Human Overpopulation

This section looks at an overpopulation definition, causes of overpopulation, effects of overpopulationsolutions for overpopulation and overpopulation facts. The latest overpopulation news is included at the foot of the page.

Overpopulation definition: occurs when the human population exceeds the carrying capacity of its ecological niche or habitat. It can result from an increase in birth rate, a decline in mortality rate, an increase in immigration or an unsustainable environment usually associated with a depletion of resources.

Causes of overpopulation

From 1950 to 2011, world population increased from 2.5 billion to 7 billion and is forecast to reach a plateau of more than 9 billion by the middle of the 21st century. Recent forecasts place the possible number of people on the planet at 11 billion or 15 billion by 2100. Sir David King, former chief scientific adviser to the UK government, told a parliamentary inquiry: "It is self-evident that the massive growth in the human population through the 20th century has had more impact on biodiversity than any other single factor." At least until the middle of the 21st century, worldwide losses of pristine biodiverse land will probably depend much on the worldwide human birth rate.


Human population growth is one of the main drivers of species extinction.


According to a 2014 study by the World Wildlife Fund, the global human population already exceeds the planet's biocapacity - it would take the equivalent of 1.5 Earths of biocapacity to meet our current demands. The report further points out that if everyone on the planet had the footprint of the average resident of Qatar, we would need 4.8 Earths and if we lived the lifestyle of a typical resident of the USA, we would need 4 Earths.


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Causes of overpopulation: decline in the death rate

At the root of overpopulation is the mathematical dynamic between the overall birth rate and death rate in populations.


If the number of children born each year equals the number of adults that die, then the population will remain stable. Typically factors that increase the death rate tend to act over shorter periods of time, the ones that increase the birth rate tend to do so over longer periods of time.


Advancements in disease prevention, medical care, diet, health education, lifestyle and working conditions have contributed to the growing imbalance between birth and death rates. Current estimates suggest that every minute of every day, the net population grows by around 150 people.

Causes of overpopulation: better medical facilties

A few generations have made a world of difference. On average, a child born in the United States in 1900 would live to age 47. By 1965, life expectancy in the United States had increased to about 70 years. Infants born in the United States today can expect to live to age 80.


Better food and cleaner water have helped some. But the most important gains were in fighting diseases that were unrelated to water quality and malnutrition. Over the past century, life expectancy has been increasing primarily because of the development of effective medicines.


In the early part of the 20th century, the first 'battle' was won against infectious diseases such as tuberculosis, pneumonia, and typhoid fever. Deaths from these illnesses dropped rapidly, especially among children, and life expectancy increased as a result.


The effect of medical innovation is undeniable. By the 1960, deaths from infectious disease were no longer common. These illnesses were replaced by diabetes, heart disease, stroke, mental illness, and cancer as the greatest medical threats to life and well-being. Between 1950 and 1980, new medicines for all these diseases were introduced. Death rates declined and life expectancy grew.

Causes of overpopulation: advancement in fertility treatment

In 1934, a scientist at Harvard successfully conducted in-vitro fertilisation (IVF) experiments on rabbits – leading to the suggestion that the same procedure might be successful in humans. The scientist was quickly denounced for his “unethical” work and for “playing God”, but the idea was loose in the world, and couldn’t be stopped. IVF basically takes the natural fertilisation process outside of the human body.


Starting in the 1940s, IVF experiments began on humans, but researchers were timid in the face of public opposition, so the first successful embryos were never implanted in humans. Eventually, however, the first IVF baby, Louise Joy Brown, was born in England on July 25th, 1978. With the birth of this baby, which gave hope to millions of infertile couples, public opinion reversed almost overnight in favour of IVF.


In the few decades since the first successful IVF procedure, reproductive science has grown by leaps and bounds. Spurred by constant innovation, the rate of success for each individual IVF cycle has risen more than 20% points in the last 30 years. 30 years ago, the chance of a succesful outcome following a cycle of IVF treatment was 10%, now the chances have risen to over 30%.


In summary, IVF has provided an uplift to birth rates because couples who previously would not have been able to conceive are now able to do so. 

Causes of overpopulation: agricultural advancements

From a historical perspective, technological revolutions have coincided with population explosions.


There have been three major technological revolutions – the tool-making revolution, the agricultural revolution, and the industrial revolution – all of which allowed humans more access to food, resulting in subsequent population explosions.


Agricultural advancements in the twentieth century on the back of scientific discovery have allowed humans to increase food production and yields further.


Fertilisers, herbicides, and pesticides have been used to increase land under cultivation as well as crop yields. Genetic engineering is now leading the vanguard of the latest wave of scientific advancements. 

Other causes of overpopulation


Overpopulation can be considered at the global or local level. Taking a local view, looking at the net movement of people into or out of a region is important. Many people desire a move to developed countries like the U.S., U.K., Canada and Australia where the best opportunities are available in terms of medicine and healthcare provision, education provision, security and employment prospects.


Conflicts often lead to the displacement of large numbers of people who cross borders to find safety and security. Unfortunately, this often causes tension and further conflict between regional populations.


Family planning knowledge

Many developing nations have a large number of people who are illiterate, live below the poverty line and have little or no knowledge about family planning.


In this context, children often marry at an earlier age and start families at an earlier age increasing birth rates disproportionately.


There is a lack in education and knowledge surrounding the impacts of family planning choices and in many cases, religious or cultural pressures exacerbate the problem.

World population growth from 1A.D. to the present in under 6 minutes

Effects of overpopulation

Overpopulation is an undesirable condition where the number of existing human population exceeds the carrying capacity of Earth. Overpopulation is caused by number of factors. Reduced mortality rate, better medical facilities, depletion of precious resources are few of the causes which result in overpopulation. It is possible for a sparsely populated area to become densely populated if it is not able to sustain life.

Depletion of resources caused by human overpopulation

The effects of overpopulation are profoundly severe. The first of these is the depletion of resources. The Earth can only produce a limited amount of water and food, which is falling short of the current needs. Studies suggest that if every member of the human race had a consumption pattern similar to that of the average U.S. citizen, it would take 4 planet Earth's to make this a sustainable proposition.


Most of the environmental damage being seen in the last fifty years is because of the growing number of people on the planet. We are cutting down forests, eliminating biodiversity in a reckless manner, causing pollution in the air, on land and in the sea and creating a host of problems.


Overpopulation puts pressure on resources including fresh water and arable land leading to geopolitical tensions. These tensions can escalate to acts of agression and full-scale warfare.


Overpopulation has resulted in poor sanitary conditions and the destruction of rivers and water bodies especially in sub Saharan Africa, Asia and other developing countries. 

UNICEF and WHO reported in 2004 that every year, unsafe water, coupled with a lack of basic sanitation,kills at least 1.6 million children under the age of five years – more than eight times the number of people who died in the Asian tsunami of 2004. 

Degradation of the environment caused by human overpopulation

With the reliance and growing use of fossil fuels, it has started producing some serious environmental impact.


Aerosol pollution, air pollution, deforestationglobal warming, land degradation, ocean acidification and ozone layer depletion to name a few. 


The slow but conclusive melting of polar ice caps, changing climate patterns and rises in sea level add to the body of evidence which suggests that planet Earth cannot sustain current levels of human activity on an on-going basis.

Human overpopulation pressures

Conflict and warfare caused by human overpopulation

Overpopulation particularly in developing countries puts a major strain on the resources it should be utilising for development.


Conflicts over water, oil, gold, minerals and monetisable assets are a source of tension between countries, which often result in wars and armed conflict. It is usually the most vulnerable members of society who suffer - the young, the old, the infirm, the uneducated.


Increase in infectious diseases resulting in pandemics and epidemics caused by human overpopulation

High densities of population increase the chance of the emergence of new pandemics and epidemics. 


For many environmental and social reasons, including overcrowded living conditions, malnutrition and inadequate, inaccessible, or non-existent health care, the poor are more likely to be exposed to infectious diseases. Poverty is linked to other factors which are relevant - unhygienic living conditions associated with water resource depletion, discharge of raw sewage and solid waste disposal can all increase the risk and impact of infectious diseases. 


Increase in famine, starvation and malnutrition caused by human overpopulation

Starvation, malnutrition or poor diet with ill health and diet-deficiency diseases such as rickets become more likely when resource availability is scarce.


Rickets, for example, usually occurs because of a lack of vitamin D or calcium - a condition that affects bone development in children, it causes the bones to become soft and weak, which can lead to bone deformities.


Famine is typically associated with less-developed regions and there is a high correlation with poverty levels.

Solutions for overpopulation

Government and personal actions to reduce human overpopulation pressures

Overpopulation has two addressable aspects. One is managing the availability of resources for a given number of people, the other is working out how much resource is available and managing populations around this 'carrying capacity'. There are many examples of measures that have been taken on both fronts. China's 'one-child' policy attempted to manage population size - with mixed success.


Better education

One of the first measures that needs to be implemented on a global scale is a shift in human awareness that resources are limited. This needs to happen at the level of the individual and through governments via policy development. Simply acknowledging that current activity is not sustainable is the first step on the path to progress.


Family planning, sex education and efficient birth control

Raising awareness among people regarding family planning and letting them know about the serious impact of population growth can help contribute to curbing population growth. Safe sex techniques and contraceptives methods should also be part of educational programmes to help combat unwanted pregnancies.


Imparting sex education to children at an early (but appropriate) age should be a must. Parents might feel shy in discussing such things with their kids but the availability of 3rd party information or discussions with peers means that it is always better to have constructive conversations in a controlled environment. It is therefore important for parents and teachers to shed any existing inhibitions and make their kids or students aware of the sex education basics.


This is a challenging area given the global variation in cultural and religious viewpoints.


Tax benefits, concessions and social marketing

Governments have a responsibility to develop policies to incentivise managed population growth.


Tax incentives for couples who have either no, one or two children has been suggested. 


Some societies have already begun to implement social marketing strategies in order to educate the public on overpopulation effects. The intervention can be widespread and done at a low cost. A variety of print materials (flyers, brochures, fact sheets, stickers) can be produced and distributed throughout the relevant communities such as at local places of worship, sporting events, local food markets, schools and at car parks.

Human overpopulation news

For the latest human overpopulation news stories and other environmental news, check out our news page


Human overpopulation news, including commentary and archival articles published in


Human overpopulation news, including commentary and archival articles published in The Independent.


Human overpopulation news, including commentary and archival articles published in ScienceDaily.


Human overpopulation, including commentary and archival articles published in the Guardian.


Human overpopulation, including commentary and achival articles published in the Huffington Post.






Overpopulation facts

Until 1804, the world population was below a billion. It reached two billion in 1927, three billion in 1960 and four billion in 1974

In 1950 there were 83 cities with populations exceeding one million; but by 2007 this had risen to 468 cities reflecting the bias of population growth around urbanised areas.

The world population was six billion in 1999 and seven billion in 2011. It is currently 7.5 billion

Urbanisation: in 1800 only 3% of the world's population lived in cities. By the 20th century's close, 47% did so.

By 2050, the global population will be around 9 billion

Almost all growth is expected to take place in the less developed regions, where today's 5.3 billion population of underdeveloped countries is expected to increase to 7.8 billion by 2050.


By contrast, the population of the more developed regions will remain mostly unchanged, at 1.2 billion. 

Every second of every day, 4.2 people are born and 1.8 people die. This means the planetary population grows by approximately 75 million every year

The world population at the time of the birth of Christ has been estimated at about 300 million, which is just below the present US population

Half the people in the world today are below the age of 30

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