Scientists Find New Climate ‘Feedback Loop’ in Lakes

Warming global temperatures have helped boost the growth of freshwater plants like cattails in the world’s lakes in recent decades.  Now, scientists have found that this surge in aquatic plant growth could double the methane being emitted from lakes — already significant sources of methane — over the next 50 years.

The research, published in the journal Nature Communications, reveals a previously unknown climate feedback loop, where warming triggers the release of greenhouse gases, which in turn triggers more warming — similar to what is happening with Arctic’s melting permafrost.  Freshwater lakes currently contribute as much as 16 percent of the world’s methane emissions, compared with just 1 percent from oceans.

Lakes produce methane when plant debris is buried in sediment and consumed by microbes.  The scientists studied differences in methane production from biomass that originated in lakeside forests and from dead aquatic plants growing in the water.  They found that forest-derived biomass helped to actually trap carbon in the lake sediment, reducing methane emissions.  But aquatic plant biomass actually fueled methane production.  Lake sediment full of decaying cattails produced over 400 times the amount of methane as sediment with plant debris from coniferous trees, and almost 2,800 times the methane from deciduous tree-filled sediment.

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