as a data scientist focused on conserving biodiversity. 

“The whole sea change in the assemblage of animals that live in our cities will have a large impact on how we behave in our day-to-day activities and what we value.” 

Filazzola conducted the research with Marc Johnson, a professor of biology at U of T Mississauga and former director of CUE. His work was also supervised by Scott MacIvor, an associate professor of biological sciences.

To gather data on animal species, the researchers – who engaged leaders from Credit Valley Conservation, Conservation Halton and the Toronto and Region Conservation Authority to understand their top concerns in managing biodiversity – turned to the Global Biodiversity Information Facility, a free public resource featuring data about all types of life on Earth.

They modelled the historic and future distributions of 2,019 land-based animals in highly developed cities – 13 in Canada and 47 in the U.S. – with more than 400,000 residents. The computer modelling projections were shaped in part by bioclimactically relevant historical variables for each city, including average monthly minimum and maximum temperatures, and monthly precipitation. 

The results predicted the highest introduction of new species in temperate cities – Quebec City and Ottawa in Canada, and Omaha and Kansas City in the U.S. Midwest. The largest declines in species are projected to take place in the subtropical parts of the U.S. and coastal California. Cities in arid parts of the U.S. – including Las Vegas, and Mesa and Tucson in Arizona – are expected to experience the fewest changes in species richness.  

Meanwhile, cities that have historically experienced colder temperatures are predicted to have significantly higher gains in novel species and fewer losses in resident species. Urban areas with historically high precipitation were projected to have the highest species turnover – both the greatest gains and the largest losses. In the scenario with more intense development and greenhouse gas emissions, cities would experience significantly more species lost and gained. 

The urban animals expected to be most negatively affected by climate change are amphibians, canines and loons. 

“When the modelling predicts a big spike in temperature or a big drop in precipitation, you get a unique climate, and some species can endure it and some cannot – these are the ones that are probably going to be the most impacted and most likely to be lost,” Filazzola says. 

The study notes that as urban ecosystems continue to transform due to global warming, shifts in our urban wildlife will have implications for our cultural identity and heritage – given how much animals figure into our national symbols and sports teams, the researchers say – and even our mental health. 

“We know that having more green space and natural areas around us is very important for our well-being,” Johnson says. “If we lose nature, and the animals associated with it, it can negatively affect our psychological health.”