The Environmental Impacts of Overpopulation



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The current population of the Earth is almost 7.6 billion people and growing. It is projected to reach over 8 billion by 2025, 9 billion by 2040, and a whopping 11 billion by 2100. Population is growing rapidly, far outpacing the ability of our planet to support it, given current practices.

Overpopulation is associated with negative environmental and economic outcomes ranging from the impacts of over-farming, deforestation, and water pollution to eutrophication and global warming. While a lot of positive steps are being taken to better ensure the sustainability of humans on our planet, the problem of having too many people has made lasting solutions more challenging to find.

Overpopulation, Briefly Defined

The term overpopulation is used to describe a situation in which the world or area has a population so large that the people there are suffering as a result. In other words, the population exceeds the region or planet's carrying capacity--the number of people, other living organisms, or crops that can be supported without environmental degradation. Their suffering may include a shortage of food, limited access to healthcare and other public services, overcrowding, and high unemployment.

Causes of Overpopulation

Overpopulation is largely attributed to trends stemming from spike in birth rates in the mid 20th century. Overpopulation of specific locations can also result from migration. Oddly enough, the overpopulation of an area can occur without a net gain of population. It can result from a population with an economy reliant on exports outgrowing its carrying capacity coupled with slim changes of migration. This has been called "demographic entrapment."

Environmental Effects of Overpopulation

The relationship between overpopulation and environmental impacts are often interrelated and complex. Below are some of the key sustainability challenges associated with overpopulation. For the sake of simplicity they are listed separately, but understand the connections between them are complicated, which makes them more challenging to manage. 

Farming impacts

A growing agricultural base to feed an expanding world population comes with its own complications. As the global population increases, more food is needed. Such measures may be met through more intensive farming, or through deforestation to create new farm lands, which in turn can have negative outcomes. Agriculture is responsible for about 80 percent of deforestation, worldwide. 

The yield of existing farmland can be increased through intensive farming to feed our rapidly growing population. This approach is characterized by reliance on mechanization, pesticides and chemical fertilizers. Such practices can be associated with soil erosion or depletion. According to the World Wildlife Fund, the land used and abandoned in the last 50 years globally may be equal to the amount of land used today. As well, the agricultural runoff of excess fertilizers is one of the main causes of eutrophication, which depletes waters from oxygen and results in significant negative impacts for marine life.


Deforestation in turn leads to a reduced ability to capture CO2, thus exasperating the greenhouse gas problem. Deforestation is also strongly associated with loss of habitat and extinctions. Agriculture, as mentioned above, is responsible for nearly 80% of global deforestation. Another 14 percent is attributed to logging, 5 percent to firewood collection, and the balance resulting from other causes.

Human population increase is related to all of these deforestation pressures. More people means we need more food, more wood products, and more firewood. 


Agricultural runoff is one of the main causes of eutrophication, the presence of excessive nutrients in bodies of waster, such as large pockets like the Dead Zone of the Gulf of Mexico. Worldwide, there are more than 400 marine 'dead zones' caused by eutrophication, collectively covering an area six times the size of Switzerland.

Eutrophication causes the dense growth of plant life that consumes oxygen, resulting in the death of aquatic animals. Other major sources of eutrophication are industry and sewage disposal--both related to population growth. The cost of mediating eutrophication in the U.S., in 2013, was estimated at over over $2.2 billion annually. Recent research points out that there are other important impacts other than food production, such as clothing and manufactured good production. Cotton or linen production, for example, can involve direct agricultural impacts. The use of fossil fuel for electrical production to power factories also creates combustion byproduct emissions, which can ultimately be absorbed by oceans through rainwater.

Loss of Fresh Water

While there is plenty of water on the planet, it is very much a scarce resource. Only 2.5 percent of water resources are fresh water, and just a small fraction of that is available as unpolluted drinking water.

One of the byproducts of population growth has been stress on freshwater supplies. "Water stressed" is defined as a case of demand exceeding the supply of suitable water available. According to one report, around 40 percent of the world's population endure water scarcity, and that amount has been projected to skyrocket by 2030 as global demand for water increases by 50 percent. Another commentator expects 2/3 of the world's population to be living with water shortages by 2025, which he attributes to population growth. Also consider that population growth is most rapid in part of the world where water is in high demand already, such as Africa and Asia. 

Global Warming

Human population growth and climate change have grown hand in hand as the use of fossil fuels has exploded to support industrialized societies. More people necessitates more demand for oil, coal, gas, and other energy sources extracted from below the Earth’s surface that spew carbon dioxide (CO2) into the atmosphere when burned, trapping warm air inside like a greenhouse. Most fossil fuel consumption comes from developed countries. It is a sobering thought that most developing nations aspire to similar industrial economies as they experience economic growth, which further escalates CO2 emissions into the atmosphere.

Deforestation is another important component of greenhouse gas emissions. Globally, forests store more than twice the amount of carbon dioxide than is found in the atmosphere. As forests are cleared and burned, that CO2 is released into the atmosphere, accounting for an estimated 12 percent of total greenhouse gas production.

Outlook for Overpopulation and Sustainability

There are issues aplenty to overcome. Clearly, initiatives to switch to clean energy sources such as solar, improve agricultural practices, better manage water resources and fully embrace the principles of the circular economy will help us mitigate the impact of population growth. At the other end of the spectrum, policies that encourage family planning, education, gender equity and other measures to help slow population growth will help reduce pressure on the planet. Take time to understand the issues, and support policies that will make a difference.