Road building on Walbran Karst: A Sinking Idea
By Charly Caproff
‘Environmentally responsible’ Teal Jones has proposed to construct logging roads through a landscape characterized by sinkholes, disappearing streams and caves.
Sinkholes are caused by the dissolution of limestone by slightly acidic rainwater. Surface water seeps through the epikarst and opens intricate cave chambers within the subterranean environment. They can also occur due to the lowering of the water table. As the limestone dissolves, the organic material at the surface can no longer be supported, leading to the ground caving in rapidly and with little warning.
Peter Cressey and I ventured into the heart of Cutblock 4403, a magnificent old-growth rainforest, to observe the proposed route. Cressey was actively involved in the Walbran Valley blockades during the 90’s. Approximately 10 meters from the proposed road route we found an exposed sinkhole. It was roughly two feet in diameter, and directly below the proposed route on a steep bank. There had been a heavy rainfall that weekend and crystal clear surface water was rushing into the dark, mysterious depths. To the right of the sinkhole, an immense western red cedar towered overhead. As I continued to explore the rainforest, I moved cautiously as the forest floor was covered with depressions.
Karst is a constantly developing, dynamic system and there is limited knowledge of the extent of most groundwater systems. Due to the unpredictability of sinkhole formation on karst terrain, they are precarious environments for infrastructure development.
It is estimated that human activity on karst has cost billions of dollars for preventative measures and infrastructure damage worldwide (Ford & Williams, 1989).
Last year, a sinkhole developed in the Kentucky Corvette Museum, resulting in five million dollars worth of damage.
Not only is development on these environments costly and dangerous, but it is also detrimental for the fragile karst hydrological and biological systems.
Karst is a dynamic system connecting the surface to the largely unexplored subterranean world. Rainwater transfers dissolved organic carbon and nitrogen from the soil into the karst ecosystem. According to the Karst Waters Institute, these inputs from the surface are crucial for the functioning of karst food web, as many troglobites, or cave-dwelling species, are completely reliant on the microbial film found on rocks (produced by organic inputs into the karst system) and the dissolved nutrients as energy sources (White & Martin, 2009). It has been approximated that globally there are between 20,000 – 100, 000 species endemic to karst caves, one-third of which are aquatic (Bonacci et al., 2009).
River systems fed by alkaline and cool karst groundwater are also important for aquatic species on the surface, such as salmon. With increasing freshwater acidity and temperature, karst hydrological systems will play an increasingly important role in buffering the impacts of climate change (Strong et al., 2014).
To prevent the road or logging equipment from becoming swallowed into the depths of the earth, forestry often fills in the surrounding sinkholes. By altering the drainage system, this severs the connection between the surface and the subsurface. Road building also leads to the contamination and plugging of karst systems due to increased sediment erosion and runoff of deleterious substances (Stitt, 1997). This polluted water rushes rapidly through the system with minimal filtration and eventually reemerges at the surface.
As we traversed through the karstified landscape, I was mesmerized by the Walbran’s intrinsic beauty. We crossed several karst streams flowing over pure white bedrock into the Walbran River below. Limestone jutted through the emerald green moss beds and at the roots of impressive stands of coniferous trees. I had the pleasure of meeting ‘Sir-Karst-A-Lot’, a majestic western red cedar 35 feet in circumference.
There is something magical about the Walbran Valley. To destroy it for short-term economic gain is not only cruel, but also extremely shortsighted. The remaining ancient forests are important climate regulators and support an abundance of diverse species.
The logging of an old-growth forest underlain by sensitive karst terrain is an unsustainable practice. Once the karst is removed, it is gone forever.
Bonacci, O., Pipan, T., & Culver, D. C. (2009). A framework for karst ecohydrology. Environmental Geology, 56(5), 891-900.
Ford, D. C., & Williams, P. W. (1989). Karst geomorphology and hydrology. London, UK: Chapman & Hall.
Stitt, R. (1997). Selected forest management issues related to karst. Bellingham, WA: 1997 Karst and Cave Management Symposium.
Strong, A. L., Kroeker, K. J., Teneva, L. T., Mease, L. A., & Kelly, R. P. (2014). Ocean Acidification 2.0: Managing our Changing Coastal Ocean Chemistry. BioScience.
White, W. B., & Martin, J. B. (2009). Frontiers of Karst Research: Proceedings and recommendations of the workshop held in San Antonio, Texas on 3-5 May 2007. Charles Town, WA: Karst Waters Institute.