Global observations of atmospheric drying — known by scientists as a rise in vapor pressure deficit — have been observed worldwide since the early 2000s. In recent years, this concerning phenomenon has been on the rise, and it’s predicted to become more severe in the coming decades as climate change intensifies.
In a new paper published in the journal Global Change Biology, research from Western University and the University of Minnesota shows that global atmospheric drying significantly reduces productivity of both crops and non-crop plants, even under well-watered conditions. The new findings were established on a large-scale analysis covering 50 years of research and 112 plant species.
In their analysis, researchers suspected plants would sense and respond to this phenomenon in unexpected ways, generating additional costs on productivity. Findings bear out that various plant species — from wheat, corn, and even birch trees — take cues from atmospheric drying and anticipate future drought events.
Through this process, plants reprogram themselves to become more conservative — or in other words, plants grow smaller, shorter and more resistant to drought, even if the drought itself does not happen. Additionally, due to this conservative behavior, plants are less able to fix atmospheric CO2 to perform photosynthesis and produce seeds. The net result? Productivity decreases.
On a positive note, the analysis indicates different species or varieties within species respond more or less strongly to this drying depending on their evolutionary and genetic make-up. For example, in wheat, some varieties are less responsive to this new stress compared to others, and this type of variability seems to exist within other non-crop species as well.
Danielle Way, a Western plant physiologist and co-author of the study, says this discovery heightens our understanding of ecosystem resilience to climate change.
Danielle Way
“Variation in plants’ sensitivity to atmospheric drying could be used to predict how natural ecosystems will respond to climate change and manage them in ways that increase their resilience to climate change,” said Way, an associate professor at Western’s department of biology.
“This finding is particularly promising as it points to the possibility of breeding for genotypes with an ability to stay productive despite the increase in atmospheric drying,” said senior author Walid Sadok, an assistant professor of of agronomy and plant genetics at the University of Minnesota.
Ultimately, the researchers say this investigation calls for more focused interdisciplinary research efforts to better understand, predict and mitigate the complex effects of atmospheric drying on ecosystems and food security.
“When there is a high vapour pressure deficit, our atmosphere pulls water from other sources: animals, plants, etc.,” said Sadok. “An increase in vapour pressure deficit places greater demand on the crop to use more water. In turn, this puts more pressure on farmers to ensure this demand for water is met — either via precipitation or irrigation —so that yields do not decrease.”
“We believe a climate change-driven increase in atmospheric drying will reduce plant productivity and crop yields — both locally and globally,” said Sadok.
The international team of researchers believe their findings can be used to design new crop varieties and manage ecosystems in ways that make them more resilient to atmospheric drying. However, new collaborations are needed between plant physiologists, ecologists, agronomists, breeders and farmers to make sure the right kind of variety is released to farmers depending on their specific conditions.
Atmospheric drying (referred to as water vapor pressure deficit or VPD) is expected to increase as a result of climate change. This could reduce crop yields and make trees shorter. Illustration by Maria H Park (University of Minnesota)
“As we race to increase production to feed a bigger population, this is a new hurdle that will need to be cleared,” said Sadok. “Atmospheric drying could limit yields, even in regions where irrigation or soil moisture is not limiting.”
The research was supported by the Canadian Natural Sciences and Engineering Council, the U.S. Department of Energy, the Research School of Biology at the Australian National University, the Minnesota Wheat Research & Promotion Council, the Minnesota Soybean Research and Promotion Council and the Minnesota Department of Agriculture.
