Compelled to compensate for fish habitat destroyed by their mining operations, some of the biggest players in the oilsands are constructing man-made lakes.
Compensation lakes are designed to emulate every aspect of their naturally-occurring counterparts.
“If you destroy fish or fish habitat, fisheries law says you have to put it back, and often it says you have to put twice as much back because making something from scratch is a lot harder than keeping what’s existing,” said Mark Poesch, an associate professor in the University of Alberta’s department of renewable resources.
The lakes provide habitat for small vegetation, invertebrates, amphibians and fish. Researchers like Poesch are working with operators to ensure they become self-sustaining ecosystems that won’t create imbalances in the surrounding watershed.
“The engineering of a compensation lake actually quite straightforward,” Poesch said in an interview with CBC Radio’s Edmonton AM.
“The hard part is, how do you replicate a natural system? And how do you replicate it in a way that’s going to stay there for years, if not decades to come, because that’s the intent.
“We’re really, in a way, playing God, putting things in the lake that we think are going to be there for Albertans to enjoy throughout time.”
Ecosystems ‘from scratch’
As the geographical footprint of the oilsands continues to grow, there has been increasing interest in compensation lakes as a reclamation strategy.
Alberta already has five, and at least five more are planned for construction.
Imperial’s compensation lake, Muskeg Lake, was completed in 2010, filled with water pumped from adjacent Kearl Lake. A connector channel, built in 2013, allowed fish to migrate into the new lake, which is now home to northern pike and northern redbelly.
Suncor is planning to construct a compensation lake in the Beaver River watershed as part of its habitat rehabilitation plan for the Voyageur South Mine north of Fort McMurray.
CNRL was the first to construct a compensation lake. Built in 2008 at its Horizon site near Fort McMurray, Horizon Lake covers 80 hectares and, at its centre, plunges more than 20 metres deep.
It was established beside the Tar River in the lower Athabasca watershed. The company plans to eventually connect the lake to the river.
CNRL describes Horizon Lake as a self-sustaining ecosystem that has seen native fish species “repopulate and thrive.” The lake will sustain twice the fisheries habitat that will be lost during the life of the mining operation, the company said.
We don’t just study the fish, we study the entire food web.– Mark Poesch
Poesch and his team have been studying the lake and the surrounding watershed for more than five years. Now its final year, the study has focused on building lakes that sustain diverse fish stocks and mimic the ecosystems of nearby natural wetlands.
“We want fisheries that don’t crash,” he said. “We study all aspects of the lake. We don’t just study the fish, we study the entire food web.”
The CNRL lake has experienced a marked increase in species diversity with populations of brook stickleback, lake chub, fathead minnows and longnose suckers — and dozens of invertebrate species.
“Many of the lakes in that area end up having winter kill because they’re shallow and lose oxygen so it was purposely designed to be quite deep in the middle,” Poesch said.
“It houses a broad range of species including one that’s sensitive called the Arctic grayling that people are concerned about.”
Fish populations in Horizon Lake are being tracked through netting and the use of an echosounder. The instrument collects 2D images of fish, allowing researchers to categorize populations by species.
While the lake is supporting a relatively diverse population, it is home to a food web unlike those seen elsewhere in the watershed. For instance, there is a lack of predator fish and overall fish populations have experienced unpredictable fluctuations, suggesting an imbalance in the ecosystem.
There are also concerns about the survivability of the Arctic grayling once the lake is connected to the river. Introducing predator species could destabilize the food chain.
Poesch is hopeful that with a deeper commitment to ongoing scientific research, operators will be able to strike the right balance so nature can take its course.
“Each lake is different,” he said. “In the beginning, they tend to go through boom and bust cycles so the companies are meant to keep monitoring.
“Right now were just making sure that it’s doing what it’s supposed to be doing and providing advice so that this lake, in the long term, will be robust.”
‘Higher risk of failure’
In a recently published study, Poesch reviewed 577 compensation projects in freshwater ecosystems across North America and Europe and found a troubling trend.
Although billions of dollars are spent on biodiversity offset projects each year, studies evaluating their overall effectiveness remain rare, the study found.
To create sustainable ecosystems, operators and regulators need to move beyond basic regulatory guidelines and focus on diverse management practices, Poesch said.
And in the end, rehabilitating a damaged ecosystem is always going to be easier than creating entirely new ecosystems.
“A high level of compliance did not guarantee a high degree of function,” the study found. “Despite considerable investment in offsetting projects, crucial problems persisted.”
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