1. 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

2. 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

3. 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

4. Future World Population

5. 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

6. 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 carrying capacityConsider carrying capacity

7. Carrying Capacity How many people can Earth support? carrying capacity –Calculations of carrying 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

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

9. Carrying Capacity Rapa Nui Example of Rapa 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