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This week’s mailbox: Dr. Gilles Wendling on cumulative effects

Cumulative effects: What are they, and why are they important?

Cumulative effects: What are they, and why are they important?

Modification of the land referred to as “land disturbance” due to roads, pipelines, powerlines, drilling pads, plant footprint, railway corridors, harbours, airports, communities (villages and cities), and industrial activities (e.g. mining, forestry, fishing, energy, manufacture of goods) will each individually and locally modify the vegetation, the movement of water at surface and in the subsurface, and release some contaminants in the water and/or in the air. Added together we have cumulative effects, and they are very difficult to quantify.

The challenges are many. First, they involve several media: the air, the water, the vegetation, and living species.

Second, we somewhat understand how some elements (e.g., arsenic) can affect receptors, such as fish or humans and there are regulations that describe acceptable concentrations. However, we don’t have the scientific knowledge to estimate what will happen when we put several elements together. For example, let’s put a little bit of arsenic with some chromium and some cadmium, and three pinches of selenium. Will this be good for the fish?

Third,we have only recently developed the tools to generate maps that layer the individual impacts of the various activities that we know are disturbing the land and the environment, whether it is a network of roads, pipelines, areas being logged, the local discharges of treated effluent or landfills, etc. We can superimpose these maps and observe the combined effects of these activities. However, it is like adding apples and oranges. What are the true cumulative effects?

Fourth, the interaction between a variety of different components can be very difficult to measure. For example, spawning salmon rely on quality water for their survival. Bears rely on spawning salmon for their food. Bear scat provides nutrients for plants and trees, thus linking returning spawning salmon to a healthy forest! Addressing the release of contaminants in the environment, on the land, in the water, and in the air and how they cumulatively affect a wide range of species, their food chain, and what they drink and breathe is extremely complex.

Fifth, fragmentation of the land consists of breaking up continuous space by features such as a road, a highway, a pipeline, a seismic line, a railroad, a power line, a reservoir, etc. This will affect and in certain cases prevent the mobility and migration of species, reducing the space they need to forage, hunt, mate, and develop. We have been observing this for decades and we can only sadly witness the dramatic loss in biodiversity.

So, what can we do to prevent the creation of negative cumulative effects from exploration and development? We must examine every proposed project and activity that will create potential negative impacts such as fragmentation of the land or the release of contaminants in water. We know that these impacts do not stand alone, but rather that they will compound one another and will create cumulative effects. In order to protect our water and biodiversity, we might need to refuse applications for exploration and development permits, or to implement a moratorium while we consider possible negative cumulative effects.

We have observed, when the human world almost came to a standstill at the peak of COVID-19, how wildlife returned to the center of cities, and how a metropolis inhabited by millions of people could again enjoy a blue and clear sky. These are cumulative effects in reverse.

Dr. Gilles Wendling


Submitted By Yukoners Concerned