Has the efficiency of water use by plants decreased?

A study at the University of New Hampshire is challenging the theory that an increase in atmospheric carbon dioxide levels can positively affect the water-use efficiency of plants. Through the development of research models, the researchers noted that since 2001. the downward trend in plant growth response continues, for their water consumption has increased significantly.

Water use efficiency – do plants take up more water than carbon dioxide?

Carbon dioxide is a nutrient essential for plant life. By absorbing it from the atmosphere, green plants can, in short, carry out photosynthesis, which makes them grow. The uptake of carbon dioxide allows them to grow faster and increases water use efficiency. Photosynthesis is the basic biological process that determines life on Earth. During the day, it allows plants to produce and supply themselves with organic matter. At night, on the other hand, plants emit carbon dioxide back into the atmosphere.

Due to climate change, causing an increase in global temperature and carbon dioxide levels in the atmosphere, it was widely believed that increasing_CO2 emissions could positively affect the way plants use water. This assumption is referred to as water use efficiency (WET). WUE – water use efficiency). Until now, it was thought that higher WUE levels meant that plants used less water and absorbed more carbon dioxide, increasing their growth and helping to reduce the effects of climate change. But are you sure?

The new finding, by researchers at the University of New Hampshire, showed that water efficiency has been stunted since 2001. This means that in recent years plants have been taking up less carbon dioxide and more water, which could have a significant impact on the carbon cycle, agricultural production and water resources.

Global water use efficiency stalled

Researchers have developed 24 types of models for 5 major vegetation types: forests, scrublands, savannas, grasslands and agricultural fields. They were created using satellite and micrometeorological data from the global Fluxnet network (which consists of towers to measure the exchange of carbon dioxide, water vapor and energy between the biosphere and atmosphere). Artificial intelligence technology in the form of machine learning (AI) was also used. ML – machine learning).

It was noted that the models created for each of the five ecosystem types indicate slower plant growth and continued growth since 2001. An increase in their water consumption. The probability of such results may be due to the increasing vapor pressure (vapor pressure) deficit. VPD – Vapour Presurc Deficit – an indicator that takes into account the effect of temperature on the air’s ability to retain water, which drives transpiration of the leaf surface). When VPD increases, it potentially slows or suppresses photosynthesis and enhances water use by plants, thereby weakening their growth and reducing water use efficiency in global ecosystems.

“We observed an increase in the efficiency of water use by plants between 1982 and 2016, with a significant increase between 1982 and 2000. Then the value stalled,” said Professor Jingfeng Xiao, who works at the Center for Earth Systems Research at the University of New Hampshire. – “The increase in carbon dioxide allows plants to grow faster and use water more efficiently, but this study shows that some of the natural methods that scientists believe could help achieve carbon neutrality may be undermined by the adverse effects of a warming climate, and that plants are not using water as efficiently as scientists might expect.”

Increase in water use by plants

In the face of rising temperatures and rising atmospheric_CO2 levels, the complex trade-off and multifaceted dynamics between carbon dioxide gain and water loss are still poorly understood. The researchers emphasize that a number of factors have been analyzed, and it emerges that water use efficiency does not appear to be the result of changes in vegetation regrowth or reduced photosynthesis as a result of too much or too little nitrogen or phosphorus. However, the climate change-related phenomenon of rising temperatures and projected increases in VPD could significantly affect soil carbon levels, ecosystem water cycling and plant growth, all on a global scale.