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Ontario lake holds climate clues


Dr. Francine McCarthy and her team drag a sediment core across Crawford Lake. Click here to find out more about Dr. McCarthy's work
Dr. Francine McCarthy and her team drag a sediment core across Crawford Lake. Click here to find out more about Dr. McCarthy's work

Alexandra Pope, staff writer

April 4, 2011 — Crawford Lake in Milton, Ontario has long been a popular draw for nature enthusiasts because of its peaceful forest setting and rich Iroquois history. But beneath its pristine waters, the lake hides clues about the historic relationship between people and their environment.

Layers are clearly visible in the sediment core, each one providing evidence about the weather and human activity around the lake
Layers are clearly visible in the sediment core, each one providing evidence about the weather and human activity around the lake

On a chilly January day, Dr. Francine McCarthy and a team of scientists from Toronto and Austria hiked across the frozen lake, dragging sleds loaded with coring equipment.

Their mission? To extract sediment cores from the bottom of the lake.

McCarthy, a professor of Earth Sciences at Brock University in St. Catharines, Ontario, is interested in what the lake has to say about changes in climate and how human behaviour impacted the environment.

“I’m interested in how things have changed in the past, both in the lake and in the surrounding area,” she told The Weather Network's Kelly Noseworthy.

Crawford Lake is a “meromictic” lake, making it ideal for this type of research, McCarthy explained.

“The bottom waters have no oxygen, so nothing can live down there (and) it doesn't get disturbed,” she said.

That has allowed layers of sediment to pile up over thousands of years. Just as the rings inside a tree reveal information about the weather over the tree's lifespan, corn pollen, charcoal and other deposits in the sediment layers offer clues about the climate in the Crawford Lake area and how its human inhabitants adapted.

McCarthy, left, and a student examine a sediment sample in the lab
McCarthy, left, and a student examine a sediment sample in the lab

The layers of sediment are developed and analyzed in the lab, and McCarthy and her team can piece together the agricultural history of the area, from the Iroquois settlement to the arrival of Euro-Canadian settlers in the 19th century.

“We can see what happened to the plankton, to the sediments, to the vegetation,” she said.

That information could prove useful for further study of how human activity affects ecosystems.

“We do have a strong impact on the climate and on the environment, on the quality of the water,” McCarthy said. “I'd like for people to recognize that it's inevitable.”

As for Crawford Lake, conservation officials are doing their best to make sure this incredible scientific and historic resource remains intact. Swimming, boating and fishing on the lake are strictly prohibited, but those curious about its unique history can check out the Visitors Centre or explore the elevated boardwalk and interpretive stations around the lake.

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