In the natural world there has been an almost unimaginable change of scale, which reflects the vast and growing domination of humanity over one of the most vital resources on our planet: fresh water.
According to what researchers say is the world’s first survey of human impacts on the water cycle, scientists have used NASA’s satellite measurements to remotely quantify changes in water levels in a impressive number of bodies of water: 227,386 of ponds, lakes and reservoirs, whether small or large.
While human-managed reservoirs, such as man-made dams, account for only 3.9 percent of this giant planetary-scale water storage system, this small fraction masks a mind-boggling truth about control. which really exerts humanity over freshwater fluctuations.
When calculating the number of global changes in water levels in both natural and human-managed systems, it turns out that human-controlled reservoirs account for 57% of all water variability. surface, more than half the flow and ebb of freshwater systems.
“We tend to think of the water cycle as a purely natural system: rain and melting snow sink into rivers, which go into the ocean, where evaporation begins the whole cycle again.” , explains geophysicist Sarah Cooley of Stanford University.
“But humans really intervene substantially in this cycle. Our work demonstrates that humans are responsible for most of the seasonal variability of surface water storage on Earth.”
The results, collected from 22 months of data collected by NASA’s Satellite 2 Ice, Cloud and Earth Elevation (ICESat-2), provide a unique snapshot of its entire water storage type. the world, capturing and measuring bodies of water as small as a football field within the survey.
“Previous satellites haven’t been able to come close to that,” Cooley says, but while scientific achievements are admirable, takeaway meals aren’t.
“There are many ways in which this is harmful to the environment.”
The risks range from negative effects on natural ecosystems due to water scarcity, to the spectrum of greenhouse gas emissions from artificial reservoirs.
Of course, there are also other positive aspects of human-functioning reservoirs: beyond the simple control of water supply, they allow hydroelectric systems, while dams can also offer flood protection.
However, the finding that we have taken the majority control over something as natural as the flow and ebb of fresh water is a disturbing discovery.
Another reminder of the effect our species has on the environment around us, with such incredibly great consequences that we can only hope to see them from space.
“Of all the volume changes in freshwater bodies around the planet (all the floods, droughts, and melting snow that push lake levels up and down), humans have reached almost 60 percent of that variability, ”says environmental scientist Laurence Smith of Brown University.
“This has a big influence on the water cycle. In terms of human impact on the planet, this is right up there with impacts on land cover and atmospheric chemistry.”
The findings are reported in Nature.