Human population growth peak
- time required for a population to double in size
- calculated by dividing annual growth rate (%) into 70
Unprecedented growth rate due to
- lower death rates and infant mortality
- improved sanitation
- better medical care
- increased agricultural output
- "Essay on Population"
- warned that overpopulaion would deplete resources and harm humanity
- Population growth is exponential (J-shaped)
- Food production increases linearly (straight line)
- When population exceeds food, it will lead to war, famine, and disease
Paul and Annie Ehrlich
- “The Population Bomb”
- Echoed Malthus
- Over-population will lead to war and famine
population is not a problem if new resources can be found to replace the depleted resources.
- represents how humans' total impact (I) results from the interaction among three factors - population (P), affluence (A), and technology (T)
- I = P x A x T
- A sensitivity factor (S) can be added to the equation to denote how sensitive a given environment is to human pressures
- I = P × A × T × S.
- Impact can generally be boiled down to either pollution or resource consumption.
- study of human population
- The application of population ecology principles to the study of statistical change in human populations is the focus of the social science of demography.
- Demographers study population size, density, distribution, age structure, and sex ratio, as well as birth and death rates, immigration and emigration.
the absolute number of individuals
Age structure diagrams
show the number of people in each age class and are especially valuable to demographers in predicting future dynamics of a population
population w/ many young and high death rate (short average lifetime) - portends a great deal of reproduction
population with large elderly population and small youth population (declining growth)
birth rate and death rate a re low, little change in population size
Column w/ a bulge
event in the past caused a high birth or death rate for some age group
- ratio of males to females
- can affect population dynamics
- The naturally occurring sex ratio in human populations at birth features a slight preponderance of males.
- But males die at faster rate
Total Fertility Rate (TFR)
- the average number of children born per woman during her lifetime
- Replacement fertility is the TFR that keeps the size of a population stable; for humans, it is 2.1
the average number of years that an individual in a particular age group is likely to live
- a theoretical model of economic and cultural change that explains the trend of declining death and birth rates that occurs when nations become industrialized
- Stage 1: the pre-industrial stage; characterized by conditions in which both death rates and birth rates are high; population size relatively low and stable
- Stage 2: the transitional stage; death rates decline and birth rates remain high; leads to rapid population growth
- Stage 3: industrial stage; birth rates fall to more closely match death rates; employment opportunities for women; Don’t need to have as many children to ensure that some survive;
- Population growth begins to stabilize, but the population size is large
- Stage 4: post-industrial stage; both birth rates and death rates remain low; populations stabilize or decline slightly
- key approach for controlling population growth
- limits the number of children one bears by reducing the frequency of pregnancy
- relies on contraception
- family planning - effort to plan the number and spacing of one's children, so as to assure children and parents the best quality of life possible
Top-down Approach to population policies
government mandates, incentives and punishment or coercion
Bottom-up approach to population policies
education, equality, access to contraceptives
Poverty is correlated with population growth
- The causality is thought to operate in both directions: poverty exacerbates population growth, and rapid population growth worsens poverty.
- This is unfortunate from a social standpoint, because these people will be added to the nations that are least able to provide for them.
richest 20% of the world's people uses 86% of the world's resources
Governments of AIDS-infected countries are experiencing this
demographic fatigue - government cannot address problems other than AIDS/HIV because they are overstretched.