The main component of the climate change currently occurring on Earth is the emission into the atmosphere of greenhouse gases (such as CO₂) whose primary origin is human activities such as the use of fossil fuels. Based on this basic principle, various interrelated phenomena are occurring on the surface of the planet (air, sea and land) which, in many cases, become circular (feedback) processes that increase the scope of climate change itself. . A well-known phenomenon of this type is the decrease in the albedo effect due to the loss of ice masses; With warming, the white surface that reflects solar radiation decreases and, therefore, temperatures increase even more.
A less studied phenomenon until now is how global warming affects the communities of microorganisms (microbiome) that live naturally on the surface and internal layers of soils practically all over the planet (even in Antarctica).
A team led by experts from the University of Vienna (Austria) has now published the results of a study in which they conclude, as the most notable factor, that global warming is facilitating an increase in the variety of species (taxa) of microorganisms that They live on the ground. The authors indicate that the phenomenon must be studied in more depth because until now it was believed that warming only produced greater activity of the microorganisms present, but not an increase in the active species (fungi, bacteria and viruses). Both factors are important because they can cause greater emissions of greenhouse gases such as CO₂. In particular, high-latitude soils contain large stores of carbon that are vulnerable to being lost (released into the atmosphere) with warming due to acceleration of microbial activities.
"Warmer soils harbor a greater diversity of active microbes," summarize the researchers from the Center for Microbiology and Environmental Systems Science (CeMESS) at the University of Vienna in their conclusions. This new study, published in the journal Science Advances (February 23), represents "a significant change in our understanding of how microbial activity in the soil influences the global carbon cycle and possible feedback mechanisms on climate," highlights the University of Vienna in an informative note of the results obtained by its experts.
Until now, scientists have assumed that higher soil temperatures accelerate the growth of microbes, thereby increasing the release of carbon into the atmosphere. However, this increased carbon release is actually caused by the activation of previously dormant bacteria, the authors of the new study say.
"Soils are the largest reservoir of organic carbon on Earth," says Andreas Richter, lead author of the study and professor at the Center for Microbiology and Environmental Systems Science at the University of Vienna. "Microorganisms silently dictate the global carbon cycle, breaking down this organic matter and releasing carbon dioxide," says Richter. As temperatures rise (a scenario considered unavoidable under current climate change), microbial communities are thought to emit more carbon dioxide, further accelerating climate change in a process known as soil carbon-climate feedback. .
"For decades, scientists have assumed that this response is driven by higher growth rates of individual microbial taxa in a warmer climate," explains Richter. In this study, researchers visited a subarctic grassland in Iceland that has suffered more than half a century of geothermal warming, resulting in elevated soil temperatures compared to surrounding areas. By collecting soil cores and using cutting-edge isotope probing techniques, the team identified active bacterial taxa, comparing their growth rates at both room temperature and elevated temperatures, the latter being 6°C higher.
"We saw that more than 50 years of constant soil warming increased microbial growth at the community level," says Dennis Metze, a doctoral student and lead author of the study. "But surprisingly, microbial growth rates in warmer soils were indistinguishable from those in normal temperatures." The key difference was in bacterial diversity: warmer soils supported a more diverse range of active microbial taxa.
"Understanding the complexities of the soil microbiome's reaction to climate change has been a considerable challenge, often making it a 'black box' in climate modeling," adds Christina Kaiser, associate professor at the Center. This new finding transcends the traditional focus on community aggregate growth, laying the foundation for more accurate predictions of microbial behavior and its consequent effects on the carbon cycle in the evolving climate scenario. The insights gained in this study illuminate diverse microbial responses to warming and are vital for forecasting the impact of the soil microbiome on future carbon dynamics.
