Alarming Study Reveals Human Impact on Earth’s Freshwater Cycle

Il ciclo dell’acqua non è più quello di prima: un inquietante studio guidato dall’Università di Aalto (Finlandia) ha dimostrato che l’essere umano lo ha profondamente modificato, tanto che ora è ben lontano dalle condizioni preindustriali

A recently published study led by Aalto University in Finland has unveiled disturbing evidence that human activity has drastically altered Earth’s freshwater cycle, deviating significantly from its pre-industrial state. This groundbreaking research highlights the extent to which, over the last century, human actions have pushed the planet’s freshwater systems beyond their historical stable conditions.

The research

The study meticulously analyzed the monthly flow and soil moisture across the globe, using hydrological models that incorporate all major data on human impacts on the freshwater cycle. With a spatial resolution of approximately 31×31 miles (50×50 kms), the researchers compared conditions during the pre-industrial period (1661-1860) against those in the industrial era (1861-2005).

Their findings indicate a significant increase in the frequency of exceptionally dry or wet conditions, with marked deviations in flow and soil moisture. Since the early 20th century, there has been a consistent occurrence of these deviations over larger areas compared to the pre-industrial period. Overall, the global land surface affected by such deviations has nearly doubled.

A broader context

This research comes on the heels of another alarming study that showed how humans are disrupting the natural salt cycle globally, making the Earth’s air, soil, and freshwater more saline—a change that could pose an “existential threat” if current trends persist.

Now the water cycle is at risk

“The conditions that were once rare are now much more frequent and widespread than before,” explains Vili Virkki, co-author of the study, underscoring how human actions have definitively altered the state of the global freshwater cycle.

Through high-resolution spatial and temporal analysis, the study unveiled geographic differences in these deviations. Unfortunately, exceptionally dry flow conditions and soil moisture have become more frequent in many tropical and subtropical regions. Meanwhile, many boreal and temperate areas have experienced an increase in exceptionally wet conditions, particularly regarding soil moisture.

These patterns align with changes in water availability attributed to climate change, with river basins like the Nile, Indus, and Mississippi experiencing notably dry flow conditions and moist soil moisture, indicative of changes driven by irrigation.

“A consistent and comparable method across hydrological variables and geographic scales is crucial for understanding the biophysical processes and human actions driving the changes we’re seeing in freshwater,” states Miina Porkka, the lead researcher.

The scientists emphasize that understanding these dynamics in greater detail could guide policies to mitigate the resulting damages. However, our immediate priority should be to reduce human pressures on freshwater systems, essential for life on Earth.

Source: Nature Water