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Freshwater bodies are a larger source of methane than expected

By Jose Neves     Mar 7, 2011 in Environment
According to a recent international study, lakes, rivers and other freshwater bodies emit unexpected amounts of methane, a powerful greenhouse gas. Indirectly, this could impact the expected effects of reforestation programs to fight climate change.
Greenhouse gas emissions from freshwater bodies amount to one quarter of the carbon stored in continent soils said lead David Bastviken from the University of Linköping (Sweden).The study was published in Science. It was long thought that their contribution to carbon balance was negligible because
of the relatively small surface of lakes and rivers compared to land. But we were mistaken
.
The international team comprised of American, Swedish, and Brazilian members directed by Mr. Bastviken concludes that emissions of methane represent about a third of freshwater’s greenhouse gases. The researchers analyzed more than 474 ecosystems in different parts of the world to draw their conclusions.
This means that forests and other vegetation, which are carbon sinks, will offset
less significantly polluting emissions from lakes and rivers. In connection with agreements on the fight
against climate change, it is possible for an emitter of greenhouse gases to buy carbon credits (a licence to pollute) sold by organizations doing reforestation. The results of Bastviken’s study could make these pollution permits cheaper.
The Swedish geochemist, however, reluctant to venture under these assumptions. "Emissions of GHG
freshwater certainly vary according to latitudes and the specific conditions of ecosystems. In the North, for example, emissions occur especially during the formation and the melting of ice. We believe our estimate is conservative, the emissions bodies of freshwater could represent an even higher proportion of carbon stored in land, half instead of a quarter. But it’s still too early to apply these figures to reforestation programs.
On the other hand, these results indicate that the impact of hydroelectric dams and their reservoirs are much
more negative than expected. Yves Prairie, UQAM biologist who studied CO2 emissions from freshwater bodies, confirms that these results change completely the calculations of the continents contribution to greenhouse emissions. Before, we had a carbon footprint for
oceans, continents and atmosphere
said Prairie. Now, a separate balance sheet for freshwater and soil will be required.
A study he conducted in the Eastmain tank, shows that 11% of the sequestered carbon in soils settles to the bottom of freshwater streams, 42% is released into the atmosphere and the rest gets into the Ocean.
More about Co2, Methane, Freshwater ecosystem, Freshwater
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