An important natural carbon sink could soon become a carbon source

As long as humans do not find a way out of the climate catastrophe that we have caused, we must rely on natural carbon sinks, such as oceans and forests, to suck up carbon dioxide from the atmosphere. atmosphere. Ecosystems are deteriorating as a result of climate change. Once destroyed, they risk not only absorbing carbon from the atmosphere, but also emitting it.

Ecosystems that harbor a type of carbon-rich soil called peat are the most effective natural carbon sinks on the planet. When they are not disturbed, they store more carbon dioxide than any other type of vegetation on Earth. But when they are drained and deforested, they can release nearly 6% of global carbon dioxide emissions each year. Climatologists worry that many carbon-absorbing peatlands will soon do the opposite.

"The world's peatlands cover only about 3% of the total area of ​​the globe, but contain about 30% of the soil's organic carbon," said Qianlai Zhuang, professor of earth sciences, atmospheric and planets at Purdue University. "Peatlands act as a" terrestrial ocean "because of their carbon sequestration, but will this large amount of peat carbon be released under a warmer climate, causing further warming?"

In collaboration with Sirui Wang, Ph.D. candidate for Purdue, Zhuang has turned to the peat bogs of the Peruvian Amazon to try to answer this question.

According to a land-based model dating back 12,000 years to 2100 AD, this relatively small basin could lose up to 500 million tons of carbon by the end of the century. This represents about 5% of global annual carbon emissions from fossil fuels, or 10% of US emissions, released into the atmosphere.

According to most estimates, South America will become both warmer and wetter by the end of the century. The conclusions of Zhuang, which were published in Proceedings of the National Academy of Sciences Monday, show that higher temperatures lead to greater peat carbon loss, while increased precipitation slightly improves peat carbon accumulation in the long term. Together, this will likely increase peatland carbon losses in the atmosphere.

The peatlands of northwestern Peru remain almost intact, but this is not the case in most places where there are large peat stocks, which are being cleared to make way. to agriculture. Peatlands in parts of the world, including Canada, Siberia and Southeast Asia, have already become important sources of carbon. The same fate could soon arrive for the Peruvian peat bogs.

"If the area we examined could represent all Amazonian or tropical peatlands, the loss of peat carbon in the atmosphere under future climate scenarios should be of great concern to our society. "Zhuang said. "The intensification of agriculture and the increasing disruption of land use, such as forest fires, threaten the persistence of peat carbon stocks." These peatland ecosystems can turn into sources of carbon instead of sinks, unless the necessary measures are taken. "

Explore further:
Peatlands will store more carbon as the planet heats up

More information:
Sirui Wang el al., "Potential passage of a carbon sink to a spring in Amazon bogs under a changing climate" PNAS (2018). www.pnas.org/cgi/doi/10.1073/pnas.1801317115