The Central Yukon reporting
unit
consists of four ecoregions that cover a swath that includes many
of the main mining communities in the Yukon such as Dawson City,
Faro, Mayo and Elsa. Approximately 4,000 people live in this region
and the main employers are mining related (22%), tourism and the
service sector. Many of the environmental issues raised in this
area are related to mining activity.
Half of the 14 Yukon First Nations have part of their traditional territories in this region. The pursuit of traditional subsistence activities has been upset in some areas because of mine development, access roads and mineral exploration. For example, the development of the Faro mine in the Mount Mye area disrupted the use of traditional hunting and fishing areas by members of the Ross River Kaska Dena. As Arthur John, a Ross River Elder explains,
Now no one goes there. The mine tore up half the mountain now. People from that country try other areas, could not find anything as good. After that, just like people get lost, don't know where to go. They tried back in there, up that way. Not as good as down there no more. So people don't get good living like long time ago.
In recent years, operators of the Faro mine have addressed some First Nation concerns by taking measures to preserve access for native harvesters, conserve habitat and provide opportunities for economic benefits to the original inhabitants of Mount Mye.
The central Yukon contains geological features that are particularly associated with the formation of mineral deposits. These features include:
Volcanic activity associated with faulting, which produced the
Tintina Trench, resulted in gold deposits, while important mineral
deposits are found in the Yukon Tanana terrane. The forces of
erosion and deposition have also concentrated secondary deposits
of gold in river valleys. In most of the Yukon the glacial or
ice-melt processes have dispersed the secondary gold deposits
or covered them with thick layers of sediment. However in the
Klondike Plateau ecoregion there was little or no glaciation and
the gold deposits are relatively undisturbed and easily accessible.
The environmental impacts of mining vary with the type of method used to recover minerals. Placer mining is used extensively in the unglaciated areas of the Klondike Plateau such as the Klondike and Sixtymile Rivers. Placer mining uses gravity to recover gold from a natural mixture of sand and gravel. Water is used to flush away unwanted material, leaving behind gold, which is 19 heavier than water. Modern placer mining uses heavy earth moving equipment as well as large volumes of water to strip vegetation and overburden from gold bearing "pay" gravels. This pay dirt is then washed or sluiced to recover the gold. The use of water to carry away unwanted material can lead to water quality problem downstream because of sediment carried in the water. Placer mining operations within valleys or on adjacent terraces can cause land and streambed disturbances. As a result, tailings piles, land stripped of vegetation and topsoil, settling ponds, and abandoned camps and equipment are common in the areas around placer mines.
Hard rock mining uses a different approach than placer mining and this introduces several additional environmental concerns:
Many Yukon ore bodies are sulphide deposits which release acid when exposed to air and water. The acid conditions, in turn, can mobilize naturally-occurring heavy metals, such as zinc, which may be present. Zinc is harmful to fish populations at low concentrations and this is a concern downstream from several mines in the area.
When ore bodies are depleted or world metal prices and financing make mining uneconomical then mines shut down. There are numerous abandoned mines in the central Yukon and these have been identified by in a recent study.
The environmental concerns at these sites include:
