Why are grizzly bears considered bioindicator species?

Grizzly bears are considered bioindicator species primarily because their population trends can reflect the health of their ecosystems. When grizzly bear populations decline, it often indicates excessive human impact, such as habitat destruction, pollution, or other anthropogenic pressures. These impacts can lead to reduced food sources and habitat fragmentation, which can negatively affect not only grizzly bears but also other species in the same ecosystem. Therefore, monitoring grizzly bear populations can provide valuable insights into the overall condition and stability of the environment they inhabit, making them key indicators of ecological health.

In contrast, the other options do not accurately capture why grizzly bears are used as bioindicators. While abundance in ecosystems is important for certain species, it is not true that grizzly bears are abundant everywhere. Their adaptability to changing environments, while a valuable trait, does not specifically identify them as bioindicators. Lastly, being the largest species in their habitat does not inherently make a species a bioindicator; it is their sensitivity to environmental changes and the implications of their population status that are crucial to this designation.