Humans have pushed Earth’s freshwater cycle out of a steady state: research | World News – Business Standard

These patterns are consistent with changes in water availability due to climate change

Human activity has pushed Earth’s freshwater supplies far beyond stable conditions before industrialization, a study shows.

The findings, published in the journal Nature Water, show that the updated planetary limit for freshwater change was exceeded in the mid-twentieth century.

This is the first time that change in the global water cycle over such a long timescale has been assessed with an appropriate reference baseline, the researchers said.

Human pressures, such as dam construction, large-scale irrigation and global warming, have altered freshwater supplies in ways that threaten their ability to regulate vital ecological and climatic processes, they said.

The international team calculated monthly streamflow and soil moisture at a spatial resolution of approximately 50×50 kilometers using data from hydrological models that combine all major human influences on the freshwater cycle.

The researchers determined the conditions during the pre-industrial period (1661-1860). They then compared the industrial period (1861-2005) with this baseline.

The analysis showed an increase in the frequency of exceptionally dry or wet conditions – anomalies in streamflow and soil moisture.

Dry and wet anomalies have occurred consistently since the early 20th century over significantly larger areas than during the pre-industrial period, the researchers said.

Overall, the global land area with anomalies has almost doubled compared to pre-industrial conditions, they said.

“We found that exceptional conditions are now much more common and widespread than before, clearly demonstrating how human actions have changed the state of the global freshwater cycle,” said Vili Virkki, a doctoral researcher at Aalto University in Finland, and one of the leading researchers. authors of the article.

Because the analysis was conducted at high spatial and temporal resolution, the researchers were able to examine geographic differences in the anomalies.

In many tropical and subtropical regions, exceptionally dry flow and soil moisture conditions became increasingly common, while many boreal and temperate regions saw an increase in exceptionally wet conditions, especially in terms of soil moisture.

These patterns are consistent with changes in water availability due to climate change.

There were more complex patterns in many regions with long histories of human land use and agriculture, the researchers said.

For example, the Nile, Indus and Mississippi River basins have experienced exceptionally dry flows and wet soil moisture conditions, indicating changes due to irrigation, they said.

“Using a method that is consistent and comparable across hydrological variables and geographic scales is crucial for understanding the biophysical processes and human actions that drive the changes we see in freshwater,” said Miina Porkka, who co-led of research in Aalto before going to the University of Eastern Finland.

With this comprehensive picture of changes in streamflow and soil moisture, researchers are better equipped to investigate the causes and consequences of changes in the freshwater cycle.

“Understanding these dynamics in more detail could help guide policies to limit the resulting damage – but our immediate priority should be to reduce human-induced pressures on freshwater systems that are essential to life on Earth.” reduce,” says Aalto Associate Professor Matti Kummu. senior author of the study.

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First print: March 4, 2024 | 5:20 PM IST