Government regulators and proponents for drilling in the Arctic National Wildlife Refuge in Alaska have generally assumed that conducting seismic activities in the winter would avoid damaging the sensitive tundra ecosystem.
However a new study in the journal Ecological Applications throws this assumption into doubt.
Janet Jorgenson and her colleagues present results from a long-term monitoring program on the recovery of arctic tundra vegetation following seismic exploration for oil and gas. Their findings show that the recovery can be much slower than expected.
The researchers revisited permanent vegetation plots six times between 1984 and 2002 to measure percent cover of various plant growth forms in different vegetation communities and soil types.
The study found that the arctic tundra has low resistance to disturbance. All plant forms in all community types showed initial decreases in cover.
Some plant forms underwent a quick recovery. Grasses and sedges quickly dominated many disturbed areas, leaving seismic trails highly visible by the dense graminoid growth. Evergreen shrubs and other plant types, however, struggled to regain the percent cover found on reference sites.
Greatest disturbance did not come from the seismic survey vehicles, which are relatively light. Rather the large, heavier camp vehicles following the machinery had much greater impact on the tundra.
The loss of bryophyte cover was particularly worrisome. A dominant plant type in the study area, bryophytes have greater percent cover than all other forms combined. They play a key role in permafrost insulation, but were found to be highly disturbed by seismic traffic. In non-riparian areas, they showed “little recovery, even after 18 years”.
The underlying permafrost played a key role in plant community recovery. This iconic feature of arctic ecosystems varies in depth and water content across the tundra. Where ground ice was more abundant, plant recovery tended to be delayed.
The study findings suggest that seismic impacts could combine with climate change to greatly alter the permafrost and arctic ecology where seismic activities occur. The authors write,
"Climate change is likely to make permafrost even more sensitive to seismic exploration activity in the future. We speculate that warming in the past two decades has exacerbated some of the thawing on trails reported in this paper"
--Reviewed by Ian Adams
Jorgenson, J., Hoef, J., & Jorgenson, M. (2010). Long-term recovery patterns of arctic tundra after winter seismic exploration Ecological Applications, 20 (1), 205-221 DOI: 10.1890/08-1856.1