Seite - 18 - in options, Band summer 2016

18 options + summer 2016 www.iiasa.ac.at A s we hike along woodland paths, or rush down crowded sidewalks, we rarely think about the ground beneath us. Yet under our feet, the soil teems with microbial life that turns old life into new—breaking down dead plant and animal material into the nutrients needed for new growth. This process releases gases like CO2 and methane that contribute to global warming but on the other hand soil can also sequester these gases, locking them away and protecting the planet from future warming. Healthy soil is also fundamental to farming and vital for clean water. But increasingly, soils are under pressure. “Just like birds and animals can be endangered, some soils are endangered,” said soil scientist Rattan Lal during a public  lecture at IIASA last winter. The question is how resilient is the soil system? It can recover from many perturbations, Lal  said, but if pushed too far, through erosion, top soil removal, or  unsustainable farming practices, it can reach a tipping point called “irreversible  degradation,” transforming the landscape from verdant farmland to a wind‑blown wasteland in just years. From the tiniest microbes to the big picture of climate change and food security, IIASA researchers are exploring how soil works and interacts with other planetary systems. Their findings suggest that taking better care of soil can help with mitigating climate change, protecting biodiversity, and feeding the planet’s growing  population. THE SECRET LIFE OF SOIL To understand how soil works at  the smallest levels, IIASA researchers have been developing a theoretical model of microbial interactions in soil that helps explain the processes of decomposition and carbon uptake and storage. In a recent study, Tina Kaiser, a former IIASA postdoctoral fellow, now an assistant professor at the University of Vienna, used this model to examine the social interactions between soil microbes. She showed that microbes that rely on other microbes around them to make enzymes for digesting plant material can regulate the rate of decomposition and increase the amount of microbial remains in the soil. The study identifies a new possible control mechanism—enabled by social interactions among individual microbes—that may help to explain the massive reservoir of carbon and other nutrients in soil. “The unique thing about this model is that it simulates the life and death of individual microorganisms in a tiny space, and  can encompass the positive and negative influences between neighboring microbes,” says Kaiser. “In contrast to a traditional soil decomposition model, our model can elucidate mechanisms that depend on social dynamics that emerge on the microbial community level, but are driven by individual interactions among microbes competing for food and space at the smallest scale.” Soil on our planet—fundamental to agriculture,  biodiversity, and water— is under increasing pressure from  human influence.  But it may also hold the solution to  some of our most pressing problems. Soil in the spotlight