Toronto’s climate was not so hot 120,000 years ago

By Shaheen Bagha, EEB

New analysis of ancient leaves has revealed that Canada’s ancient climate was cooler than previous thought. By examining fossilised leaves, wood and pollen, the Toronto-based team now think that 120,000 years ago parts of Eastern Canada were covered with extensive northern temperate woodland.

Previous analysis of the veins and shape of leaves preserved in ancient interglacial beds from around Toronto misidentified sycamore leaf fossils as maples. This misidentification, along with inaccurate claims that certain insect species were extinct, led scientists in the early 20th century to falsely conclude that Toronto used to be much warmer than it is now.

The fossils, now housed at the Royal Ontario Museum in Toronto, were taken from sediments that extend from the edge of Lake Ontario under much of southern Toronto, and are  known as the Don Formation and the Scarborough beds.  The latest analysis by botanists John McAndrews and James Eckenwalder from Royal Ontario Museum and University of Toronto show that temperate spruce trees dominated the Toronto area, and therefore the climate of the time must have been similar to what it is now; far cooler than the previous predictions.

The adjusted temperatures could help predict the implications of rapid warming global temperatures on plants and animals because determining if animals and plants were able to adapt to a shift in temperatures in the past can tell us if species will respond in a similar manner to future temperature changes. Scientists can use this information to make predictions about which species are threatened because of climate change, and which species might adapt or migrate to higher or lower latitudes.

Shaheen Bagha is a graduate student in the department of Ecology and Evolutionary Biology. She studies the impact of global warming on rice reproduction in order to combat looming food crises due to the impact of climate change on crop yields.