Adding inland waters to the equation

Elisse Lorenc

In his most recent research, John Downing, professor of ecology, evolution and organismal biology, has discovered a vital contributor to the global carbon budget.

Inland waters, which entails grasslands, welands, marshes, lakes and rivers, sequester carbon as well as release methane into the atmosphere.

“How well we know the budget of carbon in the atmosphere dictates how good our predictions of climate change are going to be, and up until now fresh water systems have been completely ignored, so we really don’t know how they would contribute to the overall budget,” Downing said.

The release of methane is a natural process. Organic matter that is located at the bottom of a lake or river, is broken down by bacteria which is then released into the atmosphere as methane.

“Methane is a potent greenhouse gas in addition to carbon dioxide and nitrous oxide,” said Kirsten Hofmockel, professor of ecology, evolution and organismal biology. “Typically that’s not considered in budgets and so including methane in these budgets and realizing this is a new source of methane, this could have considerable impacts.”

The release of methane occurs in two different ways. If there gets to be too much methane in the water with respect to how much is in the air, the gas will naturally seek equilibrium between the air and water. The other is ebullition, or forming bubbles, Downing said.

Negating inland waters from the carbon budget isn’t Downing’s only concern, but the increase in methane emissions from these watery enivronments as well.

“Everybody is aware of how CO2 is increasing in the atmosphere and arising changes in temperature,” said James Raich, professor of ecology, evolution and organismal biology. “Methane is doing the same thing, but it’s not obvious why. It’s 20 times more powerful than CO2 in terms of its warming potential.”

Downing is part of an international team of scientists researching the effects between carbon sequestration and methane releases in inland waters. The team of scientists hopes to find a balance between the two.

“The overall picture is people just haven’t looked at freshwaters at all as part of the carbon picture and the greatest rate of everything, emissions, uptake, sequestration, are all found in watery environments,” Downing said.

Hofmockel stresses the urgency in finding the balance.

“Methane release is the opposite of carbon sequestration so it would counteract any source of sequestration, which would then have negative impacts and in determining that balance is really important, methane has a different global warming potential than CO2,” she said.

Downing’s research entails a global caution. Collaborating with scientists from Sweden to Brazil, the team hopes to calculate the amount of methane emitted from inland waters on a global scale.

“We’re all counting on having a good, solid, accurate, carbon budget and yet we’ve completely ignored a very important component and we might ask ourselves what other components have we ignored,” Downing said. “Inland waters are really important, we need to add them to the budget if we want an accurate budget.”