The Last 10,000 Years of Human History

• By 1810, population ~1 billion• By 1925, population ~2 billion• By 1960, population ~3 billion• By 1974, population ~4 billion• By 1987, population ~5 billion• By 1999, population ~6 billion• By 2012, projected ~7 billion

The Human Population Today

• Present population: (6 Billion +)– Growth rate = 1.3%/year– Doubling time = 53 years

• Growth rate = (birth) rate – mortality (death) rate

• Human population grows by about 80 million people per year

Future World Population

• Demographic transition theory:– Birth and death rates decline from high to low

levels because of economic and social development

• Population Reference Bureau estimates world population growth rates are dropping– From 1.8% in 1990 to 1.3% in 2003– Due to urbanization and increased opportunities

for women

Future World Population

Future World Population

• BUT the world’s population explosion continues

– From 1950 to 2000 population grew from 2.5bn to 6bn

– Growth rate of 1.3% per year means 9 billion by 2050

• Consider no. of births per woman to predict 2150 population (you will be 54 and a grandparent maybe)

– If...average 1.6 children/woman: 3.6bn

– If...average 2 children/woman: 10.8bn

– If...average 2.6 children/woman (current average): 27bn

Maths

• Too many people?– Crowding in cities– Crime– Pollution– Illegal migration– Disease

• Room for more people?– Entire world population could fit inside 42 km x 42

km square

• Consider carrying capacitycarrying capacity

Carrying Capacity

• How many people can Earth support?– Calculations of carrying capacitycarrying capacity vary

considerably– Increasing amounts of food can be produced– People can migrate from areas of famine or

poverty to less crowded or wealthier areas– BUT Earth’s resources are finite, so solutions

are temporary

Carrying Capacity

Example of Rapa NuiRapa Nui (Easter Island)– Isolated Pacific island with poor soil and little water– Settled by 25-50 Polynesians in 5th century

• Survived easily on chickens and yams, plenty of free time• Developed elaborate competition between clans with

– Civilization peaked at 1550, with population of about 7,000

Carrying Capacity

Example of Rapa NuiRapa Nui (Easter Island)– Reached by a Dutch ship in 1722

• Found 2,000 people living in caves

• Primitive society, constant warfare

– Rapa Nui’s carrying capacity had been drastically lowered by society’s actions:

• Transportation of moai had required cutting down trees

• Erosion of soil made yams scarce

• Lack of canoes made fishing difficult and escape impossible