Gold Mine Threatens Treasured Biosphere Reserve

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Photo: Acid mine drainage at US mine | Credit: Earthworks

“Paredones Amarillos” is a proposed gold mine that would be located in the Sierra la Laguna Biosphere, a pristine area recognized by the Mexican government and the United Nations for its rich biodiversity. If mining proceeds in this biosphere reserve, this natural paradise could become home to a toxic waste site.

To extract gold from the Sierra la Laguna mountains, the Canadian company, Vista Gold, proposes to carve out huge quantities of rock – each ton contains a mere gram of gold – and grind it into a sludge. Next, it will treat the sludge with cyanide, an extremely dangerous chemical. The process dissolves the gold into a liquid so it can be collected; it also produces massive amounts of toxic waste from the left-over cyanide-treated ore.

The company plans to contain this waste ore (called “tailings”) in a dam intended to store the toxic slurry forever. Unfortunately, these dams can break for various reasons, as happened at the Porco mine in Bolivia in 1996. When the Porco tailings dam collapsed, more than a quarter million metric tons of tailings flooded the river and contaminated 800 km of waterways in three countries: Bolivia, Argentina y Paraguay.

This type of open-pit gold mining can also cause a devastating problem called “acid mine drainage.” When sulfur-containing rocks are exposed to air and water, sulfuric acid is created. The acid in turn can cause toxic heavy metals to dissolve and drain into the watershed. The risk of acid mine drainage occurring in Sierra la Laguna is significant and the human and environmental cost would be tremendous: thousands of people and countless wildlife in the Sierra la Laguna desert rely on this water for survival.

Mining companies also store cyanide solutions and contaminated waters in reservoirs which, like tailings dams, can rupture or overflow. In 2000, in the worst environmental disaster in Europe since Chernobyl, a wastewater reservoir gave way causing 3.5 million cubic feet of cyanide-contaminated water to spill into several rivers, killing all of the fish and seriously harming the river ecosystems.

Depleting freshwater is a further threat. Mines use tremendous quantities of water. Because water is so scarce in the reserve, Vista Gold proposes to build a plant on the Pacific coast to remove salt from sea water via a highly energy-intensive process, and then pump the water 45 km to the mine site. The desalination poses a threat to the leatherback sea turtle, famous for its gigantic size and endangered status.

With gold selling for more than $1,000 an ounce, the mine would likely be lucrative for Vista Gold. The long-term benefit to Mexico and nearby communities is not as clear. Few industries wreak as much environmental damage as mining. In the United States alone, 179 abandoned mines are listed on the national priority list as hazardous waste sites in need of cleanup.

Such cleanup is very expensive, and governments and taxpayers often end up paying the bill. Unfortunately, because it takes time for acid mine drainage to appear, the full extent of environmental harm caused by mining may not become apparent until long after the mining company has left.

With your support, AIDA is providing legal and technical assistance to the community groups and non-governmental organizations working to prevent mining from destroying Baja’s natural treasure.