Soil macroinvertebrates, actors and indicators of soil-based ecosystem services

Soil management practices are of particular importance, as they are the basis of 60% of planetary ecosystem services. Positive environmental externalities are associated with methods inspired by agroecology, whereas conventional methods generally have elevated indirect environmental costs. Public policies that take this reality into account are needed to make agriculture a solution rather than an obstacle to the regeneration of the planetary environment. Soil-based ecosystem services, the support for primary production, climate control through carbon sequestration, hydrological services and the biodiversity associated to their delivery, are usually associated in "bundles of ecosystem services". We propose to use communities of soil macroinvertebrates, the ones visible at the naked eye, as estimators of all other services to which they are strongly correlated. Macroinvertebrates are represented by a great diversity of biological forms, and indicator species for soil functions have been identified in several studies by scientists. The 15 orders commonly found in most soils are known to soil managers. Estimating their communities is easy and inexpensive with the widely used standard ISO/TSBF method. A numerical indicator constructed from data collected in several thousand sites sampled by this method is proposed, which can be applied everywhere. It allows to calculate for any site a value that has been shown to be a reliable proxy for the global chemical, physical and biological functions that these invertebrates stimulate in the soil, in mutualistic associations with other soil organisms. In conclusion, we discuss the feasibility of a generalized use of this indicator by farmer communities as a support for public policies that will organize the fair recognition and remuneration of positive externalities generated by some practices.