1. Causes of Population Increase
Medical Advances
One of the biggest reasons because they directly effect death rate
New medicines and inoculations have added over 60+ years to the average life expectancy
Disease diffusion – the spread of disease – does not occur as widely as it used to

2. Causes of Population Increase
Quantity and quality of food
Advances in agriculture help feed billions
Technology has allowed most crops to triple in production in the last 100 years alone
Rice, corn and potatoes are the three most significant crops

3. Causes of Population Increase
Ethnic and religious issues
Many cultures forbid the use of any form of birth control
Many cultures focus on male children – women many have many children attempting to produce sons

4. Causes of Population Increase
Economic issues
If the economy if based on agriculture, the country likely has a high growth rate
If the economy is based on industry or services, the country likely has a minimal or zero growth rate

5. Causes of Population Decline
Natural Hazards and Disasters
Millions of people live in areas that are subject to natural hazards
Earthquakes, tornados, hurricanes, floods, tsunamis, volcanoes, blizzards, etc
Can kill thousands of people at a time
Famines and plagues lead to mass starvation and disease
Famines are usually caused by natural disasters – like drought – or political upheaval
Poverty and lack of health care leads to plagues

6. Causes of Population Decline
War or political turmoil
War causes death and refugees
Cambodia – 1970s – the Khmer Rouge killed millions – “The Killing Fields”
Refugees flee for fear of persecution or death if they remain – Rwanda and Uganda
Global wars impact global populations – WWII was one of the highest losses of life globally

7. Causes of Population Decline
Economic issues
The number one reason people move is for economic concerns – better employment opportunities – “out-migration”
Much of the Great Plains of the US is experiencing out-migration
Migration does not affect global population levels – just where the people are living