Wetlands - Slow Climate Change

by Gray Merriam

The amount of carbon dioxide in the atmosphere is the inescapable root of climate change. Anything affecting the rate of addition of carbon dioxide to the atmosphere is unquestionably related to climate change.

Wetlands affect the rate of addition of carbon to the atmosphere because wetlands put significant amounts of carbon into long-term storage. This carbon is sequestered by being built into the organic matter that makes up aquatic plants, including algae, and the secondary organic production of tissues in herbivores that eat those plants. When that plant and animal matter dies, much of it sinks into the sediments in the beds of wetlands. The organic compounds containing that carbon do not decompose because they do not have access to oxygen. The water and the mucky sediments seal them away from the oxygen that is required for their decomposition.

Some of this sequestered carbon can get back into the atmosphere by way of chemical changes that do not require oxygen. Some carbon is combined with hydrogen instead of oxygen and this forms methane – one carbon atom combined with four hydrogen atoms – sometimes called marsh gas. Methane can escape to the surface of a wetland and thus into the atmosphere.

So the effect of the wetland on the rate of addition of carbon to the atmosphere depends on the net difference between the carbon that is kept in the sediments minus the carbon that escapes as methane.
For a number of measured temperate wetlands the carbon stored was from 100 to 200 grams of carbon per metre squared per year (g C/m2/y). The escape of methane for those wetlands was from 45 to 55 gC/m2/y. These wetlands were putting into long-term storage about 100g of Carbon per square metre of wetland per year. Each acre of wetland stored about 40.47 Kg of carbon per year.

The Kennebec Wetland Complex in the watershed that feeds Kennebec Lake clearly has an effect on climate change. An example of the services provided by ecosystems to global society.

More information: Mitsch, W. et al. 2013. Landscape Ecology 28: 583-597