海角大神

In the mid-1980s, scientists began noticing a curious phenomenon in goose nesting grounds along the western edge of Canada鈥檚 Hudson Bay. Once-verdant salt marshes were transforming into barren mud flats. With plant cover gone, evaporation accelerated and the soil quickly became too salty for all but a few species. By August, only the reddish salt-tolerant salicornia plant remained in a landscape often littered with dead, bleached willow branches.

Lesser snow goose populations had quadrupled since the 1970s. So many geese were arriving at their summer breeding grounds that they were eating not just plant shoots, but roots as well.
The non-interventionist camp argued that goose numbers would naturally return to an equilibrium once the food ran out. But others feared that continued overgrazing would irrevocably damage the ecosystem. Humans had to intervene, they said.

The interventionists prevailed and, 10 years ago, wildlife agencies ratcheted up hunting pressure. Now they are unsure if the increased culling is working. Further deterioration of an already degraded landscape appears to have halted, but the marshes haven鈥檛 begun to recover. Unsure what else they can do, they have adopted a wait-and-see approach for now. Here鈥檚 the problem: Further population control, which would probably mean some sort of mass extermination, is as technically difficult as it is ethically questionable.

鈥淟arge-scale elimination of birds in concentration 鈥� that would be an unprecedented move,鈥� says Dale Humburg, chief biologist of Ducks Unlimited in Memphis, Tenn., a conservation and hunting group.

鈥淗ere you鈥檙e dealing with things that are ethically at the crossroads.鈥�

Saltwater marshes, like those where the geese summer, are among the most productive and diverse ecosystems on earth. They鈥檙e also rare, occurring only along coasts. For this reason, scientists are particularly concerned about the northern marshes. The transformation of these productive ecosystems into mud flats hurts not only geese, but also a suite of species that lives there. In degraded marshes scientists find fewer bugs, for example, which other birds feed on. They find fewer other birds, like the normally hardy Savannah Sparrow.

鈥淚f you can damage or impact a really robust species鈥� like the Savannah Sparrow, says Robert Rockwell, a biology professor at City College of New York who has studied the geese for 40 years, 鈥測ou can only imagine what鈥檚 happening to the most delicate species.鈥�

In times past, the lesser snow goose wintered in marshes along the Gulf of Mexico. (The greater snow goose, whose population has also risen in recent decades, winters along the US East Coast and breeds in Canada鈥檚 High Arctic.) When scientists looked into the population explosion since the 鈥�70s, they noted that goose numbers had risen in lockstep with the increased agricultural output of rice, corn, and wheat across the US Midwest. Where their numbers were once limited by the winter food supply, now they weren鈥檛. The birds were reaping the benefits of increased farm production and the government subsidies that had boosted it. For scientists, the shift in feeding behavior revealed how adaptable the geese were. They had moved from marshes, which were disappearing, to expanding rice paddies and cornfields.

鈥淲e used to characterize these things as narrowly defined niche preferences,鈥� says Ken Abraham, a waterfowl and wetlands scientist with the Ontario Ministry of Natural Resources in Peterborough. Snow geese 鈥渉ave broken every rule.鈥�

More farming has meant more geese, and more geese mean more pressure on a delicate northern ecosystem. The fact that humans are indirectly responsible for the destruction bolstered the argument that humans should correct the problem.

鈥淲e鈥檙e manipulating nature at many different levels,鈥� says Mr. Abraham. It鈥檚 irresponsible 鈥渢o stand back and say, because it鈥檚 far away, we should let nature take its course.鈥�
There was also some worry about the geese themselves.

鈥淭here could be a tremendous crash in their population,鈥� says James Kelley, the US Fish and Wildlife Service鈥檚 (FWS) Mississippi Flyway representative in Fort Snelling, Minn. 鈥淲e don鈥檛 think [that] is a prudent thing to let happen.鈥�

In the late 1990s, experts recommended halving the population of 3.2 million snow geese by increased hunting. (Some scientists say the actual population was nearer 6 million.) Over the protests of the Humane Society of the United States, which was denied a court injunction, a culling program began in 1999. Hunting seasons were extended and techniques previously prohibited, like electronic calls, were allowed. Now, between 1 million and 1.5 million geese are taken annually, according to the FWS.

And yet, it鈥檚 unclear if the increased harvest is working. The salt marsh ecosystem seems to have reached a new equilibrium, says Abraham, meaning that further degradation has halted. But the marshes are not recovering. That could mean that goose numbers are still greater than what the habitat can sustain, or that the habitat takes a long time to recover.

For the Humane Society, the so-far inconclusive results are evidence that increased hunting was pointless and unnecessarily cruel.

鈥淚t鈥檚 alarmist to suggest that 鈥� this is an ecosystem that鈥檚 on the verge of collapse,鈥� says John Grandy, senior vice president for wildlife with the Humane Society in Gaithersburg, Md. 鈥淭here hasn鈥檛 been a catastrophe. The habitat still exists. The arctic still exists.鈥�

鈥淲e鈥檝e just got to live with the notion that this is a vibrant, functioning ecosystem,鈥� he adds.

But the geese will eat through a lot more summer habitat before reaching a natural limit, says biology professor Rock颅well. 鈥淒ensity dependent regulation,鈥� in which an ecosystem supports a finite number of individuals, 鈥渙nly works if you stay put,鈥� he says. Snow geese don鈥檛. In fact, with the saltwater marshes exhausted, the ever-adaptable geese are moving into freshwater marshes. 鈥淎lmost everywhere we go, we find more snow geese,鈥� he says. Without intervention, he foresees a landscape dominated by snow geese and salicornia, and not much else.

And that raises the sticky prospect of a Plan B. What else can be done?

鈥淲e鈥檝e pretty much exhausted many of the hunting-related ap颅颅proaches,鈥� says Mr. Kelley of the FWS. Population control at the nesting grounds is too expensive 鈥� they鈥檙e too remote. And large-scale government-sponsored goose removal is none too savory.

States like Missouri do remove nuisance Canada geese, but fewer than 1,000 of them per year. And whoever wants them gone has to foot the bill. (The meat is donated to charities.) But with snow geese, hundreds of thousands of animals would have to be taken.

鈥淚 don鈥檛 think this would be feasible from a public relations standpoint,鈥� says David Graber, a waterfowl biologist with the Missouri Department of Conservation in Columbia, Mo, who has worked on goose-control contingency plans. Public sentiment aside, how would you do it, where would you do it, who would pay for it, and what would you do with the carcasses?

鈥淭he logistics are just a nightmare,鈥� he says. 鈥淚 don鈥檛 think that direct control is something that鈥檚 on the radar screen.鈥�