Summer is not over yet – but, depending on where you are in the country, you may have noticed a noticeable change in the landscape in recent weeks.
While the first day of autumn officially begins on 22 September, you may have already spotted berries ripening early, brown leaves falling from trees, and hedgerows taking on an unmistakably autumnal look.
These are all signs of what meteorologists refer to as “false autumn”, which is when the stress of extreme summer conditions prompts trees and plants to behave as if the season has changed, even if it is too early.
Dr Mike Wheeler, principal lecturer in biology at the University of Worcester, told the BBC that after a “very, very long, hot, dry summer”, nature’s resilience is being pushed to its limits – impacting wildlife and the food it eats.
But how common is the false autumn phenomenon – and how worried should we be about it?
What is a false autumn?
False autumn is a phenomenon where signs typically associated with autumn, such as fallen leaves and fruit ripening, occur earlier than usual, often in late summer, according to the Met Office.
This can be “misleading”, the forecasting service says, as it does not indicate the actual arrival of autumn.
Rather, it reflects stress in trees and plants due to adverse weather conditions, particularly prolonged dry spells and high temperatures, which prompts some trees to shed their leaves to conserve water and energy.
Sustained summer drought has caused chestnut tree foliage to turn autumnal, dropping leaves over a month early in some parts of the UK. (Alamy)
“Drought conditions cause trees to enter a kind of survival mode, dropping their leaves early to preserve themselves for the rest of the year and beyond,” the Met Office said.
“While the trees aren’t dying, they’re not thriving either, and the early leaf fall is a sign of the stress caused by the summer’s extreme conditions.”
As well as drought, the Met Office said heatwaves – four of which were declared in the UK this summer – are another prominent cause of false autumns.
What impact does it have?
The ongoing impact of climate change is also to blame for more frequent occurrences of false autumn, as ecosystems “struggle to adapt to extreme weather patterns”, the Met Office explained.
“This can lead to long-term effects on tree health and biodiversity.”
Stephen Rapin, head of arboriculture at environmental services provider Cura Terrae, told Yahoo News that berries ripening earlier than usual “is not good news for birds and other wildlife who depend on this food source at certain times of year”.
Evidence is pointing towards false autumns becoming more frequent – potentially damaging the resilience of trees and other plants. (Alamy)
He added that some trees start to “over-produce” seeds such as acorns during periods of heat stress, “which can cause problems for animals that rely on them as a food source later in the year”.
“Trees that are under stress from drought are also more prone to infection from bacteria and fungi due to their weakened condition,” Rapin said. “This means that the long-term effects of drought can take many years to show.”
Agriculture, as well as wildlife, is already feeling the impact, with Charlie Clive, owner of Clive’s Fruit Farm in Worcester, telling the BBC his apple and cherry trees in particular have struggled this year.
He said some of his apple trees looked “sad” as they had grown too many apples without enough water, leading to the fruit falling prematurely.
Why is it a cause for concern?
Kevin Martin, head of tree collections at Royal Botanic Gardens, Kew, told Yahoo News that “in the short term”, false autumns are not a “major concern”.
However, he said they are predicted to become more frequent in the South East of the UK, with shortened growing seasons reducing the energy available for new buds in spring.
This, he added, can “weaken trees’ defences against pests and pathogens”.
Martin said recent evidence suggests false autumns are becoming “increasingly normal”, and that over time, trees vulnerable to this phenomenon “may struggle and could be lost from our landscapes”.
“Repeated false autumns can weaken trees over time by shortening their growing season and reducing the energy available for spring growth,” he added. “This makes them more vulnerable to pests, diseases, and environmental stress.”
The Met Office said more frequent false autumns are a “sign of the stress our trees and plants are under due to the changing climate and extreme weather”.
“As the UK continues to experience warmer, drier summers, we can expect to see more instances of early leaf fall and other unusual seasonal changes,” the forecaster added.
Rapin said that “larger and better established trees” can survive drought conditions “longer than smaller trees or those that are already under stress”, but that “all trees will eventually begin to die as they fail to draw in enough water”.
As branches dry out and become more brittle, he said, trees “will then either die completely or recover to a greater or lesser extent the following spring”, depending on how much energy they have stored.
“If we continue to suffer the effects of climate change and have more hot and dry spells in the years to come, it will become even more important to regularly monitor the health and safety of our tree stock,” he added.
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