North Berwick and Aberdeen, Scotland
One spring day in 2003, René van der Wal was approaching Fidra, an island off Scotland's southeast coast, on a mission to collect nematodes for a graduate student, when he "saw these funny plants standing there, and I thought, Wow! That's peculiar." Then, through the mist, on Craigleith, an island a mile away, he saw more funny plants—a forest of them.
SEE RELATED SLIDE SHOW: Volunteers Clear a Seabird Island for Puffins
Small islands like these in the firth, or estuary, of the River Forth are usually barren and windswept, blanketed with nesting seabirds in summer but treeless, bleak outcroppings the rest of the year. Craigleith (pronounced Craig-LEETH) means "gray rock" in Scottish Gaelic, but it "looked like a temperate rain forest," says van der Wal, a scientist at the University of Aberdeen, 78 miles to the north. "I thought, My goodness, what's that?"
He asked the boatman and other locals on board, who were trying, unsuccessfully in the firth's frisky swell, to land so they could count puffins on Fidra. He learned that the plant was tree mallow, a garden flower from England's south coast, and that locals were concerned that it might be destroying puffin habitats on Craigleith and elsewhere.
Van der Wal, who loves ecosystems and food webs of all kinds, was fascinated. He thought, I must go there. I must find out: What was making an innocuous flower grow nine feet high and thick as a jungle, disturbing the nesting of one of the Northern Hemisphere's most charismatic birds?
So began van der Wal's scientific sleuthing of an ecological mystery, and the groundwork for SOS Puffin, an unusual collaboration between a scientist and the public.
In Scotland this past June, a puffin hatching in the wild, captured on a Webcam in Shetland, made the evening news. British people love animals, birds in particular, but puffins, with their clownish red-and-yellow beaks (in the breeding season) and awkward stance, are the koala bears of the avian world.
A seabird skip from Fidra and Craigleith lies the Bass Rock, a 300-foot-high plug of volcanic trachyte that in summer houses 100,000 nesting pairs of gannets, magnificently graceful diving birds. It is the largest gannet-nesting colony in the world. Video cameras on the islands broadcast images of the nesting birds to giant TV screens in the nearby Scottish Seabird Centre, here in North Berwick (BEAR-ick), and visitors can zoom in on gannets, kittiwakes, guillemots, fulmars, cormorants, shags, and eiders. Most people just want to see puffins.
"It's a very emblematic species," van der Wal says in his office in Aberdeen, behind a wall around the university's Cruickshank Botanic Garden. "We have nearby Stonehaven here—it's one of the biggest guillemot colonies in the U.K., with 300,000 guillemots, and there are 10 pairs of puffins. And local people go there for the puffins! Not for the 300,000 guillemots. Most of the time they only see one or two, but people go there for the puffins."
Van der Wal, a lanky, 43-year-old Dutchman who came to Scotland 12 years ago, is not an ornithologist but an ecologist with the university's Aberdeen Centre for Environmental Sustainability, where natural and social scientists study societal conflicts that often have to do with biodiversity. One of his projects today is the management of red deer, which are culturally important to Scotland "but societally causing major amounts of grief," in the form of traffic accidents and overgrazing, he says. He specializes in climate-soil-plant-herbivore interactions, like how herbivores affect arctic tundra, or how the reduced "snow lie" of warmer winters affects mosses on mountaintops.
But in 2003, he couldn't stop thinking about the "rain forest" on Craigleith, especially after he learned that the island's puffin population, which had been counted at about 28,000 burrows, or approximately 56,000 pairs, in 1999, had plummeted to 12,100 burrows. "Why on earth had this happened?" van der Wal wanted to know.
Puffins are diggers as much as they are fliers, which explains their somewhat goofy bearing. They might spend their first breeding season not breeding at all, but excavating the burrow where they will lay their eggs the next year. With those oversized bills, they loosen the soil, scooping it out with their webbed, clawed feet, pushing the earth behind them. At the end of that process the puffins emerge quite covered in dirt.
By August these truly pelagic birds are ready to flee the hazardous land, where they're an easy mark for gulls and other predators, and return to the relief of the sea. Ungainly fliers, they are superb swimmers, diving some 150 feet in search of fish. They return to the burrow the following March to lay a single egg, which the parents incubate for about six weeks.
Once the "pufflings" hatch, the real work begins for both puffin parents, who make five to 10 trips a day searching for food for their greedy offspring. Sand eels, sprats, and herring are the pufflings' favorite meals. When the young are big enough to fledge, in early August, the parents gather in flocks on the sea below, waiting to begin their migration. In the dark of the night, for safety, the pufflings emerge from their burrows, totter to a cliff, and take off. As with teenagers everywhere, no one really knows where they go.
But on tiny, 17-acre Craigleith, tree mallow was impeding that eons-old process—with disturbing success. Measured in ecosystem time, that change had occurred virtually overnight.
Van der Wal talked with local seabird-center biologists and to ornithologists at the Scottish Natural Heritage, a government preservation agency. Tree mallow, he learned, was growing so thick on Craigleith that the puffins couldn't find their burrows. In gardens in Cornwall, by contrast, tree mallow grows in clumps of one or two waist-high plants. Why was it a rain forest here?
"My personal interest was not so much to get the puffins back per se," van der Wal says. "That's a local decision. But Craigleith—I'd never seen a place like that. It's quite amazing." Navigating the tree mallow was "a bit like walking through a cornfield, but then one with many legs and arms—because it's impossible to move through. ... So my main mission was ... to try to capture the nature of this expansion, which is very, very rapid, in the last 20 years, and try to understand which factors were involved."
And not only which factors, but also whether the tree-mallow expansion was a novel, recent one, or an episodic one, which might have also attacked the island in an earlier time. If tree-mallow growth, and subsequent puffin decline, were cyclical, he reasoned, humans might not want to intervene.
"It's all nice and well to start managing the situation if you don't understand how it came about," the ecologist says. "In my eyes, it's a bit pointless, because it could quite easily reappear, or you learn very little."
So van der Wal went to the library.
The Bass Rock, about two and a half miles from Craigleith, figures prominently in history and literature. Despite its nearly vertical cliffs, people lived on the Bass, as it is called, for centuries. The first known occupant was a religious hermit in 690 AD, but then the Scots built a fortress that, in 1406, harbored James, the 12-year-old heir to the Scottish throne, on his way to exile in France. Later, atop that, they built a prison. Robert Louis Stevenson, who summered here in North Berwick, imprisoned the hero of his novel Catriona on the Bass, calling it "an unco [uncouth] place by night, unco by day; and these were unco sounds, the calling of the solans [gannets]. ... So many still, hollow noises haunted and reverberated in the porches of the rock."
But Craigleith is "the Bass's little brother," van der Wal says, hardly ever mentioned. He combed libraries in Edinburgh and East Lothian, the islands' county, for religious tracts, nature-society pamphlets, council records, even golf-club records, piecing together a botanical history.
Tree mallow had been recorded on the Firth's islands as early as the 1660s, he found, possibly introduced on the Bass in the prison garden, for the medicinal value of its large, velvety leaves. By the 19th century, the plant was coveted and even protected.
In The Bass Rock: Its Civil and Ecclesiastic History, Geology, Martyrology, Zoology, and Botany (1848), van der Wal found a reference to the plant's "gorgeous appearance, with its rose-coloured flowers streaked with darker veins." In Transactions of the Botanical Society of Edinburgh, he found the earliest reference to the plant on Craigleith, in 1966: "The glory of Craigleith is the abundance and luxuriant growth of Lavatera arborea," tree mallow's Latin name. He pored over photo archives to try to understand the rate of tree-mallow expansion on Craigleith through aerial photography. The pictures, which went back to the 1950s, showed grassy sward where the rain forest stood in 2003.
Van der Wal's hunch—that tree mallow was relatively recent on Craigleith—seemed correct, but for scientific proof, he turned to paleobotany.
"If you have a peat bog, any pollen coming into the bog will be preserved," he explains. "Just like you can see mammoths coming out of the arctic tundra and bodies of humans out of moors, the same principle applies to pollen." And it can be dated. Craigleith doesn't have peat, but it does have a lochan, which is Scots for pond, which he hoped would offer the same pollen-preservation conditions.
It did: The quality of the preserved pollen turned out to be very good, van der Wal says, happily. "You take soil cores, you break them into segments, you date these segments." With the help of Robert McCulloch, a paleoecologist at the University of Stirling, he carefully washed the soil to release the pollen, and put it under a microscope to identify species.
The scientists found little tree-mallow pollen on Craigleith in the 19th century; instead, they found oats. It's "perhaps hard to imagine," van der Wal says. Why would you bother planting oats on an island, not the easiest place to bring in your harvest?
But that was before fertilizer, which revolutionized agriculture. "If you look at descriptions in literature, you see that this was a bleak and barren place in the 1800s," van der Wal says. "But yet there were seabirds. ... There was endlessly more fertilizer than any piece of land elsewhere, so these are the places where you want to go to farm."
Van der Wal could now prove that no tree-mallow forest had existed on Craigleith for most of the past 200 years. He still didn't know what made the plant grow like gangbusters in 2003.
An old island map showed a rabbit warren. If Craigleith had once been used for growing oats, the scientist reckoned, people might have raised rabbits there, too. Rabbits had been farmed for human consumption on the nearby Isle of May, van der Wal says, since the 14th century. And while no rabbits had lived on Craigleith in recent memory, the map and the Edinburgh Botanical Society records placed them there in the 19th and early 20th centuries.
The ecologist and his graduate students planted tree-mallow seedlings, germinated from Craigleith seeds, and exposed them to grazing rabbits. Within 12 days almost all of them had been nibbled or dug out. Van der Wal knew that myxomatosis, a viral disease that kills rabbits, had been introduced to control the animals in Britain after World War II, and he learned from Sir Hugh Dalrymple, the island's owner, that it had wiped out the rabbit population on Craigleith in the 1950s.
There went one element of tree-mallow control.
Yet the aerial photos showed only a gradual spread of the plant after 1950, followed by rampant growth near the beginning of the 21st century. What else had changed?
Unless you've spent the last decade in a diving bell, you've probably thought of climate change by now. Van der Wal found that the total number of days with frost in North Berwick had dropped by 32 percent between the early 1960s and 2003, while the average daily minimum winter temperature had gone up 1 degree. His team planted eight-week-old mallow seedlings in nine sites around Scotland, selected to create an experimental spring-frost gradient. Few plants survived in locations with more than 90 hours of spring frost, as would have been the case on Craigleith until about 1980. Plants in North Berwick, half a mile from Craigleith, flourished the most. Global warming had clearly encouraged the "tree" in tree mallow.
One final factor contributed to the tree-mallow forest—the puffins themselves.
Studies by Mike Harris, an emeritus professor with Scotland's Centre for Ecology & Hydrology, showed that puffin numbers had been rising by 10 percent per year until 1999, probably because of an abundance of the small fish that puffins like to eat. As fishing fleets depleted cod and other large fish that prey on sand eels, herring, and capelin, those species thrived. So did puffins. More puffins meant more guano; hence more tree mallow.
The ecologist had solved his mystery, but not the puffins' problem.
It was now winter, with the islands void of bird life, so van der Wal took some loppers and chopped down some tree mallow. He then had volunteers work on 25-by-12&frac;-meter plots, just to test how cutting tree mallow could be done and whether enough could be cut to free the burrows. The plant covered 85 percent of the island. "It didn't take a genius to work out that you would need hundreds of people for five-plus years to make any difference," he says.
That's when the ecologist, the seabird center, and the puffins met with a stroke of luck. A private film company, RDF Media, had heard about the puffin problem on Craigleith and wanted to film an episode of Wild Thing I Love You, its popular TV documentary, there. The program features Bill Bailey, a comedian, whose team investigates and tries to solve wildlife problems around Britain. The hourlong program was aired to nearly two million viewers on Britain's popular Channel 4 in November 2006.
The publicity, and the volunteer help it generated, were astonishing. Today almost 500 people are on the volunteer list for SOS Puffin, the project to cut tree mallow on Craigleith, and now on Fidra, with boat parties of 10 or 12 people going out to the islands from August through March, six hours at a time, as many as 30 trips a year. Van der Wal, who was at first reluctant to bring in even a TV crew, is pleased. He has stepped aside from running the mallow cutting but returns to the island every few months to monitor the plants and burrows. His research is the basis of a management plan for the islands, and it brought in a grant to pay for a boat, first-aid training, and the training of volunteers, who are now coordinated by the genial John Hunt, a former director of Scottish nature reserves of the Royal Society for the Protection of Birds.
Hunt, a volunteer himself, has volunteers who have cut tree mallow on Craigleith more than 50 times. One of them, a woman, is 80 years old. "They enjoy going outdoors, coming to an attractive place," Hunt explains, "and they find the work very satisfying. When cutting tree mallow, even if you cut a small bit, you can see at the end of the day what you've achieved. And then there's the social side of it, probably the most important of all."
With the tree-mallow-cutting project now in its fourth year, birders are counting many more puffin burrows than they did in tree mallow's heyday. Although the plant grew vigorously over this past summer, since the birds left, in August, some 20 work parties have kept it at bay. Hunt thinks another three to five years are needed to get the plant, a biennial that sprouts up every summer, under control—that is, to a point where other plants take over. Occasional work parties, he says, may be needed for many years to prevent the plant's return.
Maria Chamberlain, a senior tutor in biology at the University of Edinburgh, takes several students to cut mallow every year as a practicum required for her course. Although "it's a bit like painting the Forth rail bridge," she says—by the time you finish, you have to start painting the first part all over again—she sees some progress. More important, it gives her students a chance to ask questions of experts: Why is there little or no mallow on the Island of May? What are the lowest temperatures a seedling can withstand? Why did the management plan go against the introduction of neutered rabbits? "Every year as a result of this course," Chamberlain says, "we have at least half a dozen converting to biology or ecology. They say wonderful things like, 'This is what I want to do for the rest of my life.'"
And van der Wal? "We will try to get a habitat back in a state that puffins can use," he says. "Whether the puffins come back depends on the puffins and what else happens in their lives."
Meanwhile, he is taking tree-mallow seedlings from Craigleith and planting them in Cornwall, and vice versa, to find out whether the invasiveness of the species is in its genes. He picks up a seedling from his desk to show a visitor, but then excuses himself to take an important phone call. A graduate student looking at rare butterflies on the island of Mull has developed a kidney infection. He has to figure out how to get her home.