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World Population Growth

Mathematical models of population growth

Past and current human population growth

Estimates of future population growth

The explosive growth in world population is part of a

major demographic transition

Waiting for industrial development to slow

population growth is problematic

Contraceptive use slows down population growth

Womens education promotes birth control

Limiting population growth means departing from

inherited patterns of behavior

Growth of a population is the change in the number of individuals over a

short period of time.

G = N / t

= small interval of the following variable

N = number of individuals present

t = time

Fig. 22.1: Exponential and Logistic Growth

In exponential growth, the number of additional individuals (growth, G) increases in proportion to the number of individuals present (N). In logistic

growth, G becomes zero as N approaches the habitats carrying capacity (K).

Cyclic Population Changes

Predator and prey populations often cycle with the same period.

Figure 22.2: Explosive Growth of Human World Population

Update 22.1

As of 8 April 2014, the world population

was

7. 225 billion people

according to the U.S. Census Bureau

Fig. 22.1: Exponential and Logistic Growth

The human world population keeps increasing because scientific advances increase Earths carrying capacity (K). Some applications of these advances, such as the liberal use of fertilizers and antibiotics, may not be sustainable.

Figure S22.a: Crowded Cities

In 2008, about half of the human population lived in big cities. Most of these urbanites are poor, and their numbers are increasing.

daviddarling.info/archive/econews/econews_2005_6

Total Fertility Rate (TFR) = average number of children born to a woman during her lifetime

Replacement level of TFR

under conditions of adequate nutrition and

medical care is

TFRRep = 2.06

Table 22.1: Distribution of world population & total fertility rates!

Region

Population (billions)

TFR (Average Number of Children per Woman)

World

6.5

2.6

More

developed

1.2

1.6

Less developed

4.5

2.5

Least developed

0.8

4.6

Data for year 2005 by UN Population Division

Figure S22.b: Global distribution of total fertility rates From Science 30 June 2006, p. 1895

Figure 22.3: Historical and projected world population based on different assumptions about future total fertility rates (constant, high, medium, or low).

Source: World Population Prospects - The 2008 Revision. United Nations Population Division.

Fig. 22.4: Ultimate Human

Population Size

depending on when

worldwide TFR reaches replacement level.

Note time lag between

reaching replacement TFR and leveling of population

curve.

From Potts (2000)

Figure S22.c: More than 9 billion humans in 2050, according to UN population division medium estimate released in 2011. Most of them will live in developing countries. Roberts (2011)

Figure 22.5: Demographic Transition

Figure 22.6: Age Distribution in Traditional and Developed Societies

Figure 22.5: Demographic Transition







Waiting for industrial development to slow down






Fig. 22.7: Historical Industrialization and Pollution

Historically, industrialization has been associated with pollution of air, water, and soil. In developed countries, some of the damage has been reversed by

environmental legislation and remedial funding.

Photo: Frank Gaffney

Figure S22c: Modern Industrialization and Pollution

In many developing countries, factories are still allowed to dump polluted water into rivers, and water treatment plants do not always seem to work.

Figure 22.8:

From

Scientific American December 1993, p. 62

From: Demography and Health Surveys, 1991-1999, Population Reference Bureau

Figure 22.9: Relation of Womens Education to Total Fertility Rates!












(biologically and culturally) inherited behavior

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