It is the rate of growth that is decreasing, not overall numbers. The world’s population is growing at a lower rate, but it’s still growing. In fact, we need to feed, clothe, house, transport, educate and medicate 75 million additional people – 100 cities the size of Ottawa – each year.
Also, the rate of growth is unequal. Low in the developed world (averaging 0.4%), it is very high (well over 3%) in many of the poorest areas least able to deal with it. Half of the world’s people are under 25 (in some countries, 45% are under15), so that even if replacement fertility rates were achieved, the overall population would continue to rise, and for some time.
Recent UN studies estimate that global numbers will peak between 2050 and 2100 at between 9 and 11 billion people. However, this is an informed guess. The total might be higher. Quite simply, there are insufficient resources to support the present population of 7 billon. Further increase will result in more misery and environmental degradation into the future.