Land plant evolution and global erosion rates: A comment on "The impacts of land plant evolution on Earth's climate and oxygenation state - An interdisciplinary review" by Tais W. Dahl and Susanne K.M. Arens, Chem. Geol. 547 (2020) Article 119665.

Abstract

Dahl and Arens (2020) have presented a commendable review showing how the evolution of land plants perturbed and modified global biogeochemical cycles and Earth surface processes. Its scope is comprehensive, and it well-summarizes conclusions from an array of palaeobotanical, geochemical, geological and modelling investigations. However, we here argue against a significant individual conclusion of their review: namely that "[paleorecords show] early land plants did not permanently change global erosion rate (e.g. by stabilizing soils)" (Dahl and Arens, 2020, p. 8). This conclusion utilizes a figure from a previous study by ourselves (McMahon and Davies, 2018), but invokes a common misconception that the volume and internal characteristics of the sedimentary-stratigraphic record (hereafter, 'SSR': see Davies et al., 2020) must have similar causes. This short comment aims to emphasize that global erosion rates are actually underdetermined by both global rock volume and mudrock proportion, but that the latter provides strong circumstantial support for hypotheses that land plant evolution initiated permanent changes. Figure 1 summarizes our contention.