Some species are called indicator speciesbecause the loss of a population of such a species serves as an early warning of problems arising from pollution  Environmentalists tracking the effects of pollution have increasingly paid heed to indicator species; yet environmentalists would be misguided if they attributed the loss of a population to pollution in all cases  Though declines in population often do signal environmental degradation, they are just as often a result of the natural evolution of an ecosystem
We must remember that, in nature, change is the status quo
The loss of a specific population as a result of pollution is simply part of nature's status quo.