Final answer:
Canaries in coal mines and lichens in tundras both serve as early indicators of harmful environmental conditions. Lichens are particularly sensitive to pollution, so their decline indicates ecosystem health, akin to canaries alerting miners to toxic gases.
Step-by-step explanation:
Two hundred years ago, canaries were used in coal mines as early detectors of toxic gases. In a similar way, lichens serve as bioindicators in tundra ecosystems. Like canaries, lichens are sensitive to environmental changes and pollution, so their presence, or lack thereof, can indicate the health of the ecosystem. The tundra, being a fragile environment, can be significantly impacted by soot, pollution, and climate change which affect lichen populations. When lichens are unable to survive in an area, it is often a sign that the environment has become inhospitable for other forms of life as well.
During the industrial revolution, similar to how canaries warned miners, the drastic decline in lichen populations due to pollution signaled a dramatic change in environmental conditions, much like moths had changed color due to soot covering the trees they lived on. This is an example of how living organisms can alert us to harmful environmental changes long before these changes become apparent to humans or start to affect human health directly, as seen with issues like black lung disease among miners from coal dust exposure.