human population growth

Human Population Growth

Dr. Mark A. McGinleyHonors College and Department of Biological

SciencesTexas Tech University

Human Population Growth

• Reached 1 Billion – 1830• Reached 2 Billion – 1930• Reached 3 Billion – 1960• Reached 4 Billion – 1975• Reached 5 Billion – 1987• Reached 6 Billion – 1999• Reached 7 Billion – 2011

Current Estimated Human Population

• Monday February 4, 2013– 1:40 PM

• World 7,064,109,760 people

• http://www.census.gov/main/www/popclock.html

Approximate EstimatesWorldwide

• 5 births per second• 2 deaths per second

• dN/dt = 3 individuals per second

• = 10,800 inviduals per hour

• Add new Lubbock (N = 230,000 ind) in less than 1 day!!!

Human Population Growth

• As human population size has increased there has not been a decline in the per capita growth rate– As populations have gotten larger humans have

not been forced to have lower per capita birth rates

– As populations have gotten larger humans have not been forced to have higher per capita death rates

What’s Up With Humans?

• Humans can alter the world in ways that no other species on the planet can.– 1. increase food production• Agriculture

– Irrigation, fertilization, farm more area, mechanization, crop improvement

• Interestingly, the proportion of people who are starving on the planet is about the same to day as it was in the mid 1800s (20%)

What’s Up With Humans?

– 2. Modern medicine• Decreased juvenile mortality• Increased longevity

– 3. Better public health• Waste disposal• Clean water

– 4. Don’t worry too much about predators• Occasional shark or cougar attack

Human Population Growth Problem?

• Benefits of Population Growth??

• Disadvantages of Population Growth??

Human Numbers Through Time

• http://www.globalchange.umich.edu/globalchange2/current/lectures/human_pop/human_pop.html

•http://www.youtube.com/watch?v=4BbkQiQyaYc

Where is Human Population Growth Occurring?

• Most population growth is occurring in developing countries.

Potential Problems With High Human Population Growth Occurring in Developing Countries

• Environmental problems– Most developing countries located in the tropical

regions– Habitat destruction, overharvesting, and pollution

can cause extinction in the two most diverse ecosystems on the Earth• Tropical Rainforests• Coral Reefs

Deforestation in Borneo

Hunger

Food-related Problems?

Childhood Obesity in the USA

Weight Loss Products

• Weight Loss is a 60 Billion Dollar industry in the USA

Pudgy Pets

Access to Freshwater

World Poverty

Child Labor

Urbanization

Urbanization- India

Photo by Honey Blakeman

Human Population Growth

• Human populations have basically stabilized in developed countries but are still increasing in developing nations

• Why??

Demographic Transition

Demographic Transition

• Pre-industrial societies– High per capita death rates offset by high per capita birth

rates• Slow population growth

• Transitional societies– Per capita birth rates have remained high while per capita

death rates have fallen• Rapid population growth

• Post-industrial societies– Low per capita death rates and per capita birth rates

• Slow population growth

What Causes Per Capita Birth Rates to Decline in Industrialized Societies?

Literacy Rate vs. Birth rate

Worldwide Literacy

Fertility Rate vs GDP

What Will Happen to Human Population Size in the Future???

• Human demographers predict that once all countries have completed the demographic transition that Earth’s population will stabilize.– When and how large?

Factors Increasing Mortality RatesHIV/AIDS

HIV in Africa