Unfortunately, the overpopulation of some species can cause havoc to the environment as well and can even lead to an environmental collapse (e.g. desertification). From mammals to viruses and bacteria there can always be unaccounted dominant force. Two examples come to my mind, 1) the lack of predators can lead to overpopulation and total exhaustion of the habitat (currently happening in the central Europe), 2) world supply of bananas being endangered by Panama disease. Who knows, maybe one day humanity will be conquered by super-corona