What is the primary reason for the population explosion since Industrial Revolution?

Population growth is the increase in the number of humans on Earth. For most of human history our population size was relatively stable. But with innovation and industrialization, energy, food, water, and medical care became more available and reliable. Consequently, global human population rapidly increased, and continues to do so, with dramatic impacts on global climate and ecosystems. We will need technological and social innovation to help us support the world’s population as we adapt to and mitigate climate and environmental changes.

Human population growth impacts the Earth system in a variety of ways, including:

• Increasing the extraction of resources from the environment. These resources include fossil fuels (oil, gas, and coal), minerals, trees, water, and wildlife, especially in the oceans. The process of removing resources, in turn, often releases pollutants and waste that reduce air and water quality, and harm the health of humans and other species.
• Increasing the burning of fossil fuels for energy to generate electricity, and to power transportation (for example, cars and planes) and industrial processes.
• Increase in freshwater use for drinking, agriculture, recreation, and industrial processes. Freshwater is extracted from lakes, rivers, the ground, and man-made reservoirs.
• Increasing ecological impacts on environments. Forests and other habitats are disturbed or destroyed to construct urban areas including the construction of homes, businesses, and roads to accommodate growing populations. Additionally, as populations increase, more land is used for agricultural activities to grow crops and support livestock. This, in turn, can decrease species populations, geographic ranges, biodiversity, and alter interactions among organisms.
• Increasing fishing and hunting, which reduces species populations of the exploited species. Fishing and hunting can also indirectly increase numbers of species that are not fished or hunted if more resources become available for the species that remain in the ecosystem.
• Increasing the transport of invasive species, either intentionally or by accident, as people travel and import and export supplies. Urbanization also creates disturbed environments where invasive species often thrive and outcompete native species. For example, many invasive plant species thrive along strips of land next to roads and highways.
• The transmission of diseases. Humans living in densely populated areas can rapidly spread diseases within and among populations. Additionally, because transportation has become easier and more frequent, diseases can spread quickly to new regions.

Can you think of additional cause and effect relationships between human population growth and other parts of the Earth system?

Visit the burning of fossil fuels, agricultural activities, and urbanization pages to learn more about how processes and phenomena related to the size and distribution of human populations affect global climate and ecosystems.

Investigate

Learn more in these real-world examples, and challenge yourself to construct a model that explains the Earth system relationships.

• The Ecology of Human Populations: Thomas Malthus
• A Pleistocene Puzzle: Extinction in South America

Links to Learn More

• United Nations World Population Maps
• Scientific American: Does Population Growth Impact Climate Change?

  SEE INFOGRAPHIC: World population growth [PDF].

CAUSES OF POPULATION GROWTH

World population growth is marked, according to the UN

  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.

What caused the population explosion during the Industrial Revolution?

What is the main reason for the population explosion?