High winds associated with El Niño could cause widespread mortality among tree species already weakened by a prolonged period of extreme heat and drought, experts have warned.
This summer much of Europe has been scorched by a series of record-breaking climate crisis-induced heatwaves. The impact is notable across much of England’s countryside, where once green land has turned brown, and many trees are undergoing “early autumn” – wilting and losing their leaves early – to cope with extreme heat.
Kevin Martin, head of tree collections at Kew Gardens, said to cope with these extreme conditions, trees had not grown as they normally would, and had become less flexible and more brittle.
“If we see the extreme winds that are predicted this year because of El Niño, we’re going to see potentially large impacts on trees,” he said.
The UK’s Met Office has said the El Niño event developing over the Pacific Ocean is likely to be the strongest for more than a century, with increased rainfall and storms forecast to hit the UK this autumn. El Niño is a natural phenomena that has been made worse by global heating.
Martin said this extreme weather could lead to root death, where dry weather followed by heavy rain can undermine the structure of the soil.
“We could then start to see some trees actually fail at the root plate. I’m really worried about this autumn,” he said.
This year’s weather has been so extreme that Martin thinks some species could be lost completely from certain landscapes. “We may lose species like the silver birch, the common beech and oak from landscapes where we’re used to seeing them,” he said.
While the impact is widespread, the heat is disproportionately affecting the oldest trees, with experts warning that England’s ancient oaks are dying in the hot and dry weather.
Martin said that what made ۲۰۲۶ so unprecedented was the spring heatwave, when temperatures reached ۳۵C, making it the hottest May ever recorded. “The whole growing season this year has been under stress, I don’t think we’ve ever experienced environmental impact like this before,” he said.
Simon Richmond, a technical officer at the Arboricultural Association, said trees were extremely resilient organisms, able to adapt to one-off years of extreme weather. However, he said the “danger that we face now is the likelihood with climate change of this being a prolonged pattern of weather”.
After the ۲۰۲۲ heatwave, Kew Gardens lost more than ۴۰۰ trees due to heat and drought. Martin thinks the impact of the ۲۰۲۶ heatwave could be much worse.
He predicts that at Kew and across the south-east, there will be a “significant amount of mortality”.
“From what I can see from the landscape here at Kew, we’re going to see a lot more mortality than what we saw in ۲۰۲۲ because a lot of trees that just got through ۲۰۲۲ are not going to make it through this year.” However, he said the full impact of this year’s extreme weather would not be known for the next two to three years.
Marcus Lindner, a principal scientist at the European Forest Institute, said that several years of extreme weather could push certain species over the edge, with almost all tree species at risk from the changing climate.
“Species that are normally drought-tolerant are adapted to a certain level of drought stress, but if we have continuous and repeated drought these trees will at some point not be comfortable with that any more,” he said.
