The reason for this post is to point out that all the doom and gloom about the increasing population is unfounded, meaning that there are real, achievable solutions that don't involve totalitarian government controls or genocidal population reduction measures.
First off, how much will the population grow? If left unchecked will it continue to grow forever?
The answer to the second question is no, not if the developing world continues to industrialize. The answer to the first question is about 9 billion, give or take. As the standard of living increases people voluntarily choose to have less children on average. No coercion is necessary. So to get to a stable (actually slightly declining) population we need to remove barriers that prevent the developing world from reaching western levels.
The primary barrier is energy. All resource shortages can be overcome if sufficient energy is available. We can desalinize seawater and pump it to wherever is needed if the energy is available to do so. We can grow vastly more food than we do now if sufficient water and fertilizer are available. Liquid hydrocarbons (gasoline) can be synthesized from water and carbon dioxide. All these processes are known and understood, they just require energy.
So how much energy do we need? If the US experience is any guide we need about 350 million BTUs per person, per year. So with a worldwide population of 9 billion people that adds up to over 3 quintillion BTUs per year.
Can that much power be generated? Absolutely, but you aren't going to get there with wind turbines and terrestrial solar panels.
There's one element that exists on the planet in sufficient quantities to generate the required power for a long time and that element is thorium. Each ton of thorium generates 1 GW-year (30 trillion BTUs) of energy when used as nuclear fuel, so the world's energy demand could be entirely supplied by 100,000 tons of thorium per year (compare this to the billions of tons of coal we use annually now). With 120 trillion tons estimated to exist in the Earth's crust we've got a long time before we need to start looking somewhere else, like the moon or Mars.
So the solution to the population crisis, energy crisis and pollution crisis is to stop pushing fake solutions that won't do anything except cause misery for billions of people and let us use state-of-the-art (1960s era) nuclear technology to produce abundant clean energy for everyone.