News Release 

Forest responses to climate change

Proceedings of the National Academy of Sciences

A study explores the competing effects of atmospheric carbon and temperature on forests. Increasing atmospheric CO2 can stimulate photosynthesis, but can also cause climate warming that increases water stress and inhibits plant growth. Predicting forest response to these competing influences is challenging. Using a model of plant physiology, Martin Venturas and colleagues simulated the responses of individual trees and tree stands at 20 locations across the United States to projected increases in atmospheric CO2 and temperature. The simulations allowed trees to acclimate to climate change by adjusting leaf area, photosynthetic capacity, and stand density in order to avoid stress. Without acclimation, temperature-induced increases in stress and mortality offset gains in productivity caused by increasing CO2. Acclimation enhanced CO2-driven net productivity gains and led to increased stand biomass at low levels of warming, but led to decreased productivity and biomass at sufficiently high warming. In 71% of the simulations, CO2 increased sufficiently relative to temperature for productivity and biomass to increase with acclimation. In only 55% of simulations did CO2 levels increase enough for trees to avoid chronic water stress without acclimation. Given the variability among climate projections, the ability of trees to benefit from future increased CO2 remains uncertain, according to the authors.


Article #19-13072: "The impact of rising CO2 and acclimation on the response of US forests to global warming," by John S. Sperry et al.

MEDIA CONTACT: Martin D. Venturas, University of Utah, Salt Lake City, UT; tel: 801-803-8619; e-mail:

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