From teaching the hydrological functions of healthy soils to CBPR through a replica of Charles and Horace Darwin’s observations on the action of worms

In this memory we report about aims, methods and present findings of the WormEx II experiment. The WormEx II experiment is a 4-years lasting educational experiment and a citizen-based participatory research (CBPR) performed in high-school classes, in view of attracting students’ attention on the hydrological role of healthy soils, through the observation and quantification of earthworm digging activity and of its hydrological role.

The core of the experiment consists in replicating Charles and Horace Darwin’s famous observations on the sinking of stones, published in 1881 and 1901 respectively. We reproduced a couple of wormstones (inspired by that positioned by Horace Darwin at Down House), and we placed them in the garden of the Liceo Copernico high-school in Brescia in March 2022. Since then many sinking measurements and infiltration tests (with different earthworm activity) were performed with the participation of high-school and university students, teachers and faculty staff.

The analysis of the experiment is multi-faceted and deserves intriguing interpretative keys. Firstly students meet Charles and Horace Darwin’s original works on the matter, thus (partially or integrally) reading them, under the guidance of the teachers. They go in depth with the text analysis and through their data, recognizing both Charles’ rigorous epistemological approach based on ample data collection and Horace’s attitude at designing a replicable experiment to obtain controlled and good quality data. This introduces them to the dialectics between data collection and experiment design and replicability, standing at the basis of modern Hydrology and of many natural sciences. Contextually they deal with the scientific relevance of patient practice and long lasting series. According to Charles Darwin’s definition of «minima», students appreciate how meaningful changes in Nature are mostly given by the continue and reiterated superimposition of minimal ones. They observe aspects of earthworm ecology, regarding their digging activity into relationship with the antecedent meteorological conditions and recognize the soil attitute at behaving as a low-pass filter of the meteorological variability.

Finally, by means of managing the datasets of the sinking and of the micrometeorological measures, and interpreting the infiltration tests, they qualitatively and quantitatively compare their findings with ancient ones, and approach the issue of quantitative treatment of data and of scientific reporting, thus attempting to overcome the mainly qualitative approach of most CBPR activities.