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Overpopulation: Major Causes & Devastating Effects


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Is overpopulation our greatest natural threat? Are we running out of food and resources? Where has this concern come from and how accurate were past predictions of overpopulation?

There are many questions swirling around the overpopulation debate representing many different perspectives. It’s indisputable that human poverty has been alleviated around the world over the last century but with our growing global wealth comes the inevitable growing consumption of natural resources. And only by looking at a context in which more people are consuming more of the natural environment can we really take a proper look at the overpopulation issue. 

Overpopulation Definition

Overpopulation is essentially when there are too many people for the carrying capacity of the Earth’s environment. It is a broad definition which means there are many different interpretations of what overpopulation might mean. 


At one end of the spectrum overpopulation is the condition of having a population so dense as to cause environmental deterioration. It’s signified by the impact that humans have on their environment outside of the natural order processes that have evolved in harmony since life began. From this perspective, it could be argued that the human race has overpopulated the planet for thousands of years. 

At the other end of the spectrum overpopulation is only thought to have been reached when the Earth has sustained it’s maximum carrying capacity for the human species. From this perspective Earth could comfortably sustain 10 billion people. But at those levels our climate and our natural environment may well be decimated at the expense of all other living species. 

What clear is that our population has grown exponentially in the last 200 years. We only have to look at the growth rate to get an idea about how the population developed over a millennia and how it has exploded over the last two centuries.

Overpopulation: a history of debate and controversy

Much of the counter-argument against the idea that we have overpopulated the Earth comes from a cultural reaction to a book written in the 1960s called The Population Bomb written by Professor Paul R. Ehrlich. It predicted a population explosion in which famines and starvation would become widespread and it alerted people to the problems of overpopulation and the need to feed a rapidly growing human population. It predicted that hundreds of millions of people would die and that nothing could be done to prevent this.

Clearly, whilst famines have not been eliminated they have not occured on the scale presented in the book. India has tripled its population from 400 million to 1.2 billion and many of the predictions in Ehrlich’s book did not come to pass. 

In response Ehrlich stated in 2009:

the biggest tactical error in The Bomb was the use of scenarios, stories designed to help one think about the future. Although we clearly stated that they were not predictions and that “we can be sure that none of them will come true as stated,’ (p. 72)—their failure to occur is often cited as a failure of prediction. In honesty, the scenarios were way off, especially in their timing (we underestimated the resilience of the world system). But they did deal with future issues that people in 1968 should have been thinking about – famines, plagues, water shortages, armed international interventions by the United States, and nuclear winter (e.g., Ehrlich et al. 1983, Toon et al. 2007)—all events that have occurred or now still threaten

But the population debate goes back even further. In 1798 Thomas Robert Malthus proposed in An Essay on the Principle of Population that the necessary increase in food production would not be able to keep up with the population increases and that humans would essentially use the increased security and safety of regular food production to procreate at ever greater numbers.

His predictions did also not come to pass. However, the biggest issue with the mainstream arguments highlighting the devastating effects of overpopulation is that they only focus on the devastation that might be inflicted on human life, human culture and the human world as a result of overpopulation. They do not consider the increasing annihilation that we wreak upon the natural world and the now-globalised nature of that as we break down natural systems, species and ecologies in our ever increasing exploitation of the natural world.  

Major causes of overpopulation

The human population has, through-out history, soared, and at times fallen, but underscoring all variations in population are the numbers of births and the numbers of deaths.

Essentially human populations in countries around the world increase in number when the rate of people being born exceeds the rate of people dying. This is a clear indicator of whether or not a population is increasing or decreasing.

However, throughout history and today, in our globalised society there are many other factors which have influenced the birth and death rates. This video from the American Museum of Natural History shows the human population through time and some of the key events which enabled it to expand:


From about 10,000 BC, Our transition from hunter-gathering societies to farming societies provided security and the human population rapidly grew. More recently the agricultural revolution and the industrial revolution provided food and wealth for populations to rapidly expand. As our civilisations have evolved, developed and create wealth we have provided new opportunities for food security and the basic resources for communities to have larger familles. 

Advances in Food Production

Human Overpopulation - sheep

Whilst the industrial revolution provided the mechanics for industrialising old farming practices or previously wild spaces, it was huge scientific advances in food production in the last 100 hundred years that has massively increased the amount of food available to us. 

The Green Revolution set in motion technological advances in the 1950s and 1960s which paved the way for massively increasing food production worldwide. The introduction of chemical fertilisers, high-yielding varieties of crops and irrigation practices enabled countries to radically transform their farming practices. Nitrogen based fertiliser enabled existing crops to yield more food. This in turn enabled societies to feed their increasing populations and broke the connection between food insecurity and population growth. With enough food to feed everyone any limitations were removed. 

Medical Advances & Reduced Mortality Rates

As human societies increasingly became more crowded so did the diseases that were inflicted upon them. And human ingenuity responded. The development of vaccines, something we all take for granted today, meant that untold human suffering could be brought to an end. 

In 1976 Dr. Edward Jenner successfully prevented a young boy from getting smallpox, a virulent diases which was estimated to have killed a third of all those it infected and which killed, in the 20th century alone, 300 million people. That’s almost the population of the entire United States today. 

Anaesthetics, clean water, antibiotics and antivirals, penicillin and, more recently, the birth control bill all followed. These medicines had a huge impact on the human societies around the world and ultimately, with the exception of the birth control pill, led to a world in which countless billions of lives were saved. When you consider the centuries that have passed since these innovations and the many generations that have otherwise lived as a result of these medical advances, the consequences for the human population are immeasurable. 

These medical advances changed the world. They changed the course of human destiny and whilst they removed human suffering at an unimaginable level they also created an environment that was much more conducive to supporting the expansion of the human species around the world. 


In the 21st century overpopulated world poverty and overpopulation go hand in hand and there are some key statistics from organisations working to alleviate poverty, and overpopulation, around the world:

  • The UN projects the population of the 48 poorest countries in the world will double from 850 million in 2010 to 1.7 billion in 2050.
    (Population Institute)
  • More than 40 percent of the world’s extremely poor people are estimated to live in just two countries by 2050: Nigeria and the Democratic Republic of Congo.
  • “Based on current trends, a growing proportion of babies will be born in places where adults have to devote most of their resources to survival, leaving very little to invest in their families, their communities and their countries.”
    (Bill and Melinda Gates)
  • Poverty and the lack of access to education leads to higher birthrates and overpopulation.
  • “Where rapid population growth far outpaces economic development, countries will have a difficult time investing in the human capital needed to secure the well-being of its people and to stimulate further economic growth. This issue is especially acute for the least developed countries, many of which are facing a doubling, or even a tripling of their populations by 2050.”
    (UN Population Fund)

Research shows that improving the general health and wellbeing of women in some of the poorest nations around the world enables them to break out of the cycle of poverty, to exert free will over the size of their families and to reduce the number of children they choose to have.  

The 2019 Gates’ Foundation Goalkeepers Report explores in detail the reasons for inequality around the world and what can be done to fix them. 

Devastating effects of overpopulation

The effects of overpopulation are essentially the effects of modern humans on the planet tracked against an exponential increase in the number of humans alive at a single point in time. 

What this means is that overpopulation isn’t itself the only problem associated with our increasing number on the planet; the desire for many countries to adopt a Western consumerist, resource intensive lifestyle compounds the challenge of overpopulation. 

The effects of overpopulation can be devastating and it’s difficult to argue with Ehrlich who describes the current state of the planet and our exploitation of it in a 2017 article with The Observer:

Rich western countries are now siphoning up the planet’s resources and destroying its ecosystems at an unprecedented rate. We want to build highways across the Serengeti to get more rare earth minerals for our cell phones. We grab all the fish from the sea, wreck the coral reefs and put carbon dioxide into the atmosphere. We have triggered a major extinction event … A world population of around a billion would have an overall pro-life effect. This could be supported for many millennia and sustain many more human lives in the long term compared with our current uncontrolled growth and prospect of sudden collapse … If everyone consumed resources at the US level – which is what the world aspires to – you will need another four or five Earths. We are wrecking our planet’s life support systems.

Whilst Ehrlich might have made sensational predictions that did not materialise about the ability of humans to live out this century at our current rate of growth; it’s more difficult to dispute his assessment of the our exploitation of the natural world when the evidence is all around. 

The most serious effects of overpopulation also include:

Conflict over water

Exacerbated by climate change conflict over water is set to become a big priority for overpopulated countries. Jakarta home to 10 million people, located in Indonesia, which is one of the most overpopulated countries in the world is sinking and could be entirely submerged by 2050. And one of the biggest factors in causing this problem is the extraction of ground-water by an overpopulated city.

Poverty, child labour and lower life expectancy

One of the most serious effects of overpopulation is the impact on human societies. Unfortunately child labour is a symnptom of overpopulation as children become a means to support the family. Research shows there is a clear correlation between poverty, child labour and overpopulation.

Environmental Devastation & Species Extinction

All of our environmental problems become easier to solve with fewer people, and harder – and ultimately impossible – to solve with ever more people.

David Attenborough, patron of the charity Population Matters

The unlimited exploitation of the natural world has led to some catastrophic consequences for the environment around the world. From the destruction of the amazon in Brazil to the palm oil plantations eradicating the home of the Orangutan in Indonesia, the environment is disappearing at an alarming rate. And this is because of the demands our ever-growing number place upon it.


During a flash, in ecological terms, we have cut down over 20% of the Amazon, with a much greater part of it under threat of deforestation. We have emptied the oceans and, according to one study, we have caused the loss of 83% of wild mammals and half of all plants. 

The complete environmental devastation across the planet has led scientists to declare that we are entering the age of the Anthropocene a biological era, completely influenced by human activity. 

Population Matters has highlighted a frightening correlation between the growth of human populations and the rate of extinctions. 

Consumption of Natural Resources

Our modern Western lifestyles also depend entirely on the high levels of unrestrained consumption that we place upon the natural world. Over consumption has knock on effects, such as the emission of carbon from fossil fuels, which cause other problems. In relation to overpopulation the degradation of the environment can lead to conflict as fierce wars break out over the control and supply of our limited natural resources.

The Global Footprint Network has estimated that we are currently using the resources of 1.5 Earth’s explaining on their site how the Ecological footprint is calculated:

On the demand side, the Ecological Footprint measures the ecological assets that a given population requires to produce the natural resources it consumes (including plant-based food and fiber products, livestock and fish products, timber and other forest products, space for urban infrastructure) and to absorb its waste, especially carbon emissions.

The Ecological Footprint tracks the use of six categories of productive surface areas: cropland, grazing land, fishing grounds, built-up land, forest area, and carbon demand on land.

On the supply side, a city, state or nation’s biocapacity represents the productivity of its ecological assets (including cropland, grazing land, forest land, fishing grounds, and built-up land). These areas, especially if left unharvested, can also absorb much of the waste we generate, especially our carbon emissions.

Exacerbation of Climate Change

It might be an uncomfortable truth to acknowledge, but the number one contributing factor towards carbon emissions is the birth of new people. 

CO2 emissions

Climate change exacerbates all of the problems that burgeoning populations in developing countries have to deal with. It makes life miserable for billions of people around the world facing floods, extreme weather events and possible food shortages. But overpopulation contributes to the causes of climate change creating a cycle that will require a radical and imaginative approach to the solutions of overpopulation. 

How can we fix overpopulation? 

Overpopulation is a simple problem with devastating consequences. The solutions are not complex, but integrating them around the world, in a meaningful way is. How can governments dictate to parents in poorer countries the number of children they should have?

One child legislation

In some countries this is exactly what has happened. China has claimed success with its One Child Policy and whilst birth rates and population growth may have decreased (fertility fell from six births per woman in the 1960s to 1.5 in 2014) there have been some other serious consequences, including a skewed population towards males due to a strong cultural preference for baby boys. 

However, the policy is highly controversial and there are a number of proposed solutions that could be implemented within less draconian societies. 

Comprehensive Sex Education

For all children, including the importances of consensul relationships and an understanding about the consequences of having sex will enable young people to make more informed decisions. 

Family Planning Services & Free Access to Contraceptives

Providing information to young families about the impacts of overpopulation the strain on resources via the rollout of family planning services will help couples to plan more effectively for the future. Empowering young women so that they can exert their own free will and make their own choices will radically reduce birth rates in some of the poorest countries in the world. 

It is estimated that worldwide nearly 40% of pregnancies are unintended whilst around 350 million women in the poorest countries either did not want their child or wanted the ability and choice to space their pregnancies. 

David Attenborough raised this point in The Independent:

The only ray of hope I can see – and it’s not much – is that wherever women are put in control of their lives, both politically and socially, where medical facilities allow them to deal with birth control and where their husbands allow them to make those decisions, birth rate falls. Women don’t want to have 12 kids of whom nine will die.

Government Incentives

Governments around the world often incentivise childbirth by providing parents with tax credits and payments in order to support their families. This could be reduced to providing tax incentives for only one child. Again policies such as this would be controversial; they would have social implications that would not fit easily within modern democratic societies, especially the notion that only those who could afford to have children should.

However, as our environment becomes increasingly depleted and loses its ability to maintain the structures of life itself, we may find ourselves seeking out more controversial policies in time. 


Urbanisation might seem like a strange solution to the problem of overpopulation given that some of the most populous countries and cities in the world are also some of the most degraded, in terms of an environmental perspective.

However, birth rates in highly urbanised areas do fall. Researchers have found that:

In sub-Saharan Africa, the urban fertility rates are about 1.5 children less than in rural areas; in Latin America the differences are almost two children. Therefore, the urbanization of the world is likely to slow population growth. It is also likely to concentrate some environmental effects geographically. 

Barbara Boyle Torrey,

The historical debates around overpopulation, arguments and counter-arguments about how many people the Earth can sustain, have been going on for centuries and that’s probably because they focus mainly on the physical capacity of the planet to sustain the current and growing number of humans who inhabit it. 

What these arguments fail to consider are the lives, and the right, of all other wild animals, plant species and whole ecosystems to exist. Humans have achieved so much in the ecological blink of an eye. We’ve brought culture and art, language and beauty to our appreciation of the world around us. No other animal can wonder in awe at the night sky and then communicate, describe or write down the way that feels in the context of a vast world full of life. But none of that will matter if we continue to destroy the uniqueness of our world to feed our ever growing number. 

Human overpopulation is a serious threat to all wildlife on the planet, but we have the intelligence, tenacity and creativity to solve the challenges of overpopulation if we choose to act in time. If we fail to act, wildlife and natural ecosystems around the world face an uncertain future. For many species this might include extinction but, like cave paintings from our ancestors before us, we will at least have proof these species once roamed free.





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