Carrying capacity is not a fixed number. The issue of overpopulation is equivalent to that of global warming: where consequences appear minimal, but without worldwide lifestyle changes could have serious repercussions. Currently, the current world population stands at approximately 7.5 billion people, with a growth rate of 1.13 percent per year (estimated at around 85 million people per year). Most modern estimates for the carrying capacity of the world vary widely between 4 billion and 16 billion people. Why is there such a discrepancy? It varies with a wide range of factors, most of them fitting under the umbrella term “lifestyle.”
Imagine a world in which humans never left hunter-gatherer mode. The Earth’s carrying capacity for such a lifestyle would be about 100 million people, according to How Stuff Works. But, with the production of food and living in multiple-tiered buildings, that number increases significantly. A different lifestyle causes a dramatic change in the global carrying capacity.
For example, if everyone lived like a middle-class American, consuming more than three times the necessary amount of food and roughly 250 times the amount of necessary clean water, the Earth could only sustain about 2 billion people. Most developed countries consume so much that 75 percent of the rest of the world’s population is left with barely enough resources to survive. Conversely, if everyone attempted to consume only what they needed (such as converting from a meat-based diet to veganism), the Earth could theoretically sustain a number closer to 40 billion.
No one knows what the population will be in a few hundred years. However, scientists have made educated guesses using past and present trends in birth and mortality rates. What they find is a pattern very similar to the Malthusian Principle, where populations grow exponentially. While it took humanity up to the 19th century to reach a world population of one billion, the second billion was achieved in only 130 years (1930), the third billion in less than 30 years (1959), the fourth billion in 15 years (1974), and the fifth billion in only 13 years (1987), according to World Meters, a website which gives real time statistics of global population. By 2100, the world population is suggested to reach somewhere between 9.6 billion and 12.3 billion. If left unchecked, the human population can easily outgrow its resources. American Biologist Paul Ehrlich stated in his best-seller The Population Bomb, “We have a finite planet with finite resources. In such a system, you can’t have infinite population growth.”
This theory has been hotly debated by the public yet widely accepted by scientists. According to Pew Research, when asked whether the growing population will become a major issue, 59 percent of Americans agreed the growing population will strain the planet’s natural resources while 82 percent of members of the American Association for the Advancement of Science agreed. In fact, Scientific American says global population growth is “the most overlooked and essential strategy for achieving long-term balance with the environment.”
However, the main issue isn’t in overpopulation itself but the localization of population growth. The biggest increases will occur in the poorest countries — those least equipped to meet the needs of the new arrivals and invest in their future. Scientific American stated, “growth is expected to occur mostly in Africa and abate in the Americas, Europe, and parts of Asia, especially as families in more developed nations have fewer children than they used to have.” In many developed nations, the total fertility rate has actually dropped below the rate of about 2.1 lifetime births per woman; In 2013, the U.S. fertility rate fell to 1.86. According to the Population Reference Bureau, “in contrast to the more developed countries, the less developed countries — in Asia, Africa, and Latin America — had both higher birth and death rates in the 1900s than Europe and North America had in the 1700s, and these higher rates have continued throughout the 20th century.”
On paper, the world can produce enough food to nourish all of its current inhabitants (in terms of raw volume). Given the current global standing, the world is not overpopulated by any means. With that said, by 2050, global food production could simply be insufficient; the world’s farmers will have to double their crop production. Jonathan Foley, a climatologist of the University of Minnesota, says it’s one of the greatest challenges of the 21st century. “How will we feed 9 billion people without destroying the planet?”
The consequences of increasing population while maintaining modern lifestyles are already apparent. According to the UN Food and Agriculture Organization, 1 billion people — or one in nine people in the world — do not have enough to eat. 98 percent of the world’s undernourished people live in densely populated developing countries, including Asia, Sub-Saharan Africa, and Latin America. Water is an even greater obstacle for billions in developing countries. 1.1 billion people in developing regions have inadequate access to water, and 2.6 billion lack basic sanitation resources.
If we, as members of “developed” society, maintain our current lifestyle of consuming more than three times more food and roughly 250 times more clean water than needed, our Earth will not be able sustain such a large, growing population. Unless we begin to change our perspectives, lifestyles, and consumption, we will put a great strain on the world’s resources. Deforestation, pollution, global climate change, and even famine are in the scope of humanity’s future if the population continues to rise. Unless we plan on making the film, WALL-E a reality, it’s time we switch to sustainable practices.