I've been hearing about this crisis my whole life, and it just hasn't materialized.
A big question is whether human beings can exist in harmony and large numbers with the earth's environment, and I think the answer is that it can, but we need technological advancement in key areas, most notably in energy production. If we used clean, abundant, non-polluting energy sources (such as the energy within the vacuum or fabric of the universe), then we could largely solve our pollution problems, but if we do not convert to a new energy industry, we will greatly ruin the planet and impoverish the people.