![]() Notice that the highest growth is occurring in less economically developed countries in Africa and Asia. ![]() The percent growth rate of population in different countries is shown. Stable population diagrams are rounded on the top, showing that the number of individuals per age group decreases gradually, and then increases for the older part of the population. In the slow growth model, the number of individuals decreases steadily with age. The rapid growth diagram narrows to a point, indicating that the number of individuals decreases rapidly with age. Typical age structure diagrams are shown. The actual growth rates in different countries are shown in Figure 4, with the highest rates tending to be in the less economically developed countries of Africa and Asia.įigure 3. The age structure of these populations is more conical, with an even greater percentage of middle-aged and older individuals. Other developed countries, such as Italy, have zero population growth. Age structures of areas with slow growth, including developed countries such as the United States, still have a pyramidal structure, but with many fewer young and reproductive-aged individuals and a greater proportion of older individuals. This pattern is most often observed in underdeveloped countries where individuals do not live to old age because of less-than-optimal living conditions, and there is a high birth rate. Countries with rapid growth have a pyramidal shape in their age structure diagrams, showing a preponderance of younger individuals, many of whom are of reproductive age (Figure 3). Models that incorporate age structure allow better prediction of population growth, plus the ability to associate this growth with the level of economic development in a region. Age structure is the proportion of a population in different age classes. The age structure of a population is an important factor in population dynamics. ![]() Age Structure, Population Growth, and Economic Development These advances in technology were possible, in part, due to the exploitation of fossil fuels. Technological advances of the industrial age have also supported population growth through urbanization and advances in agriculture. The reduction in life expectancy caused by HIV/AIDS was estimated to be 7 years for 2005. For example, life expectancy in sub-Saharan Africa, which was increasing from 1950 to 1990, began to decline after 1985 largely as a result of HIV/AIDS mortality. Naturally, infectious disease continues to have an impact on human population growth, especially in poorer nations. In the past, diseases such as the bubonic plaque of the fourteenth century killed between 30 and 60 percent of Europe’s population and reduced the overall world population by as many as one hundred million people. ![]() Also, medical innovations such as the use of antibiotics and vaccines have decreased the ability of infectious disease to limit human population growth. Clean drinking water and proper disposal sewage has drastically improved health in developed nations. The fundamental cause of the acceleration of growth rate for humans in the past 200 years has been the reduced death rate due to changes in public health and sanitation. The time between the addition of each billion human beings to Earth decreases over time. Changes on a global scale including depletion of the ozone layer, desertification and topsoil loss, and global climate change are caused by human activities. Human technology and particularly our harnessing of the energy contained in fossil fuels have caused unprecedented changes to Earth’s environment, altering ecosystems to the point where some may be in danger of collapse. Long-term exponential growth carries with it the potential risks of famine, disease, and large-scale death, as well as social consequences of crowding such as increased crime. Earth’s human population and their use of resources are growing rapidly, to the extent that some worry about the ability of Earth’s environment to sustain its human population. Humans, however, have the ability to alter their environment to increase its carrying capacity, sometimes to the detriment of other species. For example, beaver dams alter the stream environment where they are built. Humans are not unique in their ability to alter their environment. Human population growth since 1000 AD is exponential.Ĭoncepts of animal population dynamics can be applied to human population growth.
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