Question

How has air pollution contributed to the decline in caribou populations?

Answer 1

It has destroyed some of the lichens they feed on.

Step-by-step explanation:

Answer 2

The air pollution makes the caribou unhealthy, and this makes them more vulnerable to predators and diseases.

Specifically, the food the caribou digest (for example lichens) absorb the pollution dispoportionally, which means that the caribou ingest many unhealthy particles.