Why are this year's autumn colours so late?

As he enjoys an autumn walk in the woods near his home in the New Forest, Bill Reynolds has noticed "things have altered a bit".

"There are a lot of oak trees here - they seem to be late in developing the autumn colours.

“I think the difference is about a fortnight, and it’s slowly getting later still”.

He has been taking photos of the area for several years and sharing them on his Southampton to the New Forest Facebook group where other members have also spotted trees staying greener for longer.

"I'm just a layman, but it's what I've noticed - it's not happened overnight, it's being going on for some time," he added.

The annual golden display of autumn leaves as the daylight hours fade is down to weather conditions

Professor Liz Bentley of the Royal Meteorological Society said: "The shortening of days and lower light levels stops the production of chlorophyll - the green pigment in leaves.

"As the green pigment fades - due to the trees withdrawing sugars from the leaves - the underlying colours of reds, oranges, browns and yellows become apparent."

"Good levels of sunshine and rainfall is needed to build up sugars in the leaves, a lack of rain causes stress for the trees with potentially early shows of yellow or brown autumn colour and leaf fall."

The end of the very hot dry summer in 2022, a so-called false autumn saw leaves turn brown and drop in August - due to the stress on the trees.

With the mild, warm and wet conditions we have seen this year, chlorophyll in the leaves continues to be made and so they stay green.

Met Office statistics show average autumn temperatures in south central and south-east England increased from 5.8C between 1961 and 1990 to 7C from 2014 to 2023.

The Woodland Trust has been building a picture of long-term trends in the cycle of the seasons through its Nature's Calendar citizen science project.

It has built of a database of timing of key seasonal events - the first snowdrop in spring, when swallows return from Africa, when autumn fruits ripen or leaves start falling from trees.

The trust's Dr Kate Lewthwaite said: "This year the growing season is effectively extending as temperatures have remained mild."

It is hoped the project will help scientists gain a better idea of how species are responding to climate change.

"Changes in times of season events are the first things scientists tend to note.

“We’re really at the very early stages of time and study – we think that there will be winners and there will be losers, as a result of climate change.

"For some species it will produce really ideal conditions. But for many others, far less than ideal conditions.”

The National Trust also warned the "mixed bag" of weather experienced this year could have an impact on the seasonal displays at its properties and gardens.

Pamela Smith, its senior national consultant for gardens and parklands, said: "As the predictability of weather patterns continues to alter due to a changing climate, the timings of a traditional autumn with its colourful canopy displays become less certain."

Tree crowns remaining at "full sail" also increases the threat of damage caused by autumn storms, it warned.

Scientists studying phenology - nature's recurring phenomena - believe plants and insects' life cycles could become out of sync as a result of shifting seasons.

Dr Rob Salguero-Gómez, Associate Professor in Ecology in the Department of Biology at the University of Oxford, said shifts in seasonal events seen around the globe were "very much due to climate change".

“If plants are shifting their phenology four times faster than insects, which do eat them or pollinate them, that mismatch could really compromise that entire pyramid of the ecological system, where they are inhabiting.

“We discovered that 60% of the tandem between insects and plants that coexist in any one location across Europe is changing significantly.

"They are advancing their phenology, they are waking up earlier, they are growing faster, they are reproducing sooner.

"Plants are doing this four times faster than insects, meaning that even though insect phenology is also advancing in time, they are lagging behind, and that’s causing phenological mismatches.

“Us humans, we tend to be higher up in a pyramid of consumption. We can eat other animals, we can eat vegetables. Vegetables and other plants are at the base of the pyramid. We all ultimately depend on how well plants do.”

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