Global warming increases greenhouse gas capture by Canadian prairie lakes

News Release Release Date: February 25, 2015 12:01 p.m.

A ground-breaking study led by scientists at the University of Regina shows that decades of global warming have changed the chemistry of Canadian prairie lakes, allowing them to capture carbon dioxide (CO2) from the atmosphere. The study was published online on February 25, 2015, in the journal, Nature. It also shows the increase in CO2 capture offsets about one-third of CO2 emissions from agricultural activities on the Prairies.

The authors, led by Dr. Kerri Finlay, measured historical changes in climate conditions, ice cover on lakes, and the chemical composition of water in 26 lakes in southern Saskatchewan. This area includes about 40 per cent of agricultural lands in Canada. All lakes that were studied showed  marked declines in ice cover as a result of global warming, leading to reductions in the acidity of lake water, and an increase in ability of the water bodies to capture CO2 from the atmosphere.

“The fact that all lakes in a quarter-million square kilometer area did the same thing at the same time suggests this pattern is of global significance,” explains Dr. Finlay.

The study was conducted as a collaboration of researchers at University of Regina and University of Minnesota.  Other co-authors are Dr. Richard Vogt and Dr. Matthew Bogard of the University of Regina Limnology Laboratory, Dr. Björn Wissel and Dr. Gavin Simpson of the Institute of Environmental Change and Society at the University of Regina, and Benjamin Tutolo of the University of Minnesota. 

Research funding came from the Natural Sciences and Engineering Research Council of Canada, Canada Research Chair program, Canada Foundation for Innovation, and the Province of Saskatchewan, which helped fund the Institute of Environmental Change and Society where many of the analyses were performed. 

Nature, published in the United Kingdom, is the highest ranked international journal in the field of environmental science.

Note: News Release revised Feb. 25 at 2:30 p.m. to clarify publishing date in Nature was Feb. 25 online, not Feb. 19.


CO2  and lakes

Burning fossil fuel and deforestation are two key ways humans increase the amount of carbon dioxide (CO2) entering the atmosphere. Once in the atmosphere, this greenhouse gas can increase global temperature by trapping heat, unless the gas is first captured by natural CO2 traps or sinks. 

"A substantial amount of the carbon dioxide emitted during fossil fuel burning is absorbed by the oceans,” says Dr. Lars Tranvik, carbon expert and member of the Royal Swedish Academy of Sciences. “Finlay et al. show that (prairie) lake types are common around the globe and may also act as a carbon sink in response to global warming.”

These prairie lakes have been studied since 1993 by members of the University of Regina’s Institute of Environmental Change and Society as part of the Qu’Appelle Valley Long-Term Ecological Research program. Now in its 22nd season, the Qu’Appelle project is one of Canada’s longest running freshwater research programs. Dr. Leavitt, who also directs the Canadian Institute of Ecology and Evolution, says these long-term research programs are essential for understanding the decades-long effects of climate change and human activities such as urbanization, land use change and atmospheric pollution. 

“The importance of long-term studies is clearly illustrated by the world-renowned Experimental Lakes Area in northwestern Ontario, where research has uncovered the hidden effects of nutrient pollution, acid rain, hormone pollution and many other environmental stressors,” says Dr. Leavitt. 

“Until this study, it was assumed that atmospheric warming would increase CO2 emissions from lakes,” says Dr. Jonathon Cole, international authority on lakes and greenhouse gases with the Cary Institute of Ecosystem Ecology in Millbrook, New York. “Now it appears that shorter duration of ice, especially in the hard water lakes, has led to an increase in pH, switching the lakes from sources to sinks of atmospheric CO2.” 

This switch is equivalent to between 25 per cent and 35 per cent of all agricultural CO2 emissions in the study area, meaning that the lakes temporarily help slow the rate of global warming, says Dr. Leavitt, a Canada Research Chair and corresponding author of the report. 

While prairie lakes give society a better chance to develop engineering solutions to CO2 buildup, such as Saskatchewan’s Boundary Dam project, lakes by themselves are only a temporary means of offsetting industrial greenhouse gas emissions.       

“At some point, ice cover will decline to where there can be no further change in CO2 capture by lakes,” explains Dr. Leavitt.  “Furthermore, because these same lakes are heavily used for domestic, agricultural and mining water uses, and are subject to desiccation by droughts, we should not rely on them to solve the global warming problem.” 

"Their study is a clear example of how climate change affects ecosystems and alters their interactions with the atmosphere. It also illustrates the complexity and diversity of responses to warming," Dr. Tranvik says.

Dr. Finlay and the co-authors note that Canadian prairie lakes experience nearly 50 days less ice cover now when compared to records from the late 19th century. However, rather than declining smoothly from year to year, this long-term trend is punctuated by decades-long periods when temperature and ice cover change rapidly, even reversing in some decades, such as the middle of the 20th century when atmospheric ash from volcanoes reflected heat away from the Earth. The effects of global warming are highly apparent in the Canadian Prairies, where average temperatures are near freezing and small changes in temperature have a large effect on the duration of ice cover.

“Really, it was just good luck that we started to study the effects of climate in the late 1990s when atmospheric temperature increased rapidly, ice cover declined, and the lakes started to suck in CO2,” Dr. Leavitt says. 

Although the report focused mainly on lakes of southern Saskatchewan, the findings could be relevant to a region of nearly 15 million square kilometers. This enormous area is located mainly in the middle of the northern continents where temperature, precipitation and soil conditions are broadly similar to those found in the Canadian Prairies. In fact, the authors note that changes in ice cover and water chemistry like those in Canada have been recorded in the Caspian Sea, a basin which includes nearly 40 per cent of all hardwaters on the planet.

“Although it’s difficult to scale up accurately to encompass the entire planet, our study suggests that if hardwater lakes in this large region experience the same type of global warming, then they may exert an important influence on the global carbon cycle,” says Dr. Leavitt.

Dr. Peter R. Leavitt
Canada Research Chair in Environmental Change and Society
Director of Canadian Institute of Ecology and Evolution
Director of Institute of Environmental Change and Society
University of Regina
Cell:  (306) 591-2659
Skype: PeterRLeavitt (in Saskatchewan, Canada)

Please note: Dr. Leavitt is currently on sabbatical leave as a Fulbright Visiting Research Chair at University of California, Santa Barbara. He is traveling from Feb. 19 to March 24, and can be reached by email, Skype and cell phone.


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