The values of soil animals for conservation biology

It has taken time for the international community to accept the idea of biodiversity values, a concept which had previously been restricted to the limited aesthetic and touristic aspects of wildlife. This situation changed following the International Convention on Biodiversity in Rio de Janeiro (1992), which focussed on “the forgotten environmental problem” of biodiversity erosion and made the first clear reference to the values of living species. Biodiversity values refer to direct or indirect, economic or non-economic interest, a given species or ecosystem may represent for human populations. These values are generally split into intrinsic and instrumental (use) values, the last category itself being divided into direct and indirect economic values. Obviously, each of these values carries different weights, and cannot be considered as being weighted equally in terms of justification for species or ecosystem conservation. Soil is probably one of the most species-rich habitats of terrestrial ecosystems, especially if the definition is extended to related habitats like vertebrate faeces, decaying wood, and humus of hollow trees (i.e. epiphytic soils). The diversity of soil communities (sensu lato) thus probably encompasses a large part of terrestrial animals. This highly speciose fauna has been the subject of recent research efforts, and current trends in soil fauna studies include aspects of biology, autecology, ecotoxicology, or functional ecology. During the past 20 years, recognition of the importance of soil fauna in the functioning of soils and by extension of terrestrial ecosystems has been continuously growing, ending in some important applications in agronomy. However, despite the general agreement about the ecological importance of soil fauna and its economic consequences, the absence of concern about this group from conservationists in their studies is conspicuous. This paper aims at presenting soil fauna within the scope of conservation biology concepts, trying to identify the different values of soil fauna and how they participe to the provisioning of key ecosystem services. Finally, the enormous gap between their recognised usefulness and their consideration in protection policies is discussed.