Facing climate change, Swiss trees get mist before they're missed
Switzerland is experiencing increasingly dry summers - by 2060, there will be 25% less rain in summer, and droughts will last longer.
The objective of the trial is to develop forestry strategies and influence the choice of tree species to plant in future.
For more climate change news and analysis, go to News24 Climate Future.
In a Swiss pine forest, the treetops are being sprayed with mist in a bid to discover the effect that drier or wetter air has on their ability to survive.
Eighteen scaffolding towers have been erected between the trees in the Pfynwald in Switzerland's southern Wallis region. High-pressure nozzles mounted on the towers spray vapour over the canopy of some 60 Scots pines, standing 15 metres tall.
The study is a unique experiment designed to separate out and analyse the different effects of soil drought and air dryness in a natural forest ecosystem.
"The goal is not to spray forests to save them, but to understand why a lack of water in the atmosphere has such a significant impact on forests," project director Charlotte Grossiord told AFP.
The trial is being conducted by the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) and the Swiss Federal Institute of Technology in Lausanne (EPFL).
The vapour studies aim to measure the rate of dieback in trees, where the leaves and branches start to wither away. It should help experts anticipate when similar forests will be affected, said Giovanni Bortolami, one of the researchers.
The objective is to develop forestry strategies and influence the choice of tree species to plant in future, as Switzerland experiences increasingly dry summers.
By 2060, there will be 25% less rain in the summer and droughts will generally last longer, the environment ministry has said.
Another goal is to better understand tree mortality, given that trees "allow us to estimate the concentration of carbon dioxide in the atmosphere", with CO2 being the main climate-warming greenhouse gas, said Grossiord, a professor of plant ecology.
Thirsty air
The Pfynwald is one of the biggest continuous Scots pine forests in Europe. It counts roughly a thousand trees, all around a century old.
At 615 metres above sea level, and surrounded by towering Alpine mountains in the Rhone river valley, the forest is one of the hottest and driest places in Switzerland - ideal conditions for the researchers.
They have been working in the Pfynwald since 2003, studying the dieback of Scots pines due to soil dryness.
Some parts of the forest are irrigated, while in others, translucent plastic prevents rainwater from reaching the soil.
The mist-creating sprays were introduced last year to study the effects of air dryness, as climate change is resulting in another worrying environmental parameter: thirsty air.
At equal humidity, warm air is more "thirsty" than cold air. This "thirst" is called vapour pressure deficit (VPD).
VPD is a major factor in determining how much water trees will evaporate through their leaves. With global warming, VPD is increasing, which can cause water stress in vegetation.
"Imagine a glass of water in a desert and a glass of water in a rainforest. The temperature is the same. The glass of water empties very quickly in the desert, but not in the rainforest," said Bortolami.
It's "exactly the same for trees", which evaporate much more water if the air is drier and therefore "consume water from the soil more quickly", the plant ecophysiology researcher explained.
Surprising results
The nozzles diffuse water vapour onto part of the canopy during the day to reduce air "thirst" by about 20-30%.
The researchers then compare the data with the trees that did not get the water vapour spray.
Cables on the forest floor are hooked up to sensors on the tree trunks, which continuously measure their diameter and sap flow - an indicator of water stress. The researchers take other monthly measurements on site.
The study will continue until 2028.
The initial results show that a lack of water in the soil speeds up the dieback of foliage - an expected outcome for the researchers.
"However, we observed that a dry atmosphere will slow down the dieback process rather than speed it up. That's what really surprised us," said Grossiord.
The measurements revealed that with less moisture in the atmosphere, trees close their pores to conserve water.
But these acclimatisation mechanisms can only help a tree so much. In the Pfynwald, as in other dry Alpine valleys, Scots pines are dying out while young oak trees, some only waist high, are taking their place.
Hashtags
Try Our AI Features
Explore what Daily8 AI can do for you:
Comments
No comments yet...
Related Articles
Yahoo
3 hours ago
- Yahoo
Climate change and aerosol pollution made drought inevitable in the US Southwest: Study
The combined effects of climate change and air pollution have led to direct declines in precipitation in the U.S. Southwest, making drought inevitable, a new study has shown. These circumstances, which began taking hold in about 1980, are likely here to stay as the planet warms, according to the study, published on Wednesday in Nature Geoscience. Its authors attributed this decades-long trend toward less precipitation to La Niña-like conditions, weather patterns that lead to cooler surface temperatures in the tropical Pacific Ocean. Even if El Niño-like conditions had prevailed instead, the Southwest would not have experienced a corresponding surge in rainfall, the researchers found. 'There's a uniform warming trend because of historical climate change, as well as emissions from anthropogenic aerosols, that both create a certain circulation pattern over the North Pacific,' said lead author Yan-Ning Kuo, a doctoral student at Cornell University, in a statement. 'Those two factors prevent the precipitation for the Southwestern U.S. from increasing, even under El Niño-like trends,' Kuo added. The researchers drew their conclusions by abandoning popular climate models that they said in recent years have not accurately reflected sea surface temperatures as observed in real time. Instead, they designed their own simulations in which they could insert data from satellites and statistical models, and thereby isolate the impact of each contributing factor. The post-1980 period in the U.S. Southwest exhibited the fastest soil-drying among past and future periods of similar lengths — a result that the authors attributed to human-induced warming and a decline in precipitation. Even in a simulation of El Niño-like trends, the authors identified a tendency toward precipitation decline, counter to what they described as a 'canonical El Niño teleconnection,' or the relationship among weather patterns spanning the Pacific. That 'unintuitive yet robust circulation change' is rooted not only in warming, but also in the radiative effects of manmade aerosol pollution, according to the study. Co-author Flavio Lehner, an assistant professor in Earth and atmospheric sciences at Cornell, said in a statement that this change points to a bigger shift in the so-called teleconnection that spans the Pacific Ocean. 'These external influences really modulate that relationship, so it doesn't behave exactly how we expect it to behave,' Lehner added. While emission from vehicles and industry will likely decrease as countries in East Asia make air quality improvements, Lehner noted that warming temperatures could offset this positive momentum. These gains, in other words, are 'unlikely to substantially alleviate the currently projected future drought risk,' according to the study. 'The warming is going to continue as far as we can tell,' Lehner said. 'That will gradually outweigh those benefits, as a warmer atmosphere tends to be thirstier, gradually drying out the Southwest,' he added. Copyright 2025 Nexstar Media, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
Yahoo
3 hours ago
- Yahoo
How scientists discovered toxic algae blooms are increasing in the Arctic
Harmful algae blooms have been rapidly producing in a place previously too cold to host the toxin: the Arctic. And climate change over the last several decades is to blame, according to new research. Scientists have found a link between rising ocean temperatures and an increasing amount of toxins from algae blooms entering the marine food chain by analyzing the feces of bowhead whales in the Arctic, according to a paper published Wednesday in Nature. MORE: Toxin detected in Lake Erie weeks earlier than ever before, NOAA says Collaborations with native tribal communities in the Arctic helped researchers in their findings, said Kathi Lefebvre, a research biologist for NOAA fisheries at the Northwest Fisheries Science Center in Seattle and lead of the Wildlife Algal Toxins Research & Response Network (WARRN-West). Researchers at WARRN-West have received fecal samples from 205 bowhead whales from the indigenous groups that were collected by either subsistence harvesting or found stranded in an unusual mortality event in the Beaufort Sea over the past 19 years, which put them in a unique position to monitor the progression of harmful algal blooms on the West Coast of North America, Lefebvre, lead author of the study, told ABC News. By studying the samples, the biologists could look at algal toxin concentrations in the food web, Lefebvre. The krill and copepods that ingest the toxins are then eaten by the bowhead whales, which are filter feeders. Over the past century, sea surface temperatures in the region have been rising, causing the amount of sea ice to shrink significantly. The warmer waters combined with more open water is leading to the higher concentrations of at least two algal toxins: Alexandrium, which are dinoflagellates that produce saxitoxin -- a neurotoxin that can cause Paralytic Shellfish Poisoning; as well as domoic acid, which is produced by Pseudo-nitzschia, a needle-like group of single-celled algae, and causes amnesic shellfish poisoning, according to the study. "We know from laboratory studies that these algae grow faster in warmer conditions," Lefebvre said. "There's more light because the open water is there and the ice is not reflecting the light." MORE: How humpback whales are playfully communicating with humans, according to scientists The cells have always been present in low concentrations in the Arctic, but the potential blooms are now larger, longer lasting and more toxic, Lefebvre said. Alexandrium drops cyst-like seeds that lay dormant in the sediments until conditions are right to produce. "So seeds have been dropping from these Alexandrian cells for hundreds, maybe thousands of years, and these seeds need a certain temperature to be able to germinate," she said. MORE: What to know about the toxic algae bloom killing marine life in Southern California In the past, the bottom waters of the Arctic have been too cold for the cysts to germinate, but as the ocean warms, conditions are becoming ripe for reproduction. This is the first study of its kind to quantitatively show a direct link between climate change, sea ice loss and harmful algal bloom concentrations in the food web, Lefebvre said. The Arctic tribal communities that collected the samples are still fully reliant on marine resources for subsistence, Lefebvre said. "Marine resources are utilized for survival, for cultural practices, for economic well being, etc.," she said. "They've been doing this for thousands of years." In most places around the world, there are protections in place to test for these toxins for commercial seafood. But in the "vast remote" regions of the Arctic, such testing would be difficult to conduct on a regular basis, Lefebvre said. The communities harvest everything from clams, crabs, sea birds and anemones. "We're finding these toxins in all of these species," Lefebvre said. MORE: 'Demonic' sea lion reports spark concerns about toxic algae on California coast It is unclear how many whales in the Arctic have died as a result of harmful algae blooms, but walrus populations in the region, which feed on clams found at the bottom of the ocean, have been likely dying off as a result, Lefebvre said. Lefebvre has been studying harmful algae blooms for her entire career and was involved in the first-ever study in 1998 that found domoic acid was impacting marine mammals in Central California. Ever since, dozens to hundreds of marine animals have been documented to suffer from domoic acid poisoning every year, Lefebvre said. Southern California is currently recovering from its worst harmful algal bloom event, which impacted more than 1,000 marine animals overall since it began earlier this year, according to the Marine Stranding Network.
Yahoo
3 hours ago
- Yahoo
Warming climate, volcanos raise risk of ice falls on Chile's glaciers
SANTIAGO (Reuters) -Chile's glaciers are facing a higher risk of collapse and landslides due to rising temperatures and the country's seismic and volcanic activity, according to an academic study. The study, published in the Journal of South American Earth Sciences in late May, modeled variables such as the possible sudden emptying of glacial lakes, mud and debris flows, avalanches, landslides, or abrupt glacial advances beyond normal speeds. "The study determined that around 10 glaciers ... would be highly susceptible" to one or more of those main destabilizing factors, said geologist Felipe Ugalde of the University of Chile, one of the study's authors. That included some glaciers at risk of ice avalanches, others that had steep overhangs, and some that could be affected by declining glacial lakes. Others faced risk from volcanic eruptions in the nation that sits on the Pacific "Ring of Fire," a belt of volcanos and earthquakes. "Three highly susceptible glaciers are those closest to the main emission centers of the San José volcano, highly susceptible to lahars," Ugalde said, referring to volcanic mud flows that are usually a mix of water, volcanic ash, and rock debris. The geologist added that glaciers globally were retreating amid warming temperatures, causing them to lose mass and become less stable over time. "When temperatures are high, water infiltrates either through rain or through rapid melting of the snowpack. This water percolates into the base of the glacier and acts as a lubricant," Ugalde said, adding this could cause ice to fall off more rapidly in a natural process called calving. "This is ultimately a response to the imbalance that glaciers are experiencing as a result of increasingly higher average air temperatures, even in high mountain environments," he said.
