2.3 Trends in human population growth

7 billion people and growing

We recently hit a population milestone of seven billion humans on the earth’s surface. The rapidity with which this happened demonstrated an exponential increase from the time it took to grow from five billion to six billion people. In short, the planet is filling up. How quickly will we go from seven billion to eight billion? How will that population be distributed? Where is population the highest? Where is it slowing down? Where will people live? To explore these questions, we turn to demography, or the study of populations. Three of the most important components affecting human population growth are fertility, mortality, and socioeconomic status.

Comparing these three countries reveals that there are more men than women in Afghanistan, whereas the reverse is true in Sweden and the United States. Afghanistan also has significantly higher fertility and mortality rates than either of the other two countries. Do these statistics surprise you? How do you think the population makeup impacts the political climate and economics of the different countries?

Concepts of animal population dynamics can be applied to human population growth. Humans are not unique in their ability to alter their environment. For example, beaver dams alter the stream environment where they are built. Humans, however, have the ability to alter their environment to increase its carrying capacity sometimes to the detriment of other species (e.g., via artificial selection for crops that have a higher yield). Earth’s human population is growing rapidly, to the extent that some worry about the ability of the earth’s environment to sustain this population, as long-term exponential growth carries the potential risks of famine, disease, and large-scale death.

Although humans have increased the carrying capacity of their environment, the technologies used to achieve this transformation have caused unprecedented changes to Earth’s environment, altering ecosystems to the point where some may be in danger of collapse. The depletion of the ozone layer, erosion due to acid rain, and damage from global climate change are caused by human activities. The ultimate effect of these changes on our carrying capacity is unknown. As some point out, it is likely that the negative effects of increasing carrying capacity will outweigh the positive ones—the carrying capacity of the world for human beings might actually decrease.