Our work shows conclusively that methane, which is emitted from lakes in bubbles, is the dominant greenhouse gas coming from lakes and surface waters globally. The greener or more eutrophic these water bodies become, the more methane is emitted, which exacerbates climate warming.
Tonya DelSontro, Lead Author & Researcher - University of Geneva.
Green lakes result from disproportionate fertilization by nutrients, such as nitrogen and phosphorus, and when sediment amasses in lakebeds. Such "greening" is referred to as eutrophication.
Our research team assembled the largest global dataset on lake emission rates of carbon dioxide, methane and nitrous oxide. When we analyzed the data, we found that emissions of greenhouse gases to the atmosphere were influenced by the amount of eutrophication but also that lake size matters a lot for carbon dioxide and nitrous oxide.
John A. Downing
If the lakes and other surface waters around the world become more eutrophic it could negate the cutbacks that society makes by decreasing fossil fuel emissions.
"We need to know how much of these greenhouse gases are being emitted to be able to predict how much and how fast the climate will change," said DelSontro. "This paper is significant because we developed a more effective approach to estimate current and future global lake emissions."
The authors point to four main advancements that enabled their results to be more accurate than earlier estimates: Modern advances in satellite and sensor technology, availability of comprehensive geographical data on lakes, a growing number of global lake observations, and enhanced statistical survey designs.
The authors also offer certain fairly simple things people in any place can do to protect the water in their community:
- Decrease fertilizer application on urban and agricultural land
- Manage septic systems to guarantee they work well
- Maintain large buffer or filter strips of vegetation that intercepts stormwater runoff
- Keep streets and curbs clean
Even moderate increases in lake and surface water eutrophication over the next 50 years could be equivalent to adding 13 percent of the effect of the current global fossil fuel emissions. By keeping our community waters clean, we make better water available to future generations and we decrease worldwide emissions of methane that speed climate change.
John A. Downing