Does the world have a carrying capacity for the human population?

If so, what is it? How long until we reach it?

Or have we already overshot it? What will be our “limiting factor”?

Billions 1 2 3 4 5 6 7

Year 1805 1927 1960 1974 1987 1999 2011

# of years

250,000 123 33 14 13 12 12

The amount of time to reach each “billion” milestone has been decreasing, but now appears to be leveling off

What main factors affected human population growth in early

civilization?

Changes in natural environment

What were some major events that allowed the human growth rate to

increase so dramatically?

• Inventions in farming, technology, and transportation

• Better sanitation• Antibiotics

Are all countries growing at the same rate?

• The growth rates are different among countries

• Birthrates, death rates, and age structures of populations are different

• Scientific study of human populations = demography

• Highest growth rate = India

How does the birthrate of a developed country differ from that of a developing

country?

• Developed countries = Lower birthrates

• Ex: USA, Japan, Europe

• Developing countries = Higher birthrates

• Ex: Latin America, Africa

• India and China are both undergoing intense population control efforts

• Countries with overall low birth and death rates have stable populations

• Countries that have high birth/death rates are in demographic transition

• Africa’s fertility rate – 5 births/female• Since 1960

– African population = tripled – Asian, Latin America and the Caribbean

population = doubled – US has only grown by 50%– Europe by only 20%

Age structure diagrams

How does the age structure of a population affect its growth rate?

• In the US- age structure more rectangular

• Developing countries are pyramidal

• Population is dominated by young people

• What happens as females at the bottom of the pyramid move up to reproductive age?

Why is the exponential growth of the human population considered a

“success”?

• It shows advances in medicine, food distribution and food production

• People are living longer

How is this rapid growth dangerous?

• Increased environmental destruction

• Shortage of natural resources • Water, food, and energy

shortage   

Americans make up 5% of the global population (300 million), yet we use 25% of the world’s energy

• Scientists have identified 9 “planetary boundaries” – limits that humans must not cross, otherwise the natural systems of the planet may be in jeopardy– Climate change – Arable land (farmland)– Biodiversity loss– Chemical pollution– Nitrogen and phosphorus cycles– Ocean acidification– Freshwater use

Exponential? Or going into logistic?

• Is the human growth rate speeding up or slowing down?

• Is Earth at it’s carrying capacity?

• How long until we reach carrying capacity?

• What limiting factors will affect us the most? What will we run out of first?