As CO2 levels increase, it accelerates plant growth, which leads to increased absorption of CO2 through photosynthesis. In the past, it has been assumed that this led to more carbon being stored in wood and soil, slowing climate change.

In the present study, published in Science, a team of scientists analysed published results from 53 experiments in forests, grasslands and agricultural fields around the world. Each of these experiments measured how increased atmospheric CO2 affects plant growth, production of CO2 by microbes, and the accumulation of soil carbon. The researchers combined the data and compared them with various models and also tested for general patterns across the studies.

The results suggested that the extra carbon provides fuel for soil microorganisms, whose byproducts (such as CO2) are released into the atmosphere. ‘Our findings mean that nature is not as efficient in slowing global warming as we previously thought,’ said the study’s lead author, Kees Jan van Groenigen of Northern Arizona University. ‘By overlooking this effect of increased CO2 on soil microbes, models used by the IPCC may have overestimated the potential of soil to store carbon and mitigate the greenhouse effect.’

This story was published in the June 2014 edition of Geographical Magazine