Transcript Chapter 13: Human Population

Chapter 12 and 13 “People and
Their Needs” and “The Human
Popluation”
Pgs 186-213 (chapter 12 and 13)
12.1 A Portrait of Earth
• All systems on Earth are connected.
– Ex: Movement of continents change ocean
basins which changes circulation of sea water.
– This leads to change in climate and thus change
in ecosystems.
• Matter and Energy
– Matter = closed system
• Earth does not gain or lose matter.
– Energy = open system
• Receive energy from the sun and radiate energy into
space as heat.
• Energy absorbed powers Earth’s systems
(movement of ocean currents, formation of clouds,
growth of animals, etc)
A Global Perspective
• The Gaia Hypothesis states that:
– Earth functions as a living organism,
all aspects are connected
– Life affects the environment at a
global level
– Life manipulates the environment
for the maintenance of life
– Earth is capable of physiological self
regulation (maintains homeostasis)
www.josephinewall.co.uk/sadness.html
• Gaia Hypothesis: Earth is a single, living
organism that regulates itself to maintain
life.
– James Lovelock
• Debate:
– Do you agree with the Gaia hypothesis? Why
or why not (provide reasons for your answer)?
Check for Understanding:
1. How could species in the rainforest canopy
be affected by a moving continent?
2. Describe how Earth is a closed system
with respect to matter, and an open system
with respect to energy.
12.2 Human Societies
• Hunter-Gatherer Societies: people gather
natural food, hunt, and are nomadic.
– Move from place to place.
– Small impact on environment due to low pop.
density and allow environment to regenerate.
• Agricultural Societies: crops are grown and
people have specialized roles.
– Farming caused: 1.) people to settle in one
place and 2.) divide work among people.
– Increase in food supply due to plow and
domestication of animals.
– Harmful to environment: increased logging,
overgrazing, poor farming destroyed soil, little
time for environment to regenerate.
• Industrial Societies: production of food and
other products is performed by machines,
demanding large amounts of energy and
resources.
– Started in 1700s.
– Severe environmental damage: pollution, raw
materials running out, we affect composition of
atmosphere and climate.
Check for Understanding:
1. What technological advance increased
food production in all agricultural
societies?
2. How do an industrial society and an
agricultural society differ?
12.3 Sustainable
Development
• Reduce demand, recycle, conserve, use
resources wisely.
• 3 Basic Components:
– 1. Resources are limited and are not all meant
for human consumption.
– 2. Humans are part of nature and obey natural
laws.
– 3. Human success is living in harmony with the
natural world.
• Renewable Resource: resource that
regenerates quickly.
• Nonrenewable resource: resource that does
not regenerate quickly.
Chapter 13: Human Population
13.1 History of Human Population
13.2 Growth and Changing Needs
13.3 Challenges of Overpopulation
THOMAS MALTHUS
• 230 years ago (1798)
Thomas Malthus
published An Essay on
the Principle of
Population.
• Stated the human
population grows
geometrically
(2,4,8,16,32,64…)
while the resources to
support it grow
arithmetically
(1,2,3,4,5,6…).
Thomas Malthus
• The population will
outgrow the supply of
food that is available.
• Predicted that
population growth
would destroy the land,
cause famine, disease
and war.
Malthus’ Population Theory
• Malthus presented his
theory in response to the
“frontier ethic” that said we
controlled our environment
and owned everything in it.
• Improvements in agriculture
and the industrial revolution
prevented Malthus’ theory
from happening. But his
ideas are still applicable
today.
HUMAN POPULATION GROWTH
Since 1960, several factors have dramatically
reduced infant and child mortality throughout the
world:
•use of DDT to eliminate mosquito-borne malaria
• immunization against cholera, diphtheria, polio,
smallpox and other diseases
•discovery of antibiotics
The "Green Revolution" greatly boosted food output:
• development of new disease-resistant rice, wheat
and corn and other staple
• the use of fertilizers and more effective farming
methods.
These changes have contributed to a dramatic
increase in human population growth rates.
The Earth's population reached 6 billion in September, 1999.
It will increase this decade by another billion, the fastest
population growth in history.
It was only 2 billion in 1930.
Every second, three people are added to the world.
Every day a quarter of a million (2 times the population of
the city of Irvine) are added to the world.
 Every year, about 87 million people are added to the world.
In the next 2.5 years, the equivalent of the current U.S.
population will be added to the planet.
In this decade one billion people (the population of China)
will be added.
U.S. National Academy of Sciences and British Royal Society
state that population is growing at a rate that will lead to
doubling by 2050.
CARRYING CAPACITY OF THE EARTH
The earth cannot continue to support a massive population
growth indefinitely.
Ecologists have often made use of the concept of carrying
capacity
Measuring the pressures that rapidly increasing populations put
on their environments.
Carrying capacity is the largest number of any given species
that a habitat can support indefinitely.
Another way of looking at global capacity is to examine the
degree to which humans already dominate the Earth's
ecosystems.
we have already transformed or degraded 39-50% of the Earth's land surface
(agriculture, urban).
we use 8% of the primary productivity of the oceans (25% for upwelling areas
and 35% for temperate continental shelf areas).
we have increased atmospheric CO2 concentration by 30%
we use more than half of the accessible surface fresh water
over 50% of terrestrial nitrogen fixation is caused by human activity (use of
nitrogen fertilizer, planting of nitrogen-fixing crops, release of reactive
nitrogen from fossil fuels into the atmosphere)
on many islands, more than half of plant species have been introduced by
man; on continental areas the fraction is 20% or more
about 20% of bird species have become extinct in the past 200 years, almost
all of them because of human activity
Fisheries: 20% increase in fish catch before the alarming decline in
Atlantic Cod and other major fisheries.
Nine of the seventeen major fishing areas of the world are in serious
decline, and all of them have either reached or exceeded their
limits.
Cropland. Between 1980 and 1990, cropland area worldwide
expanded by 2%.
It expanded quickly, given that the areas already taken are the ones
that are easiest to cultivate
Land is being rapidly lost to various kinds of development.
Rangeland and Pasture. Similar calculations show a decline of 22%
(and about 20% of this area is declining in productivity because of
overgrazing).
Forests. Due to a combination of deforestation and population
growth, forest area is decreasing by 30%.
Increase in population population leads to:
•increased habitat loss
•pollution problems (both local and global)
•high energy use
Most of the 3.6 billion people added to the world between
now and 2030 will be born in the developing nations, where
the overall growth rate is 2.1% per year.
The top 3 fastest growing continents are Africa, South
America and Asia:
•Kenya, fastest growing, doubling time of 20 years
•Latin America will double in 30 years
•Asia will double in size in 36 years
Many regions are already exceeding their carrying capacity;
(cannot produce enough food to support their populations).
Equatorial Africa is undergoing very rapid desertification and is
unable to support the population presently living there.
Sub-Saharan Africa has the highest birth rate, the highest rate
of population increase and the lowest use of contraceptives of
any major region in the world.
Average annual population increase in sub-Saharan Africa is 3
percent, ranging from 2.5 percent to 3.8 percent.
Food supply increases by only 1%.
12 countries of the region, women average more than seven
children per family.
Population of sub-Saharan Africa will double by 2016.
Another area with very rapid population growth is Israelioccupied Gaza --with a fertility rate of 7.9 children per woman,
the highest in the world, and annual population increase of 4
percent, also the world's highest.
It is expected to double in population by 2007.
Other Middle Eastern countries where women have seven or
more children are Iraq, Syria and Yemen.
13.2: Growth and Changing Needs
Doubling Time: the length of time required for
a population to to double
Growth Rate: Subtract the death rate (per 1000 people)
from the birth rate (per 1000 people)
Demography: The science of changing vital statistics
in a human population.