A new study highlights an underrated part of the global water cycle. It is suggested that land-use changes may be intensifying this cycle, leading to more heavy rain events. Why the speed of the cycle was unexpected is not made clear. According to theory the process of water movement in plants depends mainly on osmosis.
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A study from Chapman University provides the first comprehensive global estimates of water storage in Earth’s vegetation and the time it takes for that water to flow through plants, says Earth.com.
The research fills a critical gap in our understanding of the global water cycle and its sensitivity to climate and land-use changes.
Published in the journal Nature Water, the study reveals that Earth’s vegetation holds about 786 km³ of water, a mere 0.002% of Earth’s total freshwater.
However, the significance lies in the rapid movement of water through plants.
This transit time, from absorption to release into the atmosphere, is among the fastest in the water cycle – ranging from five days in croplands to 18 days in evergreen needleleaf forests.
For perspective, water in lakes takes around 17 years to cycle, and in glaciers, the process spans 1,600 years.
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A forgotten element of the water cycle
“Plants are the forgotten part of the global water cycle,” noted Dr. Andrew Felton, lead author and professor at Montana State University. Despite their critical role in returning water from the ground to the atmosphere, plants are often excluded from water cycle diagrams.
“Our results show that the transit of water through plants occurs on the order of days, rather than months, years, or centuries, as it does in other parts of the water cycle,” said Dr. Felton.
By combining plant water transit estimates with those for the atmosphere (8–10 days) and soil (60–90 days), researchers can now approximate the total time a drop of water spends in the terrestrial cycle.
Intensification of the water cycle
One striking finding is the rapid transit of water through croplands. During peak growing seasons, water cycles through crops in less than a day. This speed, consistent across global croplands, hints at a broader environmental implication.
“Land use change may be homogenizing the global water cycle and contributing to its intensification by more rapidly recycling water back to the atmosphere where it can turn into heavy rain events,” explained Dr. Gregory Goldsmith, senior author and associate professor at Chapman University.
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Implications for a changing planet
The study highlights the sensitivity of plant water transit times to environmental events like deforestation, drought, and wildfires.
“The results suggest that the transit time of water through plants is likely to be very sensitive to events such as deforestation, drought and wildfire, which will fundamentally change the time it takes for water to flow through the water cycle,” said Felton.
By shedding light on the dynamic role of vegetation, this research highlights the interconnectedness of ecosystems and the urgent need to understand how land-use changes influence the global water cycle.
Full article here.
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Image: Global hydrological exchanges [credit: Wikipedia]
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January 13, 2025 at 06:05AM
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