Along the banks of the Quatre Fourches River, 125 miles downstream of Alberta’s massive tar sands development, Joe Wandering Spirit once lived in a single-room cabin with a crazy cat and a team of sled dogs that he kept tied up outside year-round.

As Wandering Spirit knows, living in the heart of the Peace-Athabasca Delta — one of the world’s largest inland freshwater deltas — has never been secure. In this 2,200-square-mile expanse of waterways and wetlands, seasonally meandering rivers and streams can abruptly flow in opposite directions and sometimes flood their banks, especially when ice jams along narrow choke points. Big lakes can dry up one summer and reappear the next. For Wandering Spirit, the last of 400 aboriginal people who once lived here year-round, the art of navigating through this world was a life-long lesson in recognizing these dangerous ebbs and flows.

Recently, however, the delta has been undergoing more profound change than Wandering Spirit — or any of the other Cree, Dene, and Métis people whose lives depend on this world — have seen before. Most noticeably, the delta has been drying out, the result of natural cycles of drought as well as human impacts. But two important human influences — the swift warming of the alpine and boreal forest regions across Canada and the diversion of water for tar sands mining — are expected to intensify, potentially putting even more stress on the delta.

If the drying of the Peace-Athabasca Delta continues, it could threaten one of North America’s most vibrant ecosystems, home to as many as a million birds; a commercial fishery that relies on walleye, pike, and lake whitefish; the world’s largest free-roaming bison herd; and a unique pack of gray wolves that preys on them. No other waterfowl staging area in Canada is as important as the delta, which harbors 219 species of birds, more than 300 species of invertebrates, 22 species of fish, and 43 species of mammals.

Such diversity is the reason why the delta has been designated a wetland of international significance under the Ramsar Convention. The delta also is the defining feature of Wood Buffalo National Park, a United Nations World Heritage site and the second largest national park in the world. (Eighty percent of the delta lies within Wood Buffalo park.)

“Without a flood in the next few years, the basins of the delta are going to continue to dry up and there will be more willows and non-native plant species taking over,” says Stuart MacMillan, Parks Canada’s manager of resource conservation in Wood Buffalo National Park. “It could get worse if climate change continues to reduce the amount of water coming out of the mountains and foothills of the Rockies. There’s also the possibility that upstream developments may further reduce the amount of water that is reaching this part of the world.”

MacMillan is referring primarily to the development of Alberta’s tar sands, a 54,000-square-mile repository of bitumen, or heavy crude oil, that is extracted from sand formations using large amounts of water from the Athabasca River. The Athabasca, along with the Peace River, is what has fed the basin for millennia with a steady flow of water gushing from the snowpack, glaciers, and foothills of the Rocky Mountains.

Scientists are attempting to sort out the role of human and natural influences behind the worrisome drying trend. They have also been trying to determine the prospects for the region as climate change continues to buffet northern Alberta. In addition to tar sands development and climate change, the past and proposed construction of hydroelectric dams upstream on the Peace River may affect the delta’s future.

Parks Canada is sufficiently concerned that it has joined with 17 aboriginal organizations, provincial and federal agencies, and conservation groups to establish the Peace-Athabasca Delta Environmental Monitoring Program, which will use western science and traditional First Nations knowledge to track stresses in the delta.

Recharged by periodic flooding, the region hasn’t experienced a significant delta-wide flood since 1997. Following the flood of that year, 55 percent of the north end of the delta, which is recharged by the Peace River, was covered in water or shallow marshes. By 2008, that figure had fallen to 33 percent. The south end of the delta, which is recharged by the Athabasca River, is in better shape. But it, too, is steadily becoming dryer.

Many waterfowl species are still doing fine, according to the U.S. Fish and Wildlife Service, which conducts surveys in the region. But those surveys show that some species such as scaup, which rely on these wetlands, have declined by 70 percent or more since the 1950s. And pollution, which may have been mitigated to some extent by higher water volumes, is likely to increase as the development of the tar sands intensifies, according to ecologist and water expert David Schindler of the University of Alberta.

Ecosystem change is nothing new in the Peace-Athabasca, as Kevin Timoney, a former Parks Canada biologist notes in his recently published book, The Peace-Athabasca Delta: Portrait of a Dynamic Ecosystem. The delta, he says, has dried many times in the past.

“Simple cause and effect are rare in complex delta systems like this one,” Timoney said in an interview. “Here, ecosystem change tends to be episodic, with periods of slow change punctuated by major changes. Understandably, people view the delta on the time scale of their own experiences. But the reality is those time scales limit our ability to understand the complexity of what has been going on over the longer term.”

Nevertheless, Timoney acknowledges that the ecological integrity of the delta could be seriously compromised by further tar sands expansion, climate change, pollution, salinization, and possibly by new hydroelectric dams such as Site C, which the government of British Columbia is considering building on the Peace River. If the 20-story dam goes ahead, it will flood as much as 40 square miles of boreal forest and potentially exacerbate the river flow changes that are already affecting the delta downstream.

It was a hydroelectric dam that first brought the fate of the delta to the world’s attention. When the W.A.C. Bennett Dam was built upstream on the Peace River in the late 1960s, the amount of water flowing down the river into the north end of the delta was severely reduced during the time it took to fill the reservoir. Water levels in some parts of the delta dropped by several feet. A severe drought that followed kept those water levels low once the reservoir was full. No longer able to make a living hunting, trapping, and fishing on a full-time basis, almost all of the indigenous people who inhabited the delta — including Joe Wandering Spirit — eventually moved to Fort Chipewyan, a town of about 1,000 people.

The delta did recover eventually as the flood cycle resumed. Continuing impacts, however, are still being felt to some degree because of the Bennett Dam’s interference with seasonal water flows and by climate change that is reducing the amount of water coming from the snowpack and glaciers that feed the river system.

Research conducted by Environment Canada scientists has shown that flow regulation by the Bennett Dam in fall results in more water going downstream into the delta during freeze-up. This results in ice on the river building up at higher than normal levels. The problem is that there is no longer enough water melting off the snowpack in spring to create the ice jams that are necessary for the river water to back up, overflow its banks, and flood the delta.

A worrisome threat to the future of the delta centers on the amount of water being diverted for the tar sands industry.

For Timoney and other scientists, however, a more worrisome threat to the future of the Peace-Athabasca Delta centers around the amount of water being diverted for tar sands development. Industry now withdraws about 170 million cubic meters of freshwater annually from the Athabasca River to drive its operations. That amount could triple by 2035 if the industry expands at the rate being forecast.

Industry officials argue that the amount of water currently taken from the Athabasca is very small — about one percent of the annual flow. But as Timoney points out, these withdrawals can amount to as much as 10 percent or more in winter when river flows are at their seasonal minima. Tripling the volume of water currently being diverted, he says, could make the situation much worse.

The University of Alberta’s Schindler and other scientists are also concerned about tar sands pollutants reaching the delta as oil-mining operations expand. An industry-funded study of core samples from lake bottoms in delta lakes showed no evidence of pollution, other than from naturally occurring polycyclic aromatic compounds (PACs).

However, one recent Environment Canada/Parks Canada study has found that high levels of mercury found in some nesting bird populations in the delta are almost certainly coming from the tar sands. What’s needed, says John Smol, a Queens University professor and Canada Research Chair in Environmental Change, is a study in which tracers might be used to track the flow of contaminants downstream. This has yet to be done.

At the top of Timoney’s list of concerns is climate change, which is already leading to rapid warming across Canada and which could further dry out the Peace-Athabasca Delta. Recent declines in winter snowpack that melts MORE FROM YALE e360

With Tar Sands Development, Growing Concern on Water Use Environmental questions about Canada’s massive tar sands development have long centered on greenhouse gas emissions. Now there are mounting concerns about the huge volumes of water used by the oil industry and the impact on the vast Mackenzie River Basin.

Climate scientists and hydrologists predict that the dramatic springtime warming occurring in the region is going to get much worse, further reducing snowpack and cutting the flow of water to the delta.

Timoney says that if current trends continue, there is a distinct possibility that large, fish-filled lakes such as Mamawi and Baril could turn into shallow marshes. Smaller basins, which sustain waterfowl populations, will likely continue to dry up, he says. The prospect of salinization, brought on by increased rates of evaporation and possibly by increased loading of solutes from the tar sands, is not out of the question, he says.

On the one hand, Timoney is hopeful because the delta can never be mined, logged, or exploited for its energy resources as long as it remains part of Wood Buffalo National Park. Still, he says, “Development continues to creep downstream toward the delta. Unless it’s controlled or managed more efficiently, the death of the delta may well happen — maybe not in our lifetime, but sometime in the future.”