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 2017, population ~7.6 billion The present human population of the world is a little more than ______________.  In the last 50 years of the 20th Century, world population grew from ______ billion to over 6 billion.

The Human Population Today Growth rate = (birth rate) – (death rate) Human population grows by about 70 million people per year Present population of the world id 7.6 Billion The growth rate is 1.1% per year Doubling time = 200 years (In 2217 it will be 15.2) The growth rate of the world population equals ________________.

MATHS: 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 We need the number of births per woman to predict 2050 population (you will be 47 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 At present, after subtracting deaths from births, world population increases 1.3 percent per year for a doubling time of __________________. At present, the world population of humans grows by over ______ million per year. 

Future World Population

What about? 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 capacity

Carrying Capacity How many people can Earth support? 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

Carrying Capacity Example of Rapa Nui (Easter Island) Isolated Pacific island with poor soil and little water Settled by 25-50 people from polynesia 400AD Survived easily on chickens and yams, plenty of free time Developed elaborate competition between clans with Civilization peaked at 1650, with population of about 10,000

Carrying Capacity Example of Rapa Nui (Easter Island) Reached by a Dutch ship in 1722 Found 2,000 people living in caves Primitive society and at war with each other. 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