The human population growth rate is now declining, but the planet is likely reaching the population threshold that it can support, of 8 billion people.
It’s 2020 and we are in midst of coronavirus pandemic. Besides Covid19, there are several other problems plaguing the planet too: droughts and famines, global warming and excessive pollution, deforestation and habitat loss, species extinction crises, widespread unemployment, and economic and financial struggles.
There is a common denominator tying all of these issues together—the human population explosion.
Many studies have concluded that reducing global population would solve a lot of these issues. The thing is, however, that exponential population growth is natural for any species on the planet. Everything has evolved to propagate, so most natural systems are geared to reproduce and increase progeny.
So… why are humans being singled out here?
Get ready for some interesting number crunching.
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Why is human population growth exceptional?
In the wild, everything strives for balance. There is always a mechanism in place to curb overpopulation, whether this is in the form of predators or limited resources, which balances the ratio of births to deaths. If there is an overshoot, the graph will eventually return to a relative equilibrium.
However, humans have a highly skewed birth to death ratio – 2.5 births for every death, at the current rate. Statistics estimate that every day, there are ~400,000 births and ~150,000 deaths. That translates to a worldwide population increase of about 250,000 per day, or 90 million per year! (Source)
Our access to healthcare is a unique determinant (among other factors, such as evolution, cognition and ethics) that dictates this trend. Healthcare leads to longer, healthier lives and more surviving offspring, as well as older and longer reproductive periods. Therefore, our growth curve is steeper (or more rapid) than the curve found in most other natural systems. However, will our curve straighten out soon? Is there a limit to how much we can grow? The answer is yes. Throughout history, population explosions have never lasted forever, and neither will ours, but let’s take a look at the trend thus far.
The figure below shows global population growth trends since the mid-1700s, with a predictive curve extending to 2100. In the 1700s, growth rates were stable and population sizes were low. Back then, a high proportion of babies born died soon after birth or early in their childhood, and life expectancy was a measly 35 years old in England. As overall human health and agriculture improved, more children survived to reproductive age, and the population boom started in the early 1900s, peaking in the 1960s.
With fertility rates dropping in recent years, the good news is that our growth has already slowed from around 2% in the 1960s to 1.14% in 2014 and 1.08% in 2019-20. That’s comforting, certainly, but why is this happening in the first place? How is this growth slowing down?
What does ‘decreasing fertility’ mean?
Fertility rate refers to the average number of children a woman has in her lifetime, which is different from the birth rate (the number of babies born per 1000 individuals per year). A decrease in the fertility rate means that worldwide, women are generally having fewer children.
Causes of decline in fertility
Three main factors contribute to this trend, none of which are physical limitations (e.g., low sperm count). Firstly, fewer infant and childhood deaths lead to women having fewer babies throughout their lifetimes. Secondly, there is greater awareness and access to contraception, which reduces accidental conceptions. Lastly, there are now more women in higher education and the workforce than ever before, leading to later childbirth and smaller families (Source).
The flip side of having a longer lifespan has translated into the world getting older. Today, the fastest-growing age group is the 65-and-above category. According to the UN, for the first time in history in 2018, the number of people aged 65 and older exceeded the number of children under 5 years of age around the world! They also expect the 80-and-above group to triple in number by 2050. With an older population, the proportion of reproductive-age adults also drops (Source).
The planet has limited resources. It cannot sustain numbers beyond a certain threshold, but scientists are conflicted as to what that threshold truly is. This is because of the discrepancy in resource usage by different populaces, and many possible scenarios of changes in sustainable living and technology over time. In 2012, the UN reported 65 possible maximum population limits, based on many assumptions, ranging anywhere from 2 billion to 1,024 billion, with several results oscillating around 8 billion (Source).
What should we do to keep population growth under control?
The distribution of all these factors is highly uneven, differing greatly between urban centers in low-income countries, urban centers in wealthier countries, and rural areas. Ultimately, changing the population growth rate is a gradual process. This growth trend is so deeply ingrained at the moment, that even if the whole world employed a one-child policy, or if 2 billion people died tomorrow, by 2100 there would still be as many or more people on the planet as there are today. Therefore, a gradual change in worldwide lifestyle may ensure a better chance of survival for the human race (Source).
Even with the falling growth rates, we’re expected to reach a global population of 11 billion people by 2050. That’s much higher than the widely-stated 8-billion mark. In the end, we must be careful about how we run our lives, and if all of us try to live sustainable lifestyles and use fewer resources, more people on Earth would be able to live at a higher quality of life. We’re not the only species on the planet, and the biodiversity of Earth depends on a delicate balance of resources and interactions.
We’re part of that biodiversity too, right?
How to Build a Habitable Planet: The Story of Earth from the Big Bang to Humankind – Revised and Expanded Edition