Overpopulation is a demographic state characterized by the fact that the number of individuals of a living species exceeds the carrying capacity of its habitat, that is its capacity to:
• to provide the necessary resources to ensure the survival of this species;
• to repair the aggressions (pollution, disruption of natural ecological regulations) inflicted by this species on its environment.
This notion can be envisaged at the level of a territory (which may be local, regional, national, continental) or planet Earth itself. In this case, the demographic limits to be taken into account include the safeguarding of global regulatory processes (regulation of the temperature and chemical composition of the atmosphere and oceans, rainfall, marine currents, etc.) which tend to keep the Earth system in a state conducive to life.
The concept is sometimes applied to the veterinary or livestock (animal population) or to geographical or social subunits (for example, "prison overcrowding").
This article focuses on the case of human overpopulation.
The origin of overpopulation: the demographic transition
The phenomenon that led to the demographic explosion observed since the eighteenth century took place in two phases:
• The previous situation was a situation of equilibrium, characterized by a high birth rate and a high mortality rate, which resulted in a low natural increase. This long-term global balance was punctuated by numerous peaks of mortality due to famines, epidemics or wars; often, these three factors combined, reinforcing each other. The high birth rate offset both these peaks in mortality and the high rate of infant mortality.
• First phase of transition: the mortality rate drops sharply (improvement of food, hygiene, health progress, industrialization ...) while the birth rate remains strong or even increases. The natural increase is therefore strong, which means a rapid growth of the population.
• Second phase of transition: mortality continues to decline, but more slowly, and the birth rate is also decreasing by a change in mores adapted to previous progress. The maximum natural increase is reached at the beginning of this second phase. Then the birth rate declines more sharply and the rate of increase of the population is decelerated.
• Modern demographic regime (post-transition): Birth and death rates stabilize at a low level. Mortality is roughly equal from one year to the next, and the population is now regulated by the fluctuating birth rate (during the traditional regime it was mortality that had this regulating role). Sometimes the rate of natural increase may become negative, which in turn leads to the aging of the population and later to a decrease in population. This case is found in a growing number of countries, mostly in Europe, where the rate of natural increase is negative: Russia, Germany, Japan, Italy, Ukraine, Romania, etc. (see the list of these countries in the article Demographic growth).
اضرار الزيادة السكانية
ونقدم لكم موضوع عن أضرار التزايد السكاني باللغة الانجليزية
While the concerns of the different NAPA reports regarding rapid population growth and climate change are diverse, three key themes emerge: (i) reducing supply – rapid population growth and climate change act cumulatively to degrade the source of key natural resources, for example through soil erosion and deforestation; (ii) increasing demand – rapid population growth is projected to escalate the demand for resources that are diminished by climate change, including fresh water and food; and (iii) vulnerability to natural disaster – rapid population growth heightens human vulnerability to natural disasters caused by climate change, such as by forcing more people to migrate and settle in areas at risk of floods, storms, drought and infectious disease.
Projecting population growth and greenhouse gas emissions to the year 2100 in one integrated model showed that slowing population growth would reduce future emissions: “by the end of the century, the effect of slower population growth would be ... significant, reducing total emissions from fossil fuel use by 37-41 per cent.”