Seismic lines – petroleum exploration corridors – crisscross the Alberta landscape, and are well-known to those who spend time in the province’s backcountry. For those who do not, perhaps a short introduction is in order. Seismic lines are linear clearings about 2-8 m wide, which are cut into the forest to allow seismic equipment to be deployed in the hunt for oil and gas. They look like narrow road allowances, but without the road.
To say that there are a lot of seismic lines in Alberta would be an understatement. Seismic exploration has been going on in the province since 1929, and there are more than 1.8 million km of seismic lines on our landscape. If open-pit mines are the large wounds of oil and gas development in Alberta, then seismic lines are the 1.8 million cuts.
Many studies have looked at the effects of seismic lines on Alberta wildlife (they have been implicated in the decline of woodland caribou, for example) but relatively little is known about their impact on wetlands. The problem is that the effects are difficult to measure. Individual seismic lines are relatively small, and don’t show up in the type of remote sensing datasets used by most researchers.
In a new paper published in the Journal of Geophysical Research Biogeosciences, Julie Lovitt and her co-authors used imagery from drones to quantify – for the first time – the impact of seismic lines on a forested bog near Peace River, Alberta. Her work showed that seismic lines leave two main physical imprints on wetlands: a flattening of terrain and a decrease in the depth to water.
Outside of vegetation removal, the visual effects of the seismic lines on wetlands are quite subtle. However, the implications of these disturbances is large. For example, Julie and her co-authors showed that the small (15.4 cm, on average) decrease in depth to water found on the seismic lines in her study area could be expected to boost methane emissions by 20-70 kg over the course of a single growing season. Methane is a potent greenhouse gas with 84x the global-warming potential of carbon dioxide, and the 16 km of seismic lines that Julie measured is a pittance compared to the many thousand km of other lines that cross wetlands throughout Alberta.
How might these effects scale up to the entire province? Stand by.
Lovitt, J., M. Rahman, S. Saraswati, G.J. McDermid, M. Strack, and B. Xu, 2018: UAV remote sensing can reveal the effect of low-impact seismic lines on methane release in a forested Boreal bog. Journal of Geophysical Research: Biogeosciences, 123, 1117-1129. https://doi.org/10.1002/2017JG004232