How the vicious circle between soil, microbes and climate change works

Researchers warn: soil microbes react to global warming by emitting huge amounts of carbon dioxide. A study in a tropical area shows alarming data

by Matteo Cavallito

 

According to several scientists the interaction between global warming and soil microbes could worsen the effects of climate change in terms of increased carbon emissions. The latest alarm has come from a study released in the journal Nature Communications. A research team led by Andrew Nottingham, an ecologist at the University of Edinburgh, warmed a portion of tropical soil on the island of Barro Colorado, in Panama. Their first goal was to emulate temperatures expected in the coming decades. The CO2 release that was measured o exceeded by 55 percent the amount recorded in soils not exposed to the heat sources. “The loss rate is huge and it’s a bad news story,” said Nottingham, quoted by The New York Times.

Microbes play a key role

The main problem is the role of microbes, which are key players in the regulation of the soil ecosystem, but also critical factors in the climate change scenario. Funded by the EU, the Tropical Carbon project led by the University of Edinburgh aimed to reveal the interactions between microorganisms and rising temperatures. Carbon stored in the soil surface, writes the NY Times, “feeds hordes of bacteria and fungi, which build some of it into more microbes while respiring the rest into the atmosphere as carbon dioxide.” Many of these microbes “grow more active at warmer temperatures, increasing their digestion and respiration rates.” The data “is another example of why we need to worry more” about how fast the Planet is warming,” Eric Davidson, an environmental scientist at the University of Maryland who was not involved in the research, told the newspaper.

Tropics store one third of global carbon

You just have to look at a few numbers to understand the extent of the discovery. “Tropical soils contain one-third of the carbon stored in soils globally,” according to the study. “So destabilization of soil organic matter caused by the warming predicted for tropical regions this century could accelerate climate change by releasing additional carbon dioxide to the atmosphere”. The tendency of tropical soils to release CO2 at greater rate than those at higher latitudes has been well known for quite long. However, numbers recorded during the experiment were significantly higher than expected.

 

Worrisome scenarios

As early as the 1990s, researchers began investigating the problem of emissions generating from warmed soils. A 2016 study conducted in 49 different sites in Asia, Europe and North America had suggested that by 2050 global soils could release the same amount of CO2 emitted by a nation as large as United States. A study carried out in California and published in 2017 had found a 34% to 37% growth in the respiratory activity of soil microbes in response to a 4°C increase in temperature. Those numbers are impressive but still significantly lower than those identified by the Nottingham research.

According to reserchers estimates quoted ny NY Times, if the data found by the latest study were confirmed across the whole Tropics, “65 billion metric tons of carbon would enter the atmosphere by 2100 — more than six times the annual emissions from all human-related sources.”