10 June 2016
As 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.
A theoretical model of microbial community dynamics provides insight into carbon and nitrogen cycles.
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 and the climate
Models like Kaiser’s provide vital information for researchers looking at the bigger picture of how soil dynamics influence climate change. IIASA researcher Stefan Frank, for example, has been exploring the links between farming practices and climate mitigation. In a recent study, he found that the EU could reduce agricultural greenhouse gas emissions by up to 7% through enhanced carbon sequestration of cropland. These reductions would come through economic incentives (i.e., a carbon price of US$ 100 per ton of CO2) for farming practices that keep carbon in soil. As national policies also have impacts beyond country borders, Frank also assessed how reduction targets within Europe would affect emissions on a global scale. “If strict agricultural emissions targets are only adopted inside Europe this could lead to increased emissions in other parts of the world, which could significantly compromise global emission reduction targets,” he said.
The good earth
Soil is obviously also central to food production. And with an estimated 795 million people today who are undernourished, and a projected population size of 9 to 11 billion by the year 2050, future agricultural production poses a major question. Yet Lal argues that more land for agriculture is not the solution—instead, he says, we need to increase yields on existing land, producing more from less.
IIASA research backs him up. For example, a 2015 study showed that 24–80% more food calories could be produced worldwide by optimizing fertilizer and irrigation methods. Another IIASA study from 2014 showed that imbalances between nitrogen and phosphorus are already limiting production in Africa and could drive yields even lower in the future.
While soil holds great potential for addressing the planet’s food security and climate challenges, researchers also point out the simplest way to reduce pressure on food security and soils could be in our own kitchens—each year an estimated one third of all food is spoiled or thrown away. Lal said, “Each one of us is responsible. There are 7.2 billion of us. If everyone makes a very small incremental improvement, it can have a major impact.”
Text by Katherine Leitzell
Last edited: 20 June 2016
OPTIONS SUMMER 2016
Kaiser C, Franklin O ORCID: https://orcid.org/0000-0002-0376-4140, Richter A, & Dieckmann U ORCID: https://orcid.org/0000-0001-7089-0393 (2015). Social dynamics within decomposer communities lead to nitrogen retention and organic matter build-up in soils. Nature Communications 6: no.8960. DOI:10.1038/ncomms9960.
Frank S ORCID: https://orcid.org/0000-0001-5702-8547, Schmid E, Havlik P, Schneider U, Bottcher H, Balkovic J ORCID: https://orcid.org/0000-0003-2955-4931, & Obersteiner M ORCID: https://orcid.org/0000-0001-6981-2769 (2015). The dynamic soil organic carbon mitigation potential of European cropland. Global Environmental Change 35: 269-278. DOI:10.1016/j.gloenvcha.2015.08.004.
van der Velde M, Folberth C ORCID: https://orcid.org/0000-0002-6738-5238, Balkovic J ORCID: https://orcid.org/0000-0003-2955-4931, Ciais P, Fritz S, Janssens IA, Obersteiner M, See L, et al. (2014). African crop yield reductions due to increasingly unbalanced Nitrogen and Phosphorus consumption. Global Change Biology 20 (4): 1278-1288. DOI:10.1111/gcb.12481.
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