NSF Funds Research on Greenhouse Gases Emitted by Wetlands

04/23/2013
By Edwin L. Aguirre

When people talk about climate change, the first thing they often mention is carbon dioxide (CO₂). Although CO₂ emissions get most of the media attention, methane (CH₄) — a colorless, odorless and highly flammable gas that is a major component of natural gas — also contributes greatly to global warming.

“Methane concentrations in the atmosphere are much lower than that of carbon dioxide. However, methane is about twenty-five times more potent as a greenhouse gas compared to carbon dioxide, and it is accumulating faster in the atmosphere than carbon dioxide,” says Prof. Mark Hines of the Department of Biological Sciences and acting dean for the College of Sciences.

Methane is released into the atmosphere mainly by leaky gas pipes, the raising of livestock and emissions from the petroleum industry, but a considerable amount enters from natural sources, especially wetlands in the tropics and high latitudes.

“This natural flux of methane is increasing rapidly due to the fact that the Arctic is warming up faster than anywhere else on Earth and, when combined with melting permafrost, a lot of organic material stored in high-latitude soils is now newly available to be degraded,” notes Hines.

Hines is part of an international team of researchers that was recently awarded a three-year grant by the National Science Foundation (NSF) worth more than $1.6 million. The project aims to use new measurement and remote-sensing satellite technologies to greatly fine-tune our knowledge of methane production in northern wetlands and help create a more accurate model of methane emissions on a global scale.

Other team members include the University of New Hampshire, which is heading the NSF project, as well as Florida State University, the University of Arizona, Stockholm University and Lund University in Sweden, McGill University in Canada, the U.S. National Oceanic and Atmospheric Administration, Applied Geosolutions Inc., and Aerodyne Research Inc.

Pathways to Methane Production

The production of methane is a bacterial process that occurs in the absence of oxygen and is widespread in flooded wetlands. It takes place via two main paths: the conversion of CO₂ to CH₄ when hydrogen is consumed and the splitting of acetic acid into CH₄ and CO₂.

“Our previous work showed that the conversion of carbon dioxide to methane dominates in the north, contrary to temperate wetlands which usually convert acetic acid to methane,” explains Hines. “However, the preponderance of one path versus the other is controlled by environmental conditions, with nutrient-poor acidic wetlands such as bogs converting carbon dioxide to methane, whereas wetlands dominated by vascular plants such as grasses and sedges, like fens, tend to prefer acetic acid as a precursor of methane.”

As the north warms up, the wetlands evolve from bogs to fens, and acetic acid becomes an increasingly important source of CH₄, he says.

“This can lead to much higher rates of methane emission into the atmosphere,” says Hines. “More methane means increased global warming, which exacerbates the conversion to more methane release. Hence, there is a strong positive feedback leading to more warming. The cause and rate of change in the path of CH₄ production are poorly known, but they are essential to predicting future rates of global warming and the consequences of that warming.”

The team will conduct field work in New Hampshire and Alaska and in Canada, Sweden and Greenland to better link vegetation distribution and changes with the rate and pathway of CH₄ production. This includes taking ground samples as well as imaging the wetland areas using small drones.

“This will allow us to expand or ‘scale-up’ ground data to large areas so we can calculate gas production and eventually emissions at continental or larger scales,” says Hines. “These results can be used to predict future methane-production scenarios.”

Surpassing the Tipping Point

Not too long ago, it was thought that a drastic reduction in the production of greenhouse gases, primarily CO₂, could prevent significant global warming from occurring. However, these reduction measures have not been implemented and emissions are continuing to increase.

“It is now clear that considerable warming has already occurred,” says Hines. “Now we talk about trying to keep the warming from increasing even further. We have already surpassed the ‘tipping point’ of reaching a 2° Celsius increase by the end of the century, and we now hope that governments will act to prevent a much higher increase.”

Although 2° Celsius does not seem like much, there are already notable changes in world climate such as severe droughts, powerful storms and severe coastal erosion as sea level rises and storm severity increases.

“These changes are due to human activity and the scientific community is nearly unanimous on this fact,” notes Hines. “Our predictions made thirty years ago about humanity’s effect on climate all came true and almost exactly as predicted. The only prediction that seems to have been a bit wrong was that sea level is rising faster than anticipated. This is only the beginning. Things are destined to get a lot worse and to last for centuries if immediate action is not taken.”

He adds: “Climate change is a global problem requiring global solutions. However, how can we expect the rest of Earth to respond when the United States, which produces more greenhouse gases per capita than anyone, is not willing to do much?”

Technological solutions to decrease emissions, such as capturing CO₂ in the atmosphere and burying it underground, are poorly developed and extremely expensive, as is alternate energy solutions.

“There are ideas of ways to decrease global warming directly by, for example, altering Earth’s upper atmosphere to block the sun’s incoming radiation,” says Hines. “However, there are myriad examples in which humans attempted to change ecosystems that backfired badly, such as introducing non-native animals or vegetation to solve an infestation problem or food shortage, and then ending up with an even worse situation.”