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“People are everywhere. Some People say that there are too
Many of us, but no one Wants to leave.”
According to your book, There are over 6 billion people
In the world. (2000)
World Population Clock
As we’ve said before, many Scientists think that this rapid Growth is a fundamental cause
Of many environmental problems.
Usually, an organism can Produce many more offspringThan can survive to grow up
And reproduce.
For example, a herring may layUp to 1 000 000 eggs a year.
But each population has a Characteristic maximum
Growth rate.
This maximum growth rate, Also known as biotic potential,
Is the rate at which a populationWould grow if every new
Individual survived to adulthoodAnd reproduced at its
Maximum capacity.
Given the right conditions, anyPopulation can grow
Exponentially.
An exponential curve, or A “J” curve.
The biotic potential for humansIs around 6% per year, but For rats it is 1.5 % per day,And for bacteria it is 250%
Per hour!
However, these are under the Right conditions, there are Limits on how a population
Can grow.
As a population grows, it Consumes greater amounts
Of resources.
Eventually a resource will runOut. The resource that limits
A population from growingIs called a limiting resource.
Limiting resources for animalsInclude food, water, shelter,
And nesting sites.
For plants; water, sunlight, And certain nutrients are
Limiting resources.
When a population increases,Its individuals compete forThese limiting resources.
The combined effect of all theFactors that limit population
Size is called Environmental resistance.
The population eventually Ceases to grow as it reaches,
And often exceeds, itsCarrying capacity.
The carrying capacity is the Maximum population size
An environment can support For a long time.
The earth’s human populationIs increasing by about 149
People per minute, 8956 eachHour, 214934 each day,
And 78 million each year!
Like a single ecosystem,The earth has a carrying capacity.
The issue is that no one knows What that carrying capacity isBecause of advancements in
Technology and society.
Throughout about 99% of ourHistory, humans were hunter-
Gatherers.
Or people who obtain food byHunting, fishing, and
Gathering wild plants.
Today, very few people surviveThat way.
It is estimated that only about1 million people were on the
The entire earth when humansWere hunter-gatherers.
Then the agricultural revolutionTook care of all that and
The population grew to about1 billion around 1800 AD.
Agriculture allowed peopleTo produce more food than theyCould ever get by gathering it.
So farming increased the Carrying capacity of the land.
So after thousands of years ofSlow growth, the population of
The earth doubled by 1930.
Then add another billion by 1960,Another in 1975, another in 1987
And yet another in 1999.
Why so fast?
Simple, people were living longerBecause of sanitation,
Nutrition, and medicine.
Although it seems that thereIs an explosion (and there is
In certain places), in industrialcountries, it has slowed.
This is because birth rates haveSlowed since there is no need
for extra kids to work the farms.
There is a theory to support this…
It is the theory of demographicTransition by Frank Notestein.
This states that the economicAnd social progress of the Industrial revolution affects
Population growth in 3 stages.
1.Both birth and death ratesAre high in preindustrial
Societies, and the populationGrows slowly, if at all.
2. When health care improves,The population size increases.
The birth rate stays high, and People are living longer, so The population grows by 3%
Each year.
3. Birth rates fall until they areRoughly equal to death rates,
And population growth Slows and stops.
Why do birth rates fall?
Women usually get a better Education, and parents see kidsNot as workers, but as a huge
Financial responsibility.
Some countries are stillIn the second stage.
Population pyramids
The united nations and the World bank have determined
That fuel wood is a Limiting resource in many
Developing countries.
Without the ability to have a Fire to cook their food,
Many people suffer from Malnutrition or even starvation.
People in industrialized Countries feel safe drinking
Water from the tap,However many people in
Underdeveloped countries Die from parasites by drinking
Unboiled water!
Each year about 10 million peopleDie of diseases contracted
From dirty water.
As a country’s population grows,More and more people move
Toward The cities searching for work.
The united nations projects thatUp to ¼ of the world’s
Population will be homelessBy 2020.
Environmental refugees are People who are driven from
Their homes by severeEnvironmental damage.
The millions of people who leftTheir homes in Kenya, Somalia,
And Ethiopia in search of Food are also environmental
Refugees.
Slowing the growth of the Human population is considered
Vital to future peace and Prosperity throughout the world.
In order to be rich…SEE THE SIGN ON THE WALL!
Developed countries contain Only 21% of the world’s
Population, but they consume 75%Of its energy, produce 70% of
The global CO2, and 90%Of the global hazardous waste.
To achieve a sustainable future,The problems of overpopulationAnd overconsumption must be
Solved.
