1. Chapter 4 Human Populations
Chapter four includes a consideration of human populations, which is termed Demography.

2. Chapter Four - Topics Population growth
Limits to growth: some opposing views
Human demography
Population growth: opposing factors
Demographic transition
Family planning and fertility control
The future of human populations
These are the specific topics to be covered in chapter Four including population growth, how we have limits to the growth of human populations, including opposing views of why population growth is limited, human demography or human population. Included are opposing factors or things that slow growth down or stop it. Demographic transition, how human population changes, family planning and the impact of fertility control on human populations and projections on trends in human populations.

3. Part 1: Population Growth
At the present time the current population of the earth is 6.47 billion (October 12, 2005), having reached six billion on 19-Jun-99 at about 5:56:07 AM GMT. For a current estimate, see the Population Clock web page at:
World population now 6.47 billion (Oct 12, 2005)
Click here for current US and World population estimates ->

4. Current Birth and Death Rates
Every second: about 4 children are born, while about 2 other people die
Net gain: 2.3 humans added to the world population every second, 72 million added every year
The human population continues to grow rapidly. I am not sure if these statistics put it into perspective, but basically, every second twice as many children are born as people die and the impact of this of this is that 2.3 people are added to the world population every second. There are over 31 million seconds in every year, which means that about 72 million people are added each year.

5. Human Population Levels Throughout History
ADD FIG. 4.2
This graphic shows the estimated size of the human population over the past few thousand years. We are not exactly sure how long what we call humans have been around, but something on the order of a couple million years seems about right. Prior to the modern era, human population had a minor impact on the earth and the population of humans grew very slowly. The utilization of tools, agriculture, medicine, and so on, greatly increased the ability of human beings to feed and take care of themselves, with the result that population increased and the population growth rate also increased. In particular, through modern science, we have increased how much food we can produce, how closely we can live together safely, and the work we can do with machines. These factors, together with the advent of modern medicine, has allowed the human population to grow unchecked through the last few hundred years in a characteristic J-shaped growth curve.

6. ADD TABLE 4.1
In demographics, we use a term called doubling time. This is the period of time it takes a population to double. (Doubling time can also be applied to biomass and other factors such as resource use.) This chart represents some of the human population doubling times estimated and measured over the last few thousand years. Notice that the doubling time for the human population has typically decreased (meaning that the population growth rate has increased) with the exception of 1200 AD, when major famines and other upheavals caused the doubling time to increase. The decrease in doubling time continued until about the mid-1990's, when the doubling time increased (the growth rate of the human population decreased). We estimate that by the year 2020, the doubling time will increase above what it was a few decades earlier. However, at that point , something on the order of eight billion people will reside on the earth.

7. Part 2: Limits to Growth Varying Perspectives
Overpopulation causes resource depletion and environmental degradation
Human ingenuity and technology will allow us to overcome any problems - more people may be beneficial
Resources are sufficient to meet everyone's needs - shortages are the result of greed, waste, and oppression
Clearly, there are real limits to the potential population of the earth. We don't know what those numbers are, but we hope that we never know, as a world where humans numbers are maximized would not likely be a very nice place. The World Bank, the United Nations and many other groups have started to try and influence the size of human families with an eye to improving the average human condition overall. There are a wide variety of factors, cultural, religious, and economic, that typically dictate the size of a family. Historically, children have been sort of a social security policy for taking care of parents during old age. In addition, in the past, most people worked on farms and additional labor from children was useful. Also, children are fun to have around, as they make life more enjoyable. These components that increase family size must be balanced against the negative impacts of overpopulation.

8. The size of families – and ultimately, the size of populations - is influenced by a wide variety of factors. One of the most important is competition for resources. This includes not just food and immediate shelter, but also industrial resources and social well being. There is a tendency for populations that are "fat and happy," like we are in the United States, to have fewer children. In other cases, stress and lower economic conditions may bring about larger families. In some cases, increased population can negatively affect the social and economic well-being of the society, and then political decisions are made to try and compensate. Probably the best example is that of the Catholic Church forbidding any kind of birth control with the exception of abstinence. ( Most American Catholics basically ignore the Catholic Church's teachings relative to reproduction.)
Decisions on how many children to have are influenced by many factors, including culture, religion, politics, need for old-age security, and immediate family finances.

9. Part 3: Human Demography
Demography - vital statistics about people, such as births and deaths
Two demographic worlds
Less-developed counties represent 80% of the world population, but more than 90% of projected growth
Richer countries tend to have negative growth rates
Demography is the study of human population, particularly birth rates and death rates and the growth of populations. Demographers divide the world into two groups. The first includes the less-developed countries that represent 80% of the world's population and the vast majority of the projected growth of the population. The second group includes richer countries that tend to have negative growth rates, and any increase in population, such as in the United States, is mostly because of emigration from other countries rather than internal growth rates. The poorer, less-developed countries are often referred to as the "third-world". The terms first, second, and third worlds originally were coined in 1955 to describe the poorer, non-aligned countries (third-world), the west (first-world) and the communist-bloc countries (second-world). Only the term "third-world" is now in common use.
What a stupid term…click below for definition of "third", "second", and "first" worlds…

10. This slide shows how the more developed regions of the world continue to grow at different rates than the less developed regions. There are a variety of reasons for this difference. Most developed nations have forms of social security (care in old age) other than having children. The cultural and economic ability to use children in less-developed countries and the lack of that in developed regions also come into play.

11. By 2050, India will probably be the world's
most populous country.
(297)
This table shows the rankings of the most populous countries in the world. Note that China and India both have more than a billion people. But because China has a strong one child policy, by the year 2050, India may greatly surpass China, with an estimated 1.6 billion versus an estimated 1.3 billion for China. The United States will continue to grow quite fast primarily because of immigration. One of the interesting facts is that Brazil will lose its place as the fifth most populous country in the world due to a decreasing birth rate and emigration. Though the internal birth rate in Brazil is higher than in the US, the population in Brazil increases at a slower rate than the US. Some of the other countries in the world, particularly countries in Africa, will continue to gain population and become ranked among the ten most populous countries in the world. Some of the Asian countries will lose that ranking. In nearly all cases, all countries will grow in population.

12. Fertility and Birth Rates
Fecundity - physical ability to reproduce
Fertility - the actual production of offspring
Crude birth rate - number of births per year per thousand people
Total fertility rate - number of children born to an average woman during her reproductive life
Zero population growth (ZPG) - occurs when births + immigration just equal deaths + emigration
There are a number of population terms that are used in different ways but actually have specific meanings. Fecundity is the actual physical ability to reproduce. For a female, it is the ability to get pregnant, and for the male, the ability to father a child biologically. Fertility is the production of offspring, or the birth rate. The crude birth rate is the number of births per year, expressed per thousand people. A total fertility rate is the number of children born to an average woman during her reproductive life. Zero population growth for a particular country occurs when the number of births and immigration into a country equals the number of deaths plus emigration from the country.

13. Regional Declines in Total Fertility Rates
All countries and regions of the earth have experienced regional declines in total fertility rates. In many cases, high fertility rates were necessary to replace people because of high death rates. When death rates are reduced by sanitation and medicine, fertility rates may not drop quickly. So the result is very high total fertility rates in Africa, low total fertility rates in America and Europe, and dropping rates in Asia and in the Pacific.

14. country's fertility rate from 6 to 1.8 in two decades. However,
China's one-child-
per-family policy
decreased the
country's fertility rate
from 6 to 1.8 in two
decades. However,
the policy is very
controversial.
China is on the extreme of societies that exert pressure to decrease family size. China has a "one-child" policy, which is sometimes enforced with sanctions, but mostly is enforced by patriotism and social pressure. The one-child policy has dramatically changed the population growth rate in China. When you visit China, as Rob has twice, one of the things you notice is the number of posters showing how wonderful the one-child family is. It was interesting that the child in the pictures that Rob saw was always a girl.

15. This is my "too bad you are a male" slide
This is my "too bad you are a male" slide. It shows the life expectancy in different countries in 1900 and What you will notice first of all is there has been an increase in life expectancy between all groups of people, but you will also notice that on the average, males do not live as long as females. There are a number of biological and societal reasons for the difference in male and female life expectancies.

16. As incomes rise, so does life expectancy.
The increase in life expectancy has been particularly evident in the wealthier countries of the world. You see from the graph above that life expectancy is greater in the well-developed and wealthier countries of the world. There are a variety of reasons for the relationship between wealth and life expectancy, including better diet and health care. However, in the United States, the availability of food has also translated into more obesity and more deaths related to eating excess food. Note also that there is a good deal of spread in life expectancy, particularly in the poorer countries of the world.

17. Living Longer: Demographic Implications
A population growing by natural increase has more young people than does a stationary population.
Dependency ratio - the number of nonworking individuals compared to working individuals - declining in countries such as the U.S. and Japan
If current trends continue, by 2100 the median age in the U.S. will be 60.
Increasing life expectancy has many implications. In a population growing by natural increase (in contrast to one growing by immigration), there will be more young people than old people. The major social implication of this demographic fact in the US is that younger people, through social security taxes, support older people in their retirement. What we are seeing in the United States is that the average age is increasing and could reach 60 by the year 2100, if current trends continue. The traditional retirement age of 65 or so will either create a substantial burden on a small number of young people supporting retirees, or the system will adapt or change so that young people's social security taxes are not the sole support of retirees The increase in the average age in the US presents a demographic challenge for the future.

18. Here you can see a comparison of two countries with greatly different cultures and economies, Kenya and the United States. Kenya is a country with a very high internal fertility rate and the bulk of the population consists of younger people. One of the things I noticed when I traveled ( I lived in Tanzania, which borders Kenya to the south and is similar in many ways to Kenya) was the great number of children. When I traveled to China, I noticed fewer children. In the United States there is a bulge in the population among people aged years old. This is because during the baby boom years (1946 – 1964), the United States emphasized having more than two children because the US was in the Cold War and wanted to beat the Communists in terms of economic power. Having large families, and thus more workers, was encouraged at that time. The birth rates in the US have been substantially lower since the baby boom years.

19. Part 4: Population Growth - Opposing Factors
Pronatalist pressures
Factors that increase people's desires to have children
Birth reduction pressures
Factors that tend to reduce fertility
There are a variety of different factors that influence population growth. Pronatalist pressures increase peoples' desire to have children. These pressures could could include things like government incentives such as tax breaks, but typically they included strong societal pressures. There are thousands of examples of pronatalist pressures in any society, as the birth of children is absolutely necessary to the survival of society. Balancing the pressures to have more children are birth reduction pressures. These include incentives that tend to reduce the fertility of a country, official and unofficial. At the extreme are campaigns such that as in China, where reduction in population growth will have many obvious benefits in a country that is already considered to be overpopulated. Other, more subtle pressures are also at work. Education about birth control tends to decrease the fertility rate when children are the result of sexual activity where having children was not a planned or desired outcome. Education gives people more options for avoiding unwanted pregnancy.

20. U.S. Birth Rates:
This interesting slide shows birth rates in the United States over a period of nearly one hundred years, from During that time, there was a general downward trend in birth rates. Notice, too, that some events in U.S. history have greatly impacted birth rates. For instance, birth rates dropped tremendously during the Depression era of the 1930s. Lack of hope for the future combined with extreme poverty during that time meant that people had fewer children. During World War II, the birth rate increased greatly, since it was considered patriotic to have more children. During the Cold War, and up until the 1960's, there was a "Baby Boom," resulting from encouragement by the U.S. government for couples to have as many children as possible. The government wanted to increase the population of the United States in order to reach higher levels of economic output through having more people available to work, and also possibly to have more soldiers to fight the communists, which were perceived as a threat to the existence of the US. The "earth-day" years of the 1970s saw some of the lowest U.S. population growth rates. Having large families was openly discouraged for ecological reasons. The 1970s were also the period of time when people born during the Depression (a relatively small number of people) were having their children. Birth rates increased somewhat through the 1980s and 1990s, when the US experienced what was called the "Echo-boom" – the period of time when baby boomers started having their children. For instance, my son Joseph was born in 1992 and my daughter Joanna in 1994.

21. Part 5: Demographic Transition
Optimistic view - world population will stabilize during this century
Pessimistic view - poorer countries of the world are caught in a "demographic trap" - helping poor countries will only further threaten the earth's resources
Social justice view - overpopulation due to a lack of justice, not resources
An important environmental science question revolves around the fact that utilization of resources and the production of pollution depend partly on population. What will happen in the future?
The optimistic view is that the world population will actually stabilize or drop. I mentioned earlier that the increase in the rate of population increase has dropped but it will take time for that to be reflected in a stable population, much less one that actually decreases.
A pessimistic view is that poorer countries are caught up in a situation where culturally and economically, families have to produce children to survive, and this fact will continue the trend toward population increase and yield ever more poverty, which will yield ever more population.
There is a social justice view that over-population is due to a lack of justice, not lack of access to resources. I've never bought the social justice arguments, but that may be due to my economic and social background. In my travel and work in different places in the world, including some very poor places in east Africa, China, Indonesia and Brazil, I've seen many people who aspire to improving their standard of living, with the US lifestyle as a model. Imagine nearly 6.5 billion people consuming the Earth's resources at the rate of the average American. That is a scary thought.

22. Demographic Transition Accompanying Economic and Social Development
In the above graph, you can see there are distinctive periods of transitions associated with population stabilization. For instance, in pre-development periods, when there is a lack of medicine or mechanized agriculture, food often limits population growth. In these periods, there is a very high death rate (about 30 per 1,000 people), which includes people who die before they have a chance to reproduce. So a high birth rate is required to keep the population size stable.
In the next phase, shown in the second column of the graph, a society develops better medical care and sanitation, and the death rate starts to fall. More people live into their reproductive years, so the birth rate remains high and may even increase. In the third phase, the death rate stabilizes and birth rates start to drop. The birth rate may drop for a variety of reasons - women have more access to education, or governments promote family planning, for example. Also, as a society industrializes, the labor of children is no longer needed to help the family survive, and there are other ways for people to be cared for in their old age than through their children. In the last phase of transition, represented by "developed" countries, birth and death rates stabilize. Notice, though, that the population size is greater overall than in the predevelopment phase.
If an ever-increasing population is a societal ill, then theoretically the birth rate can adjust back down to where the population will again be stable.

23. Fig. 4.13
This cartoon shows the paradox between population growth and resource use. Resource use can be increased either when a stable population increases its per capita use of resources or when an increasing population uses the same amount of resources. In the US, both the population and the per capita resource use have been increasing, resulting in greatly increased resource uses.

24. Infant Mortality and Women's Rights
There is a strong correlation between educational opportunities for women and birth rates, and this fact was the primary focus of the third United Nations Conference on World Population. The first conference, held in 1974 in Bucharest, Romania, centered on increasing wealth in poorer countries based on the correlation between income level and birth rate (the higher the income level, the lower the birth rate). At this conference, the UN concluded that if everyone was wealthy, population would decline. This policy did not work, partly because there are not enough resources to support the entire world at the levels of the richest countries. The second conference, held in 1984 in Mexico City, suggested imposing strict guidelines and, of course, that approach ignored a lot of the cultural impacts and did not work either. In 1994, at the third conference in Cairo, Egypt, participants concluded that educated women, who were capable of adjusting their birth rates, had fewer children than less educated women. The children that educated women had tended to receive higher education, which meant that they postponed childbearing, but their daughters received higher education, and so on. Educated women also have lower infant mortality rates, and children of educated women probably have many other benefits as well during their childhoods.

25. Part 7: The Future of Human Populations
We really don't know what the human population increase will be. There have been a number of different projections over time, but one of the things that seems certain is that we are going to have far more people than we do now. If many of the programs to lower population growth that are being adopted worldwide are widely accepted, even to the point of societies imposing population control on their citizens like China, the population may level off at eight billion people or so. If we continue on the same track we are on right now, the population is not going to level off at all, at least until limited resources reduce population. Estimates include a population on the order of billion people as a maximum, though this is just an estimate. That is three times the current population. Probably the middle of the road projection will be something about ten billion sometime in the 22nd century, and low estimates show the potential for population declines. There is no doubt that there will be a lot of societal changes and clashes during the next few decades over the issues of population growth. Population control and particularly abortion are highly emotional issues, and will continue to be so.