Science Spin September 2008

Clare Island: Charting species changes over 100 years

By Anthony King

Those who travel to Clare Island by ferry cannot fail to notice the castle by the pier. The small ruin is Grace O'Malley's castle, named for the high-spirited Pirate Queen of the sixteenth century. It's not certain whether the famed seafarer ever lived in the castle or hauled booty ashore. But this island four miles off Mayo has another claim to fame.

One hundred years ago, in the summer of 1909, a remarkable scientific expedition began to this island. Sixty years had passed since Charles Darwin had travelled the world as a young naturalist; the Clare Island expedition was an altogether different but nonetheless remarkable adventure for Victorian, and Irish, science. From 1909 to 1911, Clare Island was scrutinised by one hundred expert naturalists, many of them leaders in their field. This intense activity was marshalled by Irish naturalist Robert Lloyd Praeger. As Praeger later wrote, "There was no month in any of the twelve in which one of our collectors might not have been found investigating seaweeds or earth-worms or mosses."

On the Origin of the Species by Charles Darwin had been published 50 years earlier. Praeger was seeking support for Darwin's idea of natural selection by looking for subtle differences between species on the mainland and the island, explains Dr Matthew Jebb, Keeper at the National Botanic Gardens. Along with plants and animals, the project took in geology, archaeology, meteorology and agriculture.

What was extraordinary about it was that it was the first intensive survey of a small piece of Europe, said Dr Jebb. "Fifty years earlier, people like Darwin were touring the world and collecting plants and animals in places like the Galapagos Islands, but nobody had thought to earmark a small island in Europe and survey it intensely." The Royal Irish Academy says the 1909-11 survey was the most ambitious natural history project ever undertaken in Ireland and the first ever major biological survey of a specific area carried out. Experts came from Britain, Switzerland, Denmark and Germany. There's been nothing like it since.

New species

The results appeared in print from 1911 to 1914, revealing 1,253 species new to Ireland and 109 new to science. There were papers on beetles, sponges, algae and butterflies, botany, birds and archaeology: 67 in total. They appeared in three volumes, almost 2,500 pages; looking at them on the book shelf brings a sense of awe, said Dr Jebb. And it offers a point of reference for future studies to compare Ireland past and present.

The Royal Irish Academy has sought to capitalise on the resource by rerunning surveys toward the close of the 20th century. Six volumes of the New Survey of Clare Island have been published, with four in progress.

"There is no doubt that going back 100 years we have got the most fantastic benchmark of what a piece of Ireland looked like 100 years ago, which nobody else recorded," said Dr Jebb. It means that we can now revisit Clare Island and see that a large number of plants have vanished, for instance. The flora has become poorer by at least twenty percent, said Jebb, but lots of new species have also arrived. "So one of the first inklings of the importance of Praeger's work was when people revisited Clare Island many years later and realised that all these islands have a turnover of plants and animals."

The fauna and flora of an island are determined by its size, said Dr Tom Kelly of University College Cork. Dr Kelly, who has studied the birds on the island for a future volume, says this allows scientists to predict the number of species on an island. "Breeding birds are one metric by which you measure species diversity on an island," he noted. But island diversity has a great deal to say about conservation and even national parks.

If you total up the number of species on an island, it is always less than an equivalent area on the mainland. Dr Jebb explained that this "island effect" is very important because it teaches us the size you would have to make a national park or reserve if you want to preserve plants and animals. "How big should you make your reserve? And what islands teach us is the bigger the better," he said. As an island gets smaller, you get fewer species.

It also means Clare Island acts like the proverbial canary. "It will tell us which species of plants are more susceptible to becoming extinct due to modern farming practices," said Jebb. Intensive agriculture can squeeze out wild plants and animals. The shoulder high heather, which confronted the early naturalists on the island is no more, extinguished by grazing and fertilisation of the soils. But, remarkably much of the island remains as it was in 1909.

Birds

There's not a huge difference in terms of bird species on the island in the early part of the 20th century and 21st century, said Dr Kelly. Red grouse disappeared along with the heather, but ground nesting birds such as skylarks and wheatears are still very abundant on the island. Meadow pipits are common; you can watch them abseiling down a stiff breeze, all the time piping out repetitive 'zee' notes.

A three mile by five mile rock in the Atlantic, the island is unusual in having a remarkable 1,500 foot mountain and being cliff bound on all sides. The north side of the island has sheer cliffs where you can watch the wild relatives of the overfed street pigeon. "The purebred rock dove is quite rare now," said Dr Kelly. "The doves are absolutely magnificent looking, not like the feral doves you see on the mainland." These flint coloured acrobats share the island with their natural predator, the peregrine falcon, which Praeger deemed Ireland's "master of the air."

The island also has an impressive seabird colony, with large numbers of guillemots, razorbills, fulmars, petrels and kittiwakes. The garden warbler and chaffinch have gone extinct from the island, but Dr Kelly is none too worried. "Populations are so small on an island that they have a high chance of becoming extinct. Colonies never become very large and some by chance go extinct. You get new species arriving and new species disappearing."

But, Dr Kelly is fascinated by the absence of the rook. Offshore islands will have jackdaw, chough, hooded crow and raven, but not rooks. "It's a widespread terrestrial bird in Ireland and yet it is absent from all of our islands as a breeding species." Dr Kelly suspects two factors are involved: they need quite a large area to forage and they are a highly social species, breeding in large rookeries. If an area isn't large enough, there's no colony.

The island has species rare elsewhere in Europe. The bright red legs and beak of the chough distinguish this crow, a species of special conservation concern in Europe. Writing in his book The Way That I Went, Praeger describes the chough as a welcome sight with "its beautiful flight" and "the delight it seems to take in playing in the air." It remains common on Clare Island, where Dr Kelly has watched it joisting with peregrines.

Insects

Compared to the mainland, Clare Island is still fairly pristine, with intensive agriculture absent. Dr John Breen, entomologist at Limerick University, says this is good news for the ants, bees and wasps. "You will come across four or five species of ants very quickly if you turn over stones. You won't do that on the mainland. And you will come across six or seven species of bumblebee and three species of wasp without having to look too hard." As long as you know what you're looking for, that is. This would have been the experience in many rural parts of Ireland two or three decades ago, before silage and monocultures on the mainland reduced foraging for these insects. Common bumblebee species include the white-tailed, red-tailed, and garden bumblebee and the common carder bee.

The original survey for insects would have involved lots of collecting and mounting of specimens on pins; lists of species were a specialty of Victorian science. Today's studies are more focused. A PhD student working with Dr Breen is looking at the chemical and biological properties of the soil of ant nests, for example.

Plants

The high cliffs still support a remarkable alpine flora, species that are rare in the rest of Ireland. One example is Oyzeria digyna, a plant with kidney-shaped leaves and pink flowers. A gannet colony is sometimes visible on a small sea stack below the great cliffs. But, be careful walking in this area, as the cliff edge can disappear in a shroud in mist and you can be battered by wind on the steep slopes, even on a seemingly calm day.

Praeger was the ultimate field naturalist and spent every summer for five years walking and botanising around Ireland, but he also travelled abroad. "If you only live in Ireland you won't understand what is special about its flora," said Dr Jebb. "When you bring European botanists to the west of Ireland, they are surprised to see so many woodland plants growing out in the fields. Ireland is wet enough for the fields to be humid enough. Plants and animals behave differently in Ireland than in the rest of Europe." Western Ireland also has a strange collection of plants with an affinity to northern Spain. Dr Jebb said Praeger was able to put Ireland into a European context.

Water

The new survey produced a volume on freshwater and terrestrial habitats that looked at algae and phytoplankton; it found the island has an exceptionally high algal diversity of about 800 species. Another volume looked at marine inter-tidal habitats, including some extremely exposed shores that proved a challenge to study. One of the more accessible of these shores was sampled by researchers using security ropes, safety helmets and life jackets. It offered insights into limpets, mussels, whelks and barnacles.

Two ferry companies serve the island today. On the trip over, I watched common dolphins chase under the bow; the large disc-shaped sunfish is sometimes spotted by ferry passengers. The sea itself was dredged and netted during the first survey and a future survey will examine marine fauna.

Geology

Clare Island's geology is complex. And it is complex because the island comprises rocks formed on an ancient ocean floor, sediments formed on the northern margin of an ancient continent north of this ocean and subsequent tectonic squashing of this continent by another. Rocks also formed from the eroded remains of this collision, which were themselves covered by tropical seas during the Carboniferous. Because of this history, Clare Island occupies a position of international geological importance. There is still debate over the precise age of the island's rocks, but none are younger than 300 million years.

The island is, however, blanketed in a covering of more recent glacial material from the last Ice Age. Dr Pete Coxon, TCD, Department of Geography, said the island has been intensively glaciated. "The ice swept across it from east to west and shaped the whole southern coast and large parts of the north east coast," he explained. During the glacial maximum, around 20,000 years ago, the ice would have been 400 metres thick. Dr Coxon said the ice retreated about 15,000 years ago and left behind a lot of glacial till. The island is thought to even have had its own glacier.

Trees

Juniper and hazel were early colonisers after the ice melted. When man arrived 7,000 years ago or so, the island would have been completely wooded, with oak, birch and pine trees. Later Bronze Age settlement on the island is thought to have been significant.

Today the island's landscape is a mix of stony heath, bare peat bog, moss-covered bog, marshy areas, bare rock and steep cliffs. If you hike to the highest point of the island, Croaghmore, you'll have spongy bog and heath underfoot; but all this was once forested.

It wouldn't have taken a lot of people to deforest Clare Island, said Dr Coxon; wood was scarce by around 2,000 BC, he says. This would have been around the heyday of the fulachtai fia, mysterious mounds of burnt stone. They are the most plentiful archaeological monuments on the island but mystery shrouds their purpose. (In the next issue of Science Spin we will explore these prehistoric remains and also a medieval abbey with Gaelic wall paintings that may be of international importance.

Roisin Jones, of the Royal Irish Academy describes the first survey as a major achievement of world significance. "This is a great body of information across two centuries," she says "and it's our ambition to make it available to the general public." The academy sees the new survey as an invaluable source for future environmental monitoring. After one hundred years of excellent study, the academy has history on its side.

Ireland's greatest botanist

Robert Lloyd Praeger (1865-1953) trained as an engineer and worked as a librarian, but his lifelong passion was natural history. Praeger learnt his geology, zoology, botany and archaeology at the Belfast Naturalists' Field Club from like-minded amateur enthusiasts. His scientific life began in the field and continued there.

When he moved to Dublin to work in the National Library, Praeger put together a plan for a thorough study of Ireland's wildflowers. He set out each weekend to different parts of Ireland during the summers of 1896 through 1900, travelling 5,000 miles, most of it cross country. He favoured using the train for rapid transit to a desired spot, followed by vigorous cross country hiking, up to fifty miles a day.

In 1905, Praeger organised a survey to the small island of Lambay off Dublin at the request of its new owner. The project discovered 90 species new to Ireland and encouraged Praeger and the Royal Irish Academy to undertake the most ambitious natural history venture in Ireland. He knew Ireland as well as anybody alive by the time he planned and organised the Clare Island survey. It was just as well, since he was so involved in editing the mass of findings. "Materials piled up beyond expectation," he wrote.

Praeger co-founded the Irish Naturalist, served as president of the Royal Irish Academy, and was the first president of An Taisce; after he retired from the National Library as director in 1923, he set off on botanical trips to the Canary Islands, Madeira, the Balkans and the Alps. His book The Way That I Went is a celebration of the joy of walking the countryside with an enquiring mind. He sets out his philosophy in chapter one: "Who does not wish on a fine day to escape from the town into the country? And when you get there, it adds enormously to your interest and enjoyment if you understand something about the architecture of the hills and plains, and about their teeming population of birds and butterflies and trees."

Anthony King studied science at TCD and has a Masters in Communication from DCU.