45.4A: Human Population Growth
- Predict the long-term consequences of exponential human population growth
Human Population Growth
Global human population growth is around 75 million annually, or 1.1% per year. The global population has grown from 1 billion in 1800 to 7 billion in 2012. It is expected to keep growing, though predictions differ as to when and if this growth will plateau.
The “population growth rate” is the rate at which the number of individuals in a population increases in a given time period as a fraction of the initial population. Specifically, population growth rate refers to the change in population over a time period, often expressed as a percentage of the number of individuals in the population at the beginning of that period. This can be written as the formula:
population growth rate=P(t2)−P(t1)P(t1)population growth rate=P(t2)−P(t1)P(t1)
Globally, the growth rate of the human population has been declining since 1962 and 1963, when it was 2.20% per annum. In 2009, the estimated annual growth rate was 1.1%. The CIA World Factbook gives the world annual birthrate, mortality rate, and growth rate as 1.89%, 0.79%, and 1.096% respectively. The last 100 years have seen a rapid increase in population due to medical advances and massive increase in agricultural productivity.
Each region of the globe has seen reductions in growth rate in recent decades, though growth rates remain above 2% in some countries of the Middle East and Sub-Saharan Africa, and also in South Asia, Southeast Asia, and Latin America. This does not mean that the population is declining;
rather, it means the population is growing more slowly. However, some countries do experience negative population growth, mainly due to low fertility rates, high death rates and emigration.
According to the UN’s 2010 revision to its population projections, world population will peak at 10.1 billion in 2100 compared to 7 billion in 2011. However, some experts dispute the UN’s forecast and have argued that birthrates will fall below replacement rates (the number of births needed to maintain a stable population) in the 2020s. According to these forecasters, population growth will be only sustained until the 2040s by rising longevity, but will peak below 9 billion by 2050, followed by a long decline.
Long-term Consequences of Population Growth
The “population explosion” seen in the last century has led to dire predictions. In 1968, biologist Paul Ehrlich wrote, “The battle to feed all of humanity is over. In the 1970s, hundreds of millions of people will starve to death in spite of any crash programs embarked upon now. At this late date, nothing can prevent a substantial increase in the world death rate. ” Although many critics view Ehrlich’s view as an exaggeration, the human population continues to grow exponentially. The laws of nature dictate that exponential growth cannot continue indefinitely.
Despite efforts to curb population growth, such as the “one-child policy” in China (introduced in 1979 but relaxed in the early 2000s), the human population continues to grow. A primary concern regarding this growth is that the demand for ever-more food will lead to widespread shortages, as forecast by Ehrlich.
In addition to the threat of food shortages, human population growth is damaging to the environment in potentially permanent ways. Most scientists agree that climate change caused by the emission of the greenhouse gas carbon dioxide (CO 2 ) is a significant consequence of human activities. In a series of treaties in the late 20th century, many countries committed to reducing their CO 2 emissions to prevent continuous global warming; however these treaties have not been ratified by every country, largely due to economic and political concerns. The role of human activity in climate change is hotly debated in some circles. The future holds considerable uncertainty for curbing human population growth and protecting the environment.
Key Points
- Global human population growth is around 75 million annually, or 1.1% per year. The global population has grown from 1 billion in 1800 to 7 billion in 2012.
- Although the direst consequences of human population growth have not yet been realized, exponential growth cannot continue indefinitely.
- In the late 1970s, China’s “one-child” policy tried to control population growth, but restrictions were relaxed in the early 2000s.
- One of the major consequences of population growth is the potential for widespread food shortages.
- Most scientists agree that humans and human population growth are causing climate change by emission of the greenhouse gas carbon dioxide (CO 2 ).
- International treaties to limit greenhouse gas emissions have not been ratified by every country due to economic and political concerns.
Key Terms
- greenhouse gas : Any gas, such as carbon dioxide, that contributes to the greenhouse effect (continued warming) when released into the atmosphere.
- climate change : Changes in the earth’s climate, especially those said to be produced by global warming.