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)

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• 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 GROWTHSince 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 cultivateLand 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 yearsMany 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 Israeli-occupied 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 RateGrowth 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.