Leaving aside the moral decrepitude of human beings in general… humans have been too successful and have eliminated all natural predators. Population growth has been unchecked and proceeding with juggernaut speed… unstoppable.
Although humans have always fought over resources and living area, these struggles will gain new ferocity as the population continues unabated. Even now it has exceeded the sustainable level. Sure, humanity will continue for a while, but resources are rapidly being exhausted. Space is running out as well, evidenced by the inevitable extinction of any other species than human.
Talk is cheap. There are plenty of humans that have stated how the population bomb continues to tick. People look around, acknowledge the problem, then turn back to the task of making more people. At this point the solution is one nobody wants. To assume a sustainable population wherein all species would be guaranteed existence would require, in my humble opinion, the deaths of eighty percent of the human population. Establishing a no growth policy would aid in the establishment of quality of life. Deaths would be recorded and permits issued for replacements so that the “quality of life” level would not be exceeded. Actual growth of humanity would only happen when or if humans are able to establish off-world colonies. Space exploration should be a priority.