Evolution of the world population

The exponential growth of the world's population over the last century places us at a crossroads that we must resolve in the most sustainable way, both for the environment and for human beings. There are those who predict the worst case scenario, but there are also those who break with this pessimism and project a more hopeful future, as is the case of the journal The Lancet, which in a recent study. provides a figure for the year 2100 (8.8 billion people) that is lower than that predicted by the UN (11.2 billion).

Historical growth of the world population

History shows that the evolution of the world's population has not always followed the current dizzying pace. In particular, two historical moments marked this evolution:

• On the one hand, the Neolithic Revolution, in which humans began to dominate nature and agriculture and animal husbandry emerged. These developments facilitated sedentarisation of the population and a freeing up of the workforce for other jobs related to crafts, for example. This led to a population increase to around 300 million human beings.
• In addition, the Industrial Revolution, which brought about an unprecedented demographic explosion. In the 19th century, the population doubled and in the 20th century, it even tripled, reaching 6 billion in the year 2000. Medical, scientific and economic advances led to this exponential growth.

In 2011, the world's population reached 7 billion people and today the planet is on course to reach 8 billion people despite the impact of the COVID-19 pandemic since November 2019.

  SEE INFOGRAPHIC: World population growth [PDF].

Causes of population growth

World population growth is marked, according to the UN, by three factors:

  Fertility rates

Population growth is highly dependent on trends in fertility rates. The global fertility level is expected to decline from 2.5 children per woman in 2019 to 2.2 in 2050, according to the World Populations Prospects study from the UN.

  Increase in longevity

Life expectancy has increased considerably in recent decades and this trend is set to continue: the forecast is to reach 77.1 years in 2050 (currently around 73). Despite this progress, it should be noted that there is still a very large gap with the least developed countries (7.7 years less life expectancy).

  International migration

This is a less influential factor than the previous two, but it is also relevant. In fact, those countries that received large numbers of refugees or economic migrants (between 2010 and 2020, fourteen countries or areas had a net inflow of more than one million) may offer a longer life expectancy to newcomers.

Consequences of population growth

Global population growth has positive aspects for the development of society, but it also has negative effects on the planet. In the following lines, we list the most prominent of these:

  Increase in climate change

Climate change refers to the alteration of the climate, which is directly or indirectly attributable to human activity. Therefore, the more humans, the greater the impact. This is where greenhouse gases come into play, which accumulate in the atmosphere and retain heat, increasing the greenhouse effect and contributing to an increase in the average global temperature.

  Decreased food security

According to the FAO, food security is when all people have permanent physical, social and economic access to safe, nutritious and sufficient food to meet their nutritional requirements. The population explosion affects the fundamentals of food security, i.e. its availability, stability, access and consumption.

  Impact on biodiversity loss

Biodiversity loss refers to the decrease or disappearance of biological diversity, understood as the variety of living beings that inhabit the planet. Population growth impacts on biodiversity by increasing human activity and the presence of the artificial over the natural, a phenomenon known as the anthropocene.

  Overexploitation of resources

Humans are depleting the planet's natural resources. The World Wide Fund for Nature (WWF) warns: the current overexploitation of natural resources is generating a huge deficit, as 20 % more is consumed each year than can be regenerated and this percentage is growing steadily.

Projections and trends in the world population change

Having established both the causes and consequences of world population growth, the question arises: how will it evolve? Below, we contrast the estimates already noted from the prestigious medical journal The Lancet and the UN:

• The Lancet. According to this publication, we will reach peak population in the 2060s, reaching 9.7 billion people on Earth. At that point, the population will decrease and settle at 8.8 billion by 2100. The key to making this happen will be more widespread and earlier improvements in women's education. Increased access to contraception will also mean slower population growth.
• UN. According to its projections, the population of Sub-Saharan Africa could double by 2050 and India could overtake China as the most populous country, with the world's population reaching 9.7 billion. The main divergence from the forecast by The Lancet is that it states that growth will not slow down during the second half of the 20th century and that, as a consequence,the planet will reach its population peak at the end of the century, exceeding 11 billion people.

Beyond these predictions, there is a challenge ahead for humanity: to minimise the impact of population growth and therefore climate change. To avoid pushing the planet to the limit, it is necessary to work together to reduce the carbon footprint, build infrastructures and buildings in line with sustainable urban development, promote smart and sustainable mobility, aim for a circular economy and responsible consumption, promote renewable energies, etc.