Victorian meteorologists considered autumn to begin on September 1, but climate change is causing the mellow season to be less predictable, as blackberries burst out in time for Wimbledon and the full glory of russet colours creeps nearer to October 1.
This year, the Woodland Trust, which studies the timings of common seasonal events beside records dating back to the 1700s through its Nature's Calendar project (www.naturescalendar.org.uk), is receiving particularly mixed messages. Indications are that autumn fruits will be delayed, due to last winter being the coldest for 30 years-normally, the first ripe berries are found around August 4, but few have been recorded this year.
Sightings of beech leaves turning were down from 116 last year to just two, rowan berries from 808 sightings to 44 at the start of the month, bramble fruits down to 81 compared to 1,000. Yet some people are also reporting a bumper crop of big, juicy blackberries. Project manager Kate Lewthwaite says: ‘We don't know yet how significant these figures are; it may be that there are just fewer people participating in the survey than last year.
Generally, there are fewer records available for autumn anyway-for some reason, people don't seem to find it as inspiring as spring. But we do know that flowering was delayed in many species due to the cold winter, and this has had a knock-on effect on fruiting. We're some way behind, with lots of unripe fruit still on the bushes.'
The ideal conditions for producing rich autumn colours are sunny days and chilly nights, but Dr Lewthwaite thinks the different amounts of rainfall across the UK in July will lead to geographical variants in autumn palettes, with early leaf drop being reported in the drier South. ‘Leaf-tinting can create a falsely premature autumn,' she explains. ‘The tree shuts up shop if it hasn't got enough water.'
New findings by Kew's Jodrell Laboratory suggests that plants can adapt to climate change better than was suggested in 2007, when the Intergovernmental Panel on Climate Change said that 20%-30% of plant species could be at risk of extinction due to global warming. Kew's study indicates that many species could quickly adapt to a temperature rise of two or three degrees.
