Knowledge on soil invertebrate macrofauna and bioturbating vertebrates: a global analysis using data science tools.

Soil fauna support life aboveground, are important for terrestrial ecosystems and are crucial for soil health and plant- protection. Approximately 23% of all known species are animals associated with soils, but there are many taxa with a low proportion of described species. The soil macrofauna, i.e., the invertebrates visible with the naked eye, include ca. 500 thousand species belonging to seven phyla and 47 taxonomic groups, while the soil megafauna are vertebrates that live, feed, nest in the soil or find refuge there. In the present study we evaluate knowledge and expertise on large soil fauna at country and global level, by assessing the most studied taxa, potential uses and study/sampling methods using bibliographic information and data science tools. We applied customized queries and a database in PostgreSQL connected with the R statistical program, to identify worldwide scientific output as a proxy for expertise in various subtopics covering eight macroinvertebrate taxa (ants, beetles, centipedes, earthworms, millipedes, spiders, termites) and nearly 60 megafauna taxa belonging to four Classes. Publications associated with author’s country affiliations, were retrieved from Web of Science between 2011 and 2022 (macrofauna) and 2014 and 2023 (megafauna). Knowledge on soil macro and megafauna was not evenly distributed among the countries and even within the same continent. Regionally, authors affiliated to China, India, Australia, the USA, Brazil, South Africa, France, United Kingdom, Germany and Italy published the most depending on the macrofauna taxon and subtopic. Earthworms were the most studied soil macroinvertebrate worldwide and soil macrofauna were widely used as bioindicators, while bioturbating vertebrate publications were mainly from authors affiliated to USA, China, Australia and Brazil and primarily on rodents and reptiles. Especially in the African continent a major knowledge gap was identified in all aspects of the present analysis. There is a clear need for further work on soil fauna as well as a collaborative a coordinated effort to promote investment and capacity building in the countries lacking expertise, aiming to improve sustainable soil management and use and the long-term conservation of soil biodiversity.