If “biodiversity” means every living thing with which we share the Earth, how much does it matter to know what they are and how many?
We’re haunted by the rate of extinctions in the Anthropocene, the age of our impact on the planet. We’re told that half the Earth’s companion life could be gone inside a century.
Trying to slow this down, we need to know what lives where. Conserving species of land and sea, their lives and ecosystems so often interwoven with our own, depends on a worldwide jigsaw of local surveys.
Even the best surveys face problems, gaps and difficulties. The New Survey of Clare Island (its 10th and final volume published today) identified more than 1,000 different animals, terrestrial and marine. It also faced scientific problems that are shared with the global estimates of millions of species.
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The survey, by the Royal Irish Academy (RIA), repeated the remarkable project by naturalist Robert Lloyd Praeger at the start of the 1900s. In a time unshadowed by ecological angst, Praeger was intrigued by Darwin’s work on the evolution of island species.
Supported by the RIA, he recruited almost 100 field scientists for a pioneering study of the biodiversity of Clare Island, even before that term was known.
Specialists took 15 years to study the amazing diversity of the island’s freshwater algae. They recorded well over 700 species, making Clare one of the world’s few known hot spots of such variety
They discovered 109 new species and generated many volumes of data on the flora and fauna of the island from the top of its mountain to the edge of the sea. Their successors, who began work in the late 1990s, finally completed 10 reports, of which today’s volume offers research on the land and freshwater fauna, from eels and bumblebees to birds.
The overriding message from its papers, as Prof Thomas Bolger comments, is that the island’s fauna is “a subset” of mainland species, from fish parasites to midges, and from birds to mammals.
Collecting Chironomidae, or non-biting midges, for example, the new survey recorded 16 times as many species as the census of 100 years ago — but none was unique to the island. On the other hand, specialists took 15 years to study the amazing diversity of the island’s freshwater algae. They recorded well over 700 species, making Clare one of the world’s few known hot spots of such variety.
DNA barcoding
In today’s volume, Dr Bolger, retired professor of zoology at UCD, finds local surveys essential to estimating global patterns of biodiversity. But surveys tend to be biased towards plants, butterflies and birds that can be easily monitored. More difficult species are often neglected, even when they serve as important biodiversity indicators. Surveys of Irish earthworms, for example, have helped global estimates of distribution and diversity.
Taxonomy — the traditional description and naming of species — has been moving into DNA barcoding. Even some bees and ants now need genetic analysis. Changes in taxonomy and sampling were among the difficulties in comparing the two surveys of Clare Island. “[Given] the challenges of estimating even local species richness,” says Bolger, “it is clearly impossible to present a fully comprehensive assessment of biodiversity.”
The island still has one of the largest seabird colonies in Ireland, consuming an estimated three tonnes of food a day In today’s final volume, Dr Thomas Kelly records that six seabird species have joined the island’s colonies since 1912 and one — the Arctic tern — has gone.
Among arrivals, gannets have claimed most attention. Their nesting sites have grown from three in 1999 to 352 at the most recent count. In Clare Island, a book for the general reader that distils the survey science, John Feehan notes that Ireland’s gannet population increased by nearly a third in the decade to 2015.
By 2016 half the island’s properties were holiday homes. Since then Covid, the home computer and remote working have changed the perspective again
After the breeding season, the birds disperse southwards, so the hope is that Irish gannets have escaped the big plague of bird flu that has wiped out thousands, as well as other seabirds, on islands off Scotland. But it’s probable mass recurrence of the flu remains a threat to the avian natural history of these islands.
The second big survey of Clare Island wove its human heritage and farming future through the picture of its changing natural world. An island once bristling with heather and shelter for wildlife was worn bare to the summit by the grazing of subsidised sheep.
Much of the lower land, ridged and furrowed by intensive cultivation, is now grassed over. It once drew winter flocks of thrushes and blackbirds from the mainland. They don’t come now, and nor does the once-common corncrake.
In his lovely Clare Island (RIA 2019), Feehan wrote of the new dependence on supermarket food, and by 2016 half the island’s properties were holiday homes.
Since then Covid, the home computer and remote working have changed the perspective again. Young emigrants from the islands are returning and urban professionals are joining them.