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

• A. The forestry industry
• B. Air pollution (acid rain)
• C. Chemical pollution
• D. Aerial spraying of chemicals

Answer: (B)

Air pollution in the form of acid rain is a major threat to Canada's forests. When sulfur dioxide and nitrogen oxides from burning fossil fuels rise into the atmosphere and then fall with rain, they lower the acidity of the soil. This acidification leaches away essential nutrients like calcium and magnesium and can release aluminum, which hinders tree root growth and nutrient uptake. The result is weaker trees that grow more slowly, are more stressed, and are more vulnerable to pests, disease, and drought. Leaves can also be damaged by acid rain, further limiting photosynthesis and growth. Other options describe activities or pollutants that aren’t the same widespread, chemical-change threat to forest health that acid rain represents.