The idea that population growth is the key cause of ecological problems is extremely commonplace. It is, however, a gross distortion of the truth.
Capitalism is the main cause of both overpopulation and the ecological crisis.
The dire predictions of Thomas Malthus, the originator of the population myth, have not come true, yet neo-Malthusians continue to mouth his reactionary ideas. Similarly today, its utility to the ruling class ensures that it keeps surfacing every so often, until forced to disappear again once the actual facts of the case are raised. To put it simply, the hungry are hungry because they are excluded from the land or cannot earn enough to survive. Increased population is not the cause of landlessness, it is the result of it. If a traditional culture, its values, and its sense of identity are destroyed, population growth rates increase dramatically.