Figure 1: Size–density relationships for below- and above-ground organisms.
(a) Representative images of organisms that belong in the four groups that have been studied so far in extinction ecology: birds, plants, mammals and insects; (b) size–density relationships in representative belowground (in colour) and aboveground taxa (in grey). Belowground taxa size estimates are according to the study by Swift et al.83 Size estimates of aboveground taxa were obtained following searches for the size of organisms with extreme sizes. Belowground taxa density estimates were retrieved from a synthesis of data from ‘European Crop Protection Association. Soil Biodiversity and Agriculture (2010) (http://www.ecpa.eu/files/gavin/soil_bio_and_ag_012_web.pdf)’. Densities for aboveground organisms originated from projections of global population estimates for taxonomic groups found in ‘Tomasik B. (2014) How Many Wild Animals Are There? (http://reducing-suffering.org/how-many-wild-animals-are-there/)’. Note that even without consideration of microbial taxa the variability for belowground organisms exceeds that of the aboveground taxa so far studied in extinction ecology. Image credits: S.D.V.
