The natural greenhouse gas sink is smaller than believed

Past analyses of carbon and greenhouse gas exchanges on continents have failed to account for the influence of lakes, impoundments, and running water. This study, published in the journal Science, shows that natural release of the potent greenhouse gas methane from inland waters may be far greater than previously known. By difference, the net absorption of greenhouse gases by natural land environments, such as forests, may therefore be at least 25 % smaller than thought.

This is the conclusion of a study by David Bastviken, Linköping University, Lars Tranvik, Uppsala University, John Downing, Iowa State University, Patrick Crill, Stockholm University, and Alex Enrich-Prast, University Federal of Rio de Janeiro.

The increased greenhouse effect is caused by human emissions of greenhouse gases. Some ecosystems, such as forests can absorb carbon dioxide and act as greenhouse gas sinks, which is important for the greenhouse gas balance and the climate. The role of freshwater environments, integrated into continental environments, has been unclear because of underestimates of the amount of continental water and a shortage of data on greenhouse gas emissions.

Methane emissions from lakes and running water occur naturally and should not be considered an environmental threat. These gas emissions have, however, been difficult to assess and are poorly understood.

– Small methane emissions from the surfaces of water bodies occur continuously, says David Bastviken, but much greater emissions occur suddenly, and with irregular timing, when methane bubbles from the sediment reach the atmosphere. Such fluxes have been difficult to measure.

The authors have summarized methane fluxes from 474 freshwater environments. They have also used updated estimates of the global area of inland waters. Based on these data, they estimated that methane emissions from the freshwaters of the world counter-balance 25 percent of the carbon dioxide absorbed by natural land environments. The large effect of aquatic methane emission is due to the large quantity of gas emission and the stronger greenhouse effect produced by methane molecules compared to carbon dioxide. One implication of this new accounting is that the greenhouse gas sink provided by forests and other land ecosystems is substantially smaller than hitherto believed.

The terrestrial sink may even be lower than we have calculated, says David Bastviken. Because it is difficult to measure methane bubble fluxes and the global area of freshwaters may still be underestimated, we have probably underestimated the methane emissions.

If we do not properly account for natural greenhouse gas sinks and emissions, we may misunderstand the urgency of reducing anthropogenic emissions.

A smaller continental greenhouse gas sink means that the capacity of natural systems to absorb greenhouse gases is very valuable.

– We have to take great care of the remaining forests and other natural greenhouse gas sinks, because we have already reduced their area through deforestation and other land conversions, David says. An accurate accounting of all components of the continental greenhouse gas budget, including the role of inland waters, will help us evaluate the greenhouse gas uptake by land ecosystems in relation to society’s greenhouse gas emissions.

Freshwater Methane Emissions Offset the Continental Carbon Sink
David Bastviken, Lars J. Tranvik, John A. Downing, Patrick M. Crill, Alex Enrich-Prast, Science 7 January 2011: 50. [DOI:10.1126/science.1196808]
Telephone to David Bastviken +46-73 4144970, e-mail david.bastviken@liu.se
Lars Tranvik +46 -73 322 58 30, e-mail lars.tranvik@ebc.uu.se
Pressofficer Åke Hjelm; åke.hjelm@liu.se;+46-13 28 13 95

All latest news from the category: Ecology, The Environment and Conservation

This complex theme deals primarily with interactions between organisms and the environmental factors that impact them, but to a greater extent between individual inanimate environmental factors.

innovations-report offers informative reports and articles on topics such as climate protection, landscape conservation, ecological systems, wildlife and nature parks and ecosystem efficiency and balance.

Back to home

Comments (0)

Write a comment

Newest articles

Lighting up the future

New multidisciplinary research from the University of St Andrews could lead to more efficient televisions, computer screens and lighting. Researchers at the Organic Semiconductor Centre in the School of Physics and…

Researchers crack sugarcane’s complex genetic code

Sweet success: Scientists created a highly accurate reference genome for one of the most important modern crops and found a rare example of how genes confer disease resistance in plants….

Evolution of the most powerful ocean current on Earth

The Antarctic Circumpolar Current plays an important part in global overturning circulation, the exchange of heat and CO2 between the ocean and atmosphere, and the stability of Antarctica’s ice sheets….

Partners & Sponsors