Population Explosion

Although unlikely to end human life on earth, the continued population growth in much of the world threatens food supplies to the point where humans might overshoot their carrying capacity. This is made worse by the fact that the Earth is only able to support a human population at its current level due to intense "Green Revolution" farming. Peak oil would mean an end to cheap and easy high-intensity agriculture, which might eventually lead to the collapse of civilizations as the first world nations close ranks to defend their food supplies against the starving third world hordes.

The other solution is Soylent Green.

Population Explosions in Fiction

• In Mass Effect, the krogan population exploded when krogan were "uplifted" and transported from their harsh homeworld to more hospitable planets to participate in an interstellar war, resulting in a follow-up war called the Krogan Rebellions.