ES 100 Lecture 7: Chapter7

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8 Feb 2017
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Chapter 7
Every second 4-5 children are born while only 2 people die. There is a net gain of roughly 2.5
persons per second.
Current world population >7 billion and growing at 1.13% per year.
Increasing Carrying Capacity: The Population Bomb (1968 Earth’s population was 3.5
billion) predicted widespread starvation in the 1970s due to overpopulation. What happened?
Technology can boost carrying capacity as we make progress in agriculture,
engineering, commerce and medicine. These achievements make it possible to support
many more people per unit area.
Effects of population on the environment are not due to numbers alone.
I = PAT
I = environmental impact
P = population size
A = affluence
T = technology
A single American living an affluent lifestyle produces more pollution than an entire village of
farmers in Africa.
The term demography is derived from the Greek words demos (people) and graphos (to write
or to measure). Demography encompasses vital statistics about people, such as births, deaths,
and where they live, as well as total population size. In this section we will survey the ways
human populations are measured and described, and discuss demographic factors that
contribute to population growth.
Crude Birth Rate - Number of births in a year per thousand. (Not adjusted for population
characteristics such as number of women of childbearing age.)
Total Fertility Rate - number of children born to an average woman in a population during her
life
Zero Population Growth B + I = D + E
ZPG is a rate of 2.1 children per couple, not 2.0, because some people do not have
children and some children do not survive to reproductive age.
Crude Death Rate - number of deaths per thousand persons in a given year
Poor countries average about 20 while wealthier countries average about 10.
Some rapidly growing countries have very low crude death rates due to a high proportion
of young people.
Natural Increase - crude birth rate minus crude death rate
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