Cormorant debate: Which part of the ecosystem to protect?

While officials hope culling the habitat-altering cormorants will save an ecosystem that makes up just one per cent of the country, others grapple with the ethics of re-engineering nature.
Lake Erie's Middle Island has lost more than 40 per cent of its forest canopy since cormorants took up residence in 1987.
Gunshots rang out across Middle Island this month as Parks Canada launched in earnest its controversial five-year plan to protect the Lake Erie island's rare Carolinian forest from a native bird.

While officials hope culling the habitat-altering cormorants will save an ecosystem that makes up just one per cent of the country, others grapple with the ethics of re-engineering nature.

Middle Island, Canada's southernmost point, underscores the enormous philosophical divide between those who argue against what they call the arrogance of thinking we can reassemble ecosystems and those who say that in some cases, we have no choice.

Critics point out that while many of the Carolinian forests' plants and animals are in trouble in Canada where the ecosystem reaches its northern limit, they are relatively abundant south of the border.

"They are species at risk in Canada, but not in the larger ecosystem," says Liz White of Cormorant Defenders International — which was briefly able to get a court injunction that abbreviated last spring's cull.

Amber Ellis, executive director with Earthroots, agrees. The organization is one of several environmental and animal rights groups that make up Cormorant Defenders International. "We're not doing a very good job at managing very much of anything when it comes down to it," she says. "It's not cormorants that are the threat. We're the big threat."

A dying island

The first three nesting pairs of double-crested cormorants were spotted on Lake Erie's Middle Island in 1987. Twenty years later, they had ballooned to a population of more than 5,000 pairs. ((Courtesy Parks Canada) )
But Middle Island, according to proponents of the cull, is one of those cases where options are limited.

"This is about supporting a dying island that supports a dying population of plants and animals," says Marian Stranak, superintendent of Point Pelee National Park.

"Yes, these species exist over there [in the U.S], but we have an obligation and an expectation to protect species at risk that are in Canada," she says.

Parks Canada's chief ecosystem scientist Stephen Woodley argues protecting plants and animals at the limit of their range, as is the case with Carolinian species in Canada, is important for another reason.

Populations of a species at the edge of their ecological range have a unique genetic makeup that does not exist in the centre of their range, he says. That's because edge populations had to adapt to different selection pressures, such as greater extremes in temperature, sunlight and precipitation.

Woodley argues protecting those unique genes increases biodiversity, which in turn acts as an insurance policy against the kind of transformations scientists expect from climate change. In short, the more diverse a system or species, the better able they are able to adapt to change.

Startling comeback

The irony of course is that this is a cull meant to protect species at risk, but that not so long ago it was the double-crested cormorant that was in trouble.

These large, greenish-black water birds with slender hooked-tip bills and orange faces are native to the Great Lakes. In the 1950s, the region was home to about 900 breeding pairs. By 1972, there were just 136 pairs, largely due to the pesticide DDT which thins eggshells and kills chicks before they hatch.

The birds' dramatic decline sparked protective regulations in Canada and the U.S, leading to significant reductions in DDT. Starting in 1972, the cormorants made an equally dramatic comeback, increasing nearly 300 fold to 38,000 nesting pairs across the Great Lakes by 1993.

Cormorants nest "condo-style" in trees, such as the ones seen here on Middle Island in Lake Erie, breaking branches and stripping foliage for their nests and altering soil chemistry with massive amounts of guano.
The first three nesting pairs were spotted on Middle Island in 1987. A couple of decades later, they had ballooned to a population of more than 5,000 pairs — a number Parks Canada calls "hyper abundant" for an 18.5 hectare island. Its goal is to reduce the population to between 438 and 876 pairs by 2012.

The birds were able to reach such astonishing numbers on Middle Island and across the Great Lakes largely because of human-induced changes.

Alewife — a fish native to the Atlantic Coast — entered the Great Lakes through the Welland Canal in the middle of the last century, exploded in numbers and quickly became the cormorants' favoured food. Catfish aquaculture in the cormorant's wintering grounds in the southern U.S. ensures they have plentiful food after they leave the Great Lakes each fall. 

Today, cormorants literally blanket Middle Island, threatening to wipe out nine Carolinian species protected by the federal Species at Risk Act, including the eastern fox snake and the red mulberry tree.

Already, the island has lost more than 40 per cent of its forest canopy due to the birds' habit of breaking branches and stripping foliage for their nests, and to changes in soil chemistry caused by massive amounts of eye-watering guano.

Fisheries at risk

While parks officials are betting the cull will bring back the forest, many fishermen on Lake Erie are happy to see the birds killed, whatever the reason. They believe cormorants' voracious appetites — a two kilogram bird will eat half a kilo of fish a day — are responsible for declining fish stocks and have argued repeatedly for re-engineering the cormorant-fish balance.

"People say they are a beautiful bird. I say they're more beautiful when they're dead," says Mike Matta, a Lake Erie charter captain.

Much is at stake, say Matta and other fishermen. Lake Erie is the second largest commercial freshwater fishery in the world and generates millions of dollars of revenue. Little wonder someone has been letting raccoons loose on Middle Island in the hope that they will kill cormorants.

Frustration reached a peak on neighbouring Lake Ontario in 1998 when a handful of fishing guides took matters into their own hands, shooting about 800 cormorants on Little Galloo Island. But are the birds responsible for declining fish stocks?

Ministry of Natural Resources fisheries biologist Mark Ridgway recently wrapped up a six-year study in Georgian Bay and the North Channel designed to answer that question.

He and his colleagues divided the region into quadrants, oiling cormorant eggs to suffocate chicks before they hatched in some areas, and leaving others alone as a control. They estimate that in those quadrants where eggs were oiled, the birds' cumulative demand for fish decreased by 20 to 30 per cent

"We found a significant effect on the return of smallmouth bass as a result of oiling the eggs," says Ridgway, who declined to give specifics until the study is peer reviewed and released sometime this fall.

When it is released, it's sure to catch the attention of those on both sides of the cormorant debate, as well as those in government who are charged with balancing competing interests.

"There's much consternation about getting the policy right in relation to these birds," says Ridgway. "It's the first case where we've gone from having an organism that's a rarity to having a management issue [with a large number of birds]. No one's confronted this before."