It is important to note that birth rate decline is caused also by a transition in values; not just because of the availability of contraceptives. During stage four there are both low birth rates and low death rates. Birth rates may drop to well below replacement level as has happened in countries like Germany, Italy, and Japan, leading to a shrinking population, a threat to many industries that rely on population growth.
Sweden is considered to currently be in Stage 4. As the large group born during stage two ages, it creates an economic burden on the shrinking working population. Death rates may remain consistently low or increase slightly due to increases in lifestyle diseases due to low exercise levels and high obesity and an aging population in developed countries. By the late 20th century, birth rates and death rates in developed countries leveled off at lower rates.
Some scholars delineate a separate fifth stage of below-replacement fertility levels. Others hypothesize a different stage five involving an increase in fertility. The United Nations Population Fund categorizes nations as high-fertility, intermediate-fertility, or low-fertility. The United Nations UN anticipates the population growth will triple between and in high-fertility countries, which are currently concentrated in sub-Saharan Africa.
For countries with intermediate fertility rates the United States, India, and Mexico all fall into this category , growth is expected to be about 26 percent. And low-fertility countries like China, Australia, and most of Europe will actually see population declines of approximately 20 percent. As with all models, this is an idealized picture of population change in these countries.
The model is a generalization that applies to these countries as a group and may not accurately describe all individual cases. The extent to which it applies to less-developed societies today remains to be seen. Some countries, particularly African countries, appear to be stalled in the second stage due to stagnant development and the effect of AIDS.
Privacy Policy. Skip to main content. Population and Urbanization. Search for:. Population Growth. Implications of Different Rates of Growth Different rates of growth can lead to overpopulation or underpopulation, both of which have potential consequences.
Learning Objectives Discuss the implications both overpopulation and underpopulation can have for society. Key Takeaways Key Points When the fertility rate is at the replacement level, a population will remain stable, neither growing nor shrinking. Overpopulation is judged relative to carrying capacity and can have deleterious effects. When the population is too large for the available resources, famine, energy shortages, war, and disease can result.
Recently, in some countries, sub-replacement fertility rates have led to underpopulation. This can lead to economic decline, the aging of the population, and poverty. Key Terms fertility rate : The average number of children that would be born to a woman over her lifetime if she followed the current average pattern of fertility among a given group of women and survived through her reproductive years; used as an indicator of strength of population growth.
Replacement level : Regarding fertility, refers to the number of children that a woman must have in order to replace the existing population. Three Demographic Variables The basics of demographic population growth depend on the rate of natural increase births versus deaths and net migration.
Learning Objectives Explain how population growth is calculated. Key Takeaways Key Points Demography is the statistical study of human populations. Population change depends on the rate of natural increase and net migration. Natural increase is calculated by the fertility rate minus the mortality rate. Net migration depends on in-migration and out-migration. Key Terms Natural increase : Population growth that depends on the fertility rate and the mortality rate.
Net migration : The difference of immigrants and emigrants of an area in a period of time, divided usually per 1, inhabitants considered on midterm population. A positive value represents more people entering the country than leaving it, while a negative value mean more people leaving than entering it.
Problems in Forecasting Population Growth Population growth is difficult to predict because unforeseen events can alter birth rates, death rates, migration, or resource limitations. Learning Objectives Explain the various ways sociologist try to estimate the rate of population growth, such as through fertility, birth and death rates.
After all, the denial of the rights of women and girls are important factors that significantly contribute to high fertility and population growth: because they rob women of social power and self-determination. No doubt the natural world will applaud this, as will the individuals around the world benefiting from healthier communities and a more stable climate. PMC creates entertainment specifically designed to address deeply entrenched social norms, particularly addressing the status of women and girls.
By enhancing the status of women and girls, PMC eradicates the underlying causes that inflate population growth while also addressing crucial human rights concerns. About PMC Dramas. You are living in an extraordinary time — the planet Earth is, at this very moment, experiencing an incredible human population rise. It is estimated that the world population reached one billion in It was another years before it reached two billion in , but took only 33 years to reach three billion in Thereafter, the global population reached four billion in 14 years , five billion in 13 years , six billion in 12 years and seven billion in 12 years.
This rapid increase is no longer due to a high growth rate acting on a relatively small population base. For example, as recently as the year , a population growth rate of 2. Now, the situation is the opposite. But, this lower growth rate of 1.
Counter intuitively, this is resulting in even larger annual population growth than in — over 80 million additional people per year. This enormous total growth works out to eye-popping numbers: 1. Over ,00 people per day. That is 9, more people every hour, or more people per minute.
Almost 3 more people every second. And we expect the Earth to automatically and easily provide land, food, shelter and other resources for these fellow people, plus all of us already here. This is a very tall order for a finite planet to handle. We must act. We must empower women and girls. We must bring population in line with sustainable resources.
Researchers predict that similar cases of resource scarcity will grow more common as the world population increases. In the s, hundreds of millions of people will starve to death in spite of any crash programs embarked upon now. At this late date, nothing can prevent a substantial increase in the world death rate. The laws of nature dictate that exponential growth cannot continue indefinitely. A primary concern regarding this growth is that the demand for ever-more food will lead to widespread shortages, as forecast by Ehrlich.
The highest estimate projects the world population may rise to 16 billion by or it may decline to 6 billion, according to the lowest estimate. In addition to the threat of food shortages, human population growth is damaging to the environment in potentially permanent ways. Most scientists agree that climate change caused by the emission of the greenhouse gas carbon dioxide CO 2 is a significant consequence of human activities. In a series of treaties in the late 20th century, many countries committed to reducing their CO 2 emissions to prevent continuous global warming; however these treaties have not been ratified by every country, largely due to economic and political concerns.
The role of human activity in climate change is hotly debated in some circles. The future holds considerable uncertainty for curbing human population growth and protecting the environment.
Humans have exceeded density-dependent limits on population by enacting various environmental changes to accommodate our needs for hygiene, shelter, and food. Humans are uniquely able to consciously alter their environment to increase its carrying capacity. This capability is an underlying reason for human population growth as humans are able to overcome density-dependent limits on population growth, in contrast with all other organisms.
Human intelligence, society, and communication have enabled this capacity. For instance, people can construct shelters to protect them from the elements; food supply has increased because of agriculture and domestication of animals; and humans use language to pass on technology to new generations, allowing continual improvement upon previous accomplishments.
Migration has also contributed to human population growth. Originating from Africa, humans have migrated to nearly every inhabitable area on the planet. Public health, sanitation, and the use of antibiotics and vaccines have lessened the impact of infectious disease on human populations.
Today, however, the plague and other infectious diseases have much less of an impact. Through vaccination programs, better nutrition, and vector control carriers of disease , international agencies have significantly reduced the global infectious disease burden.
For example, reported cases of measles in the United States dropped from around , a year in the s to practically zero by the late s. Globally, measles fell 60 percent from an estimated , deaths in to , in The growth is more than double that of most other developed countries.
It is estimated that the population will increase to nearly million heads by , and some environmental agencies even expect it to grow to over million by than. Reasons for the expected population growth include increase in the number of young unmarried mothers, high fertility rates for some ethnic groups, and inadequate sexual education and birth control provision. Sources Cunningham W. Toggle navigation. Population growth Population growth as a driving force for environmental problems Population growth is known as one of the driving forces behind environmental problems, because the growing population demands more and more non-renewable resources for its own application.
So why exactly does the human population expand to rapidly? To understand this, we must first explain a little about the difference between linear and exponential growth, in other words, add a little basic math to the equation. Growth is usually thought of as a linear process: an increase by a constant amount over a period of time.
The new amount is not influenced by the amount already present. For exponential growth, this is different, because the increase of a factor is proportional to what is already there. When cells divide, there will be a constant doubling of the cells already present. In terms of population growth, the numbers of people already present always influences the number of children born in any country. It is however not a simple matter of a constant doubling of the amount.
Other factors, such as fertility and mortality rates, influence population growth, and the sexe and age of people already present, and rational decisions influence whether or not people will actually have one or more children.
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