chapter 6 environmental science

current world population

8 billion

population in india and china

1. india (1.429 billion)

2. china (1.426 billion)

population growing rate of human pop

70 million per year which is more than 2 ppl added every second

what kind of growth is it an example of

exponential growth where a small percentage growth rate still produces a large increase due to the size of the base population.

global doubling time

70/0.9% or 78 yrs

doubling time of a countrys pop =

70/annual percentage of growth rate

thomas malthus

british economist that argued the number of people would eventually outgrow the food supply

• paul and anne ehrlich made similar warnings in their book the population bomb

IPAT model

represents how our total impact (I) on the environment results from the interaction of population (P), affluence (A), and technology (T).

I = P × A × T

– Increased population = less space, less resources, and more waste

. – Affluence = greater per capita resource consumption.

– Technology = increase impact by enhancing our ability to exploit resources or decrease impact by improving efficiency

demography

principles of population ecology can be applied to the study of statistical changes in the human population

demographers

study several characteristics of the human population:

• size

• density

• distribution

• age structure

• sex ratio

• rates of birth, death, immigration, and emigration

population pyrmids

age structure diagrams that describe the relative numbers of individuals at each age class within a population

• valuable in predicting the future growth of a pop

naturally occuring sex ratioat birth for human populations

is 106 males born per every 100 females born

number of individuals present in a population depends on four processes

1. birth (natality)

2. death (mortality)

3. immigration (joining a pop)

4. emigration (leaving a pop

add birth and immigration

subtract death and emigration

infant mortality

the frequency of children dying in infancy, rates are closely tied to a nation’s level of industrialization

total fertility rate

the average number of children born per woman during her lifetime

Replacement fertility

the TFR that keeps the size of a population stable.

• For humans, this is 2.1.

life expectancy

(average number of years a person in an age group is expected to live)

• increases due to a drop in infant mortality.

• Industrialized countries tend to have the highest

demographic transition

Countries still industrializing will pass through a series of stages of economic and cultural change

pre-industrial stage

death rates are high due to widespread disease, rudimentary health care, and unreliable food supplies

• People compensate for high infant mortality by having many children. Birth control is not available.

• Population growth, overall, is stable.

transitional stage

Death rates decline, due to improved food production and health care

• Birth rates remain high as society has not yet adjusted to the new economic conditions.

• Overall population growth rate is very high.

industrial stage

employment opportunities increase for women and birth control becomes more widely available, decreasing birth rates

• Population growth slows and begins to stabilize.

post-industrial stage

The population growth stabilizes or begins to shrink

• The United States is in this stage, although it has higher birth rates due to an increased immigration rate

demographic fatigue

Some developing countries are so overpopulated that they may not be able to complete a transition

There are many economic and societal factors that affect fertility in a nation

• Access to contraceptives

• Acceptance of contraceptive use

• Level of women’s rights

• Cultural influences, such as television programs

• Level of affluence

• Importance of child labor

Family planning

the effort to plan the number and spacing of one’s children

Birth control

includes all efforts to reduce the frequency of pregnancy

Contraception

a deliberate attempt to prevent pregnancy despite engaging in sexual intercourse.

• Rates of use range from 83% in China to less than 25% in some African nations

reproductive window

The time at which women can become pregnant

reducing fertility rates:

• women must be given equality in decision-making power and access to education and job opportunities.

• Equal rights also lead to women having the ability to make reproductive decisions themselves, leading to further drops in fertility rates and overall better care for children

Most of the next billion people added to the human population will come from developing countries, meaning that:

• Those countries will continue to be economically strained.

• Environmental degradation will continue due to poverty

biocapacity

The amount of biologically productive land available to us

• If humanity’s ecological footprint exceeds biocapacity, it is termed overshoot, which leads to an ecological deficit

• If the footprint is less than biocapacity, there is an ecological reserve

The cultural gender preference

male children, coupled with the one-child policy, has resulted in roughly 113 Chinese boys born for every 100 girls.

• The leading hypothesis is that many parents are using ultrasounds to determine the gender of their unborn fetus, and then selectively aborting females.

The global population is older than in past years.

The median age today is 31; in 2050, it is predicted to be 36.

• This creates strain in social welfare programs in some countries, as fewer young workers are supporting more elderly.