The Biophysical Forcing of Terrestrial Vegetation: A Persistent Climate Modulator with State-Dependent Efficacy Through the Phanerozoic

Vegetation actively regulates climate through biophysical processes such as altering surface albedo, evapotranspiration, and roughness. Despite its recognized importance in modern and Quaternary systems, the role of terrestrial vegetation in shaping Earth’s climate on geological timescales remains poorly quantified. Understanding how vegetation–climate interactions vary across different background states—from icehouse to greenhouse worlds—is critical for interpreting paleoclimate proxies and for constraining future biosphere–climate feedbacks.

Here, we present a series of coupled climate–vegetation experiments using the Community Earth System Model (CESM1.2.2) with BIOME4 to systematically isolate the biophysical effects of land plants across 42 time slices from 410 Ma to the pre-industrial era. Through paired “Vegetated” and “Bare-ground” simulations, we assess the global and regional climatic impacts of vegetation across a wide range of paleogeographic and climatic conditions.

Our results show that vegetation consistently exerts a warming influence of 2–6 °C, primarily via albedo reduction, and increases precipitation by 30–105 mm yr⁻¹. This forcing is strongly state-dependent, being most pronounced during cold, high-ice climates where vegetation activates potent snow/ice-albedo feedbacks. Moreover, vegetation systematically reorganizes large-scale atmospheric circulation: it intensifies the Walker circulation, redistributing tropical rainfall, and under certain configurations can reverse the global meridional overturning circulation, thereby altering oceanic heat transport.

These findings establish terrestrial vegetation as a persistent, state-dependent climate modulator throughout the Phanerozoic, offering a unifying framework for understanding its role in past and future vegetation–climate interactions.