by As winds of 90mph hit across the UK and Europe this week, new research shows that forests with diverse tree species are more likely to remain standing than monocultures when hit by extreme weather.
Forests with two or three species of trees are on average 35% more resilient against storms than forests with only one species, researchers have shown in simulations. The type of trees is also important – forestry plantations tend to consist of tall, fast-growing trees such as conifers, but are more vulnerable to high winds than slower-growing hardwood species such as oaks .
Extreme weather events such as Storm Isha – which caused deaths, power cuts and flooding across the UK – are likely to strike more frequently as the climate crisis progresses, as warm air holds more moisture, which which causes storms. Tree destruction in storms is becoming a growing problem for foresters – in 2021, winter storms destroyed around 12,000 hectares (30,000 acres) of forest in Britain.
“The monoculture of fast-growing species such as pine, although economically valuable, is more vulnerable to storm damage,” said lead researcher Dr Julien Barrere from the French National Research Institute for Agriculture, Food and Environment (Inrae). “In a context where storm losses are increasing across the continent, our study therefore argues for forest management practices that promote diversity and slow-growing tree species,” he said.
The benefits of tree diversity were even more pronounced under extreme conditions, such as in the hot and dry regions of the Mediterranean and the cold areas of northern Scandinavia, according to the paper, published Thursday in the journal Functional Ecology.
Researchers created simulations based on data from more than 90,000 real forest plots in Europe to see how they resist and recover from extreme weather events. They say fieldwork is still needed to support the findings. Barrere said: “These are scientific conclusions, not practical recommendations.”
However, their simulations support observations from conservationists in November 2021 when Storm Arwen brought down millions of trees as 100mph winds flattened conifer plantations. Experts said at the time that many of the downed trees were single-species, single-age conifer plantations, which are more vulnerable to storms than native mixed woodland.
“The results are exactly what you would expect,” said Professor Martin Lukac of the University of Reading, who was not involved in the research. “Not only do trees growing in a mix produce more biomass, but the forests they create are better able to repel the impact of adverse factors, including wind storms.
“We have to put trees in the mix – like the old saying about not putting all your eggs in one basket. Most natural forests grow as mixtures, and are clearly able to tolerate disturbance better than any cultivated ones.”
Conservationists and foresters are working out how they can minimize the damage when the next storm hits. The National Trust is looking towards more natural tree management. Ancient oaks, for example, reduce their branches as they age to increase their stability, and conservationists hope to leave these branches where possible, rather than cutting them back. Storms can also increase forest diversity by increasing the amount of wildlife-rich deadwood and creating more diversity within plantations.
“The study seems very timely given the recent weather in the UK,” said Professor John MacKay of the University of Oxford, who was not involved in the research. “It is important to keep in mind that it is possible to act now on diversifying the composition of forests but that it will take many years and even decades to bring benefits given the time it takes for trees to establish and develop,” a he said. “Acting in the short term seems critical to their future.”
Related: ‘Nature’s crown jewel of Britain’: Plan to restore rainforest welcomed by campaigners
Previous research has shown that species diversity has other benefits including increased resistance to pests and diseases, as well as drought. At the Royal Botanic Gardens in Kew in London, head of tree collections, Kevin Martin, says he is trying to plant species that can cope with the conditions predicted for years to come and beyond. that.
He said the Kew research highlighted the “importance of genetic and tree species diversity for urban forests, not only to build climate resilience but also to ensure resilience to pests and diseases – another growing threat”.
“So it’s critical that we use results like this … and put the right tree in the right place,” Martin said. “Without this, we risk creating landscapes that will fail in a short period of time.”
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