How has air pollution contributed to the decline in caribou populations? a. it has caused them to alter their migration routes. b. it has decreased the heat-conserving ability of their fur. c. it has warmed the tundra climate. d. it has destroyed some of the lichens they feed on.

Option D, It has destroyed some of the lichens they feed on.

Explanation:

During winter, Caribou population depends majorly on arboreal lichens/or lichens which grow on trees or open land in an old forest area. These lichen can survive only in moist air condition with in the deep forest canopies and take long time to form/develop . Any disturbance caused to these forest canopies can cause the lichens to die out thereby making the  Caribou species subjected to extreme hunger and hence reduction in their population.

Also the redevelopment of these lichens takes a long time, due to which food become scarce  and caribou population reduces.

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explanation: