1. The Human Population What is our population?
How is it measured? What diagrams do we use?
What effects does this have on the Earth’s environment?

2. Studying Human Populations
Demography is the study of the characteristics of populations, especially human populations.

3. Don’t copy this….
Demographers study the historical size and makeup of the populations of countries to make comparisons and predictions.
Demographers also study properties that affect population growth, such as economics and social structure.

4. The Human Population Over Time
Exponential growth in the 1800s (population growth rates increased during each decade)
Mostly due to decreased death rates
increases in food production
clean water
improvements in hygiene
safe sewage disposal
discovery of vaccines
However, it is unlikely that the Earth can sustain this growth for much longer.

5. World Population Over Time

6. How do we visualize population trends?
How do we visualize any trends in data?

7. Age Structure
Classification of members of a population into groups by age or distribution of members of a population in terms of age groups
Helps make predictions
Countries with high rates of growth usually have more young people. Countries that have slow or no growth usually have an even distribution of ages in the population.
Graphed in a population pyramid

8. Population Pyramid

12. What determines population growth of all species?
Survivorship

13. Survivorship
% of newborns in a population that can be expected to survive to a given age
Used to predict population trends
To predict survivorship, demographers study a group of people born at the same time & notes when each member of the group dies.

16. Survivorship types can be related to humans!
Since the amount of offspring a human creates doesn’t vary (like different species do) we talk about the survivorship of the offspring that humans DO have

17. Human Survivorship in detail
Type I=most people live to be very old
Wealthy developed countries like Japan & Germany
Type II=populations have a similar death rate at all ages
Type III=many children die
Very poor, underdeveloped countries
Type I & Type III may result in populations that remain the same size or grow slowly.

18. Human Survivorship Depends on birth rate and death rate
Birth rate depends on fertility rate

20. Fertility Rate
The number of births (usually per year) per 1,000 women of childbearing age (usually 15 to 44)
Replacement level is the average number of children each parent must have in order to “replace” themselves. This number is slightly more than 2 because not all children born will survive & reproduce.

21. What else affects human population?
Migration
Life Expectancy

22. Migration
Any movement of individuals or populations from one location to another
Movement INTO an area=Immigration
Movement OUT of an area=Emigration (Exit)

23. Where is this happening in the world today?

24. Life Expectancy
Average length of time that an individual is expected to live
Most affected by infant mortality
Expensive medical care is not needed to prevent infant deaths. Infant health is more affected by the parents’ access to education, food, fuel, and clean water.

27. Human population trend changes

28. The Demographic Transition
The general pattern of demographic change from high birth & death rates to low birth & death rates, & observed in the history of more-developed countries

29. Stages of the Transition
First Stage
A society is in a preindustrial condition
The birth & death rates are both at high levels
Population size is stable

30. Stage I
Pre-Industrial Revolution!

31. Second Stage
A population explosion occurs
Death rates decline as hygiene, nutrition, & education improve.
Birth rates remain high

32. Stage II
Industrial Revolution
Improved Health Care=Lower Death Rate

33. Third Stage
Population growth slows because birth rate decreases
Population size stabilizes, but the population is much larger than before the demographic transition

34. Stage III
Higher education=lower birth rate

35. Birth rate drops below replacement level
Fourth Stage
Birth rate drops below replacement level
Population begins to decrease
It has taken from 1-3 generations for the demographic transition to occur.

36. What causes this transition?
Changes in women’s views & education and fertility

37. Women and Fertility
The factors most clearly related to a decline in birth rates are increasing education & economic independence for women.
In the demographic transition model, the lower death rate of the second stage is usually the result of increased levels of education.
Educated women find that they don’t need to bear as many children to ensure that some will survive. They may also learn family planning techniques.
Women are able to contribute to their family’s increasing prosperity while spending less energy bearing & caring for children.
As countries modernize, parents are more likely to work away from home. If parents must pay for child care, children may become a financial burden rather than an asset.

38. WHY DO WE CARE?!?!?!
WHAT THE HECK DOES THIS HAVE TO DO WITH THE ENVIRONMENT??????

39. Changing Population Trends
Big populations overwhelm Infrastructure
Infrastructure-the basic facilities of a country or region, such as roads, bridges, sewers, power plants, subways, schools, & hospitals.
Overwhelmed infrastructure=environmental problems

40. Environmental Problems Associated with Rapid Growth
If populations grow too big then:
Resources run out
Pollution
Inadequate housing
Ruined land
Overcrowding

41. YOU SHOULD CARE!! https://www.youtube.com/watch?v=5eTCZ9L834s

42. Impacts on Land
Arable land is farmland that can be used to grow crops.
Growing populations make trade-offs between competing uses for land such as agriculture, housing, or natural habitats.
For example, Egypt has a population of more than 69 million that depends on farming within the narrow Nile River valley.
Most of the country is desert, and less than 4 percent of Egypt’s land is arable.
The Nile River Valley is also where the jobs are located, and where most Egyptians live. They build housing on what was once farmland, which reduces Egypt’s available arable land.

43. Urbanization is an increase in the ratio or density of people living in urban areas rather than in rural areas.
People often find work in the cities but move into suburban areas around the cities.
This leads to traffic jams, inadequate infrastructure, & reduction of land for farms, ranches, & wildlife habitat. Meanwhile, housing within cities becomes more costly, more dense, & in shorter supply.

44. How can we stop growing?
Countries such as China, Thailand, & India have created campaigns to reduce the fertility rates of their citizens.
These campaigns include public advertising, family planning programs, economic incentives, or legal punishment.

45. In 1994, the United Nations held the International Conference on Population & Development (ICPD)
It involved debates about the relationships between population, development, & the environment.
Many countries favor stabilizing population growth through investments in development, especially through improvements in women’s status.

47. Managing Development and Population
With these goals, worldwide fertility rates are dropping as shown below.

48. Growth Is Slowing
Fertility rates have declined in both more-developed & less-developed regions.
Demographers predict that this trend will continue & that worldwide population growth will be slower this century than the last century.
If current trends continue, most countries will have replacement level fertility rates by If so, world population growth would eventually stop.

49. Projections to 2050
Looking at the graph below, most demographers predict the medium growth rate, and a world population of 9 billion in 2050.