A new study examining the world’s freshwater resources has found that human movements have especially altered the planet’s freshwater cycle. So what effect will those changes have on our water source and, by extension, food security?
The study found that the planetary limit for freshwater supply was exceeded in the mid-20th century, meaning that since then, humans have pushed Earth’s freshwater production beyond solid conditions.
According to the World Wildlife Fund (WWF), “how we address this invaluable but undervalued resource will affect people, the climate, nature and, therefore, businesses in the long term. “
Planetary barriers describe the limits that the Earth may face when it comes to the impact of human activity. Beyond those limits, the environment would possibly not be able to self-regulate, meaning that Earth systems would not serve as they should.
The findings, published in Nature Water, show that human pressures, such as dam construction, large-scale irrigation, and global warming, have altered freshwater resources to such an extent that their ability for important ecological and climate processes is threatened.
The study team calculated monthly and soil moisture using knowledge from hydrological models that combine all primary human effects on the freshwater cycle. They used the situations of the pre-commercial era (1661-1860) as a reference. Then, they compared the commercial humidity era (1861-2005) to this reference.
The research revealed an increase in the frequency of unusually dry or unusually rainy situations due to differences in stream and soil moisture. Since the beginning of the 20th century, dry and rainy deviations have consistently occurred in much larger spaces compared to the previous era. industrial period. Overall, the global scope subject to deviations has almost doubled compared to pre-industrial situations.
“We found that the situations are now much more common and widespread than before, which obviously demonstrates how human movements have altered the state of the global freshwater cycle,” said Vili Virkki, a doctoral student at Aalto University and one of the study’s lead authors. .
Because the research was conducted with the highest spatial and temporal resolution, the researchers were able to explore geographic differences in spaces. Unusually dry soil and stream moisture situations have become less unusual in many tropical and subtropical regions, while many boreal and temperate regions have noticed accumulation in unusually rainy situations, especially in terms of soil moisture. These trends correspond to observed adjustments in water availability due to climate change.
“Most likely, climate change is accelerating parts of the water cycle, as global warming temperatures increase the rate of evaporation on a global scale. On average, more evaporation leads to more precipitation. We are already seeing the effects of higher rates of evaporation and precipitation. , and those effects are expected to be more pronounced this century as the climate warms,” warns a spokesperson for UCAR’s Center for Science Education.
The team also observed more complex patterns in regions with a long history of human land use and agriculture, with the Nile, Indus, and Mississippi river basins experiencing incredibly dry flows and moist soil moisture conditions, indicating adjustments due to irrigation.
“Understanding those dynamics in more detail can help consulting policies mitigate the resulting harm; however, our immediate priority should be to decrease human pressures on freshwater systems, which are important for life on Earth,” added Matti Kummu, leader of the study. . study.
According to United Nations (UN) figures, around two billion people in the world do not have access to safe drinking water and approximately a portion of the world’s population reports severe water shortages for at least part of the year.
“Only 0. 5% of the Earth’s water is usable and available as new water, and climate change is dangerously affecting this supply. Over the past two decades, terrestrial water storage (adding soil moisture, snow, and ice) has declined. at a rate of 1cm per year, with important implications for water security,” a UN spokesperson said.
These higher rates of evaporation and precipitation are not loosely distributed around the world. As a result, some areas will enjoy heavier-than-normal rainfall, while others will be prone to droughts.
Increased threat of flooding: The effects of flooding can be devastating for farmers, with crop losses and transient loss of land to graze livestock. This is a fundamental factor for food production.
Drought: While some areas are affected by flooding, others are affected by drought. This poses an equally serious risk to food security, as harvests of some crops around the world are poor in generating regions. Recently, the value of sugar is said to have risen sharply, due to a severe drought that hit Europe, severely damaging beet crops. Similarly, sugarcane production in primary generating countries, such as Brazil, has also been affected by drought.
Climate change is already known as a major risk to the production of commodities such as coffee, and manufacturers warn that emerging temperatures and unpredictable rainfall have altered the conditions in which coffee trees are grown, leading to lower yields and increased vulnerability to pests and diseases.
Source: Significant adjustments beyond pre-industrial soil and moisture situations transgress the planetary boundary of freshwater change. Published online: March 4, 2024 DOI: https://www. nature. com/articles/s44221-024-00208-7 Authors : Miina Porkka, Vili Virkki, Lan Wang-Erlandsson et al.
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