In order to understand the controversy surrounding the proposed Pebble Mine in Alaska, we must first understand the potential threats the mine poses. As pointed out by Kelly J. Cunningham in her Master’s thesis Bristol Bay and the Pebble Project: Red or Gold?, the most important potential victim of the mine is the wild Sockeye salmon. This is the world’s largest Sockeye salmon run, with 10 to 35 million fish returning every year.
The life cycle of the salmon is part of what makes the Pebble Mine such a serious threat. Mature Sockeye spend 1 to 4 years feeding in the open ocean before returning to their natal rivers to spawn during the summer. After hatching, the salmon can spend up to three years in fresh water, feeding on zooplankton, benthic amphipods, and aquatic insects before migrating to sea. This extended time in and reliance upon freshwater ecosystems make the Sockeye especially vulnerable to negative changes in water quality.
Round Mountain open pit gold mine in Big Smokey Valley, Nevada.
The proposed development of the Pebble Mine would involve both open pit mining and block caving (underground) for gold and copper. The processes required for these kinds of mining involve removing large amounts of material, crushing the material, and soaking it in chemical solutions to finally collect a small amount of gold or copper. The leftover material, or tailings, must be stored in ponds and, as Cunningham points out, have historically led to “toxic conditions for both ground and surface water on and off of the mine site.” Copper is also one of the most toxic heavy metals to fish, and can lead to stunted growth, decreased antibody production, and altered gill structure. These are some of the most important threats posed by the Pebble Mine, and must be weighed against the benefits when deciding what policy is best for the region.
Sources:
http://archives.evergreen.edu/masterstheses/Accession86-10MES/Cunningham_KMESThesis2008.pdf
http://en.wikipedia.org/wiki/File:Round_Mountain_gold_mine,_aerial.jpg