If you want this planet to continue being habitable for everyone that lives here, you have to limit the number of inhabitants. Hunters do it by killing off the old or sick animals in a herd, but I don't think that's a very ethical way of limiting the population.

Overcrowded cities are spawning increasingly lawless suburbs. Waste is accumulating in and around them, straining the capacity to deal with it.

The living world has become impoverished. Species are being lost every day. Energy and other resources are nearing exhaustion. The environment is deteriorating. Pollution is everywhere. Climate is changing. Natural balances are threatened.

Christian de Duve Quotes