The shadows of late evening reached across the lawn to leave one little golden triangle where the grass ran into the nettles. It was just big enough for one young blackbird to spread his wings and gaze, immobile and enraptured, into the last of the sun.
Watching from the kitchen window, we were fondly amused if not quite surprised. Every sunny day for a week the same bird has arrived outside the window just as we’ve been making lunch.
He settles on the lid of the outside metal box that holds the filter treatment for our water. With a whitewashed wall at his tail, he has found the optimum location, with maximum shelter and warmth at the peak time of day. Spreadeagled to bare every glossy black wing feather, he enters a trance of voluptuous bliss, yellow beak parted, eyes fixed in an avian mindfulness.
At intervals, he remembers what he is really there for. Sunbathing birds (robins, sparrows, vultures and doves among them) are, say ornithologists, spreading their wings to drive out feather-feeding parasites and encourage the flow of glandular oil with which to preen and zip feathers into shape. Preening, for sure, is a big part of our fellow’s routine, but his sheer pleasure is obvious.
Another physical effect, it’s suggested, is that sunning helps birds convert compounds from their preening oil into vitamin D. Humans gain a similar benefit from sunlight, along with the risks of lolling around like walruses for far too long in too much of it. The deepest tan of my life was brought home from a three-month expedition in the Arctic. And there I was also struck by the rosy redness of walruses sunning themselves on the ice floes.
Were they as sunburned as they looked? Apparently not, since raising blood to the skin helps keep walruses warm. But Arctic sea mammals are being closely watched for damage from ultraviolet rays. The enormous, pale-skinned blue whale, for example, and the sperm whale that spends long periods at the surface, have been shown to develop skin lesions like those of sunburned humans.
The special concern about UV harm to Arctic wildlife arises from depletion of the polar region’s ozone layer by persistent atmospheric pollution – ozone in the stratosphere is what screens cellular life on earth from damaging solar radiation.
At his holiday home at Adrigole, in west Cork, in the early 1970s, the brilliant atmospheric scientist and inventor James Lovelock began analysing the puzzling man-made summer haze from Europe. Using his own apparatus, he measured a disturbing content of chlorofluorocarbons (CFCs).
These were chemicals then common in domestic fridges and as propellant for hairsprays and deodorants. Even in the 50 parts per trillion that Lovelock found, they were accumulating in the upper atmosphere with potential persistence for 100 years. Along with other man-made and ozone-depleting substances, scientists have found that they have created “holes” in the freezing stratosphere above the polar latitudes.
Since 1989, international agreements have progressively halted production of CFCs, and last month brought scientific reports of "the first fingerprints of healing" in the Antarctic ozone layer – indeed, a shrinkage of the hole by some four million square kilometres since 2000. In the Arctic, ozone holes so apparent in spring are variable in size but are expected to persist at least until mid-century.
With the UV band of sunlight so damaging to the DNA of living cells, how did life emerge on a planet without much oxygen or any ozone layer? It seems likely to have begun under water that filters out the more damaging wavelengths. As organisms evolved, they developed ways to resist and repair DNA damage while using the sun's energy for photosynthesis and growth.
There is general agreement that increased UV radiation related to ozone thinning threatens ecological harm – especially, it’s suggested, in damaging the tissues of ocean plankton and fish and crustacean larvae, the very life of the sea. Its infliction of human skin cancers has brought special WHO warnings to sunbathers in Australia and New Zealand, at the fringes of the Antarctic ozone hole.
James Lovelock, it must be said, has been surprisingly sanguine in his time. He is revered (not least by me) for his revelatory concept of Gaia, or Earth as a living, self-regulating organism. But in his 2000 autobiography, Homage to Gaia, he recalls how, in the 1970s, he "scorned the stories of algal destruction by ultra-violet in the southern ocean" insisting that "organisms, even tiny bacteria with the thinnest of membranes, find it easy to avoid damage from ultraviolet". But, as with the impacts of climate change, however, species need time to adapt.
Meanwhile, our sunbathing blackbird lolls, all unaware, a few centimetres above a tube of ultraviolet light, installed to execute the last sinister, subterranean bacterium that might stray up from the well.
Michael Viney's Reflections on Another Life, a selection of columns from the past four decades, is available from irishtimes.com/irishtimesbooks