Resource Extraction

Logging is one of the most recognisable impacts to our watersheds and can have devastating effects on fragile ecosystems.

In our blog post on the water cycle and ecosystem function, we detailed how native, healthy vegetation intercepts incoming water, thereby allowing it to seep easily into the permeable soil below. Organic matter, such as tree roots and mycorrhizal networks, hold soil in place and layers of detritus help to cushion the falling water. In this way, intact forests mitigate erosion and flooding, allowing water to be absorbed into the ecosystem and the ground. Intact forest canopies can also mitigate forest temperatures through regulating evaporation, transpiration, and evapotranspiration. 

When forests are cleared our watersheds suffer devastating consequences.

Groundwater aquifers dry up as the soil becomes hard and impenetrable from a lack of organic matter –  the form of living tree roots, healthy forest microbes, and natural forest creatures –  forcing even more water to flow over the surface and into streams, causing higher rates of erosion on stream and riverbanks. An intact forest canopy also provides relief from evaporation, and allows the soil to maintain its capacity to retain and release water.  This can lead to flooding, as a healthy forest will absorb water and reduce overland flow. 

Without vegetation to hold the soil in place, much larger amounts of water, filled with sediment, flow directly into streams and increase the volume of solid particles, also known as total suspended solids (TSS). High TSS can affect water quality for human consumption, leading to the need for greater water purification efforts, or even rendering the water undrinkable. Increased sediment can reduce water clarity – increasing turbidity – , thus impacting the amount of sunlight in the water body and decreasing photosynthetic activity. This can lead to potentially hypoxic (low-oxygen) conditions, interfering with microbial disinfection and allow harmful bacteria, viruses, and microbes to grow.  Increased TSS can also have devastating impacts on wildlife, like clogging fish gills and increasing stress levels. Overtime TSS may settle, and can bury fish eggs and invertebrate habitats, with heavy impacts on the food chain. 

Mining is also a major threat to watersheds. Mining practices often start with deforestation, with impacts on soil stability, sediment control, and groundwater recharge. The destruction of vegetated landscapes can lead to increased amounts of surface water runoff, not only increasing TSS, but reducing the amount of water absorbed by the soil. Mining practices associated with landscape changes can increase the amount of overland flow (water not absorbed into the ground), and impact aquifer recharge. Oftentimes mining uses water during extraction; groundwater and surface water withdrawals can damage or destroy aquatic habitats around the mine site. 

For example, mines in the northeastern Nevada desert pumped out more than 580 billion gallons of water between 1986 and 2001 – enough to feed New York City’s taps for more than a year (Hancock, 2021). 

Mine practices can also introduce contaminants into groundwater and surface water systems. Polluted water that has leached from mine waste rock and tailing ponds may need to be managed for decades to centuries after mine closures. For example, industrial activity in Howe Sound left the area polluted with copper, sulfur, and mercury. Although industry in the area has slowed down, Howe Sound is still recovering from the Britannia Copper mine, closing in 1974, and pulp and paper mills.