Population - out of control Lecture1 Frontiers in Biology Some material from 2/current/lectures/human_pop/human_pop.html

Outline for today Population Lecture Break Population Video (56 minutes) Break Group discussions and question formulation towards exams

Overview A. Population of what? B. Human population milestones C. Major eras of human history D. Population growth in historical perspective E. Bacterial growth F. Easter Island example

Population - which population? Most are equating the term population with that of the entire human race However, one could apply the term to any community of individuals Plants Bacteria Polar Bears Dogs in England But, you would be right in this instance. We are going to explore just human population growth

Man evolves According to the latest theories, man evolved from a common man/chimp ancestor some 5 million years ago in Africa Ancient man split into a number of species that came and went Around 200,000 years ago he began his migration ‘Out of Africa’

Major Milestones in Human Population Numbers NumberYear Attained 1 Billion1830 (5 million years) 2 Billion1927 (97 years) 3 Billion1960 (33 years) 4 Billion1974 (14 years) 5 Billion1987 (13 years) 6 Billion1999 (12years) Billion Billion2008 (9 years?)

Major eras in human history Pre-agricultural era (beginning~8000 B.C.) Relied on what could be caught Agricultural era (~8000 B.C ) Began to settle down and harvest food Industrial era ( present) Technology brought food to the table

The human growth curve

This curve is said to be a “J” curve - because it looks like the letter J! Wars and plagues have little impact on the upward slope of this curve! New people are entering the world at about one every 3 seconds now!

Of the 6.6 billion people Half live in poverty One in five are severely undernourished The rest are living well!!! Also, half now live in urban areas

How fast can populations grow? We can learn from microbiology… If we inoculate a flask of broth with a single bacteria at midday Then, at 12:20 there will be two bacteria - (because this bacteria can divide every 20 minutes) At 1:00 pm there will be 8 At midnight there will be 68,719,476,736 (over 68 billion cells)

Bacterial grow rates Remember that these bacteria are growing under ideal conditions Each cell always divides into two others There is no death of any cell There is always food for the cells There is always space for the cells to grow We would expect the population of our flask to take over the entire planet very quickly thereafter! Something is going to prevent this. What?

But first… Easter Island example

Real Example of Human Population Woes In 1722, on Easter morning, an English explorer landed on Easter Island in the Pacific He found a few hundred hungry people hiding in caves He saw no trees and burned grasslands He saw 100’s heavy rock statues lined up on the shores Cpt. James Cook landed on the same island two years later - he saw 4 canoes and the statues tipped over on spikes What happened here?

Easter Island Paradise The island is just 165 sq km in size Around 1600 years ago settlers from other Pacific islands came to this paradise Dense forest and fertile soils Built canoes from large trees and cooked fish with the wood Cleared forest to plant crops Had many children

Paradise gone! Mid 1400’s - 10,000 to 15,000 were living on the islandMid 1400’s - 10,000 to 15,000 were living on the island Crop yields had declinedCrop yields had declined Fish had vanished from costal watersFish had vanished from costal waters Erosion and harvesting had depleted the soilErosion and harvesting had depleted the soil All birds had been eatenAll birds had been eaten People were raising rats as foodPeople were raising rats as food They erected stone symbols to the GodsThey erected stone symbols to the Gods

Paradise lost! By 1550’sBy 1550’s No one fished offshoreNo one fished offshore No one built canoes - no suitable treesNo one built canoes - no suitable trees No fire wood remained, as all the trees were felledNo fire wood remained, as all the trees were felled They then turned to their last source of protein -They then turned to their last source of protein - each other - cannibalism!each other - cannibalism!

Decline The government collapsedThe government collapsed Small gangs began to fight each otherSmall gangs began to fight each other They burned grasslands to prevent surprise attacks and began hiding in cavesThey burned grasslands to prevent surprise attacks and began hiding in caves Winners ate losersWinners ate losers They toppled each others statues onto spikesThey toppled each others statues onto spikes

Lessons learnt The Easter Island society flourished when resources were abundant - “J” curve That same society fell apart when the resources became limiting The lesson here is that all populations are governed by the same principles of growth and sustainability no matter how large or small, or who ECOLOGY

Back to our bacteria The bacteria in our flask are no different Let the flask equate to Easter Island The broth is the food supply The bacteria are the people When we left them they were following what is called the “j” growth curve - everything is great! Eventually something has to give The bacteria can no longer grow exponentially Their growth will follow the following curve as time passes…

Population Change If the number of deaths is balanced by the number of births then there is no net change in the size of the population If births exceed deaths = population increases If the deaths exceed births = population declines The above assumes that there is no migration of individuals into or out of the community.

Exponential growth As long as the rate of births is greater than the rate of deaths the population will grow exponentially As we know from models, no population can maintain the exponential growth curve indefinitely, and that would include the human population

Human births We now know that there are 4 factors governing population size; Fertility (Birth rates) Mortality (Death rates) Beginning population size Time Current human growth rate is ~1.3% per year = we are adding ~90 million new babies to the planet each year It has been higher ( it was 2.1%) We need to reduce fertility globally - it takes time!

Differing fertility rates

Demographic Transition Developed countries have undergone a process called Demographic Transition - where their population growth has stabilized Developing countries of the World have not reached this point yet What is the demographic transition…

Medicine Hygiene Agriculture Urbanization Migration to US

Human population growth We, as a whole, are growing at an exponential rate What will give out first? Food Water Space Environment Lack of other resources

Interlinked We need space to grow food, but we also need that same space for living We need fresh water to drink, but we also need that water for irrigation We need a healthy environment but we are polluting the same with our self centered practices Data show that the rate of fertility and development are linked… this may be the silver lining

When will the human race hit the stationary phase? Human behavior and practices need to change or we will have to deal with the stationary phase shortly Disease Shortages (famine) War Remember the Alamo Easter Island!!!

When will the human race hit the stationary phase? One can use population-age pyramids to estimate future growth rates

What is the future? The video addresses this and has some answers. Each student needs to watch and answer the following questions, Which is the population of the US today? Which three countries did the video focus upon? How many children did the wife of the Raja (Shah Jahan) who built the Taj Mahal have? Remember the shape of the population pyramid for each country mentioned please for the discussion to follow