Water constraints are stunting vegetation growth in the Northern Hemisphere

Plant growth has been stunted by water constraints in a warming climate, according to a new study led by Indiana University. The researchers analyzed vegetation growth in the Northern Hemisphere over the past 30 years, and identified a troubling link between rising temperatures and plants becoming increasingly water-limited.

“Without water, living things struggle to survive, including plants,” said study senior author Professor Lixin Wang. “Changes in vegetation response to water availability can result in significant shifts of climate-carbon interaction.”

In collaboration with a multidisciplinary research team, experts in the School of Science at IUPUI set out to examine vegetation constraints on a global scale. Despite a growing need to predict plant growth trends in response to climate change, vegetation constraints have been largely unknown.

“Global temperature and the concentration of atmospheric CO2, or carbon dioxide, have been increasing,” said Professor Wang. These changes will cause increased atmospheric water demand, more extreme hot days, and more frequent drought events, explained the researchers. 

While these factors suggest that vegetation growth suffers an increasing amount of water stress in a warming climate, Professor Wang noted that quantifying these changes at large spatial and temporal scales is challenging.

To overcome this challenge, the researchers used satellite remote sensing data and data from 1982 to 2015.

“We developed our own metrics to indicate water constraints and then examined the changes in the metrics,” study first author Wenzhe Jiao. 

“The study is quite computationally extensive since we examined the relationship between vegetation growth and water deficit at each grid cell over the whole extratropical Northern Hemisphere – 604,800 data points each year – over more than 30 years.”

The study produced strong evidence of a widespread, significant increase in water vegetation constraint in the Northern Hemisphere. Some regions, including the Great Plains in the United States, were comparatively worse than others.

“Increasing water constraints on vegetation productivity may drive a shift from a period of increasing land carbon sink strength to a period in which climate change is reducing land carbon sink strength,” said Professor Wang.

“Our research shows that increasing water constraints will likely limit continuous vegetation growth, thus slowing down the removal of CO2 from the atmosphere by plants,” said Jiao.

“The results emphasize the need for actions that could slow down CO2 emissions,” said Professor Wang. “Without that, water constraints impacting plant growth – and the weakening of vegetation’s ability to removal of CO2 from the atmosphere — are unlikely to slow.”

The study is published in the journal Nature Communications.

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By Chrissy Sexton, Earth.com Staff Writer