A WILDLIFE TRUST in the UK has sounded an alarm bell over trees shedding their leaves prematurely in the wake of an intense heatwave during the summer.
It’s a problem that does not appear to have reached Ireland this year, experts say, but which adds to concerns about the impact of the changing climate on the country’s wildlife.
After suffering through a drought, some trees may shed leaves early in an effort to conserve water and energy, particularly young trees without deep roots to reach water.
In the UK, which experienced record-breaking temperatures north of 40 degrees Celsius this summer, the phenomenon has emerged as a concern ahead of the winter.
The Devon Wildlife Trust said it has observed signs of ‘false autumn’ at 60 nature reserves that it manages and that early appearances of berries and nuts spell trouble for hibernating animals that rely on their availability in October and November.
In Ireland, where temperatures in the summer, though record-breaking, were not as high as in the UK, experts say they have not seen signs of premature leaf-fall this year but the country is vulnerable to present and future changes caused by the climate crisis.
In Ireland, a spokesperson for An Taisce said that “England, particularly the southern half, has experienced 40 degree plus temperatures and low rail fall level, with resulting very low river flow levels” but that Ireland “has not experienced comparable temperatures”.
“To date, the issue of premature leaf loss in Ireland has not been brought to our attention,” they said.
“Rising global heating exposes Ireland to increased probability of heatwaves and periodic drought conditions with impact on natural habitats and species, water supply and reservoir levels, crop production and animal grazing and grassland growth, the latter having an impact in early summer 2018.”
Irish Wildlife Trust Campaign Officer Pádraic Fogarty said that Ireland’s trees are less resilient now compared to previous centuries when more of the landscape was covered by natural forests.
“Our forests were very good at absorbing water and holding on to water and then releasing it slowly, similar to how our bogs worked as well,” Fogarty said.
“Over the past hundreds of years, we’ve seen Ireland as being too wet so we’ve tried to dry it out – farmland has been drained, rivers have been drained… but I think we’re going to have to try to undo an awful lot of that work now because of the threat of drought, as well as floods. They’re two sides of the same coin.”
Scientific models show that unless humans dramatically reduce greenhouse gas emissions, average global temperatures will rise significantly, with devastating consequences for people’s lives and the environment.
The climate crisis can make extreme weather events such as heatwaves and droughts more likely to occur and more intense when they do.
“If it’s just one season of drought, trees can recover, but all the signs are that the climate is changing quite rapidly. Individual trees may not be able to,” Fogarty said.
“It all comes back to our ability to try to restore natural ecosystems in Ireland, because that’s what will give our landscape some resilience,” he said.
We need to restore our river systems so that they hold on to water. We need to restore our bogs so that they can hold on to water for longer. We need to be re-establishing our native forests because biodiversity gives you the ability to adapt to the changes that are occurring. But of course, our biodiversity is in big trouble at the moment.
“We’re just not equipped. We’re not doing the things we need to do to get a handle on this problem at all. Our landscape is very vulnerable at the moment.”
In the UK, Devon Wildlife Trust spokesperson Steve Hussey said that staff and volunteers had reported seeing leaves turning brown up to two or three months prematurely.
“A member of our nature reserves’ team told me that in the 30 years he’s been working on his sites he’s never known it to be drier and for so many trees to have experienced leaf loss so early in the year,” Hussey said in a statement on the trust’s website..
Additionally, pointing to signs of some berries and nuts appearing earlier than usual, he said that a “very early and thinner, less bountiful wild harvest will present a further challenge to many of the birds and mammals which rely on a diet of berries, nuts and seeds to build up their reserves of body fat before the onset of winter”.
“Take dormice, as just one example: these are animals which must maximise their body weight in October and November in order to have a better chance of surviving their long winter hibernation,” Hussey said.
“To do this they will consume large numbers of high-fat foods, especially hazelnuts, during autumn. But if those hazelnuts and other hedgerow fruits have already been and gone in August then that presents them with a real problem.”
Hussey said that timing in nature is “everything” for wildlife.
“The climate crisis is bringing with it seasonal weather patterns which our wildlife is just not adapted to.
“Our long, hot summer and the ‘false autumn’ will have a knock-on for many species right into the real autumn months and beyond.”
Looking beyond cases of extreme conditions caused by drought, the rising concentration of carbon dioxide in the atmosphere is likely to influence when leaves grow and fall in years to come – though not dramatically.
A 2020 study of temperate (mild) European forests by researchers at ETH Zurich, a Swiss university, found that if CO2 emissions remain high, leaf fall would happen several days earlier than it currently does. Their findings subverted previous expectations that it would mean leaves would fall two to three weeks later than at present.
One consequence of that earlier leaf fall would be a reduction in the amount of carbon that temperate forests store each year – by about one gigatonne, the researchers calculated.
To embed this post, copy the code below on your site
have your say