Global vegetation growth has decreased by 59% in the last 20 years thanks to ‘dry air’ caused by global warming, scientists discover
- Researchers found that the decline is linked to a vapour pressure deficit
- This means there is a drop in the amount of water available in the atmosphere
- This has increased sharply over 53% of vegetated areas since the late 1990s
- It means that plants can’t take in the water vapour from the air they need to grow
Plant growth has decreased by 59 per cent worldwide since 1999 due to a lack of water in the atmosphere, a new study suggests.
Experts studied four global climate datasets to try and uncover why vegetation growth has stalled in the past two decades.
They found that a drop in levels of water vapour had stopped plants from being able to photosynthesise.
Photosynthesis is used by plants, some bacteria and single-celled organisms to draw energy from sunlight, taking in carbon dioxide and water in the process.
The research suggests that computer models of how the climate may behave in the future may not fully capture how plants might respond.
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Plant growth has decreased by 59 per cent worldwide since 1999 due to a lack of water in the atmosphere, a new study suggests (stock image)
WHAT IS PHOTOSYNTHESIS?
Photosynthesis is used by plants, as well as some types of bacteria and single-celled organisms, to draw energy from sunlight.
During the process of photosynthesis, cells use carbon dioxide, water and energy from the sun to produce sugar molecules and oxygen.
This process is vital to all life on Earth, as it transforms carbon dioxide into the air most living things need to breathe.
Researchers from Sun Yat-sen University in Zhuhai, China, found that the decline is linked to a vapour pressure deficit (VPD) in the atmosphere.
VPD is the difference between the pressure that would be exerted by water vapour when the air is fully saturated and the pressure it actually exerts.
This has increased sharply over more than 53 per cent of vegetated areas since the late 1990s.
When this deficit increases, the pores on the surface of leaves that taken in carbon dioxide and release water vapour close up, resulting in lower rates of photosynthesis.
‘It’s like there’s a pump in the air, and the pump extracts the water from the soil and plants via the vascular tissue,’ lead researcher Yuan Wenping told Newsweek.
‘When the VPD increases, then the pump extracts the water faster and stronger.’
Photosynthesis is used by plants, some bacteria and single-celled organisms to draw energy from sunlight, taking in carbon dioxide and water in the process (stock image)
VPD plays an important role in ecology, as higher atmospheric VPD – which often accompanies rising air temperatures – impairs photosynthesis and can cause vegetation and forests to die.
Researchers discovered that VPD over vegetated land sharply increased near the end of the 20th century.
This rise led to a drop in satellite-based measures of live vegetation and leaf coverage on land, which had previously been increasing from 1982 to 1998, as well as a decline in tree-ring growth measurements after 1998.
They conclude that the recent upswing in VPD may be a major contributor to drought-related forest death over the past few decades.
They add that because VPD is projected to further increase throughout the century, scientists should carefully account for its impact on vegetation growth when evaluating how ecosystems respond to future shifts in the carbon cycle.
The full findings of the study were published in the journal Science Advances.