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Warmer weather makes lakes emit more carbon dioxide

David Bastviken

David Bastviken

A warmer climate will lead to the world’s lakes releasing more carbon dioxide into the atmosphere. The storage of carbon dioxide in the lakes’ bottom sediment is strongly dependent on temperature levels. This is demonstrated by LiU researcher David Bastviken and a group of Uppsala scientists in an article in the journal Nature.

“Lakes have a dual role in terms of greenhouse gases. Lakes emit both methane and carbon dioxide into the atmosphere and through this act as sources of greenhouse gases. This is balanced in part by the fact that some of the organic material in lakes is not immediately broken down to methane or carbon dioxide, but is instead stored in the sediments, and this storage serves as a carbon sink”, says David Bastviken, researcher at the Department of Water and Environmental Studies (WES).

Until now it has been unclear what it is that determines the extent to which the organic carbon remains on the seabed, rather than degrades into carbon dioxide. But in an article in the journal Nature, scientists can now show that the level of emission is strongly temperature dependent, regardless of the lakes’ nutritional levels, geographic locations or the chemical composition of the sediments.

The project was a collaboration between researchers at Linköping University and Uppsala University and funded by the Research Council Formas and the Swedish Research Council.

“In other words, lakes’ role as a source of greenhouse gases will be amplified in a warmer climate, while their role as carbon sinks through carbon dioxide storage in sediments will diminish, “ says David Bastviken.

Scientists have made an estimate of how a change in temperature levels will impact on the storage levels in sediments in the northern coniferous forest belt, which runs through Eurasia and North America and contains millions of lakes.

“Based on the predictions of the IPCC climate panel on the temperature rises up to the year 2100, out data suggest that the storage in lake sediments in boreal environments will decrease by between 4 and 27 per cent, which is significant when you consider the number of lakes”, says David Bastviken.

Inland waters play a significant role in the global carbon cycle, despite their covering only three per cent of the Earth’s total land mass. And their role can be expected to change with a change in climate.

“The study highlights an important climate link, where a temperature increase as a result of human activities will result in natural environments starting to produce more greenhouse gases. Or as in this case losing the capacity to collect and bind carbon.

The study also contributes to the emerging realisation that freshwater environments are significantly more important than previously thought in balancing greenhouse gases on a global scale.”

David Bastviken is also coordinator for the aquatic environment studies in another on-going project where scientists from four other Swedish universities are involved:

“In that project we assume a large-scale perspective on the new findings, and one of the aims is to clarify the role of forest lakes in balancing the greenhouse gases in all forest landscapes. We make detailed studies of carbon flows and greenhouse gas levels in the most prevalent eco-types in forest landscapes.”

Even the wetlands on Campus Valla play a small part in the research on natural emissions of methane and carbon dioxide from aquatic environments. Since the beginning of summer a variety of buckets are floating in the ponds in the parks and the amount of greenhouse gases accumulated in the buckets will be measured at the same time as data on temperature, barometric pressure, rainfall and solar radiation is collected.

Therese Winder 2010-08-13

Page manager: therese.winder@liu.se
Last updated: 2010-09-27