How many people can Kigali withstand?

Thomas Malthus predicted that the population of the earth was increasing at a geometric rate, while food production was increasing only at an arithmetic rate. He predicted that human population would soon outstrip their own ability to produce food, and there would be a catastrophe by the mid-nineteenth century. However, we are still here, so that obviously did not happen. Even though Malthus was wrong, his ideas remain influential. The carrying capacity of the earth at present is a hotly contested subject.