BRITAIN: A NATION TIED IN KNOTWEED - The New Wild: Why Invasive Species will be Natures Salvation - page 50

pocastanum ). It is the supplier of conkers to generations of schoolchildren and feted as the “spreading
chestnut tree” of a thousand rustic villages. As I write, newspapers report concern that an alien moth is
attacking “British” conker trees. 22 Nobody has noticed that the tree actually comes from the Balkans.
Meanwhile, some natives are assumed to be aliens. The sycamore ( Acer pseudoplatanus ) is widely
reviled. Its seedlings and leaves smother garden lawns. Its reputation is likely to sink further if botanists
are right that it is set to step into the gaps in woodlands created as ash trees succumb to ash dieback dis-
ease. 23 But the common presumption that sycamore arrived in Britain only around five hundred years
ago does not hold up. It seems to have been widespread in Roman times. 24 John Rodwell of Lancaster
University, who developed the British National Vegetation Classification, argues that it has been a nat-
ive all along. 25
The more researchers look, the more helpful many of the alien squatters appear. Buddleia ( Buddleia
davidii ), brought from China by French botanists a century ago, is known as the “butterfly bush” because
its big honey-scented purple flowers provide superior nectar for native butterflies. It is one reason that
butterflies are leaving the British countryside, where wildflowers are scarce, and heading for the nectar-
rich urban badlands where buddleia has taken root. 26 Britain's much-loved native red squirrel ( Sciurus
vulgaris ) likes conifer plantations of nonnative Norway spruce, Douglas fir, and larch. Meanwhile, the
red squirrel's alien American competitor, the gray squirrel ( Sciurus carolinensis ), prefers the native de-
ciduous woodlands. There was controversy when the Countryside Council for Wales decided to remove
alien conifers, the last local refuge for red squirrels. Under such circumstances, the legal presumption
that alien species are bad and must be kept out looks misguided. Which should take precedence, the red
squirrel or the conifer?
With all the headline-grabbing horror stories about Japanese knotweed and the rest, it is sometimes
hard to remember that most of the twenty-three hundred or so alien species in England are benign and
generally add color and variety to the landscape. Thanks to them, the biodiversity of the British Isles is
probably greater than it has ever been. “No endemic is remotely threatened by any aliens,” Dickson told
me. “From a conservation perspective, I don't think they do much harm.” But our attitude to aliens is
emotional, he says. It harks back to a “merrie England” when everything was wonderful—“a time many
think we need to get back to.”
Cambridge geographer Stephen Trudgill says that our strong sense of what plants should be where is
unhistorical. There is no true British flora, he says. Go back eight thousand years, to before we took up
farming, and there was no golden age of stable rich ecosystems full of native species. Instead, the land
was experiencing huge changes as it warmed after being covered in ice during the long ice age. Almost
the entire flora and fauna of Britain has arrived in the past ten thousand years. 27
Everything is visiting. Nothing is native. As Pearman told me, “That makes the main reason for
fearing the introduction of alien species [to Britain] invalid.” So why not celebrate the stories of their
arrival? The seeds of hoary cress were transported in straw-filled mattresses that carried home the
wounded from the Napoleonic Wars two centuries ago, and they were subsequently spread when the
straw was given to a local farmer. A taxidermist's stuffed bird conveyed the hairy-stemmed Canadian
fleabane from North America in the seventeenth century. A creeper called ivy-leaved toadflax arrived
in Oxford around the same time in the packaging of marble statues looted from Italian houses. 28 The
Romans brought devil's guts to relieve gout.