Ponds Absorb As Much Carbon As Oceans

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Professor John Downing is a limnologist (or lake scientist) at Iowa State University. Downing recently led research that found that ponds around the globe could absorb as much carbon as the world's oceans.

Constructed ponds and lakes on farmland in the U.S. bury carbon at a much higher rate than expected; as much as 20-50 times the rate at which trees trap carbon. In addition, ponds were found to take up carbon at a higher rate than larger lakes.

"Aquatic ecosystems play a disproportionately large role in the global carbon budget," Downing said.

"Despite being overlooked in the past, it's small bodies of water that are important because they take up carbon at a high rate and there are more of them than previously thought. The combined effect is that farm ponds could be burying as much carbon as the world's oceans, each year."

The research estimated there are 304 million natural lakes and ponds in the world, covering an area of 4.2 million square kilometers which is twice the area previously thought. As many as 90 per cent of these water bodies are one hectare (two acres) or less in area.

The team’s findings were published in the Feb. 15 issue of the journal Global Biogeochemical Cycles in a paper titled, "Sediment organic carbon burial in agriculturally eutrophic impoundments over the last century."

The team included members from Europe, the U.S. and Canada. The work was sponsored by the National Center for Ecological Analysis and Synthesis and the Iowa Department of Natural Resources.

Downing has presented invited seminars on this research to the International Society of Limnology, the American Society of Limnology and Oceanography, and at several major research institutions in North America and Europe.

Jeremy Biggs, Pond Conservation director of policy and research, said. "It may be that ponds will be the modern equivalent of the swamps that formed coal in the past. But before we all rush into making ponds to trap carbon we need to do some basic research here in the UK. If the rate of carbon uptake in ponds in Europe is the same as that found in the USA study, we may well have discovered an important new natural way of trapping carbon.”

Downing's ongoing research is being carried out in partnership with the United States Geological Survey. This research and his contributions to the Iowa Lakes Survey will investigate the role of small Iowa lakes in the absorption of atmospheric carbon dioxide and other important gases such as methane.