Left to themselves, islands make their own rules about the number of species they contain. New ones arrive, old ones die out, the composition of the flora and fauna is constantly changing, but the number of species stays the same, fixed by the area of land.
This is the basis of the famous Theory of Island Biogeography worked out by Edward O. Wilson and Robert MacArthur almost 40 years ago, and I have been waiting for someone to try it out on Ireland. What with ice-age extinctions and repopulations, transient land-bridges and drifting logs, waves of humans importing all manner of creatures and killing off those that were here, this island must have tested severely any long-term natural equilibrium.
A reminder of just how many pivotal species have been brought in by people, accidentally or on purpose, is offered by Exploring Irish Mammals (Town House, £20), by Tom Hayden and Rory Harrington. This splendid handbook is a collaboration of top mammalogists in NUI Dublin and Duchas (which commissioned it) with fine illustrations by Billy Clarke.
Of our 22 species of land mammals (leaving out bats and seals), the authors accept that at least 13 were introduced by humans. Along with familiar examples of imports, such as hedgehog, rabbit, mink and brown hare, even the red deer - native to the island before its last ice-age extinction - may have been re-introduced 5,000 years ago, trussed up, presumably, in Neolithic currachs.
Dr Hayden and Dr Harrington, who span a great range of species in their own research work, admit to a philosophical approach to Ireland's mammals which is "holistic, scientific and firmly grounded in evolutionary biology." This seems to add up to a positive empathy, tempered by genetics, that falls short of wanting to bring back the wolf.
Their big, solid paperback is coolly factual for the most part, offering ample, systematic information on the life and times of each of our 58 mammals. It includes, and not before time, all the whales and dolphins in the sanctuary of our waters, and even the walruses now turning up along the northwestern seaboard. Rory Harrington is a geneticist, and part of his work for Duchas lies in experimenting with hardy breeds of cattle that could replace sheep on our uplands, probably to great ecological advantage. Kerry cattle, small, black and glossy, have been at the heart of his cross-breeding trials in Killarney National Park - not always, perhaps, to the approval of those who have kept the Kerries going as a pure strain.
Kerry Cattle: A Miscellany is a collection of fondly-written stories, gathered from breeders and enthusiasts, that trace the progress of this personable cow ("smarter than the hired help, affectionate as a dog and nimble as a deer") from its Neolithic origins to its current 1,000-strong resurgence in the service of organic farming. Emblazoned with a heavy-breathing bull by Pauline Bewick, the book is available from the Kerry Cattle Society of Ireland, Cahernane, Killarney, Co Kerry (£10 pbk, £14 hbk).
When the Heritage Council decided to grant-aid publication of The Shores of Connemara, by Seamas Mac an Iomaire (Tir Eolas, £9.99), did they know how magnificently they would be rewarded? It re-introduces to modern Ireland a major cultural text, and also one of the most enjoyable and revelatory books in the whole of Irish writing about nature. I am quite bowled over by it.
Seamas Mac an Iomaire was born in 1891 on Mweenish Island off the coast of Connemara near the village of Carna. His youth was spent among fishermen and seaweed-harvesters - vivid years, still engraved on his mind as a teacher, and recalled on paper in the late 1920s while prostrate with TB in a New York hospital bed.
Cladai Chonamara was first published by An Gum in 1938 and has now been wonderfully translated by Padraic de Bhaldraithe, a marine biologist, post-primary schools inspector and hooker-skipper, who lives in Lettermullan. The flow and directness, the intense charm of Mac an Iomaire's writing come springing off the page.
He was not a naturalist in the more familiar urban, middle-class tradition of men like Praeger, but a practical coastal dweller to whom a lugworm was, first of all, a bait for fishing wrasse. "Up to 40 men would dig the strand at the end of the night, working away furiously under their soft coats of sweat" - and young Seamus was there among them. The practitioner's voice in his writing reminds me of another classic text in Irish natural history rescued from limbo in modern times - Arthur Stringer's The Experienced Huntsman, first published in 1714 and revived by James Fairley in 1977. What Stringer did for the mammals of the chase, Mac an Iomaire does for fishes, animals and plants of the shore. Even with such an historical gap, there is the same warmth of a direct relationship with nature in which the "science" of observation is tempered with fellow-feeling - the emotional awareness and sense of the wonderful lauded in the introduction by marine botanist Cilian Roden.
This book buries once and for all, as he says, "the myth that the people of Ireland were a race of thalassophobes incapable of observing their natural surroundings." Mac an Iomaire's gallery of shellfish shows just how enthusiastically they were used for food (to catch razorshells and sand-gapers you had to whistle musically to hold their attention as you plunged your arm to the elbow).
The strange and wonderful are never far away. What is one to make of the scolabord tintri, the "flashing skate" that has "light shining from its eyes" to show it the way ahead through the forests of kelp stems? But there really is a flatfish called the topknot, that has to be scraped off a rock, there really are shoals of barrel-fish (Hyperoglyphus perciformis) that lurk in drifting flotsam, and if Mac an Iomaire really didn't see an Atlantic flying fish when out in his pucan after wrack, it behaved exactly like one.
Padraic de Bhaldraithe keeps the science tactfully on the rails, and the rich illustration includes original etchings of fish by Galway's Sabine Stringer that rank with the best in marine illustration; this whole book is a labour of love.
