the term planetary boundaries It was first introduced in 2009 and sets out nine limits within which humanity must act in order to continue to sustainably use global aid resources. Water is one of the nine categories, and the sixth now defined by scientists as exceeding the permissible limit. Other categories in which humanity has already crossed the line are: climate change, biodiversity loss, biogeochemical cycles, land use and chemical pollution.
For the “water” category, we were thought to be still within the safe range, but researchers have now studied that limit in more detail. Previous assessments have mainly focused on “blue water”: the fresh water in streams, rivers, and lakes. But there is also “green water”: the water cycle that is important for plants, such as rainfall and soil moisture. By focusing only on ‘blue water’, previous assessments have missed important information about the entire water cycle.
“We are now particularly focused on soil moisture in the root zone of plants as a key indicator of the health of our water cycle. Soil moisture is important for healthy, resilient ecosystems that are able to sequester carbon. In turn, these ecosystems provide an assurance that our co-author Rod van der Ent, Professor Associate at TU Delft, “The Atmospheric Water Cycle Remains Intact”.
Everywhere from boreal forests to tropics, from agricultural to forested areas, rainfall patterns are changing as well as soil moisture. says Ari Stahl, co-author and associate professor at the Copernicus Institute of Utrecht University.
The authors state that soil moisture in the root zone in particular is important for the green water cycle. This root zone changes throughout the year and varies by ecosystem. The percentage on Earth where soil moisture in the root zone exceeds a certain baseline monthly difference is, according to the team, the most important variable by which they judged that the planet’s water limits had already been crossed.
“Over the past decade, the idea of planetary boundaries Help policy makers deal with pressing issues related to the planet. This new assessment of freshwater changes now shows that we need to take action to alter the green water cycle through climate change, deforestation and soil degradation to reduce risks to our planet.” Amsterdam.
Article published in the magazine Nature Reviews Earth and Environmentco-written by Johan Rockstrom, who received an honorary doctorate from the University of Amsterdam in 2019, and in 2021 he was the main character in David Attenborough’s documentary ‘Breaking Boundaries: The Science Of Our Planet’.
Photos: Gilger Herder; Roy van Grunsvin Gert Jan van Duyenen