杏吧原创

STANDING on the shore of Penobscot Bay in Maine, I look out on a typical New England scene: lobster boats head out to their pots, a herring gull casts a shadow across a still pool and a harbour seal bobs in the swell. But just below the surface an army of European invaders is at work. Beneath the seaweed half a dozen green crabs brandish dark serrated claws before beating a hasty retreat under the rocks. As the tide recedes, thousands of European periwinkles appear, feasting on local algae and the eggs of other species, stunting the growth of native limpets in the process. Above the high-tide line, invasive weeds 鈥� dandelions, stinging nettles and purslane, to name a few 鈥� line the roads and spread out across the country.

Penobscot Bay isn鈥檛 an isolated case. All over the world, invasive plants and animals are causing havoc for native species 鈥� eating their food, wrecking their habitat and spreading out of control. Ever since people took to the seas, they have been moving plants and animals around the world and leaving them where they don鈥檛 belong. Now planes and supertankers transport species in a matter of weeks or even hours, altering ecosystems and accelerating what Gabor L枚vei, of the Danish Institute of Agricultural Studies, has called 鈥渢he McDonaldisation of the biosphere鈥�.

But while some researchers are hard at work engineering elaborate biological control programmes based on importing the pests鈥� natural predators from their homelands, others point out that the answer to our alien species problems may have been staring us in the face all along. Why bring in more exotics, they ask, when humans have already proved themselves to be the most successful predators on the planet? We have already managed to eat several species into oblivion over the years 鈥� including the great auk and the passenger pigeon 鈥� and are having a similar effect on the world鈥檚 fish stocks. So why not put our destructive streak to a good use for a change? With initiatives ranging from local bounties to recipes by celebrity chefs and exotic food festivals, the idea is starting to catch on. All over the world invasive species are being taken out of the wild and put onto the menu.

Back in Maine, I slipped some European invaders 鈥� a green crab and a few dozen periwinkles 鈥� into a cooler and set off to the hostel where I was staying. Equipped with Euell Gibbons鈥檚 Stalking the Blue-Eyed Scallop, a book about the immense variety of foods you can gather at the ocean鈥檚 edge, a slotted spoon and a nutpick, I boiled a pot of water and set the small table with French bread and melted butter. I dropped the periwinkles in the pot for few minutes, then dragged them out of their shells and through the warm butter. The invaders were briny, firm and delicious.

As for the crab, I felt a little guilty as I removed it from the cooler, live, soft and vulnerable in mid-moult, but Gibbons鈥檚 instructions were clear: 鈥淲ith a sharp knife remove the eyes.鈥� That done, I saut茅ed it in butter and ate it with French bread. Fresh from the sea, the delicate flaky meat beat any store-bought crab I鈥檝e had, claws down.

鈥淚 felt a little guilty but Gibbons鈥檚 instructions were clear: 鈥榃ith a sharp knife remove the eyes鈥欌��

But while my foray into conservation cuisine was a definite success, convincing people to take up the fork against invaders is far from easy. The soft-shell clam Mya arenaria is a case in point. Native to the US east coast, fried clam is a popular dish among locals. 鈥淲hen you order the fried-clam basket on Cape Cod in the summer, you鈥檙e eating Mya arenaria,鈥� says Jim Carlton, an invasive species biologist at Williams College, Williamstown, Massachusetts. 鈥淥n the west coast, though, it has become the most abundant clam in the Oregon bays but is viewed as a waste clam. A hundred years [after it invaded the west coast], it鈥檚 remarkable how Mya arenaria is viewed on one coast versus the other.鈥�

Although tastes are often slow to shift, change is possible. The Hadley Bowling Green Inn in Worcestershire, UK, put grey squirrel terrine on its menu earlier this year. The North American rodent has taken the British countryside by storm, displacing the native red squirrel and destroying the bark of native trees. The inn鈥檚 accountant, David Eccleston, says that diners enjoyed the dish, which combined roasted squirrel and foie gras. 鈥淚鈥檝e had customers ring me up to express support,鈥� he says. 鈥淸They say] you鈥檙e doing the countryside a favour.鈥� The item has since been taken off the menu after animal-rights campaigners protested 鈥� not for love of grey squirrels, but because foie gras is made by force-feeding waterfowl. Eccleston says customers are already calling for the dish to be reinstated.

Cooking the enemy

In the south-west US, the Arizona Game and Fish Department is also promoting the pot as a method of pest control. The Louisiana crayfish was introduced as food for sport fish in the 1960s but soon set about devouring native plants in mountain streams before moving on to native animals, and eventually cannibalism. 鈥淐atch crayfish at every opportunity,鈥� the department tells volunteers, who come armed with hand-held nets and traps baited with chicken, pork or hot dogs. The slogan 鈥淢illions of Cajuns can鈥檛 be wrong!鈥� has sold the idea to local people, and according to state fisheries chief Larry Riley, the public 鈥渉as done a pretty good job鈥� of policing local waters.

Festivals and cookery competitions have also had an impact. Japanese knotweed, an aggressive weed that has spread across the US, UK, mainland Europe, Australia and New Zealand, is served up as knot soup and apple-knotweed pie in Pennsylvania at the annual Japanese Knotweed Festival. In Louisiana, celebrity chefs such as the native Cajun Paul Prudhomme and French-born Daniel Bonnot have taken on the nutria 鈥� an aquatic South American rodent also known as the coypu, one of the state鈥檚 most destructive alien species 鈥� with meat grinders and stockpots. Their recipes, such as Smoked Nutria and Andouille Sausage Gumbo, aim to increase public awareness of the ecological havoc wreaked by invaders while providing a few courageous diners with a gourmet meal.

Guerrilla tactics like these certainly help the cause but the massed assault of a commercial harvest is far more effective. It is also more contentious. In New Zealand, where red deer destroy native plants and prevent the forest canopy from recovering, commercial hunting from helicopters has reduced populations by more than 99 per cent. Most of the wild venison is sold to Germany, where deer are native 鈥� ironically, invaders are often shipped back home, where native populations are now too small to satisfy local demand. Dave Choquenot, an ecologist from Manaaki Whenua Landcare Research, an independent research institute based in Auckland, New Zealand, supports the hunters鈥� efforts. 鈥淔or the vast majority of pests, eradication is simply not feasible, [so] anything that contributes to lower pest densities conceivably yields benefits.鈥�

But many conservationists fear that creating a market for unwanted species may make matters worse. 鈥淭here is much scepticism among invasive species biologists all over the world about prompting industries that harvest feral animals,鈥� says Tim Low, freelance biologist and author of Feral Future: The untold story of Australia鈥檚 exotics. 鈥淥nce you have set up an industry, you may find you have created a problem rather than a solution.鈥�

Ecologist David Forsyth of the Arthur Rylah Institute for Environmental Research in Heidelberg, Australia, agrees. 鈥淚n Australia, commercial hunting of wild pigs began in 1980 and since then millions have been harvested to supply the demand for exported meat. 鈥淓ven if one technically could eradicate them,鈥� Forsyth says, 鈥渢here would be a monetary incentive for people to 鈥榢eep a few鈥� and make money from them.鈥�

Whatever the future holds, exotic meals and commercial hunts alone are unlikely to put a stop to the invasion problem. But where there is a tasty meal to be had, the solution, says Bill Walton, a fisheries specialist at Woods Hole Oceanographic Institution in Massachusetts, is to just keep eating. He has received a grant to set up a green crab fishery in New England. And at Walton鈥檚 place there will be no restrictions, no quotas and no early closures when stocks get low. 鈥淵ou have to be clear about it,鈥� he says. 鈥淓xtinction is a happy ending.鈥�