You are probably right Considerate thinker, in that the benefits of eco tourism will ultimately be limited in terms of net aerosol and other pollution effects on the net environmental budget.
Most countries have unique wildernesses of their own well worth visiting by local populations rather than attempt to attract visitors from afar. The net environmental budget effect would be considerably less and at the same time provide a more edification for local populaces with appropriate encouragement to press for more conservation measures for the benefit of future generations in that country.
The foreign tourist would not be all that interested in preservation of local environments.