Ecosystem engineers are animal species that interact with and shape their surroundings in order to create or improve habitat in ways that enhance their survival. Ant mounds can alter soil erosion and beaver dams can change riverine landscapes, but the overall nature and combined significance of animals shaping Earth's surface is largely unknown.
Starting from a large systematic review of scientific literature, authors screened more than 8,000 articles, identifying ~500 papers describing animal species with geomorphological activities. Focussing on terrestrial and freshwater ecosystems, these activities included removal of material, reworking of soil and sediment, production and accumulation of materials and stabilizing or reducing erosion.
Based on a list of 500 animals—330 terrestrial and 170 freshwater—identified at the species level, they downloaded data from GBIF to create global maps of zoogeomorphic distribution and richness, and to estimate and identify patterns in their abundance. The highest richness of geomorphic animals was seen in Western Europe and North America, but bias in both research and data may impact these patterns.
By classifying genera by size, proportion of reported geomorphic agents and taxonomic characteristics, the authors explored the potential for unknown geomorphic species, highlighting a significant potential for undiscovered geomorphic animals within large genera, especially those with small, less-studied species, among, e.g., insects.
Finally, the study estimated the combined biomass of geomorphic animal agents at 200,000 metric tons of carbon (corresponding to roughly 1.33 million tons actual body weight or the equivalent of 53 million beavers or 330 trillion ants). By applying a conservative minimum of one per cent energy contributed to geomorphic activitives, they calculated the combined expenditure of all geomorphic animals to 76,000 GJ (equivalent to the energy of hundreds of thousands of extreme floods).