Carbon sink found beneath world’s deserts

Deserts around the world could be storing carbon dioxide emitted by human activity. A new study has revealed that vast aquifers underneath deserts could hold more climate-changing carbon than all the plants on land.

About 40 per cent of the carbon dioxide emitted by humans through fossil fuel combustion and deforestation stays in the atmosphere and roughly 30 per cent enters the ocean, according to the University Corporation for Atmospheric Research.

As measurements show that plants do not absorb all the leftover carbon, scientists have been trying to find the so-called “missing carbon sink” – or the place where the additional carbon is being stored.

A new study has now shown that some of the carbon could be disappearing underneath the world’s deserts. Underground aquifers (or bodies of permeable rock) store the dissolved carbon deep below the desert where it can’t escape into the atmosphere, according to the study.

Scientists examining the flow of water through a Chinese desert found that carbon from the atmosphere is being absorbed by crops, released into the soil and transported underground in groundwater—a process that picked up when farming came to the region 2,000 years ago.

The new study estimates that because of agriculture, roughly 14 times more carbon than previously thought could be entering underground desert aquifers every year.

“The carbon is stored in these geological structures covered by thick layers of sand, and it may never return to the atmosphere,” said Yan Li, a desert biogeochemist at the Chinese Academy of Sciences in Urumqi, Xinjiang, and lead author of the study published in Geophysical Research Letters.

Knowing the locations of carbon sinks could improve models used to predict future climate change and enhance calculations of the Earth’s carbon budget, or the amount of fossil fuels humans can burn without causing major changes in the Earth’s temperature, according to the study’s authors.

Although there are likely many missing carbon sinks around the world, desert aquifers are thought to be important. The study’s authors estimate that the world’s desert aquifers contain roughly one trillion metric tonnes of carbon—about a quarter more than the amount stored in living plants on land.

Photo credit: Moyan Brenn/ CC BY 2.0

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