Human Population Chapter 8

Our World at Seven Billion Human Population is Growing Rapidly: Populations continuing to rise in most countries especially in poorest countries Leading to stress on society, resources, and environment of poor nations 70 million new people added to world population each year In 1800 world pop. reached 1 billion, in 1930 it reached 2 billion, the most last billion was added in 12 years World growth rate is 1.2%, but is as high as 3% in some countries At current growth rate world pop. will double in 53.8 year 49% of non-European nations feel their birth rates are too high

Some Countries Face Shrinking Populations: 66% of European governments think their birth rate is too low Policymakers believe population growth increases economic, political, and military strength Growth is correlated with poverty, not wealth Strong, rich nations have low growth rates Weak, poor nations have high growth rates Some nations offer incentives for more children

Demography Studying Populations: Demography - the application of population ecology to the study of change in human populations There’s a carrying capacity for all species, including humans How many humans can the world sustain? 1 billion to 33 billion: prosperity to abject poverty Population growth can’t continue forever

Demographers study: Population size Density and distribution Age structure Sex ratio Birth, death, immigration, and emigration rates People are not distributed equally over the planet Highest density: temperate, subtropical, tropical biomes and close to water Cities are local high-density areas Lowest density: away from water, extreme environments

Age Structure: Describes relative numbers in each age class within a population Diagrams (population pyramids) show age structure Wide base denotes many young High reproduction, rapid population growth Even age distribution Remains stable, births keep pace with deaths Narrow base denotes fewer young than old Population will likely decline over time

Age Structure: Sex Ratios: Many populations are getting older Median global age is 28, will be 38 by 2050 Sex Ratios: Unequal sex ratios can impact population growth Human sex ratios at birth slightly favor males For every 100 females born, 106 males are born Some cultures have preference for male over female children China’s one child policy led to selective abortion and abandonment of daughters

Population Changes: Populations grow, shrink, or remain stable depending on rates of birth, death, and migration Gap between birth and death rates have led to population expansion Immigration/emigration have become more important Overall global growth rate has declined in recent years World population continues to grow

Influences on Population Growth: Total fertility rate (TFR) – average number of children born to each female Replacement fertility – TFR that keeps the size of a population stable (about 2.1) Natural rate of population change – change due to birth and death rates alone (no migration) Crude Birth Rates - # of births per 1,000 people per year Crude Death Rates - # of deaths per 1,000 per year Doubling time - # of years it takes for population to double “rule of 70”

Demographic Transition: Life expectancy – average number of years that an individual is likely to live Demographic transition – model of economic and cultural change Pre-industrial stage – in pre-industrial societies, both birth and death rates are high High birth rates compensate for high infant mortality Population growth is slow Transitional stage – declining death rates due to increased food production and medical care Birth rates remain high since people are not used to low infant mortality rates Population grows quickly

Industrial stage – birth rates fall as jobs provide opportunities for women outside the home and children are not needed in the workforce Difference between birth and death rates shrinks Population growth slows Post-industrial stage – birth and death rates are low and stable Population stabilizes or even shrinks

Population and Society: Factors affecting fertility in a society Access to family planning Rates of infant mortality Levels of women’s rights Level of affluence Importance of child labor Government support for retirees Family planning is key approach to population growth Family planning gives women control over her reproductive window - time frame where a woman can become pregnant A woman has potential to produce 25 children during her reproductive window

Empowering women reduces fertility rates Increasing affluence lowers fertility Poorer societies have higher population growth rates In 1960, 70% of all people lived in developing nations As of 2010, 82% live in these nations 99% of the next billion will be born in these nations

Expanding Wealth Can Increase Environmental Impact: Affluent societies have enormous resource consumption and waste production Ecological footprints are huge Biocapacity - amount of biologically productive land and sea available to us