New study by researchers at Freie Universität published in “Nature Communications” shows that independent environmental stressors such as heat, drought, and microplastics affect soils differently when combined
№ 003/2026 from Jan 14, 2026
Global change – a term that encompasses climate change and phenomena such as changes in land use or environmental pollution – is increasingly putting ecosystems around the world under pressure. Urban soils in particular are susceptible to stressors like heat, drought, road salt, nitrogen deposition, surfactants, and microplastics. To date, the impact of these stressors has often been researched individually, i.e., with the impact of each individual stressor measured in isolation. This approach is, however, not representative of real-world scenarios as these factors almost always appear in combination. A new study carried out by researchers at Freie Universität Berlin shows that when these stressors are combined, their impact can change fundamentally. Even factors that have a neutral or positive effect by themselves can present an additional strain on soil health when combined with other stressors. The study, “Global Change Factors Differ in Effect when Acting Alone and in a Multi-Factor Background” was published in Nature Communications and is available online at https://doi.org/10.1038/s41467-025-68155-9.
The study investigated how stressors including warming, drought, and pollution affect soil health both on their own and when they occur together. The results show that factors that appear neutral or even positive when examined singly can, in combination, degrade soil structure or suppress the activity of microbes that are important for ecosystem functioning. This was especially evident in the case of soil warming. For example, when higher temperatures were considered alone, they were shown to actually boost the activity of microbes involved in stabilizing the soil. However, when higher temperatures occurred together with other stressors, the soils suffered. One possible reason for this is that warmer conditions speed up evaporation, which concentrates harmful substances in the soil water. These concentrated toxins then damage the microbes and lead to less stable soil aggregates – an effect that only shows up in experiments with multiple stressors.
“Experiments repeatedly show that individual treatments with global change factors such as higher temperatures can have positive effects on soils,” says biologist Rebecca Rongstock, lead author of the paper and doctoral student in the Rillig Group – Ecology of Plants at Freie Universität Berlin’s Department of Biology, Chemistry, Pharmacy. “So why should we still protect our soils from such factors? A key reason is that we simply don’t know how stressors interact when they occur together.” Together with colleagues Huiying Li and Matthias Rillig, Rongstock examined 140 soil samples using a novel experimental setup. The team compared the impact of six combined soil stressors with the impact of combinations that left out one factor at a time. In the experiment the researchers measured, among other things, the activity of soil microbes and the stability of soil aggregates, i.e., the crumbly structures that are essential for ventilation, water infiltration, and microbial life within the soil.
The study highlights the fact that ecological risks can only be realistically assessed when environmental factors are examined systematically and in combination with each other. Matthias Rillig, soil ecology professor at Freie Universität and senior author of the study, says “If we want to protect ecosystems, the most effective course of action is not necessarily to focus on the factors that show the biggest individual effects. As multiple factors of global change interact almost everywhere, it may be wiser to target the combination of factors that, together, produce the strongest negative outcomes.” At the same time, the research findings point to ways to promote recovery. If we can reduce or eliminate individual stressors – even those that seem harmless or beneficial when considered alone – core soil functions could significantly improve.