In a paper published in Nature Geoscience, a team of researchers from different countries has reported the findings from their assessment of the impact of deforestation and afforestation projects on the water cycle across the globe.
Forest
Their results suggest a need for greater attention to detail with these projects as regards the impact they could have on the hydrological cycle.
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According to previous research, the existence of a large number of trees in a particular area impacts the water table. The trees pull water from the ground in their vicinity and there is water transpiration into the air.
Trees have been planted by researchers in recent years as a means of combating climate change. They hope this would help by taking some carbon out of the air.
Water availability across the globe has risen as a result of increases seen in vegetation cover in the past two decades, as per researchers. However, this new work suggests that the hydrological impacts of vegetation changes extend beyond their immediate regions.
Impact on the water cycle
The team behind the current research was curious to find out what impact deforestation and afforestation were having globally. It, therefore, collected precipitation data from multiple sites across the world for analysis.
Along with precipitation records, the researchers also examined leaf cover to find out where tree growth patterns changed or remained the same in specific areas.
This led the team to discover a possible link between tree cover changes and surface water level changes. The experts observed that changes in vegetation cover in the period from 2001 to 2018 resulted in an increase of about 0.26 mm per year in global surface water availability.
Also, the research found that the increased water availability was more as a result of greater rainfall than evapotranspiration for roughly 53 percent of the global land surface.
The impact of vegetation cover changes on the water table was not the same in all regions, however. Increasing the number of trees caused more water to become available in certain places – both locally and in farther places located downwind.
Minimal local impact was observed in some regions. There were also places where the planting of more trees did not result in any noticeable increases in surface water availability.
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The results of this work imply a need for more attention when planning deforestation and afforestation projects. This is because of how their impacts may be felt in other regions beyond those undergoing tree cover changes. In particular, entities need to better understand how vegetation changes impact regions situated downwind.
References
Global water availability boosted by vegetation-driven changes in atmospheric moisture transport
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