Bathurst caribou on summer range (Photo:  Catherine Graydon) Bathurst caribou on summer range (Photo: Catherine Graydon)

How Far can Mining Disturbances Reach Inside the Bathurst Caribou Range?

With the dramatic decline in numbers of Bathurst caribou from a high of about 450,000 caribou in the mid 1980s to an estimated low of 20,000 today, there are concerns about possible stressors on the herd.  There are likely many factors that contribute in some way to the decline. Industry, predators, diseases, insects, harvest and climate change impacts, and other factors—and their combined effects that add up over time to create cumulative effects –-all may play a role. It is not clear how or to what extent each of the factors is involved, but there is ongoing research to learn more.

While the Bathurst herd has been declining, its range is changing as the footprint of human activity expands and the climate warms.  Since the mid 1990s,  resource development activity such as mines has increased on the Bathurst caribou herd’s range, introducing new features on the landscape – buildings and other structures, roads, noise, smells, dust and air emissions (very small particles like pollen, soot and smoke that can get into the air).  Four mines are operating just inside the Bathurst range.   

It is possible that mining developments may be a potential contributor to the population decline. A 2016 traditional knowledge study, “Ekwò zò gha dzô nats’êdè - We Live Here for Caribou”, carried out by the Tłı̨chǫ Training and Research Institute, looked at cumulative impacts on the Bathurst caribou herd.  The report noted that mining activity near the Ek’atì (Lac de Gras) area, for example, has created a “wall” blocking the main migration route, Ek’atì tataa.  Tataa are corridors between bodies of water used by ɂekwǫ̀ herds to access feeding grounds along their migration route. Community members reported that caribou have changed their migration routes and other behaviours since the mines appeared on the land.  They described how caribou have chosen to avoid mine sites due to poor-quality forage (vegetation that caribou browse for food), noise and dust pollution.

Scientific studies have also observed this avoidance, and refer to the Zone of Influence (ZOI) --the distance at which caribou change their behaviour, habitat selection and distribution in response to industrial developments such as mines.  Studies using satellite collar information and aerial surveys suggest that caribou are less likely to be seen inside the ZOI, selecting habitat farther away from a mine site beyond the ZOI. It is not known how significant the impact of mines on Bathurst caribou has been, but the herd’s distribution may be affected by sensory disturbance like noise or the sight of mining activities. Dust from mining operations may also affect the availability and quality of plants caribou use for food.   

What is the size of a mine development’s footprint? Several studies have estimated the size of the ZOI of mining operations in the Bathurst caribou summer range. One study based on caribou data estimated the ZOI at 14 km.  Other studies have estimated the ZOI at about 1 – 5 km. What causes the ZOI? Observations by community members and researchers suggest that there are environmental changes –disturbances—related to mining activities that are suspected to play a key role.  Knowing the causes is important because that can help find ways to reduce the size of the ZOI—and help researchers better understand why caribou avoid these areas. The first step in understanding the causes of the ZOI is to be able to measure these disturbances and their reach. How far away can caribou potentially hear the activities from a mine? How likely is a caribou to see a vehicle driving on a mining road at varying distances away?  

Recording the visibility of mining activites to caribou (Photo: Wenjun Chen)

Research scientist Wenjun Chen, Natural Resources Canada, is leading a project that has been measuring how far mining generated disturbances like noise, dust, particles in the air, and the visibility of mining activities can reach.  Based at the Ek’atì mine site and surrounding area, the research team conducted field surveys, laboratory analyses, and satellite remote sensing in the summers of 2015 and 2016.  Wenjun shared the project’s preliminary results at the Environmental Research and Monitoring Results Workshop in Behchokǫ̀ on January 31- February 1, 2017.

The team measured the Zone of Visual Disturbance (ZOVD), the maximum distance that caribou can clearly see the vehicles driving on a mining road and the elevated waste piles at camp.  Measuring visual disturbance from a caribou’s perspective is challenging. The team used visual observations and digital elevation changes to record the visibility of mining activities at different distances. 

It is interesting to note that are some differences in a caribou's vision compared to a person's.  In the North, there is more ultraviolet (UV) light in the environment, which in winter is strongly reflected and scattered by snow. Scientific studies discovered that caribou can see UV light.  This "super-vision" is important in winter because it may enhance the caribou's ability to find food like lichen which absorbs UV light and shows up dark against the white snow, but would be invisible to people.

Recording noise out in the field (Photo: Wenjun Chen)

Determining the Zone of Noise Disturbance and fine suspended particulates (PM2.5) was more challenging, partly because recording of noise and PM2.5 are often affected by winds, rains, and other weather conditions.  Another challenge is that the zone of PM2.5  cannot be determined using only field survey data during a short time period because the values of PM2.5 can vary quickly.  For this project, the research team took recordings of noise levels at various distances, and will continue working on how to best measure the Zone of Noise Disturbance from various mining operations. Satellite remote sensing data have been demonstrated to be useful for mapping PM2.5 elsewhere such as cities in southern Canada, USA, and China.  As a next step, the project will extend these field measurements of PM2.5 by using satellite data to map the entire caribou range around the Ek’atì Diamond Mine. 

Measuring mining-related dust and its potential effects on caribou forage is another challenge that the researchers have undertaken.  A number of different research strategies (field survey and remote sensing) were used to estimate the Zone of Dust Disturbance.  We’ll have a report on this part of the research study and its findings in our next newsletter. 

Grizzly bear on the Barrenlands (Photo:  Wenchun Chen)

Fact Box:  PM2.5

  • PM stands for particulate matter, a mixture of solid particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot, or smoke, are large or dark enough to be seen with the naked eye. 
  • Other particles, like PM2.5, are very small. These tiny particles or droplets in the air are two and one half microns or less in width. A micron is a unit of measurement for distance. There are about 25,000 microns in an inch. The widths of the larger particles in the PM2.5 size range would be about 30 times smaller than that of a human hair.