1. ENVIRONMENTAL SCIENCE The Human Population: Demographics Part I The Population Explosion and its Cause

2. Part 1 The Population Explosion and its Cause Objectives List benchmarks in the human population explosion. Discuss reasons for the human population explosion.

3. The Explosion Even though humans have been around for thousands of years, the explosion of global human population has been a phenomenon of the past couple of centuries. Human population would increase slowly with variability and periodic setbacks from the dawn of human history to the early nineteenth century (1800s).

4. The Explosion Population benchmarks. 1830One billion 1930Two billion 1960Three billion 1975Four billion 1987Five billion 1999Six billion 2012Seven billion Current population growth 80 million per year

5. The Explosion Predictions 2028Eight billion 2054Nine billion By end of 22 nd century Ten billion

7. Reasons for the Explosion Slow and fluctuating population growth prior to the early 1800s was due to the prevalence of diseases that were often fatal. Infants and children were especially susceptible to many of these diseases. Women that had eight or nine children often had only one or two to reach adulthood. Large-scale epidemics, such as the black plague of the 14 th century, and famines also were major environmental pressures that limited population growth.

8. Reasons for the Explosion High reproductive rates tended to be balanced with high mortality (especially among infants and children). In the early 19 th century, it was recognized that diseases were caused by infectious agents. Improvements in sanitation and personal hygiene were the result of the knowledge of the role of pathogens in disease. Vaccinations were later used to protect individuals from specific diseases.

9. Reasons for the Explosion In the 1930s, the discovery of penicillin played an important role as the first of many antibiotics, which have been used to combat many potentially fatal diseases. Alexander Fleming (left) was first to note the antibiotic properties of Penicillin.

10. Reasons for the Explosion Improvements in nutrition have also played a significant role in decreasing the mortality rate of populations. Just like any natural population being freed from environmental resistance, the human population – since the early 19 th century – has experienced a J-curve in terms of population growth. In the last few decades, the average fertility rate has decreased – resulting in a decrease in the rate of population growth.