Blackthorns blossom to climate warming

Another Life: When you look into it - which few of us have - a single flower of blackthorn has the beauty of wild cherry blossom…

Another Life: When you look into it - which few of us have - a single flower of blackthorn has the beauty of wild cherry blossom or a wild white rose, not surprising as they are all rosaceae. But a single blackthorn flower gets smothered in the extravagant wreaths which these spiky shrubs drape on winter's bones.

Stuart Dunlop, the Donegal computer-whiz and naturalist who daily photographs nature around his home in Raphoe, Donegal, had a first blackthorn flower to share on his website* on March 5th - a full eight days ahead of the first flower in March last year. Adaptation to climate warming is clearly proof against the odd icy spell. A sortie down our own boreen confirmed a comparable blossoming where the road twists around a fairy ring.

Back at my computer, maps generated from current reports to the UK Phenology Network (http://www.phenology.org.uk) had flowering blackthorn to offer as far north as Edinburgh, with first blossom in greater London on January 9th. Other maps offer primroses since November, rooks building nests before Christmas, queen bumblebees in southern England scarcely bothering to hibernate at all before their usual spring emergence.

This last phenomenon has been paralleled on our own east coast, almost anywhere with garden flowers and good shelter from the frosts. Bob Aldwell, a leading light in the Dublin Naturalists' Field Club, has been stalking winter bumblebees for years (in summer, he's a butterfly man). For the past three winters, in particular, he has spotted worker bumblebees from seemingly active nests at micro-climate coastal hot-spots such as the Vico Road in Dalkey.

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Ignoring the recent night frosts, Dublin's winter has, in fact, been exceptionally mild - up two degrees in November and January and about one degree in December and February. Even in a January cold front, the Vico Road could offer a club outing up to 10 degrees in sheltered, sunny spots, and a big Bombus terrestris queen and several workers laden with pollen from flowering veronica. A week later, on a mid-day walk in Monkstown, Aldwell found queens and workers busy at mahonia and early-flowering heather.

Similar observations from a garden at Ashford, Co Wicklow, help discount the idea that Dublin city's "heat island" of concrete and tarmacadam have made the winter bumblebees a special case. But on my Mayo hillside, singularly short of garden flowers in winter, a few bees were briefly abroad at warm noons in mid-February but, finding the willow catkins still locked up, ducked back to earth again.

The earlier bud-burst of trees such as oaks, however, weeks ahead of what it was 40 years ago, may be making problems for birds, such as great tits, which time their breeding to match the peak supply of caterpillars feeding on the young leaves. While day-length is giving bird hormones one kind of cue, man-made warming is giving trees and insects another.

Non-native trees such as sycamore and horse-chestnut have been showing an exceptional response to warmth, and a team in Trinity's botany department reports that the growing season of beech, poplar and bird cherry (all introduced species) has lengthened by nearly 50 days since 1966.

Such measures depend on the science of phenology, the study of seasonal cycles and the impact of climate on plant and animal life. But local conditions and variation in species can complicate comparison of results and trends. In the mid-20th century, a network of 57 International Phenological Gardens were set up across Europe, from Ireland to Macedonia and Scandinavia to Portugal, to cover every kind of climate.

In Ireland, these IPGs are at the Valentia Observatory in Kerry, Johnstown Castle and the JFK Arboretum in Wexford, the National Botanic Gardens at Glasnevin, and - the newest, created last spring - at Armagh Observatory. Along with 15 cloned species from Germany, the Armagh garden is planting selected native species proposed by the TCD botany department.

The impacts of climate change are sure to loom large at the European Vegetation Conference to be hosted in June by the botany department of NUI Galway. Delegates will be keen to visit the bogs of Connemara and the landscape of the Burren - ecosystems that have given UCG a special place in international botany. This makes it all the more extraordinary that the college's botany department, already small and hard-pressed, seems to have a most uncertain future - indeed, a degree in botany from Galway could become a thing of the past. Given the Department's history and location, that would surely be a shortsighted outcome.

The Donegal hedgerow website is http://homepage.eircom.net/~hedgerow7/index.htm