Snow goose population explosion puts pressure on Arctic habitat
Millions of snow geese will pass through the Upper Midwest during the next few weeks, flying north from the U.S. Gulf Coast to their Arctic breeding grounds.
It’s the scene of an ongoing environmental disaster.
Dr. Robert “Rocky” Rockwell has seen and studied the damage the overpopulated snow geese have caused for more than four decades. An ornithologist at the American Museum of Natural History and a professor at the City University of New York, Rockwell will be spending his 46th summer at the La Perouse Bay research camp on the southwest coastline of Hudson Bay near Churchill, Manitoba, the site of a much-studied snow goose colony that is decimating the coastal habitat in Wapusk National Park.
The birds are part of the Midcontinent population of lesser snow geese, and they continue to multiply, despite liberalized hunting regulations that include a pull-out-all-the-stops spring season in effect since 1999.
“I think we’ve got a pretty good handle on the fact snow geese are proving themselves to be one of the most successful critters we’ve got in North America,” Rockwell said.
As they feed, the geese rut up fragile sedges and other salt marsh plants, destroying the roots and leaving an Arctic desert in their wake. Hunting, the standard method for controlling wildlife numbers, obviously isn’t doing the trick, Rockwell said, and the damage the geese are causing remains unchecked.
“I don’t think any of us realized there are only so many snow geese people are willing to shoot — no matter how many you let them shoot,” Rockwell said. “I like snow geese, but there’s only so many nights a week I’m willing to have it.”
To understand how the snow goose problem began requires going back to the 1960s, when the Midcontinent population numbered about 800,000. Gradually, the snow geese took advantage of expanded crop production along their migration corridors and federal wildlife refuges that provided food and sanctuary.
Today, some estimates have put the Midcontinent snow goose population at 15 million, Rockwell says, a number that is growing by 3 percent to 5 percent a year.
Just on the Cape Churchill Peninsula where Rockwell works, the number of breeding snow goose pairs has risen from 2,500 in 1969 to about 70,000 pairs today, he said.
“When I first started working there, they occupied an area about four times the size of a football field, and now they cover 250 miles of coastline,” Rockwell said. “That population is certainly expanding.”
According to federal estimates, hunters today are shooting more than 1 million snow geese between the spring and fall seasons in the Central and Mississippi flyways — more than double the harvest in the late 1990s. But it’s not enough.
Throw in high survival rates — it’s not uncommon to get band returns on snow geese that are 20 years old — and their tendency to travel in flocks of several thousand birds, and the odds definitely favor the geese.
“It’s pretty high survival benefits being in those huge flocks,” said Mike Johnson, game management section leader for the North Dakota Game and Fish Department who has studied the effectiveness of management actions on reducing Midcontinent goose numbers. “I don’t think there’s any end in sight now, and nobody can predict what will happen.
“It’s anybody’s guess — obviously, we’re not controlling them with hunting.”
While snow geese in the spring can be here today and gone tomorrow, Johnson says hunters in North Dakota continue to take a strong interest in the season, shooting more than 20,000 birds during last year’s spring season.
“About half of our harvest now is coming from the spring,” Johnson said. “It’s kind of switched over, and probably, the reason for that is they’re not piling into the state in the fall as much as they used to.”
Rockwell says the snow geese on the southwest coast of Hudson Bay already have destroyed the delicate salt marsh and now are moving inland about 15 miles, grubbing up the vegetation surrounding small tundra ponds that other waterfowl such as scaup and scoters rely on for breeding.
“We’ve got them now all the way to the tree line,” Rockwell said. “The tree line is not just all of a sudden trees; it’s just sort of gradual, areas with 30-foot spruce surrounding these tundra ponds.”
The unknown, Rockwell said, is how long it will take the habitat the geese already have decimated to recover after they move inland to greener Arctic pastures. Researchers, he said, are exploring options such as hazing the birds by helicopter to move them out of the national park.
That only moves the problem somewhere else, but it also provides research opportunities for Rockwell and his crew of graduate students.
“How long does it take if you remove the geese for something to come back?” Rockwell said. “We don’t know anything about this. Nobody’s ever worked in this kind of circumstance before. The idea is to see if we can find some ways to protect the habitat a little bit.”
Polar bear benefits
Oddly enough, polar bears could be the answer to reducing snow goose numbers, at least in Rockwell’s study area. Only a small percentage of the Midcontinent snow geese nest there, but most of them stop en route to breeding sites elsewhere in the Arctic.
Rockwell, who spoke at the University of North Dakota in April 2009, said at the time that polar bears were beginning to overlap with snow goose nesting colonies and eating the eggs. The bears, which are being driven inland by an earlier ice melt on Hudson Bay, also are catching female geese during the 40-day period when the birds molt and can’t fly.
Calculations have shown the 300 to 400 polar bears that come to shore could make at least a localized difference in snow goose production if they ate one to two more geese a day, Rockwell said.
The bears are coming ashore earlier, but the geese aren’t breeding any earlier because nesting is tied more to daylight length than habitat conditions. And so, the bears and geese cross paths more frequently.
Studies also have shown it’s not just juvenile bears targeting the geese, Rockwell said.
“The big, old, fat guys are coming to shore earlier, too,” he said. “That’s not going to solve the whole Midcontinent problem, but it may solve the coastal problem. It’s good for controlling the geese, and it may well be helping the bears out if they’re losing their ability to eat seals but replacing them with geese” and the eggs they lay.
Rockwell said he’s not surprised by the Midcontinent snow goose population’s continued expansion, adding the liberalized hunting regulations probably came too late.
“I think we had a chance in 1996 to hold it, and it took the bureaucrats two years to act on our recommendations,” he said. “Once I saw that it was still growing in the face of that increased harvest with the spring conservation order, it was clear they were going to get away from us, and they were going to get away from us at an alarming rate.
“And that’s what’s happening.”
On the upside, Rockwell said, “the bears are happy.”
“As a scientist, I don’t have a vested interest one way or the other in the snow geese or the bears,” he said. “I’m just going to keep studying them and see what they do.
“You let them eat away the salt marsh where they’re supposed to be breeding and feeding, and they move inland. When they move inland, they go to the boreal forest, and I don’t know where they’ll stop.
“I don’t think they will unless something really bad happens.”