However, when all three key species were present, the average rate of all functions — a measure of overall ecosystem health — rose simultaneously. (sciencedaily.com)
Birds are often used as an indicator of overall ecosystem health in Wyoming, Colorado and Arizona, Hatten said. (scientificamerican.com)
In the end, the only way to judge is to assess if overall the ecosystem is degraded (e.g., through greatly shortened fire intervals). (dotearth.blogs.nytimes.com)