Putting earthworm conservation on the map: Shortfalls and solutions for developing earthworm conservation

Abstract

Earthworms are keystone organisms that influence both soil function and community assembly of other soil organisms. However, soils are increasingly threatened by global change, so there is an urgent need to consider earthworms in conservation strategies. Earthworm monitoring has been promoted in numerous European and country research programs, and the global interest in earthworm conservation is rising, resulting in a rapid increase in the availability of earthworm data. However, most research focuses on a limited number of local-scale indicators, mainly based on abundance, biomass, and species richness of assemblages along with Bouché's ecological categories. We argue that these metrics are insufficient to effectively address earthworm conservation issues. We suggest four ecological characteristics which may be more informative for the development of conservation plans. Measurement of how much a species is (i) rare or common, (ii) native/nonnative, endemic and invasive, (iii) a specialist or generalist, and (iv) a winner or loser in the Anthropocene are all promising tools to support earthworm diversity conservation. These metrics could also be applied to functional traits, but better definition of these traits is fundamental. Finally, we emphasize the need to broaden spatial scales in earthworm studies by analyzing alpha, beta and gamma components of diversity, as local diversity alone can be misleading.