Before surface or in-situ mining can occur, the boreal forest is clear-cut, its wetlands are drained, and its streams and river diverted. Soil, rocks, and clay are removed to exposure the underlying oil sand deposits, and approximately 4 metric tons of overburden are removed to produce 1 metric ton of bitumen. In order to move such vast amounts of organic material, machines are employed to dig open craters in the ground large enough to be seen in satellite images (Miller & Spoolman, 2008).
Habitat and Biodiversity Loss
The most obvious ecological effect of land clearing is habitat loss– terrestrial, wetland, and aquatic. Less food and shelter will be available for organisms and reductions in biodiversity will result. In fact, a report by Platform London, a non-profit advocacy organization, found that habitat loss as a result of surface mining could result in a loss of 14.5 million breeding birds from direct habitat loss and 76 million birds from fragmentation and habitat degradation over a 30- to 50-year period. Studies have also shown that caribou populations, which require large areas of connected forest to survive, have declined significantly in recent decades, due partly to tar sands extraction.
With respect to aquatic habitats, logging in riparian zones may reduce shading and ultimately lead to higher water temperatures and increased exposure to ultraviolet radiation. Temperatures above normal ranges may affect biological processes in aquatic organisms, while exposure to ultraviolet radiation may damage their DNA. Algae would proliferate in conditions with higher levels of sunlight, and the increased decay processes of increased amounts of organic matter would deplete oxygen levels in the immediate environment; this would lead to fish kills and the disappearance of sensitive species.
Elimination of vegetation would also lead to reductions in the nutrient flux (e.g., fallen leaves) and woody debris (e.g., fallen logs to provide cover for fish) to the stream.
Removal of vegetation leaves the land exposed to erosion by air and water. Without the cover provided by leaves (both high and low off the ground) the impact of water (e.g., raindrops) on exposed soils can dislodge soil particles that can then be carried intro streams by stream runoff. Additionally, because many surface and in-situ mining operations are located in the upper reaches of the drainage basins of tributary systems, removal of groundcover–particularly of muskeg– could result in increased runoff and cause severe erosion in the immediate area. The increased sediment loads could have adverse effects on the aquatic life downstream and introduce potentially harmful compounds to wildlife. Changes in total dissolved salt concentrations, electric conductivity, and pH would drastically limit the number and types of organisms that could survive in the altered area.
Changes in Stream Hydrology
The removal of groundcover, combined with the diversion of streams and rivers to other systems, can lead to changes in stream hydrology. For instance, trees take up water from the soil and through transpiration release it as water vapor into the atmosphere. They also provide shade over snowpack and slow the melting process; without them, less precipitation from the soil is absorbed, causing water to move quickly over land and washing away essential nutrients, particularly if the soil has been compacted by heavy equipment. Snowpacks also melt more quickly during the spring, leading to higher peak flows during shorter periods of time, leading to alternating states of flooding and aridity.
Removal of groundcover also releases carbon dioxide into the atmosphere, one of the main causes of global climate change. Half of the world’s remaining boreal forest is located in Canada, with 11% of the global terrestrial carbon sequestered in its bogs, peat, soil, and trees. Thus with growing rates of tar sands extraction, continued removal of groundcover will result in incremental increases in global temperature and the subsequent consequences: increased intensity of severe weather events, sea level rise, and expanded ranges of disease vectors are only a few of the possible effects.