Impact of population growth

The purpose of this blog is to discuss population growth and its impact on the environment. Key terms such as the IPAT equation and key figures such as Paul Ehrlich and Hans Rosling will be discussed to introduce the reader to the concept of population growth and its various consequences.

To begin with, watch the simulation in the following link to get an idea about the growth of population on global scale.

The world population exceeds 7 billion and as it can be seen in the simulation it is rising rapidly. However, it is not its rise in absolute numbers that causes scientists to worry as much as the fact that the population increases exponentially, meaning that the more the population increases, the faster its rate of increase becomes. To get an idea of the growth of world population during the past and what the growth will be in the future, given that people do not take measures, one just has to take a look at the following graph.

Pic 1.Population growth graph

As it can be seen from the graph above, after 1950 population started to increase rapidly. However, this increase is not equally divided between the developed (red) and developing (blue) world. Factors such as access to medicine, well-fare and resources, have led to a huge increase in the population of the developing world. These factors have also led to an increase in the developed world until about 2000. However, factors such as family planning and greater familiarization with contraception issues have led to a slight decrease of population after 2000. The following video can give you an idea about how we reached 7 billions (it was made in 2010):

Projecting the evolution of these variables into the future we  can see that the world population will continue to increase rapidly, reaching 9 billion around 2050. The question that inevitably rises is simple: how much more people can Earth support?

Concepts such as Earth’s carrying capacity have already been discussed in a previous post. However, deciding about the Earth’s future is not as simple as comparing these numbers. This matter, as it was natural, has been discussed in depth by various experts and two different “dogmas” have been created, each with different and opposing views about the future: Cassandras and Cornucopians.


The term cornucopian comes from the Greek mythology. According to the most famous myth, when Zeus was a baby he was fed and taken care of by a goat, called Amalthea. One day he accidentally broke one of its horns, which had the power to provide unlimited nourishment.

Pic 2.Image of cornucopia

In environmental terms, Cornucopians believe that no matter its numbers, humanity, with correct use of its technological resources, will be able to sustain itself and overcome problems in the future. Moreover, humanity will be able to conserve its resources, since technological advancements can help make more efficient use of them.


The term Cassandra comes, also, from the Greek mythology. Cassandra was the daughter of the king of Troy, Priam, and was blessed by god Apollo, who was struck by her beauty, with the gift of prophecy. However, when Cassandra rejected Apollo, he cursed her so that nobody would believe her prophecies. Cassandra is a tragic figure in the destruction of Troy, as she had tried to warn the people of Troy about the threat of the Trojan horse, yet no one believed her.

Pic 3.Cassandra

In environmental terms, Cassandras predict that “humanity is on a collision course”. The damage people have done to the environment is irreversible and we are doomed, since Earth is no longer able to sustain our growing population and needs.

The most important figure of the Cassandra “dogma” is Paul R. Ehrlich.

Pic 4.Paul R. Ehrlich

Paul Ehrlich, born 1932, is an American biologist and a professor at Stanford University. He is most well known for his book “The Population Bomb”, published in 1968, in which he predicts the end of human civilization by the end of the 20th century. The rationale behind this radical prediction was that the constant population growth would lead to higher consumption needs and thus depletion of resources, which would in turn result into famine. Consequently, wars would break out over the control of the resources and this war would lead to the end of civilization. Although this prediction may seem quite inaccurate, since we are still alive, numerous of his predictions regarding the environment have proved to be true.

The IPAT equation

Apart from “The Population Bomb”, Ehrlich is famous for the IPAT formula, which he created with professor John Holdren of Harvard University. This formula is used to calculate the impact of the three most important factors on the environment.

Impact(I)= Population(P) x Affluence(A) x Technology(T)

I= PxAxT

The formula is better described in the following video:

The IPAT formula is a very useful tool, since it allows comparison between countries that may differ significantly in various factors, regarding their impact on their environment. The comparison of the environmental impact of different countries follows:

USA (population of 308,745,538 according to the 2010 census)

Although the United States remain one of the most populated countries worldwide, it is not its population that is the determining factor in the IPAT equation. Technology and affluence are dominant and multiplied by its population result in a huge environmental impact. It has been calculated that if the rest of the world consumed as much as the average US citizen, Earth would be able to support around 2,5 billion people.

 (population of 1,339,724,852 according to the 2010 census)

Although China has made huge progress in terms of technology and affluence during the last decade, the determining factor of its impact on the environment is its population. Although China has applied the “one child policy” since 1978, its population is still increasing. This increase in population, combined with the rising technology and affluence have made China on of the countries with the biggest environmental impact worldwide.

Greece (population of 10,787,690 according to the 2011 census)

Greece’s population does not allow its environmental impact to be significant. However, its combination with the increase in technology and affluence result in a quite significant environmental impact for its small size. The problem Greece faces is that its population is declining. During the last 10 years, from the 2001 to the 2011 census, the population of Greece has decreased by 1.6% and this is a problem Greece needs to face immediately.

Hans Rosling

Hans Rosling (born 27 July 1948) is a Swedish medical doctor, academic, statistician and public speaker. He is Professor of International Health at Karolinska Institute and co-founder and chairman of the Gapminder Foundation, which developed the Trendalyzer software system. Using the Trendalyzer, Rosling creates animation of how data of countries have evolved throughout the years and using trend analysis, projects this data  in the future. His research is about the link between economic development and the growing population, focusing on developing countries, especially in Africa. He has been nominated as one of the “100 most influential people” by Times magazine in 2012. You can watch Hans Rosling’s speech on TED, below:

What impressed me more about his speech was that as countries progress in terms of economic activities, they tend to have the same behavior not only in terms of economics, but also in terms of population growth. Moreover, I found his “solution” to overpopulation of the developing countries extremely interesting.


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