human population growth

Human Population Growth

world clock

case study: one-child policy in China

Mao Zedong (1950) - believed population growth was desirable; population was 540M
by 1970, population was 790M and the average chinese woman had 5.8 children; growth rate was 2.8% - doubling time was 25 years; by 2004, the population would've been 2B; currently 1.3B

human population growth

exponential growth - the increase of quantity by a fixed percentage per unit time

largely resulted from technological innovations: improved sanitation, better medical care, increased agricultural outputs, etc. leading to a decline in death rates

population growth really a problem?

factors that affect the environment

conceptual IPAT model (Paul Ehrlich, 1974): I = P x A x T

I = total impact on the environment

P = population takes up space, uses natural resources, and generates waste

A = affluence magnifies impact

T = technology: increase impact (e.g. exploit minerals, fossil fuels, old growth forests, fisheries) or decrease impact (e.g. reduce smokestack emissions)

add sensitivity factor
add effects of social institutions

e.g. China: example of large numbers of poor people become affluent

principles of population ecology

mistake to think of humans as being somehow outside nature; like other organisms, humans have a carrying capacity set by environmental limitations on growth - pushed out the natural limits on growth through technology

demography - principles of population ecology to the study of statistical change in human population; demographers study the following in determining environmental impact:

population size
density and distribution
age structure
sex ratio
rates of birth, death, immigration, and emigration

useful for predicting population dynamics and potential impacts on the environment

Projecting Future Population Growth:

1. Doubling Time and Exponential Growth

J-shaped

Estimate doubling time:

t_d - 70/%g

Exponential Growth:

N_t = N_o e^tg

2. Logistic Growth Curve

If the population cannot increase forever, what can we expect its changes over time to be? ans. S-shaped curve, curving toward the horizontal at the inflection point to the carrying capacity;

the logistic growth curve involves assumptions that are unrealistic:

constant environment
constant carrying capacity
homogeneous population (all individuals identical in their effects on each other)
constant death rates

3. Population Age Structure

Age pyramid of U.S. 2002

Population Lag Effect

TFR - total fertility rate - average number of children born per female;

factors that influence TFR

replacement fertility - TFR that keeps the size of the population stable; for humans, the replacement fertility rate is 2.1

Woman's empowerment and family planning affected population growth rate

demographic transition - Frank Notestein (1940/50s)

pre-industrial stage
transitional stage
industrial stage
post-industrial stage

transition model may not apply to all countries

Key point: the demographic transition will only take place if parents come to believe that a small family size is to their benefit.

population policies and family planning

funding and policies that encourage family planning have been effective in lowering population growth rates in all types of nations

U.N. Population Fund - programs provide education in family planning, HIV/Aids prevention, and teen pregnancy prevention

U.S. has stopped funding for this program

Women need empowerment

many social scientists and policy makers recognize that for family-planning programs to succeed, slow down and stabilize growth, women need to be granted equal power with men in societies worldwide

Poverty is correlated with population growth

With some exceptions, wealthier societies tend to have lower population growth rates (in line with demographic transition theory)

Effects of increased population in developing countries:

environmental problems
loss of biodiversity
migration to the cities
illicit activities
immigration

Consumption of the Affluent - creates a large environmental impact

affluence in modern countries like U.S., Japan, and the Netherlands is built on massive and unprecedented levels of resource consumption; therefore, environmental impact is not only dependent on the number of people involved, but also on the way those people live

individuals from affluent societies leave a larger "ecological footprint" - an environmental impact of an individual or population as indicated by the cumulative amount of Earth's surface area required to provide the raw materials a person or population consumes and to dispose of or recycle the waste that is produced

one contributing factor for increased consumption - fewer people are living in each household

Effects of increasing affluence:

provide safe drinking water, sanitary sewage systems, and collection and disposal of garbage
afford conservation and management practices
technology cleanup
obtain resources

increasing carbon dioxide - global warming
CFCs - degradation of the ozone layer
emissions of hazardous and nuclear wastes
depletion of our natural resources
oil spills
endangered species - exotic pets

Wealth gap and population growth contribute to violent conflict

as the gap between rich and poor widens, expect tensions to increase

Exceptions to the demographic population transition theory

mortality is increasing in nations with the Aids epidemic (Malthus's fears realized)

social, political, and economic repercussions

if aggressive steps are not taken and the rest of the world does not help out, these countries may fail to advance through the demographic transition; instead their rising death rates may push birth rates back up

Conclusion:

the human population cannot continue to rise forever; the question becomes how will it stop rising?

gentle process of demographic transition, or
imposition of severe governmental intervention (e.g. China's one child policy), or
Malthusian checks imposed by disease and social conflict caused by overcrowding and competition for scarce resources

Sustainability must be done in time to avoid destroying the natural systems that support our economies and societies

encouragement:

most developed nations have passed through the demographic transition; these countries are now in a position to transit from consumption-oriented and growth-oriented economies to ecologically sustainable ones
there is progress in expanding rights for women worldwide
advance innovative technology