by Ian Brand

MOST mornings from early spring onwards I enjoy ambling around our garden. This usually takes place immediately post-breakfast, with a cup of coffee in hand. It is an exciting time of year, waiting to spot that first bumblebee, butterfly or my favourite harbinger of spring, Lesser Celandine in flower. I am in good company as it was Wordsworth’s favourite too, his poems to this member of the buttercup family outnumbering those to the Daffodil three to one.

How exactly we define spring and its arrival is contentious - 1st March for meteorologists and Spring Equinox for astronomers. Most of us, however, associate spring with various natural events: the arrival of migrant birds, finding frogspawn, spring flowers, and the budburst and first leaves of trees.

Phenology, the study of the timing of these biological events, is fascinating. Spring spreads like a wave, moving from south to north in the UK, but also west to east and climbing hills en route. The trees in Wharfedale below our house burst into leaf several days before this green wave sweeps up the hillside, eventually engulfing us too.

“Citizen science” has been a rich source of data in the study of phenology, primarily through the ‘Natures Calendar’ project at the Woodland Trust. Large numbers of the general public have become involved, sending records of first sightings of birds, insects, frogspawn, flowering of spring flowers and first leaves of certain tree species.

How quickly spring spreads north is difficult to calculate precisely. It varies so much and depends upon which species you are talking about, but a rough estimate in the range of 20 to 50 miles a day has proved a good ‘ballpark’ figure.

I was interested to know which town on the south coast was due south of our area of Yorkshire. It looks to be Swanage. 250 miles away, where spring will be arriving on average 5 to 14 days earlier than here in Wharfedale.

Perhaps more importantly scientists have used the Woodlands Trust data from the past twenty years, but also included historical accounts from the early 1900s and compared these to the metrological records. As you might expect, warmer winter and spring temperatures do result in an earlier spring, but the effects vary from species to species. On average spring now arrives 7 to 14 days earlier than it did a century ago.

If you would like to know more and perhaps become involved in the project visit: https://naturescalendar.woodlandtrust.org.uk/

Photograph with kind permission of Anne Riley

www.wharfedale-nats.org.uk