The extinction of the Java stingaree, the changes to the seasons, record-breaking temperatures – there’s a long list of victims when it comes to the negative impacts of human activity on the planet. The latest member to join the group? The freshwater cycle, according to a new study.
Freshwater is the not-so-salty type of water found in lakes and rivers and it’s continuously recycled as part of the water cycle. Prior to industrialization, this system was thought to have been in a stable state.
To assess whether or not this stability had changed with human activity, a team of researchers set to comparing pre-industrial (1661-1860) conditions with those during the industrial period (1861-2005). It’s thought to be the first time that global water cycle change, compared to a baseline, has been analyzed over such a long timescale.
They did this using data from hydrological models, using it to calculate streamflow and soil moisture – two elements that can indicate changes in the freshwater cycle and the factors that might drive it – in areas across the globe.
The results revealed that human activity had driven the Earth’s freshwater cycle far beyond its pre-industrial stable state, with a higher incidence of exceptionally dry or wet conditions.
“We found that exceptional conditions are now much more frequent and widespread than before, clearly demonstrating how human actions have changed the state of the global freshwater cycle,” said lead author Vili Virkki in a statement.
Some of the human actions identified as responsible by the study include global warming (no surprises there), forest loss, and dam construction. They also highlighted the potential role of large-scale irrigation, which the authors suggest could be responsible for the exceptionally dry streamflow and wet soil moisture seen in the Nile, Indus, and Mississippi river basins.
The researchers also spotted a number of geographical differences. For example, many tropical and subtropical regions saw an uptick in both exceptionally dry streamflow and soil, whereas more temperate areas had an increased frequency of exceptionally wet conditions.
All in all, the authors write that the conditions are indicative of changes to the freshwater cycles that “transgress the planetary boundary” keeping the system stable.
The freshwater cycle is part of a whole host of important ecological and climatic processes, so the finding isn’t exactly good news. However, having this knowledge in hand might help researchers and policymakers figure out how to allay the possible consequences of such change.
“Understanding these dynamics in greater detail could help guide policies to mitigate the resulting harm – but our immediate priority should be to decrease human-driven pressures on freshwater systems, which are vital to life on Earth,” concluded senior author Matti Kummu.
The study is published in the journal Nature Water.
Source Link: Humans Have Messed Up The World’s Freshwater Cycle
