Seemingly innocent ponds could be playing a role in climate change, a new study has suggested. According to researchers from University of Exeter and Queen Mary University of London, rising temperatures could accelerate climate change by reducing the amount of carbon dioxide stored in ponds and increasing the methane they release.
Scientists studied an array of ponds over seven years by experimentally warming them by 4-5ºC to understand how this warming could have an impact on greenhouse gas emissions and rates of metabolism. They found that changes observed after the first year became “amplified” over a longer period and after seven years, a pond’s ability to absorb carbon dioxide (CO2) was reduced by almost half, while methane release almost doubled.
As it goes, lakes and ponds cover about 4 per cent of Earth’s surface (excluding areas covered by glaciers and ice sheets), but they are disproportionately large sources of methane and CO2 to the atmosphere. According to available data, ponds of less than one square metre are responsible for releasing about 40 per cent of all methane emissions from inland waters.
“This is the first experiment to investigate the long-term effects of warming in aquatic ecosystems,” said lead author Professor Gabriel Yvon-Durocher, of the Environment and Sustainability Institute on the University of Exeter’s Penryn Campus in Cornwall. “Given the substantial contribution small ponds make to the emission of greenhouse gases, it is vital to understand how they might respond to global warming.”
Researchers were able to show through the study that warming can fundamentally alter the carbon balance of small ponds over a number of years by not only reducing their ability to absorb carbon dioxide, but also increasing methane emissions.
“This could ultimately accelerate climate change.”
Such effects are known as “positive feedbacks” – where the effects of global warming on components of the biosphere lead to changes that further climate change.
“The amplified effects of experimental warming we have observed in ponds are different to those we typically see on land, where large initial effects of warming appear to diminish over the long term,” Professor Yvon-Durocher said.
“This accelerating effect in ponds, which could have serious impacts on climate change, is not currently accounted for in Intergovernmental Panel on Climate Change models.”