Another Life Michael VineyAlong at the cliffs there's a cleft in the rock where the waves rush up in winter to deposit, along with shreds of seaweed and Spanish aftershave bottles, the empty shells gathered from the seabed.
I sometimes pause there for a rummage in the hope of finding something new. But until climate change delivers something exotic (and probably invasive) I must be content with the long-familiar: topshells, dog whelks, limpets in a broken litter of mussels, razor shells, clams . . .
For all their variety of form and often beautiful finish, these molluscs have one shell-building material in common: calcium carbonate - the same oceanic stuff that, lifted in the Earth's unrest, built the white cliffs of Dover and the limestone terraces of the Burren. I like the way that, as the shells grind to powder on the shore and blow over the dunes, they get recycled into the new shells of land snails. Calcium is one of the great structural elements of life on Earth.
It is also very soluble, especially by acid - even the mild carbonic acid that falls in normal rain. On the Burren, this has helped to carve out a whole landscape, leaving glacial boulders perched up on stems: a sculpture that has taken thousands of years.
The ocean gets its calcium from river silt and tectonic rifts, plus the constant recycling of seabed sludge piled up from shell and skeletal fragments. A stable pH - the measure of acidity - has been essential to the ocean chemistry that keeps calcium available for living structures. But the extra CO2 we have pumped into the atmosphere is being taken up at the surface of the sea and drawn down thousands of metres. This present change towards acidity is 100 times more rapid than any the ocean has experienced over the past 100,000 years.
In the human world's reaction to the threats from global warming, the implications of acidifying oceans have been slow to register - this, perhaps, because there's so little hard research to call upon.
But expert reports like those for Britain's Royal Society and the Ospar Commission for Protection of the Environment of the North-east Atlantic are bringing home what could happen if man-made CO2 emissions are not drastically curbed.
Changes due to acidification have been measurable in the deep ocean even in just the last 10 years. Much of the man-made CO2 in the North Atlantic arrives in currents from the south, rather than from local air-sea uptake, and is then swallowed down by the "ocean pump" north of Ireland. The same processes that make the ocean such an efficient, long-term sponge for atmospheric carbon make reversal impossible within a human lifetime.
Ancestors of today's marine organisms lived under higher levels of CO2, but this change is happening too fast to fit within the pace of marine adaptation and evolution.
To make shells, plates and skeletons from calcium and its salts, the seawater has to be super-saturated with calcium and carbonate ions - otherwise seemingly tough substances will start to dissolve again.
Some calcium-based structures spring at once to mind as vulnerable to an acidifying sea - the fragile globes of sea urchins, say, the plates of starfish, or the biscuity armour of crabs and lobsters that has to be reformed at each moult. As predators and scavengers, these are keystone species on the seabed. Most molluscs, too, are potential victims, from oysters and a hundred other bivalves to the myriad forms of sea-snail. They are especially at risk in their first settlement from larvae, when building of a shell begins.
Much of the impact of acidification will be at a microscopic scale but nonetheless hugely significant. In the near-invisible world of plankton, which helps to regulate the ocean's carbon cycle as well as being vital to its food-web, several groups of plants and animals are calcifying organisms.
Among them are the single-celled coccolithophores, reckoned to be the most productive phytoplankton on Earth (their skeletons, drifting down to an ancient seabed when these islands were in tropical waters, made the chalk of the white cliffs of Dover).
Coral, too, is calcareous, and an acidifying sea threatens not only the tropical reefs, already seriously damaged by sun-bleaching, but the newly-discovered cold-water reefs in the deeps to the south-west of Ireland.
These are precious hubs of ocean biodiversity amid plains of limy mud.
Raised levels of CO2 not only acidify the water column but change its chemistry. All ocean organisms need oxygen to manufacture the compounds that give them energy, and a changed balance with CO2 may well lead to poorer growth and development. The long-term physiological impacts on fish and their ability to carry oxygen in the blood have yet to be tested. What seems all too probable is that they will be swimming through a very different undersea world.
EyeOnNature
Two buzzards have been flying around the field at the back of my house calling and swooping at one another, sometimes landing in a large ash tree.
I did think that they might be pairing but it seems late in the year for that.
David Murnane, Dunshaughlin,
Co Meath
It is late for mating, as paired buzzards are incubating now. They were probably a young, pre-breeding pair practising.
In a recently discovered collared dove nest outside my window I spotted two (or maybe more) chicks. They were covered in a yellow, grass-like material and seemed very young. Three days later, the nest was completely empty and there was no evidence of the chicks having fallen out.
Padhraic Moran, Callan, Co Kilkenny
The yellow covering was their pin feathers. It seems likely that a magpie or a sparrowhawk visited the nest.
A brave pair of blue tits have built a nest inside the timber panelling of my electric gates, flying through small openings at either end. They are feeding six chicks even when the noisy gates are opening and closing.
Wyn Beere, Kilternan, Co Dublin