For the two hundred years from 1750 to 1950, the fastest population growth took place in the world’s most advanced economies. Their rising productivity and improving governance ushered in previously unseen prosperity, and fuels optimism for the future.
But in the next century, the fastest population growth will take place in the world’s least advanced economies and some of its worst-governed countries. A global effort to improve governance and education in those countries, allowing the world to benefit from the human potential of billions of additional people, could again usher in a new stage of global prosperity. But failure to meet this challenge may consign billions of people to live in countries with failing states, brimming with angry and frustrated youth, prone to high levels of violence, and recurrent humanitarian disasters on ever-larger scales. There is still time to build partnerships and make investments to respond to this challenge, but every week, another three million children are born in the poorest countries, and the clock ticks on.Matt Ridley, The Rational Optimist:
The peak is in sight. Even as the population passes seven billion, the growth rate of the world population has halved since the 1960s. The United Nations Population Division issues high, medium and low forecasts. Inevitably the high one (fifteen billion people by 2100) gets more attention than the low one (six billion and falling). But given that the forecasts have generally proved too high for the past few decades, let us imagine for a moment what might happen if that proves true again.
Africa is currently the continent with the highest birth rates, but it also has the fastest economic growth. The past decade has seen Asian-tiger-style growth all across Africa. HIV is in retreat, malaria in decline. When child mortality fell and economic growth boomed like this in Europe, Latin America and Asia, the result was a rapid fall in the birth rate. For fertility to fall, contraception provides the means, but economic growth and public health provide the motive. So the current slow decline in Africa’s birth rate may turn into a plummet.
If that happens, the low UN estimate could prove more accurate with the world population peaking a little above eight billion and falling to a billion less than today by the end of the century.Good things might happen: "agricultural productivity continues to rise", "EU tariff barriers against African produce are lifted and America’s crazy policy of diverting food into motor fuel is reversed", "with more people able to afford fossil fuels, fewer will depend on forests for cooking fuel", "water use grows steadily more efficient with the spread of drip irrigation". So:
It is quite possible that your great grandchildren will not only be fewer in number, but will live in a world with huge nature reserves, vast forests and rich seas.