The severe heat and drought in Europe this summer will lead to a massive wave of tree deaths over the next two or three years even if there is enough rainfall to bring the drought to an end, experts are warning.
鈥淣ot only next year, but also in the following two to three years we will see a cascade of tree mortality,鈥� says at Tartu Observatory in Estonia.
Numerous studies around the world are showing that the extreme heat and droughts caused by global warming are killing off ever more trees, from tropical rainforests to boreal forests in the far north. Last year, for instance, George鈥檚 team reported that the drying out of soils in Europe is increasing tree death rates across the continent.
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His study, like others, found that these deaths typically occur a year or more after a drought, rather than at the time. In other words, many trees that at present appear to have survived the drought and widespread wildfires could still end up dying.
The last drought in Europe in 2018 led to the , and at the Technical University of Munich, Germany, . 鈥淲e thus expect that this year and next, tree mortality will be high,鈥� says Senf.
It is too soon to tell whether even more trees will die this time, says Seidl. 鈥淲hat made the 2018 event so detrimental was that it in fact was a three-year drought in many places,鈥� he says. 鈥淔or the 2022 drought, we鈥檒l have to see how the next months and years will play out.鈥�
A 2021 study of tree rings from living and preserved trees found that the series of droughts in Europe since 2015 . 鈥淭here is no recovery time any more between droughts,鈥� says George.
There are several why droughts can lead to trees dying a year or more later. They can starve and the tissues that transport water can be permanently damaged. Trees weakened by droughts are also much more vulnerable to pests and diseases, such as bark beetles and fungi.
Warmer conditions are also adding to the stress on trees in another way, by allowing pests such as the horse chestnut leaf miner to start attacking them earlier and thus to do more damage. 鈥淎 lot of insect pests appeared sooner this year,鈥� says at the Royal Horticultural Society in the UK.
Trees have a vital role, says Hunt. They not only help reduce global warming by soaking up carbon, they can also help limit the effects of warming by cooling cities and reducing flooding, he says.
Trees that die shouldn鈥檛 simply be replaced with the same species, says Hunt. Now is the time to start adapting to the future by planting more resilient species, he says, ones that are able to cope with all kinds of weather extremes, not just droughts.
Europe is far from the only place where drought is killing trees. In the US, power companies are warning that drought-stressed trees could . Such an event is said to have and destroyed 200 homes in New Mexico earlier this year.
