Much of this ability is related to human intelligence, society, and communication. This ability is responsible for human population growth because it resets the carrying capacity to allow for more humans to be supported. Humans are unique in their ability to alter their environment in myriad ways. The global fertility rate is expected to be at or below the replacement rate of 2.1 children per woman by the year 2050. Total fertility rates are falling globally and in every region of the world. These factors are discussed in more detail below. Demographers attribute this reduction in fertility to many factors, most of which are related to increasing standards of living as the wealth of countries increases over time. If this trend continues, the world will achieve the replacement fertility rate by 2050, meaning the population will begin to stabilize. The global TFR in 1950 was nearly 6 children per woman, but it has fallen to just below 2.5 as of 2019. Note that the replacement fertility rate would need to be somewhat higher than 2.1 in countries with an especially high child mortality rate.įertility rates have dropped dramatically since the “baby boom” of the 1950s and 1960s (Figure 2). In general, a population with a fertility rate higher than 2.1 is expected to grow, while a fertility rate of less than 2.1 leads to a shrinking population. This number is known as the replacement fertility rate, as it would allow for the replacement of two parents, with a slight allowance for children who die before reproducing. For a population to remain stable, a total fertility rate of about 2.1 is required. The growth rate of a country (or the world as a whole) is largely driven by the total fertility rate (TFR), or the average number of children born to women during their reproductive years. Most demographers (scientists who study population trends) doubt the population will double again to 16 billion due to this slowdown. This means that while the human population continues to grow exponentially, the rate of growth is slowing, and in fact is likely to level off within a few decades. Inputting the 2020 growth rate of 1.05% reveals that it would take about 67 years for the population to double again:ħ0\div 1.05 = 66.67\:years Population\:doubling\:time\:in\:years = 70\div growth\:rate\:% We can use the so-called “rule of 70” calculate a rough estimate of when an exponentially growing population can be expected to double: However, the current growth rate is much lower than the peak growth rate of 2.1% per year in 1962. Although this may not seem like much, this growth rate results in the addition of about 82 million people per year. Currently, the global growth rate, or the percent change in population per year, was 1.05% in the year 2020. Predicting how quickly the population will grow in the future is difficult, since there are so many factors that affect birth and death rates around the world. But will that number double again? Figure 1. As of 2018, there were about 7.6 billion people on the planet, and that number is expected to reach 8 billion by 2024 (Figure 1). But it only took 80 years for the population to double again to two billion, and 45 years to double yet again to 4 billion. The population was about 500 million people in the year 1650 and it took 200 years for that number to double to one billion. The world’s human population is presently growing exponentially. A consequence of exponential growth rate is that the time that it takes to add a particular number of humans to the population grows shorter over time. This has introduced a new set of economic and social problems. The human population is still growing, but at a slower rate, with some countries even experiencing a population decline. However, the exponential growth rate appears to have reached its peak in the 1960s. Long-term exponential growth carries with it the potential risks of famine, disease, and large-scale death, as well as social consequences of crowding such as increased crime. Earth’s human population and their use of resources are growing rapidly, to the extent that some worry about the ability of Earth’s environment to sustain its human population. Humans, however, have the ability to alter their environment to increase the carrying capacity, sometimes to the detriment of other species. For example, beaver dams alter the stream environment where they are built. Humans are not unique in their ability to alter their environment. Concepts of animal population dynamics can be applied to human population growth as well.
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