Empirical evidence suggests that earthworms are efficient “ecosystem engineers” 8 and play a prominent role in remediating adverse soil compaction 9 that affects nearly 5% of the world’s arable land (about 68 Mha) 10. Overall, earthworm activity is attributed to significant enhancement in specific crop yields of up to 25% 7. Soil ingestion by earthworms can augment microbial activity and stimulates the formation of soil aggregates 6.
In locations with abundant plant-derived particulate organic carbon (POM), earthworms ingest POM-rich soil 5 and often line their burrows with secreted castings. They are hot spots of biological activity that can be reused by growing roots, improve groundwater recharge and soil water retention, and support oxic conditions in soil profiles 3, 4. Soil biopores formed by burrowing earthworms serve as preferential pathways for water flow and aeration 2. Subterranean activity by earthworms influences soil structure and provides numerous ecosystem services 1.
The mechanistic model delineates the potential for earthworm migration via connectivity of hospitable sites and highlights regions sensitive to climate. Earthworm activity is strongly constrained by seasonal dynamics that vary across latitudes largely due to soil hydromechanical status. We include additional constraints that exclude earthworm activity such as freezing temperatures, low soil pH, and high sand content to develop the first predictive global map of earthworm habitats in good agreement with observed earthworm occurrence patterns.
A mechanistic biophysical model is developed here to link the biomechanical limits of earthworm burrowing with soil moisture and texture to predict soil conditions that permit bioturbation across biomes. Hence, their activity is constrained by soil hydromechanical conditions that permit deformation at earthworm’s maximal hydroskeletal pressure (≈200kPa). Earthworms use their flexible hydroskeleton to burrow and expand biopores. Earthworm activity modifies soil structure and promotes important hydrological ecosystem functions for agricultural systems.
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