This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Soil is the foundation of our food supply. It stores water, carbon and nutrients and is home to a large share of the world's biodiversity.
More than half of global biodiversity is estimated to live below ground. Yet biodiversity, and with it soil health, is declining worldwide, with consequences for agriculture, food security and the functioning of entire ecosystems. In 2021, researchers from the University of Zurich (UZH) and Agroscope, the Swiss federal center of excellence for agricultural research, launched the citizen science project Proof by Underpants (Beweisstück Unterhose) to draw attention to this often-overlooked ecosystem and collect scientific data.
Following a standardized procedure, 1,000 volunteers buried more than 2,000 pairs of cotton underwear and 12,000 tea bags at around 1,000 locations across Switzerland. Two months later, they dug them up, photographed them and sent them to the laboratory together with a soil sample for further analysis. The results, a map of soil activity, have now been published in the journal Plants, People, Planet.
The analysis shows that the underwear decomposed at very different rates depending on the location, with the decomposition rate providing a measure of biological activity: The more active the soil organisms, the faster they break down the cotton material. The underwear decomposed most rapidly in private gardens, where the researchers found the highest levels of organic matter—ideal conditions for earthworms, fungi, bacteria and other soil-dwelling organisms. Soil organisms were least active in lawns, while agricultural fields and meadows fell somewhere in between.
"Our results show that how soil is managed can significantly affect both soil life and soil quality," says co-study leader Marcel van der Heijden, UZH professor of agroecology. "Healthy, biologically active soil is crucial for fertility, nutrient cycling and many other ecosystem services." Measures that can promote soil life include keeping the soil permanently covered, adding compost, diversifying crop rotations and limiting the use of mineral fertilizers and pesticides. Land use proved to be the most important factor influencing how quickly the underwear decomposed.
Whether a site was used as a garden, meadow, cultivated field or lawn explained the differences better than most of the soil properties measured. Chemical soil characteristics, such as nutrient levels, also played a significant role. The results also show that rapid decomposition of the underwear often indicates high soil fertility and a good supply of nutrients.
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