Populations are healthlist if kept within an upper and lower limit.
Renewable resources can be sustainable if usage is limited to natural supply rates.
Non-renewable resources can be sustainable if recycled and we constantly substitued more abundant resources. Pollution can be generated at the rate it can be degraded by the enviornment or collected for recycling. The environment is constantly changing and so are we. This awareness has a impact on how we protect ecosystems. We need to be cautious and monitor rates of change.