1. Do we need to worry about the large increase in the global population between now and 2050?

“Not really. Production and consumption, rather than population, are the central concerns.”

2. But won't that increase trigger an environmental catastrophe?

“Doubling the incomes of the world’s poorest 650 million people would take the same resources as adding a little under 1% to the incomes of the world’s richest 650 million. We do that and more every year, year in and year out.”

3. What’s the best way to reduce environmental stresses then?

“If we want a resource-neutral global income path, we should get it not by locking the world’s poorest into poverty, but by taxing the rich. They are the ones who are consuming at an unsustainable rate.”

4. What would be the best way to go about limiting impacts on the environment through population control?

“If we did want to limit populations on neo-Malthusian grounds, it is clear that we should not start by limiting the reproduction of the masses of the poor as suggested by the good Reverend Malthus. We should start with the largest consumers. Sterilize the world’s billionaires first, then move to a one-child policy for Switzerland, Luxembourg and the United States.”

5. How many people can the planet sustain?

“Historical assessments of the human carrying capacity of the Earth go back to 1679, when the Dutch scholar Antoni van Leeuwenhoek suggested that the number was 13.4 billion people.”

6. Is this figure still credible?

“Astonishingly, this figure appears to remain at about the midpoint of more recent calculations. That’s assuming we move towards a low-carbon economy with more appropriate use of non-renewable resources, of course.”

7. Where will the global population actually peak?

“According to the UN, the global population will plateau around 2050 at approximately nine billion."

8. How should the world go about ensuring sustainable development?

“Richer countries should immediately introduce carbon taxes (or cap and trade — whichever we can get). And natural resources, including water, should be properly priced. There’s a big role for incentives covering research and development of green technologies.”

9. What’s another part of the equation?

“Again, rich countries should provide resources to assist poor countries preserve biodiversity stocks and move on to a low-carbon growth trajectory. But overall, our response to concerns around sustainable development should include the adoption of a Hippocratic approach.”

10. Meaning?