Climate change is forcing wildlife to move north — and they're bringing diseases with them

CBC's Great Lakes Climate Change Project is a joint initiative between CBC's Ontario stations to explore climate change from a provincial lens. Darius Mahdavi, a scientist with a degree in conservation biology and immunology and a minor in environmental biology from the University of Toronto, explains how issues related to climate change affect people across the province and explores solutions, especially in smaller cities and communities.

COVID-19 has shown us how quickly a new disease can spread, upending our lives. Even if it doesn't happen within our lifetimes, research suggests there will be another pandemic and it will likely happen through a disease that reaches humans from animals. 

In Canada, the risk of diseases being passed from animals to humans is relatively low — but not zero. Based on existing trends, some scientists expect the rate of emergence of new diseases to triple over the next several decades due to increased interaction between humans and animals. 

Invasive species — those that enter a new habitat and out-compete native wildlife — may also bring new diseases, which can be devastating. 

With both native and invasive species often having no choice but to move through densely populated areas when searching for new habitats, there is a higher risk of those diseases being passed from animals to humans. 

This is known as zoonosis. 

Zoonosis events can lead to outbreaks of novel diseases, such as SARS-CoV-2, the virus that causes COVID-19. 

Scientists have estimated there are over 10,000 viruses with the potential to infect humans and that are currently residing in animal hosts — and that doesn't include bacteria or other pathogens. 

A recent paper published in the journal Nature shows climate change is increasing the risk of those viruses crossing the species barrier and infecting humans. 

In other cases, known carriers of existing human diseases are being given the opportunity to move into new areas, increasing the risk of transmission.

Here in Canada, many native and invasive species can host and transmit diseases — one of many reasons scientists are wary of species expanding into new areas. 

Enter the blacklegged tick, Ixodes scapularis, found across the eastern provinces, and its cousin the western blacklegged tick, Ixodes pacificus, found on the Pacific Coast. 

Though not likely to cause a pandemic, in Canada, they are the only known carriers of Borrelia burgdorferi, the bacteria that causes Lyme disease, which has been on the rise over the past decade.

They can carry a variety of other pathogens as well.