From the bottom of the hill to the far horizon is terra incognita, a landscape permanently veiled. I furnish it with second-hand images: glimmering sand, blurred shadows of rock and weed, submarine wildlife caught aghast or fleeing into infinity. Imagine living beside a valley, a plain, a canyon, and resting content with such unknowing.
More than half the population of Ireland lives within 10 km of the coast, and remains almost pathologically unschooled and incurious about the world beyond the sea's edge. A recent hi-tech calculation added an extra 100 km to the coastline (bringing it to some 7,500 km) which is, in its own way, a neatly symbolic discovery.
This piece of information comes near the start of a new document which, for all its bureaucratic wrappings and numbered paragraphs, has a lot of the fascination of a colonial explorer's report to the queen. Along with reports on wildlife and precious minerals, come descriptions of hidden river and great plains and chasms to excite the mind's eye. Also, news of strange plagues and drifting poisons.
Its title is deadpan: Ireland's Marine and Coastal Areas and Adjacent Seas: An Environmental Assessment - and its fat 388 pages cost £20 from the Marine Institute. But this synthesis of current knowledge about Ireland's marine surroundings has the power of revelation: a vital prompt for what we teach in schools, and a thinking man's guide to a largely unconsidered realm of Ireland.
Seals and seabirds, dolphins and fish stocks, life on the "benthos" or sea-bed, are all grist to its encyclopaedic scope. Along with offshore topography and terrain, and the surge of currents and tides, comes an understanding of the ocean's cycles of life and how these are governed by changing, three-dimensional boundaries: glass walls and ceilings in the sea.
Just now, for example, the Atlantic shelf waters beyond the islands in my window are developing their summer thermocline - a horizontal barrier between the warmer surface layers and much colder water below about 40 metres. In the upper levels, penetrated by sunlight, the early bloom of plant-plankton - mostly diatoms - is falling back, as nutrients in the water are used up.
In other places, especially off south-west Ireland, this barrier is broken now and then by upwellings of the deeper, nutrient-rich water, so that swimmers on the nearby Cork coast may find the waves freezingly cold. At the vertical boundaries of mixed and stratified water - "fronts", as they are known - there can be surges of rich plankton growth. Between Fastnet Rock and Bantry Bay, for example, a summer front can treble the plankton production. Upwellings further out on the continental shelf can nourish such explosive productivity in the foodchain that fish, whales, dolphins and gannets are all drawn together to feed.
There have been great strides in understanding how climatic forces influence winds, waves, currents and salinity, and shape the different habitats and ecosystems around the Irish coast. But, as the report's authors readily admit, it's still difficult to distinguish between changes that are natural and those due to human intervention.
There is concern, for example, about the way that chemical nutrients pouring out from the rivers (in sewage and agrochemicals) may produce marine eutrophication of the sort we see in lakes. Even in Ireland, this is linked in many minds with blooms of toxin-producing algae among the marine plankton (chiefly dinoflagellates) that are making increasing problems for the shellfish industry.
The toxins build up in filter-feeding bivalves such as oysters and mussels, so that harvesting for humans has to cease for weeks or months, especially in the bays of the south-west. Other "red tide" blooms and their decay can kill fish, or foul tourist beaches with a skin-irritating foam. Irish marine scientists are exploring the possible links with human activity, but the new report's authors are more inclined to think the changes are driven by trends in climate, or in the North Atlantic circulation.
Natural toxins are one thing: man-made poisons quite another. One of the most disquieting sections in the chapter on marine chemistry concerns an organochlorine pesticide called toxaphene. Banned in the US since 1986, but still used extensively in Central and South America, it is now "a widespread contaminant in fish from the Northeast Atlantic".
Mercury, too, builds up in the marine food chain. While its levels in fish and shellfish around Ireland are generally safe for human consumption, the northern Irish Sea is now a "hot-spot" for mercury contamination, and concentrations in the livers of seals, porpoises and dolphins are now pressing at the limit of tolerance.
TBT (tributyltin) introduced into marine anti-fouling paints in the 1970s, was, the report says, "one of the most misguided and harmful practices in the history of marine pollution". Ten years after a partial ban on TBT, its biological effects can still be found at all but the most remote coastal sites. This is the poison that makes female whelks grow penises and thus progressively sterilises them; contamination can be toxic to scallops and oysters as well.
"Red tides" - natural or unnatural - will be a leading topic of a major international conference on restoring coastal shellfish resources, to be held in Cork, September 28th to October 2nd.
The first such conference, held in South Carolina in the US in 1996, brought fresh attention to shellfish as a keystone species in coastal ecosystems, and to the priority of restoring the beds of original native molluscs. For the Irish conference, the scope is broadened to take in nonmolluscan shellfish such as sea urchin and lobsters. Details from Dr Gavin Burnell, Department of Zoology and Animal Ecology, UCC, Lee Maltings, Prospect Row, Cork (email: g.burnell@ucc.ie).
