Feral
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The North American roc (Aiolornis incredibilis), had a wingspan of sixteen feet and a hooked bill the length of a man’s foot. No skull of another predatory bird, the Argentine roc (Argentavis magnificens) has yet been found, but the available bones suggest that its wings were twenty-six feet across and that it weighed twelve stone.50 On the Pacific coast, sabretooth salmon (Oncorhynchus rastrosus) nine feet long migrated up the rivers.
All these remarkable beasts disappeared at around the same time. generally between 15,000 and 10,000 years ago. Their extinction coincides with the arrival and dispersal of the first technologically sophisticated people in the hemisphere: hunters using finely worked stone weapons. The evidence suggests that it was not, as many palaeontologists first supposed, primarily climate change that wiped out the American megafauna:51 it had survived massive fluctuations in the recent past, and the habitats that many of the missing species required still exist. They were hunted to extinction.*2
The animals of the New World had never encountered humans before, except perhaps some scattered bands with basic technologies. So, like the unfortunate beasts of the islands discovered by Europeans, they probably stood and watched, without fear, as the hunters approached.
Had the Mesolithic people of the Americas eaten everything they killed, they would scarcely have trimmed the herds of game, so small were their numbers. One ground sloth could have fed a clan of hunters for months. The speed with which the megafauna of the Americas collapsed might suggest that they slaughtered everything they encountered.†3 Among those who broke into the New World, anyone could be a Theseus or a Hercules: slaying improbable monsters, laying up a stock of epic tales to pass to their descendants. Like all those who have discovered wildlife in its unexploited state–the sailors who found the dodos in Mauritius or the whales in the southern oceans, the fishermen who first assayed the Grand Banks off Newfoundland–they might have thought the sport would last for ever. Perhaps the care with which some indigenous people of the Americas engage with the natural world came later.
Slaughter of this kind revolts us, but are not most of our great myths built on such adventures? Do Ulysses, Sinbad, Sigurd, Beowulf, Cú Chulainn, St George, Arjuna, Lâc Long Quân and Glooskap not survive in a thousand current tales? All of us have ancestors who, regardless of the continent they inhabited, must have battled with beasts many times their size, armed with horns and tusks and claws and fangs, and must have passed down tales of their triumphs and tragedies, sagas which mutated and evolved across hundreds of generations, but which maintain their essential form today. Are these struggles with the beasts of prehistory not imprinted in our subconscious as surely as Homer’s epics were eventually committed to papyrus?
To re-enact these quests, the Romans scoured Africa for monsters to release into their amphitheatres. The Spanish breed black bulls with the temperament of giant aurochs. The Maasai risk long prison terms, mutilation and death to hunt lions. Societies throughout Europe engaged until recently in cruel sports involving bears, badgers, dogs–any creature fierce enough to reawaken the ancestral thrill. The absence of monsters forces us to sublimate and transliterate, to invent quests and challenges, to seek an escape from ecological boredom.
An interesting question arises. Why, when the megafauna was eliminated in the Americas, in Australia, New Zealand, Madagascar and Europe, does it survive, at least in part, on mainland Africa and in some places in Asia? There creatures exist which, were we not familiar with them, would invoke the wonder and incredulity with which we contemplate the glyptodont, the elephant bird and the marsupial lion. Elephants, rhinoceroses, giraffes, hippos, eland, cheetahs, tigers: all of them, had they lived in other parts of the world, would have been–or were–exterminated. The answer is surely that in Africa and southern Asia, they evolved alongside hominids and early humans. They learnt to fear the insatiable ape, the diminutive monster which could look back upon its deeds and forward to their embellishment.
People who call themselves Pleistocene rewilders seek to recapitulate the prehuman fauna of the Americas.54 They point out that the extinctions terminated trophic cascades and other processes that must have shaped the ecosystems of the New World. Species which evolved alongside the missing megafauna, such as the pronghorn, whose remarkable speed–up to sixty miles per hour–is likely to have been an adaptation to the presence of the American cheetah, now inhabit an ecological vacuum, in which they are constrained by neither predation nor competition. These rewilders call for the introduction of proxy species to the Americas: exotic members of the groups that became extinct, or animals which fulfil a similar ecological role.
They talk of introducing Bactrian camels, which live in central Asia, to replace a similar animal, Camelops, which lived in large numbers in North America until humans arrived. They suggest importing the African cheetah to hunt pronghorns, the African lion to pursue feral horses (which, now widespread, are good proxies for the wild horses which once roamed the continent), African and Asian elephants to replace the mammoths, mastodons and other such monsters. (Perhaps Americans should be grateful that there is no living substitute for the giant sabretooth or the short-faced bear.) Not only, they argue, would these beasts help to revive American ecosystems and heighten people’s interest in conservation and rewilding, but they would also be better protected from extinction if they were living in the wild on more than one continent.
It would not be correct to report that these proposals have been greeted with universal enthusiasm in North America. Aside from obvious concerns about the release of lions and elephants, some ecologists have objected that superficial similarities can mask major genetic differences: the American cheetah (a larger animal than the African species) was more closely related to the puma, for example.55 The proxy species evolved in some cases in response to ecosystems and climatic conditions different from those that prevailed in America before humans arrived. It would be surprising if the way in which they engaged with the remnant American ecosystem closely mimicked the ecological relationships of the species they are supposed to replace. But the idea is worthy of investigation, and perhaps a few experiments.
There are fewer biological obstacles to the reintroduction of a missing megafauna to Europe. Unlike the extinct American beasts, the monsters which once ranged across this continent have close relatives in Africa or Asia. The hippos submerged in Trafalgar Square were of the same species, Hippopotamus amphibius, that lives in Africa today. It survived in parts of Europe until around 30,000 years ago, when it appears to have been hunted to extinction.56 The last temperate rhinoceros species to disappear from the continent bear some resemblance to the black rhinoceros, which is likely to fill a similar ecological niche. The Asian elephant might be a good proxy for its relative the straight-tusked elephant.
Reintroducing elephants to Europe would first require a certain amount of public persuasion. To find enough forage, wild elephants would have to make long migrations, especially in the winter. Gardeners, farmers and foresters are unlikely to applaud the proposal, though it would take our minds off the slugs and aphids with which so many of us are obsessed. But if very large areas of land are allowed to rewild as farmers depart, it would be a pity not to remember and at least consider the most powerful of our missing species.
The Pleistocene Park being established in north-eastern Siberia by Sergey Zimov and other visionary ecologists is, most of the time, less contentious. The rewilders began, in 1988, by releasing Yakutian horses–believed to be closely related to the wild horses that lived in the region towards the end of the Ice Age–into a park of 160 square kilometres (the size of Liechtenstein). Reindeer, moose and wild snow sheep (similar to the North American bighorn) already lived in the area, as well as lynx, wolves, bears and wolverines. Since then, musk oxen, forest bison and red deer have been reintroduced.57 At some point the park will be expanded by a further 600 square kilometres, becoming a little larger than the island of Minorca.
Zimov and his team are either considering or bei
ng urged to consider the introduction of several other species which once lived in the region or which are closely related to those that did. Among them are saiga antelope, Bactrian camels, Amur leopards, Siberian tigers and lions. Already, as Zimov’s experiments predicted, the new grazers are turning the moss and lichen tundra into grassy steppe. The question of whether this transition will accelerate climate change needs to be carefully examined. His assumption that the restoration of grassland will reduce global warming could be optimistic,58 and has been partly contradicted by no less an authority than, er, Sergey Zimov,*4 lead author of a paper written ten years earlier.60
Some people appear to be giving serious consideration to the idea of restoring another missing member of the Siberian ecosystem. Whatever the drawbacks may be, the notion (which might or might not be fanciful61) of resurrecting the woolly mammoth by extracting genetic material from frozen corpses and injecting it into the eggs of Asian elephants possesses the virtue of firing the imagination on all cylinders. But it seems odd that, while there has been so much attention and money given to this project, the idea of simply reintroducing the Asian elephant to parts of Europe and Asia, from which it or its sibling species (the straight-tusked elephant) has been extirpated, has not yet taken root; or even, as far as I can discover, been discussed. The elephant in the forest–the huge and obvious fact that almost everyone has overlooked–is the most prodigious instance of Shifting Baseline Syndrome I have chanced upon so far. Who knows what else we might all have missed?
The North American debate raises another important question, which is relevant everywhere: is a healthy and desirable ecosystem necessarily composed of native species? Certain exotic animals and plants destroy ecological diversity of all kinds in the places they infest. Without natural predators or parasites or diseases, attacking native species which have evolved no defences against them, they can quickly overwhelm an ecosystem, sometimes to the point at which (as I have seen in small streams in England infested by American signal crayfish) the last robust ecological process still taking place consists of big ones eating little ones.
In some places the progress of these invasive species looks like the plot of a Gothic novel. The walking catfish, for example, native to south-east Asia, has escaped from fish farms and ornamental ponds in China and the United States, and now crawls overland at night, colonizing water that no other fish can reach.62 It eats almost anything that moves. It slips into fish farms and quietly works through the stock. It burrows into the mud when times are hard and lies without food for months, before exploding back into the ecosystem when conditions improve.
The cane toad, once confined to Central and South America, has been widely introduced in the tropics to control crop pests. Unfortunately it also controls many species which are not considered pests. It appears to be almost indestructible: one specimen was seen happily consuming a lit cigarette butt.63 Scarcely anything which tries to eat it survives: it is as dangerous to predators as it is to prey. Unlike other amphibians, it can breed in salty water: it could have waddled out of the pages of Karel Capek’s novel War with the Newts.
The world’s most important seabird colony–Gough Island in the South Atlantic–is now being threatened by an unlikely predator: the common house mouse. After escaping from whaling boats 150 years ago, it quickly evolved to triple in size, and switched from eating plants to eating flesh. The seabirds there have no defences against predation, so the mouse simply walks into their nests and starts eating the chicks alive. Among their prey are albatross fledglings, which weigh some 300 times as much as they do. A biologist who has witnessed this carnage observed that ‘it is like a tabby cat attacking a hippopotamus’.64
But even more mundane invasions can be devastating to the richness of native ecosystems. Rhododendron ponticum, which–as the name suggests–is native to the shores of the Black Sea and lands at similar latitudes, works its way through British woodlands, smothering and poisoning other plants. It can kill even the mature trees among which it grows. I have seen entire stands of ash dying from canker, apparently as a result of the moist conditions sustained around their boles by the rhododendron’s thick cover. It harbours sudden oak death fungus, which kills a number of trees in Britain, though not, as it happens, oaks. While the hawthorn in Britain supports 149 species of insect, the birch 229 and the oak 284, the rhododendron is reported to harbour none.65
This is one of the reasons why it thrives here: it has escaped from the restraints imposed by the plant eaters of its native lands. Interestingly, however, Rhododendron ponticum was native to these islands during a previous interglacial period.66 Its natural pests, predators and competitors appear to have been destroyed by subsequent ice advances, allowing it, once imported by enthusiasts, to return here unchallenged, our flora’s deus invictus. Is it possible that one of our missing herbivores–the ancient elephant or the Merck’s or narrow-nosed rhino, for example–was able to eat it? If it is not controlled, it will eventually supplant almost all the vegetation of the places it invades.
I am struck by how unassuming some of the species which cause havoc abroad are in their native range. In the Himalayas where it belongs, and where despairing householders might fervently wish it had stayed, dry rot is a fungus living on pine and yew trees. It is so rare that between 1953 and 1992 it was officially recorded only three times,67 and it may be in danger of extinction in the wild. In Britain, purple loosestrife is an occasional and delightful native ornament of our riverbanks and lakesides. In North America and New Zealand it is a rampaging, uncontrollable menace, smothering wetlands and choking rivers.
But there are many exotic species which cause little discernible harm to the countries they colonize. Until recently I had not realized that the little owl does not belong to our native fauna: it was introduced to Britain in the nineteenth century. But its presence here is uncontroversial: it persists in fairly small numbers without driving out native species. The knowledge that it did not originate here will do nothing to dampen my delight next time I see one.
Many of the plant species–157 according to one estimate68–that we once saw as native now appear to be what botanists call archaeophytes: exotic species which arrived before the year 1500. A handful reached Britain during the Neolithic, their seeds probably lurking in the grain brought here for sowing by the first farmers, or, perhaps, stuck to the feet of travellers or in the hides and fleeces of the animals they imported.
Some archaeophytes are familiar to anyone who loves nature, and their inclusion on the list of non-native species is often surprising: field poppy, greater burdock, cornflower, wormwood, scarlet pimpernel, shepherd’s purse, fumitory, corncockle, deadnettle, common mallow, crack willow, common vetch, field pansy, mayweed and white campion, for example.69 You can find several of them in the packets of wildflower seeds we are encouraged to sow in spare corners of our gardens, to save Britain’s native flora. As their lovely names suggest, they have seeded themselves in our culture and are as embedded in our lives as the species that arrived before we did.
Among these archaeophytes are plants which are now extremely rare. The pheasant’s eye, for example, which appears to have arrived in the Iron Age, is marked as endangered on Britain’s Red Data List,70 and officially classed as a priority species for conservation here.71 Is it illogical to seek to save these plants, even in the knowledge that they were brought here by humans? They do no harm and afford delight and wonder to those who appreciate them, which is surely all that is required to make something worthy of preservation. Even so, it compounds the confusion–seldom acknowledged, let alone resolved–between conservation and gardening.
Some animal species might also have been mistakenly seen as native. The eminent mammal biologist Derek Yalden presents compelling evidence that the brown hare was brought here by people.72 The bones of what appear to have been mountain hares (a different species) are found in England and Wales in deposits from the early Mesolithic, soon after the ice sheets retreated. They appear to have been d
riven out (perhaps surviving in Scotland) as the land became forested. Possible records of brown hares begin to appear in the Bronze Age; more certain remains in the Iron Age. In Commentarii de Bello Gallico, Julius Caesar records that the Britons considered hares, fowl and geese ‘unlawful to eat, but rear them for pleasure and amusement’.73 This raises the possibility that brown hares were brought to Britain either as pets or to be hunted for sport.
Restoring a functioning ecosystem does not equate to purging all non-native species. It requires only that we control or suppress those species which deprive many others of a foothold here. Even some of the most prolific exotic animals could be subdued by native predators. Grey squirrels, for example, are currently storming through the ecosystem, defying attempts by humans to restrain them. Ecologists hate them, with good reason. But pine martens and goshawks love them74 (in the purely carnal sense). Had landowners not waged war on all predators, regardless of their impacts, they might not have had to wage–and lose–the current war against grey squirrels. Martens and goshawks, now returning to some of the places from which they were exterminated, may have the potential to reduce the grey squirrel to such an extent that it begins to function ecologically much as a native species would.
Where rivers contain healthy populations of predatory fish, they appear to thrive on invasive crayfish. Sometimes when I have caught a fat perch for my dinner, I have found a crayfish or two in its stomach. Perhaps because of the acidity of the fish’s stomach, the shell dissolves before the flesh does: I have extracted from the insides of a perch perfectly peeled crayfish tails, which look as if they have just been shovelled off a fishmonger’s slab. I have noticed that where large chub lurk, the crustaceans are more reluctant to emerge from under their stones. Twice in my crayfish nets I have trapped enormous pike–one of which must have weighed well over twenty pounds and pulled the net all over the river as I tried to retrieve it–though I cannot say whether they had come after the crayfish or the bait. I would be surprised if these aquatic locusts were not also consumed by barbel, trout and eels. It is possible that in places where pollution levels are low enough for fish to thrive, these predators will eventually suppress the crayfish population until it ceases to threaten some of the native wildlife it now displaces.