A new study shows that the future functions of ecosystems will increasingly depend on the availability of water. Using a series of simulations from state-of-the-art climate models, several “hotspot regions” are discovered, where ecosystems are strongly affected by increasing water limitation. For example in Central Europe, the Amazon and the western part of Russia. These ecosystems become less healthy and less productive in the future. It is essential to identify these regions: healthy ecosystems are vital for human life, as they provide several key services, such as food and water security, carbon dioxide (CO2) sequestration and evaporative cooling.
Healthy ecosystems need enough energy from solar radiation and soil water to carry out photosynthesis. During photosynthesis, tiny openings on the surface of leaves, called stomata, open to absorb CO2 of the atmosphere. At the same time, they allow water to evaporate from plants into the atmosphere, providing a cooling effect. This cooling is particularly useful during heat waves, as it can help mitigate the highest temperature extremes and associated heat stress, potentially saving thousands of human lives.
Simulations provide insight into water availability
Climate change introduces changes in the availability of energy and water for plants. While energy availability is constantly increasing across the world, regional changes in water availability are more uncertain in the future. In a new analysis, a group of researchers from the Netherlands, Germany and Australia used (future) simulations from a suite of state-of-the-art climate models. They analyzed data from 1980 to 2100 to investigate the effect of simultaneous changes in water and energy availability on ecosystem functions, using a new index.
“We have found that ecosystems globally are becoming more thirsty as they become increasingly water constrained,” says Jasper Denissen, a PhD student at Wageningen University & Research and first author of the study, recently published in Nature Climate Change. “We have identified several “hotspot regions” where this shift towards water limitation of ecosystems is particularly rapid, including large areas in North America, South America, northern Eurasia and East Asia. ballast.”
Increase water dependence in three different ways
The growing dependence on water manifests itself in three different ways. Not only is water dependence increasing in already water-limited ecosystems, but many regions where ecosystems were previously energy-limited are actually turning into water-limited ones. According to the study, an additional 6 million km2 of our earth’s surface will become water-limited by 2100 compared to 1980. And this effect doesn’t just happen in space, it also happens over time. The duration of water limitation will increase to 6 months per year in nearly half of the study area.
These changes in space and time leave vegetation hungry for water in larger areas and for longer consecutive periods. This will endanger the stability and health of ecosystems, reducing their functions for societies. This could lead to food and water scarcity, land degradation, disruption of CO2 sequestration by terrestrial ecosystems, reduction in biodiversity and the duration, intensity and frequency of extreme events.