The latest analysis of freshwater resources worldwide reveals a grim reality: humanity has surpassed the planetary boundary for freshwater change by the mid-twentieth century. The stable conditions that existed prior to industrialization have been disrupted by human activities such as dam construction, large-scale irrigation, and global warming.
The research, recently published in Nature Water, highlights the significant alterations in freshwater resources that have taken place over the past century. The international team of researchers calculated monthly streamflow and soil moisture at a resolution of approximately 50 x 50 kilometers. By comparing data from the pre-industrial period (1661–1860) to the industrial period (1861–2005), they were able to identify a concerning trend of increased frequency of exceptionally dry or wet conditions.
The analysis revealed a surge in deviations in streamflow and soil moisture, with dry and wet conditions occurring over larger areas since the early 20th century compared to the pre-industrial era. The global land area experiencing deviations has nearly doubled, indicating a substantial impact on freshwater systems worldwide.
The study also highlighted geographical differences in the frequency of deviations. Tropical and subtropical regions experienced more frequent dry conditions, while boreal and temperate regions observed an increase in exceptionally wet conditions, particularly in soil moisture. These patterns align with changes in water availability due to climate change.
Regions with a history of extensive human land use and agriculture, such as the Nile, Indus, and Mississippi river basins, displayed noticeable changes in streamflow and soil moisture conditions. The study pointed to irrigation as a driving factor behind the alterations in these areas.
Importance of Consistent Methodology
The researchers emphasized the need for a consistent and comparable method for analyzing hydrological variables across different geographical scales. This approach is crucial for understanding the complex interactions between biophysical processes and human activities shaping the freshwater cycle.
By gaining a comprehensive understanding of changes in streamflow and soil moisture, researchers are better positioned to investigate the causes and consequences of disruptions in the freshwater cycle. The study’s senior author, Associate Professor Matti Kummu, underscored the urgency of reducing human-driven pressures on freshwater systems to safeguard life on Earth.
The analysis sheds light on the critical state of global freshwater resources and serves as a wake-up call to take immediate action to protect and preserve these essential ecological and climatic processes. It is imperative that comprehensive policies are developed to mitigate the harm caused by human activities on freshwater systems.
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