Global‐Scale Shifts in Rooting Depths Due To Anthropocene Land Cover Changes Pose Unexamined Consequences for Critical Zone Functioning

• DOI: 10.1029/2022ef002897
• Publication Date: 2022-11-05T00:14:05Z
• Authors: Emma Hauser; Pamela L. Sullivan; Alejandro N. Flores; Daniel Hirmas; Sharon A. Billings
• Keywords: Hydrosphere; Anthropocene; Earth system science; Land Cover; Global Change; Biogeochemical Cycle; Alternative stable state; Root (linguistics)

Abstract Rooting depth is an ecosystem trait that determines the extent of soil development and carbon (C) water cycling. Recent hypotheses propose human‐induced changes to Earth's biogeochemical cycles propagate deeply into subsurface due rooting from agricultural climate‐induced land cover changes. Yet, lack a global‐scale quantification responses human activity limits knowledge hydrosphere‐atmosphere‐lithosphere feedbacks in Anthropocene. Here we use data sets demonstrate root distributions are changing globally as consequence expansion truncating depths above which 99% biomass occurs (D99) by ∼60 cm, woody encroachment linked anthropogenic climate change extending D99 other regions ∼38 cm. The net result these two opposing drivers global reduction 5%, or ∼8 representing loss ∼11,600 km 3 rooted volume. Projected scenarios 2100 suggest additional future shallowing up 30 generating further losses volume ∼43,500 , values exceeding experienced date suggesting pace will quicken coming century. Losses deepest roots—soil‐forming agents—suggest unanticipated fluxes water, solutes, C. Two important messages emerge our analyses: dynamic, human‐modified should be incorporated earth systems models, significant gap deep research inhibits accurate projections their consequences.