As David MacKay’s book describes in detail, producing enough energy for everyone on Earth to live like the average European is possible using renewable forms of energy, though it would require a colossal effort and the conversion of a huge amount of land into renewable energy facilities like wind farms and concentrating solar plants.
Given that, the case for reducing population size within rich economies seems even stronger. Would Canada really be a worse place if it had a population of 50% what it does now? What about 10%? As long as the transition was gradual and done in an appropriate way, it could lead to a world in which there are more resources available per person, where the planet is better suited to dealing with our wastes, and where more of the planet can be left in some kind of a wild state, rather than converted for human purposes. Rather than cities that constantly spill beyond green zones into sprawling suburbs, we could live comfortably in the facilities we already have. With fewer workers around, each would be able to demand higher wages and benefits. There would also be more capital available per person for investment.
With a global population 1/10th of the current size, there would obviously be fewer brains out there, so the absolute pace of innovation would probably slow. At the same time, it would give the planet some welcome relief from the relentless pressure than human beings put on it, and would offer an opportunity for humanity to learn to live in a sustainable way before it destroys itself.
If the average number of children per woman can be reduced to well below the replacement rate, a falling population could result. The means of encouraging that need not be coercive, and many of them are beneficial in themselves. Better sexual education can be provided, particularly for girls. Universal access to contraception can likewise be provided, at the same time as women are given better educational opportunities and better treatment in the workplace. Governments can halt policies intended to promote large families, and instead concentrate on the task of reducing the burden humanity is placing on the Earth to a level that can be borne indefinitely. It would also be nice if improved mechanisms were developed for men to control their fertility, including through the development of drugs akin to hormonal birth control pills, which allow for fertility to be temporarily suspended.
People often assume that population control in poor countries with fast-growing populations is the key issue, when it comes to population and the environment. That view misrepresents the relative impact of different lifestyles, and the level of inequality that exists when it comes to resource use and waste production. The most important thing is probably to have fewer absolute gluttons – like Canadians, Americans, and Australians – and to work on providing the energy needs of the people who remain using safe, renewable sources of energy.