Current Climate Change Reports· 2026Q1
One Metric, Many Meanings: Reconciling Water Use Efficiency Definitions
- 2citations
- Q1SCImago
- 2026year
Short summary
Water Use Efficiency (WUE) definitions vary widely, but a new framework clarifies differences between ratio-based (e.g., A/E) and optimality-based (e.g., ∂E/∂A) approaches, highlighting their distinct environmental dependencies and underlying assumptions.
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Key points
- Ratio-based WUE metrics (e.g., A/E, A/gsw) measure realized carbon-water exchange but are environmentally sensitive.
- Optimality-based approaches (e.g., ∂E/∂A) provide a mechanistic understanding of water-use strategy.
- WUE definitions vary based on measurement approach, scale (leaf to ecosystem), and discipline.
- A proposed framework categorizes WUE formulations by their carbon/water variables, scales, and assumptions.
AI-generated from the title and abstract; the full text is not read.
Abstract
Abstract Purpose of Review Water Use Efficiency (WUE) is widely used to describe carbon-water coupling, but its meaning varies among disciplines, measurement approaches and spatial and temporal scales. We review commonly used WUE definitions and formulations and clarify their conceptual differences. Recent Findings Ratio-based metrics, including WUE ( A /E) and intrinsic WUE ( A /g s w), describe realized carbon–water exchange but remain sensitive to environmental conditions. Optimality-based approaches distinguish these ratios from the marginal water cost of carbon gain (∂E/∂ A ), providing a mechanistic perspective on water-use strategy. We also highlight differences among leaf, plant, ecosystem, isotope, and model-derived estimate. Summary WUE is best understood as a context-dependent metric rather than a universal functional trait. We propose a framework linking each formulation to its carbon and water variables, spatial and temporal scale, environmental dependencies, and underlying assumptions. This approach supports transparent metric selection and improves comparisons across studies, scales, and methods.
The authors' abstract, as published at the source. Current Climate Change Reports, 2026 · DOI ↗
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