Study: Agricultural Lands May Store More Carbon Dioxide in Rivers Than Forests

A new study demonstrates a decades-long increase in the export of dissolved alkalinity from the Mississippi River – a process that removes the greenhouse gas carbon dioxide from the atmosphere – and also suggests that agricultural lands may sequester more atmospheric carbon dioxide in rivers than forests.

The study, conducted by researchers at the Yale School of Forestry & Environmental Studies and the Institute for Ecosystem Studies in Millbrook, N.Y., was published in the July 4 issue of Science magazine.

Atmospheric carbon dioxide (CO2) dissolved in rain and water in the soil acts as an acid, reacting with subterranean rocks to form dissolved carbonate alkalinity, which is then transported to the ocean. Peter Raymond, assistant professor of ecosystem ecology at Yale, and Jonathan Cole, an aquatic biologist at the Institute of Ecosystem Science, show that dissolved carbonate alkalinity emanating from the Mississippi River, which is the largest river in North America, has increased dramatically over the past 47 years. They argue that the increase in dissolved alkalinity export is linked to increases in precipitation, which are documented for the Mississippi watershed. Scientists believe that the atmospheric buildup of carbon dioxide is contributing to climate change.

“These findings have two important implications,” said Raymond. “First, they demonstrate the ability of a large watershed to sequester more atmospheric CO2 in response to increases in rainfall, itself a projection of global warming. Second, previous researchers have argued that re-converting agricultural fields to forests increases the removal of atmospheric carbon dioxide by locking it away in living trees and soils. But we show that agricultural lands export more dissolved carbonate alkalinity than forested lands and, therefore, may sequester more atmospheric carbon dioxide than forests through this pathway.”