1. Population Concepts Population growth Human population
Problems from a growing population

2. Population Growth How populations change in size Populations grow if…
Additions – births and immigration
Subtractions – deaths and emigrations
Populations grow if…
… additions are greater than subtractions
Populations decline if…
… subtractions are greater than additions

3. Patterns of Population Growth
Unlimited population growth
More than enough resources such as food, water, space, light, etc.
Births exceed deaths
Population growth is “exponential” – the larger the population, the faster it grows – indefinitely
“J-curve” pattern to graph of population vs. time

4. Patterns of Population Growth
Limited population growth
One or more resources (food, etc.) are limited or other factors increase deaths (disease, predators)
Births become roughly equal to deaths
Population size stabilizes and fluctuates around the “carrying capacity” of the environment
“S-curve” pattern to graph of population vs. time

5. Patterns of Population Growth
Exponential growth
Carrying capacity
J curve
S curve
Population
Time
DISEASE
SPACE
PREDATORS
FOOD

6. Human Population – a special case
Slow life-history pattern (pre-1800 CE)
99% of human history – hunter gatherers – population only about 1 million
10,000 years ago – agricultural revolution
Farming increased the carrying capacity for humans
More food led to larger families who could grow even more food
By 1800 CE, human population reached 1 billion

7. Human Population – a special case
Exponential growth (post 1800 CE)
Population
Year
Years to Add
1 billion
1800
All human history
2 billion
1930
130
3 billion
1960 30
4 billion
1975 15
5 billion
1987 12
6 billion
1999
7 billion
2011

8. Human Population – a special case
Exponential growth (post 1800 CE) (+)

9. Human Population – a special case
Demographic Transition Model

10. Human Population – a special case
Humans use science and technology to change the natural limitations on our population – to change the carrying capacity of our environment
Exponential growth since 1800
Increased food production, safer preservation
Better sanitation, safer drinking water
Improved health care, better disease management
Broader range of habitable locations (energy!)
More people educated, higher levels of knowledge
Lifestyle and cultural changes, urbanization

11. Impacts of Population Growth
Shortage of firewood
A limiting resource in many developing countries
Necessary for cooking (malnutrition/starvation)
Necessary for sanitizing water
Water that kills
10 million deaths per year from tainted water (e.g., dysentery, typhoid, cholera, parasites)
Same source for drinking and sewage disposal

12. Impacts of Population Growth
Urban crisis
Population grows faster than infrastructure
Contributes to disease and social unrest
Social unrest
Domestic unrest from unemployment, urban crisis
Conflicts between ethnic groups within a country
Disputes between countries over shared resources