Seismic lines from energy exploration an uncounted greenhouse gas source: study

By The Canadian Press
June 26, 2019 - 11:15am

CALGARY — Seismic lines used in energy exploration are a significant source of a highly potent greenhouse gas that hasn't yet been taken into Canada's national account, new research suggests.

In a paper released Wednesday, Greg McDermid of the University of Calgary says seismic lines through peatlands release enough methane to increase national estimates of emissions from land use by at least seven per cent.

"Our paper's as much a call to action as anything," said McDermid, a geographer. "There's a lot we don't understand about methane and seismic lines."

About half of Alberta's oilsands deposits are covered by peatlands, which are major absorbers of carbon dioxide. Much has been written about the impact of seismic lines — a narrow strip of bush cleared to allow geologists to study what's underneath — on wildlife, but their effects on soil are largely unknown.

One of McDermid's findings is that Alberta has a lot more seismic lines than previously thought.

To reduce their impact, new lines can be as narrow as one metre, which makes them hard to spot on satellite imagery. To get a better idea of how many lines exist, researchers used new high-resolution techniques.

They found at least 345,000 kilometres of seismic lines on about 1,900 square kilometres of peatlands. That's about twice as many as previously suggested by public data sources.

McDermid and his colleagues found that those lines change the soil.

Running machinery over it compacts it. Its vegetation changes. Its average temperature goes up. Most of all, the water table rises.  

Biologists have long known those factors cause peatlands to release more methane. Combining that knowledge with estimates of the amount of land disturbed by seismic lines allowed McDermid to calculate the amount emissions grew.

His calculation concluded that seismic lines caused Alberta peatlands to release an extra 5,000 tonnes of methane annually.

That's a small portion of the 251,000 tonnes peatlands release naturally every year (while storing more than two million tonnes). But U.S. figures say the extra methane is equivalent to emissions from about 27,000 cars — emissions not currently accounted for in national inventories.

Nor are those emissions fading. Seismic lines, particularly through wetlands, remain on the landscape for decades.

"The mistake that was made around seismic lines was that we could just cut them and they would naturally regenerate," McDermid said. "It turns out to be not really the case, especially around wetlands."

Industry is aware of the problem, said McDermid.  

"They're working on the problem. I think that in lots of cases, leading petroleum industries are really pioneering how to work in the boreal forest and restore seismic lines."

McDermid acknowledges there's wide uncertainty in his study — mostly because of the lack of field work on the impact of seismic lines on soils.

"Most of the treatment that's happening on seismic lines now is designed to address the problem of caribou. What we don't know is if their treatments also help with methane and the peatland impacts."

McDermid noted the study used conservative estimates. Whatever the actual amount of methane emissions caused the lines cause, there's little doubt they are an issue.   

"We need better practices on activities in and around peatlands and throughout the boreal forest, and certainly around reclamation and restoration."

— By Bob Weber in Edmonton. Follow @row1960 on Twitter

The Canadian Press

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