The Human PopulationChapter 9

The human population of Earth has grown faster in the 20th century than in any other time – & led to environmental problems

Demography – the study of populations – particularly the human population

study historical size and makeup of the populations of countries to make

comparisons and predictions

Demographers study properties that affect population growth

Countries with similar population trends are often grouped together

I. Studying Human Populations

2 Types Of Countries

Developed countries – higher average incomes, slower population growth, diverse industrial economies, and stronger social support systems

Developing countries – lower average incomes, simple and agriculture-based economies, and rapid population growth

A. The Human Population Over Time

After growing slowly for thousands of years, the human population grew rapidly in the 1800s and underwent exponential growth

Increases were due to increases in food production and improvements in hygiene that came with the industrial and scientific revolution.

Ability to expand into new habitats – improved navigation and sailing

It is unlikely the Earth can sustain this growth for much longer

 

After growing slowly for thousands of years, the human population grew rapidly in the 1800s and underwent exponential growth

Increases were due to increases in food production and improvements in hygiene that came with the industrial and scientific revolution.

Ability to expand into new habitats – improved navigation and sailing.It is unlikely the Earth can sustain this growth for much longer 

A. The Human Population Over Time

World Population Over Time

B. Forecasting Population Size

Age structure – the distribution of ages in a specific population at a certain time

-if a population has more young people than old, the population will likely increase

-graphed in a population pyramid – a type of double-sided bar graph that shows the age structure of a population

Age Structure Diagrams

Age Structure Diagrams

• high rates of growth – pyramid has a fat bottom – or lots of young people

• slow growth or no growth – pyramid is evenly distributed

• -shrinking population – pyramid is inverse

SurvivorshipSurvivorship – the percentage of members of a group that are likely to survive to any given age-to predict survivorship a demographer studies a group of people born at the same time and notes when each member of the group dies

The results plotted is called a survivorship curve –

One of 3 typesType I – wealthy, developed countries because most of the group lives a long time

Type II – populations have similar death rates at all ages

Type III – very poor countries in which many children die

Fertility rate

Fertility rate – the number of babies born each year per 1000 women

Total Fertility Rate (TFR) – or the average number of children a woman gives birth to in her lifetime

Replacement Level Fertility– the average number of children each couple must have in order to “replace” themselves in the population

-slightly higher than 2 (2.1) because not all children will survive to reproduce

total fertility rates in the US remained below replacement level for most of the 1990s, but the population has continued to grow

-children of the baby boom grew up and had children at a lower rate – you all are called echo babies

Hello Echo Boomersy’all are important to the

economy!http://www.cbsnews.com/video/watch/?id=815162n&tag=related;photovideo

MigrationAnother reason the population continued to grow was that immigration increases

Migration – the movement of individuals between areas

-immigration – movement into an area-emigration – movement out of an area

Migration between and within countries is a significant part of population changeThe populations of many developed countries might be decreasing if not for immigration 

C. Declining Death Rates

The dramatic increase in Earth’s human population in the last 200 years has happened because death rates have declined more rapidly than birth rates

Death rates have declined because more people now have access to adequate food, clean water, safe sewage disposal, proper medical care (vaccines)

– the average number of years a person is likely to live-most affected by infant mortality – the death rates of infants less than a year old

-in 1900 the average life expectancy was about 40, now the average is 67 years, but in developed countries the life expectancy is almost 80 years

-infant health is most affected by parents’ access to education, food, fuel, and clean water

-life expectancy influenced by contagious disease like tuberculosis and AIDS

Life Expectancy

D. The Demographic Transition

Demographic transition – a model that describes how these changes can occur-based on observations of the history of many developed countries

-industrial development causes economic and social progress that then affects population growth rates

Stages of the transition

Preindustrial stage – birth and death rate are both high and population size is stable-most of the world was at this stage until about 1700 when the scientific and industrial revolution began

Transitional stage –population explosion occurs-death rate declines due to improvements in hygiene, nutrition, and education happen-birth rates remain high and so the population explodes

Stages of the transition

Industrial Stage – population growth slows because the birth rate decreases-as the birth rate becomes close to the death rate, the population size stabilizes the population is much larger than before the demographic transition

Postindustrial Stage – the birth rate drops below replacement level so the size of the population begins to decrease

Total Fertility Rate & Population Growth in the U.S.

Demography World Wide

Women and Fertility-the factors most clearly related to a decline in birth rates are increasing education and economic independence for women

-educated women find they do not need to bear as many children to ensure some will survive

-learn family planning techniques-contribute to their family’s increasing prosperity while spending less energy bearing and caring for children

countries that want to reduce birth rates have placed a priority on the education of females

-large families are valuable in communities where children work or take care of older family members

-as countries modernize, parents are more likely to work away from home, parents must pay for child care, and so they are more likely to become a financial burden rather than an asset

elderly will not need the support of their children if pensions are available

-all of these reasons contribute to lower birth rates

-today the total fertility rate in developed countries is about 1.6 children per woman, while in developing countries the rate is about 3.1 children per woman

A rapidly growing population uses resources at an increased rate and can overwhelm the infrastructure of a community.

infrastructure – the basic facilities and services that support a communitypublic water supplies, sewer lines, power plants, roads, subways, schools, hospitals

-symptoms of overwhelming population include suburban sprawl, overcrowded schools, polluted rivers, barren land, and inadequate housing

II. Changing Population Trends

A. Problems of Rapid Growth

A rapidly growing population can use resources faster than the environment can renew them

-wood removed from local forests faster than it can grow back

-wastes overwhelm local water sources

-vegetation, water, and land are the resources most critically affected by rapid growth

A. Problems of Rapid GrowthShortage of fuelwood

-in many of the poorest countries, wood is the main fuel source

-when populations are stable people use fallen tree limbs for fuel which does not harm trees, but when

populations grow rapidly deadwood does not accumulate fast enough to provide fuel

-people cut down living trees which reduces the amount available in each new year

-a supply of fuel ensures a person can boil water and cook food

Problems of Rapid Growth

important to boil water as public supplies of water are not safe to drink and can carry waterborne diseases

-food also is unsafe and harder to digest if uncooked

-without enough fuelwood many people suffer from disease and malnutrition

Unsafe waterIn places that lack infrastructure, the local water supply may be used not only for drinking and washing but also for sewage disposal

-the water supply becomes a breeding ground for organisms that cause disease such as dysentery, typhoid, and cholera

-places with rapidly growing populations, the water systems cannot be expanded fast enough

Unsafe water

Impacts on landArable land – land that can be used to grow crops-growing populations also make trade-offs between competing uses for land such as agriculture, housing, or natural habitats

Urbanization – more people living in urban areas than in rural areas-suburban sprawl – when people find work in the cities but live in the suburban areas

-leads to traffic jams, inadequate infrastructure, reduction of land for farms, ranches, and wildlife habitat

-housing within cities becomes more costly, more dense, and in shorter supply

B. A Demographically Diverse World

Not every country is progressing through each stage of the demographic transition according to the model

In recent years the international community has begun to focus on the least developed countries

-show few signs of development, increasing death rates, birth rates remain high

-given priority for foreign aid and development programs

C. Managing Development and Population Growth

Countries such as China, India, and Thailand have created campaigns to reduce the fertility rate of their Citizens

-family planning programs, economic incentives, or legal punishments

1994 the UN held the International Conference on Population and Development (ICPD)-debates about the relationships between population, development and the environment-favor stabilizing population through improvements in women’s status and other investments in development

5 main goals by 2015

-universal access to family planning and reproductive health services

-reduce infant mortality rates

-close the gap in maternal mortality

-increase overall life expectancy

-universal access to and completion of primary education and access to secondary and higher levels of education for girls and women

D. Growth is Slowing

The human population is 6.5 billion and still growing

-the worldwide population growth peaked at about 87 million per year between 1985 and 1990

-it grew by 85 million between 90 and 95

-fertility rates have declined but rates are still much higher in developing regions