1st ESO

3rd ESO

4th ESO

Biology 2nd Baccalaureate

Index by courses



Skip navigation

9.6. Overpopulation and its consequences

Overpopulation and its consequences


The overcrowding or overpopulation occurs when the high population density produces a worsening environment, a decrease in quality of life or famine and conflict.

The world population has been growing slowly until the beginning of the XIX century, but since then, its growth has been exponential, producing a demographic explosion. But this growth has not been uniform in all countries, but has been much higher in developing countries.

Population growth

The main cause of population growth has been the decrease in mortality, which has been due to:

  • Health improvements. Advances in health have prevented epidemics. Medications, antibiotics, etc., allow people to live longer.
  • Feeding improvements. More and better food is produced.
  • Hygiene improvements. The sanitary measures and toilet, plus the arrival of drinking water to households, has made diminish some diseases.

The main effects of the high population growth are:

  • Growth in demand for food.
  • Deforestation of forests and jungles to create areas for agriculture, livestock, wood industry, paper, etc.
  • The grazing causes depletion of grass and vegetation preventing regeneration.
  • The uncontrolled hunting of animals for zoos, pets, ornaments, footwear, etc., can cause the disappearance of these species.
  • Overfishing can lead to the depletion of fishing grounds.
  • High consumption of natural resources, such as water, fossil fuels for energy, minerals and rocks for construction materials and other uses. They can lead to your exhaustion.
  • Construction of buildings and infrastructures in places where it can affect the soil and the ecosystem.
  • Important migratory flows of people from countries with fewer resources to more developed ones with better living conditions.
  • Depopulation of rural areas and excessive growth of large cities, with the appearance of slums and other social problems.
  • Worsening of people's quality of life.
  • Increase in waste and related diseases.

SuperpoblaciónAglomeración de gente en Jaca (Huesca)

Solutions to avoid overcrowding problems:

  • Birth control. Sex education campaigns that inform about the different contraceptive methods and facilitate their access.
  • Educational improvements. The longer the schooling lasts, the more the childbearing age will be delayed, in addition, logically, to the benefits that education brings to the person.
  • Reduce energy and resource consumption in the most developed countries.
  • Rational and equitable distribution of resources worldwide. There is currently a large and growing gap between the resources available to rich and poor countries. The rich are getting richer and the poor poorer.
  • Development aid program that allow the best and most sustainable technology in developing countries so that they do not make the mistakes made by developed countries.
  • Fair trade that allows the development of countries and the fight against poverty, respecting the environmental and cultural environment.

Curiosity: World population counter.

Interactive video: The ecological footprint.

Impacts on biodiversity

The biodiversity is the variety of different species of living creatures that have originated by a process of evolution as a result of adaptation to the ecosystem. This diversity of species allows a genetic variability to exist that ensures the maintenance of life when some catastrophic event threatens life on Earth.

The extinction of species is mainly due to the following environmental impacts:


The deforestation or logging is produced by the timber industry, or for obtaining land for agriculture, livestock and mining. The realization of infrastructures and urbanizations also contributes to deforestation.


Many species die from watersoil and air pollution.

Sneaky activities

Poachers and poachers illegally capture specimens that can cause many species to disappear for commercial reasons (for ivory, fur, etc.).

Introduction of foreign species

The exotic or alien species are found in a different area from which they originated. Instead, invasive species are those that proliferate, entering into competition with native species, damaging the environment and human and economic activities.

Many exotic species, such as potatoes or corn, without being native to Spain, are not invasive because they do not adapt to the environment. Other species, on the other hand, do manage to adapt, and since they do not have predators to control them, they can harm other species.

Book (in pdf): Invasive alien species in Aragon.

The fires

Fires are very serious because all components of the ecosystem are affected: soil, water, atmosphere and biodiversity. The habitat of the species is seriously impaired and the diversity of species is greatly affected.

Statistical data: Forest fires in Spain.

Animation: Fires produced in the world in recent years.

Consequences of species extinction

The extinction of species carries with it the following effects:

Animation: Impacts on biodiversity.

Answer in your notebook

9.6.- Why do you think it is important to conserve biodiversity?


The desertification is the process of environmental degradation in the soil loses its fertility as a result of loss of vegetation cover and subsequent erosion. This process is aggravated in arid climates, where the scarcity of water and vegetation leaves the soil unprotected. The fertile soil becomes desert soil, with no possibility of recovery.

Some of the causes of desertification are:

  • Natural causes. In arid areas, with very little rainfall, without vegetation, the soil is lost through erosion.
  • Caused by human action:
    • Loss of water due to overexploitation of aquifers and surface waters for agriculture, urban consumption, leisure, etc.
    • The excess of cattle produces an overgrazing that does not allow the vegetation to recover and ends up making it disappear.
    • The poor technical and intensive farming of some species weakens and dries out the soil.
    • The abandoned farmland.
    • The deforestation makes no vegetation that protects the soil from erosion.
    • The fires destroy vegetation that protects the soil.
    • The overexploitation of aquifers and the salinization of soils causes the loss of vegetation.

Animation: Desertification.

Activity: Analysis on desertification.


Legal warning






Follow us if it has been useful to you

Biology and Geology teaching materials for Compulsory Secondary Education (ESO) and Baccalaureate students.