Population and Environment-2

Chapter Outlines: Population growth in percent, Total Fertility Rate ( TFR) and Replacement Level Fertility of human population, Age structure, Factors affecting birth rate and death rate, Demographic transition.

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Percent of Population growth per year =

Birth rate – Death rate ×1001000

• World Population growth rate dropped 43% between 1963 and 2003 from 2.2% to 1.26% .

• 1963- 3.2 billion people • 2004- 6.4 billion people

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Changes in Global Fertility

(1)Total Fertility Rate(TFR)= average number of children expected to be born to a woman during her child bearing years ( 15-45 yr).TFR has dropped sharply between 1950 to 2003 from 5 to 2.8 children per women.

(2)Replacement Level Fertility = number of children needed for population to remain at current level. It is 2.1 per couple in developed and 2.5 per couple in developing country. It is high developing country because of high child mortality.

Different TFR, different outcomes

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Lecture4 5

If each of today’s couple had an average 2.1 children , the world population will grow for at least another 50 years. ( assuming the

death rate constant)

It is because of Age Structure:

prereproductive ( ages 0-14) reproductive ( ages 15-44)

postreproductive ( ages 45 and above)

Population Age structure

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In 2003, 30% of the people on the planet were under 15 years old. These 1.9 billion young people are poised to move into their reproductive stage.

Male Female Male MaleFemale Female

Factors Affecting Birth Rates

•Children as part of the labor forceMajor factor developing, rural areas

•Cost of raising & educating childrenMajor factor in developed areas

•Availability of pensionsReduces need for children to support parents in old age

•UrbanizationBetter access to family planning; children not part of workforce

•Educational & employment opportunities for womenBetter educated and/or working women have fewer children

•Infant mortality ratesLower rates = fewer births

•Average age of first birthFewer children when women wait until they’re older

•Availability of reliable birth controlReligion, social factors often play a role 7Lecture4

Factors Affecting Death Rates

•Decrease in crude death rates over last 100 yearsIncreased food suppliesBetter nutritionAdvances in medicineImproved sanitationSafer water

•Life expectancy average number of years a newborn infant can expect to live1955-2004: global life expectancy increased from 48 to 67 years

•Infant mortality –deaths before age 1 per 1000 bornDeveloped countries: dropped from 20 per 1000 born to 7Undeveloped countries: dropped from 118 per 1000 born to 61

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Demographic Transition

• Hypothesis of population change: As countries become industrialized, death rates then birth rates decline.

4 Stages of Demographic Transition

•Preindustrial –growth limited due to harsh living conditions•Transitional –death rates drop but birth rates rise.•Industrial –birth rates drop and eventually approaches death rate•Postindustrial –ZPG then population decline

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Demographic Transition

• Note that limits to human population levels reflect societal choices rather than limiting factors that control wildlife populations.

Demographic transition

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“Population control alone will not solve our environmental problems; however, it is certain that

we cannot solve those problems without first controlling the growth of the human population.”

Final Voice on Population and Environment

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