Which of the following is listed as a threat to Canada's forests?

• A. Avian predation
• B. Urban expansion
• C. Soil erosion
• D. Forest fires

Answer: (C)

The main idea here is understanding how soil health affects forest health. Forests rely on nutrient‑rich, stable topsoil to anchor roots, supply nutrients, and hold water. When soil erodes, that topsoil is washed or blown away, nutrients are lost, and the soil becomes less able to support tree growth. Erosion also destabilizes seedlings and roots, making forests slower to regenerate after disturbance. In Canada, activities like road construction, logging, and land clearing can expose soil to rain and runoff, accelerating erosion, especially on slopes. The result is degraded forest vigor and capacity to recover, which is why soil erosion is listed as a threat to forests.

Avian predation mainly affects wildlife populations rather than the forest structure itself. Urban expansion indeed threatens forests by reducing area and fragmenting habitat, and forest fires are natural and managed disturbances that can threaten forests in the short term, but erosion directly erodes the medium—the soil—that forests need to grow and sustain themselves over time.