(Edmonton) University of Alberta researchers have determined that while the influence of Northern peatlands on the prehistoric record of climate change was overestimated, the vast Northern wetlands must be watched closely as the planet grapples with its current global warming trend.
Alberto Reyes and Colin Cooke were PhD students in the U of A's Department of Earth and Atmospheric Sciences when they began their research into the response of Northern peatlands to climate change.
Northern peatlands, which are a boggy mixture of dead organic material and water, cover more than four million square kilometres. The largest Northern peatlands occur in the subarctic regions of Canada and Russia. As peatlands grow they sequester carbon in the form of carbon dioxide from the atmosphere. However, as old peat is buried and begins to decompose, it emits large amounts of methane, a potent greenhouse gas.
Reyes says the research began with the examination of radiocarbon dates of ancient peatlands. "We wanted to find out how peatlands first colonized Northern regions at the end of the last ice age," said Reyes. "This was a period of rapid global warming."
Atmospheric carbon dioxide and methane levels rose dramatically 10,000 years ago at the end of the last ice age. "In the past, scientists had suggested that Northern peatlands were an important, if not the principle, source of the dramatic increase in atmospheric methane," said Cooke.
But the U of A team revealed the peatlands did not colonize the North until 500-1,000 years after the abrupt increases in atmospheric methane. "These results show that other methane sources must have contributed to the warming at the end of the last ice age," said Reyes.
The researchers point to tropical wetlands as the likely drivers of the initial rises in methane levels during that period. Today, tropical peatlands are the second-largest source of methane emissions to the atmosphere, after human activities such as the burning of fossil fuels and large-scale agriculture.
Reyes and Cooke say their work points to the miscalculation of the role of Northern peatlands as an example of the complexities involved in studying huge and dynamic areas of the planet. Unraveling how Northern regions will respond to future warming remains a critical research topic for Canada and other Northern nations.
"Our future research will focus on Northern peatlands as nature's own carbon-capture mechanism," said Reyes. "On the flipside of that role we'll look at the peatlands as a major emitter of carbon in the form of methane gas."
The research was published online last month in Proceedings of the National Academy of Science.