This is the taboo question. According to French demographers like Hervé Le Bras or François Héran, there is no risk of overpopulation in the world, quite the contrary. The world population would even be in the process of stabilizing by the end of the 21st century at 9.5 billion inhabitants. The problem would even be the excessive drop in the birth rate in certain developed countries, which will lack in the future the workforce and contributors to finance pensions.
According to climatologists, demographic problems are unrelated to climatic problems, because it is the smaller populations of the rich countries that pose the problem by their consumption model, and not the large and rapidly growing populations of the developing countries whose he ecological impact per inhabitant remains very low. Finally, dealing a little too closely with the evolution of the world population, population policy would have a somewhat liberticidal character, prejudicial to everyone’s freedom.
Aren’t there some nuances to bring to this consensus? The first is due to the fact that the explosion of climate problems and loss of biodiversity did not arise until the 1950s on a planet with 2.6 billion inhabitants. It was from the 1980s that the economic take-off of highly populated emerging countries such as China, India, Indonesia and Brazil began, which gradually swung into mass consumption at the West, heavily dependent on fossil fuels. If these countries had been very sparsely populated, the climatic problems would not have had the same acuteness. It is therefore the combination of a large population size and a Western-style development process in the developed world and the highly populated emerging world that poses a problem. The second nuance to add is that the lack of development in many parts of the world means that some countries can no longer produce the agricultural goods needed to feed their population. This dependence has greatly increased throughout Africa. However, to feed the planet, it is necessary to intensify production, to use pesticides, in short to move towards a green revolution based on inputs that call on fertilizers and chemical molecules that not only have a strong impact in CO2 but degrade the biodiversity of the planet. Of course, we may wish to move towards green agriculture. But this development is inevitably accompanied by a drastic drop in yields that is difficult to reconcile with a planet to feed with 9.5 billion inhabitants in 2050.
The third nuance is that the long-term well-being of a population that will reach 9.5 billion inhabitants in 2050 presupposes that a sustainable economic model be put in place quickly throughout the planet. However, both developed and emerging countries are finding it very difficult to get out of mass consumption based on fossil fuels. It is by no means certain that low-income countries have the ability to move directly towards clean, sustainable development, a path that has never been taken immediately by any country in the world. Under these conditions, access to development for a continent like Africa, whose population size will be considerable in 2050 (2 billion, i.e. a doubling), has the potential in the long term to have strong impacts on the climate and the biodiversity. Sobriety and degrowth are not solutions for developing countries. To deny it would be irresponsible.