Work

No Net Increase in Ecosystem Water Limitation Under Greenhouse Warming

Year: 2026

Type: article

Abstract: Energy and water availability are essential controls on terrestrial ecosystem functions such as evapotranspiration. Accurately identifying the dominant regime of water or energy limitation on evapotranspiration is crucial for understanding ecosystem responses to climate change. Recent studies using Earth System Model (ESM) projections suggest widespread shifts from energy‐ to water‐limited conditions under global warming. We demonstrate that incorporating a thermodynamically appropriate energy indicator fundamentally changes this projection. Surface energy availability for evapotranspiration and related ecosystem functions is primarily determined by net radiation ( R n ) rather than downwelling shortwave radiation or air temperature. Using this R n ‐based ecosystem limitation framework, we find no significant net increase in projected water limitation on either evapotranspiration or transpiration toward the end of the century. Idealized ESM CO 2 experiments attribute this pattern to CO 2 ‐induced physiological effects on vegetation—primarily stomatal regulation and enhanced water‐use efficiency—that largely dampen the increased water limitation from enhanced radiative forcing under greenhouse warming. Key physiological variables such as net primary production and leaf area index also show coherent and mechanistically interpretable responses to shifts in R n ‐based water–energy limitation regimes in transitional zones. These findings are consistent with patterns reported in other ecohydrologically based studies and are supported by empirical evidence of reduced vegetation sensitivity to dry conditions under elevated CO 2 . Our study bridges ecological and physical theories to improve ecosystem water‐energy limitation analysis and provides a clear mechanistic understanding of future ecosystem dynamics.

Source: Earth s Future

DOI: 10.1029/2026ef008222

Authors: Jiameng Xu, Kaighin A. McColl, Alexis Berg, Yu Liang, Jian Yang, Yuanchao Fan