Water use efficiency sits at the heart of one of the most consequential debates in global change research. As atmospheric carbon dioxide concentrations climb, plants can partially close their stomata, the microscopic pores through which they exchange gases, while still maintaining photosynthetic carbon uptake. That physiological adjustment has underpinned expectations that ecosystems will become increasingly economical with water as the century progresses, a trend documented in forests through eddy-covariance measurements and tree-ring isotope records. Yet recent work has complicated the picture. A 2023 study in Science reported that global water use efficiency is saturating because rising vapor pressure deficit, the thirst of the air, is pushing transpiration rates up even as stomata narrow. The new analysis adds wind speed to this already intricate balance, and finds that its influence is strong enough to rival the factors scientists have been tracking for decades.

The evidence base for the conclusion is unusually broad. The team compiled growing-season observations from the major regional flux networks, including FLUXNET2015, AmeriFlux, OzFlux and the European ICOS infrastructure, sites where towers measure the vertical exchange of carbon dioxide and water vapor between vegetation and the atmosphere with high temporal resolution. Across this global dataset, the researchers divided wind conditions at each site into percentile-based categories and examined how ecosystem water use efficiency varied among them. The pattern held after controlling for air temperature, precipitation, carbon dioxide concentration, solar radiation and vapor pressure deficit, and it appeared across plant functional types ranging from evergreen needleleaf forests and deciduous broadleaf forests to shrublands, savannas, grasslands, wetlands and croplands. Nonparametric Kruskal-Wallis tests followed by Dunn’s post hoc comparisons confirmed that the differences among wind-speed categories were statistically robust.

The mechanism the authors identify is rooted in boundary-layer physics. Stronger winds enhance aerodynamic conductance, the ease with which water vapor is stripped away from leaf and canopy surfaces and mixed into the bulk atmosphere. When aerodynamic conductance rises, the coupling between the ecosystem and the atmosphere tightens, and the effective atmospheric demand for water amplifies. The result is a marked increase in evapotranspiration, the combined flux of transpiration from plants and evaporation from soil and canopy surfaces. Because the denominator of the water use efficiency ratio grows faster than the numerator, the ratio itself falls. The team’s pathway analyses show that this wind-driven increase in water loss is the primary route by which wind suppresses water use efficiency, with a secondary contribution coming from reductions in gross primary productivity, the total carbon fixed by photosynthesis at the ecosystem scale.

That secondary effect is itself revealing. Wind does not merely dry the air around leaves; it bends stems, vibrates leaves and abrades cuticles, responses that ecologists have documented from individual plants to whole forests for decades. Prior research has linked wind exposure to reduced leaf expansion, altered biomass allocation and changes in xylem hydraulics, and a 2025 study in Nature Ecology and Evolution connected wind speed to plant hydraulic properties at the global scale. The new findings suggest that these mechanical and physiological stresses, translated into slightly lower photosynthetic carbon uptake, compound the hydrological effect of enhanced aerodynamic conductance. In other words, wind pushes the water use efficiency ratio downward from both directions at once, increasing the water plants spend while modestly reducing the carbon they earn.

The contrast with leaf-scale studies is one of the most scientifically interesting aspects of the result. Earlier experimental work, including a 2016 study in Plant, Cell and Environment, found that wind can actually increase water use efficiency at the level of a single leaf, because moving air cools leaves and can reduce the leaf-to-air vapor pressure gradient under certain conditions. The new analysis, together with prior comparative work showing that leaf and ecosystem water use efficiencies differ in their global patterns and drivers, demonstrates that this leaf-level intuition does not survive the journey to the canopy. At ecosystem scale, the dominant effect of wind is to accelerate the removal of vapor from the entire canopy-air volume, overwhelming any local cooling benefit. It is a cautionary example of how scaling from leaf to landscape can reverse the sign of an ecological relationship.

The implications extend into the future, because near-surface wind speed is itself changing. Much of the twentieth century experienced terrestrial stilling, a widespread decline in wind speeds, though observations reported in 2019 documented a reversal of that trend in many regions. Earth system models from the CMIP6 archive, which the team used to extend their observational findings, capture the negative sensitivity of water use efficiency to wind speed and project that future wind changes will materially shape ecosystem water economies. Under high-emission scenarios, intensified reductions in wind speed enhance water use efficiency, partially offsetting the drying pressure imposed by warming. Under low-emission scenarios, weaker stilling reduces this wind-related boost. The sign and magnitude of the wind effect therefore depend directly on which emissions pathway humanity follows, an unexpected coupling between mitigation policy and plant water relations.

For the modeling community, the study delivers a pointed message. Land surface models have historically represented aerodynamic conductance carefully, since it is essential to the surface energy balance, but the downstream consequences for carbon-water coupling have rarely been isolated as a distinct sensitivity. The finding that wind speed exerts a first-order control on water use efficiency means that projections of ecosystem drought stress, carbon sequestration and vegetation-climate feedbacks could carry systematic biases if wind trends are mischaracterized. It also connects to a growing body of work on wind’s ecological reach, from demonstrations that wind drives ecosystem carbon release in drylands to evidence that declining winds have delayed autumn senescence at high latitudes and promoted vegetation growth more broadly. Wind, it appears, is not a residual term in the ecosystem budget but an active regulator.

The study also sharpens interpretation of the carbon dioxide fertilization record. If wind speed has been declining across substantial portions of the land surface, some fraction of the observed historical increase in water use efficiency may owe less to stomatal physiology than to a calmer atmosphere. Disentangling these contributions matters for forecasting the future terrestrial carbon sink, because the assumption that rising carbon dioxide will keep delivering water savings underpins many projections of ecosystem resilience in semi-arid regions. By establishing wind speed as an independent, quantifiable driver, the new analysis gives researchers one more lever to pull when reconciling tower observations, satellite records and model simulations, and one more reason to treat the carbon and water cycles as a single, wind-stirred system.

What remains to be resolved is how the wind sensitivity varies with ecosystem structure, soil moisture and disturbance history, and whether extreme wind events leave lasting legacies in the carbon-water balance beyond the immediate growing season. The authors have made their preprocessed data and primary code openly available through Figshare, lowering the barrier for the modeling and flux communities to test the robustness of the relationship across new sites and future model generations. But the central conclusion is already clear and, in its simplicity, striking: the air in motion above a forest, grassland or cropland is not neutral background. It is a measurable force that determines how much carbon the biosphere banks for every unit of water it spends, and as the climate changes, that force is changing with it.

Subject of Research: The effect of wind speed on ecosystem water use efficiency across terrestrial ecosystems

Article Title: High wind speed reduces water use efficiency across terrestrial ecosystems

Article References: High wind speed reduces water use efficiency across terrestrial ecosystems. (n.d.). https://doi.org/10.1038/s41558-026-02781-z

Image Credits: AI Generated

DOI: 10.1038/s41558-026-02781-z

Keywords: water use efficiency, wind speed, evapotranspiration, gross primary productivity, eddy covariance, aerodynamic conductance, carbon-water coupling, terrestrial ecosystems, climate change, Earth system models, vapor pressure deficit, CMIP6