ERAs 7 and 8 Overview: TWENTIETH CENTURY 2 HUMANS AND THE EARTH - PowerPoint PPT Presentation

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ERAs 7 and 8 Overview: TWENTIETH CENTURY 2 HUMANS AND THE EARTH

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Title: ERAs 7 and 8 Overview: TWENTIETH CENTURY 2 HUMANS AND THE EARTH


1
ERAs 7 and 8 Overview TWENTIETH CENTURY (2)
HUMANS AND THE EARTH
How did human relations with the environment
change in the 20th century?
Day 3, Session 3B Craig Benjamin
How important are environmental issues today?
What is Gaia? Why should humans care about Gaia?
2
Humans and the Environment
  • Most history is about humans and human societies
  • So it is easy to forget
  • that humans are just one part of a biosphere
    which contains perhaps 100s of millions of other
    species
  • that human life is supported by the rest of the
    biosphere
  • As a result of the changes of the 20th century,
    our species is now having a significant impact on
    the entire biosphere

www.geog.uni-heidelberg.de
3
In the 20th century, environmental change may
have been the most important phenomenon of all
  • John McNeill Something New under the Sun, p.
    4
  • The human race, without intending anything of
    the sort, has undertaken a gigantic uncontrolled
    experiment on the earth. In time, I think, this
    will appear as the most important aspect of
    twentieth-century history, more so than World War
    II, the communist enterprise, the rise of mass
    literacy, the spread of democracy, or the growing
    emancipation of women.

4
A survey of our changing relationship to the
environment
  • To understand the changes of the 20th century, we
    must go back in time
  • To survey how our relationship to the environment
    changed over 250,000 years

5
Pt. 1 Humans begin to leave their mark on the
planet
  • We are different from other animals because of
    collective learning
  • Unlike other animals, we slowly change the way we
    relate to the environment
  • These changes became apparent even in the
    Palaeolithic Era

Paleolithic Cave Paintings, Chauvet, France
www.mediacritica.net
6
The difference between humans and apes
Savanna lands of Africa our original home
www.findercreations.us
  • Chimpanzees
  • like most animals, chimps have stayed in the
    environment in which they evolved
  • using technologies that have hardly changed
  • Humans
  • evolved in the savanna lands of Africa
  • but, through collective learning, they have
    developed new ways of relating to the environment
  • which has allowed them to move into new
    environments

7
Migrations Adapting within Africa
Learning to live in deserts
Learning to live in tropical forests
The human homeland Savanna lands
8
Evidence of New Technologies
McBrearty Brooks, The Revolution that wasnt,
2000
9
New Technologies meant control over more energy
and resources
  • Each new technology gave humans control over
  • More resources
  • More energy
  • Increasing control of resources allowed human
    numbers to grow, until began to have an impact on
    their environment, and other species
  • Evidence of our impact on other species during
    the Palaeolithic era comes from
  • studies of
  • Fire-stick farming
  • Megafaunal extinctions

10
Controlling the energy of fire Firestick farming
Australian aborigines fired the land to
increase productivity for perhaps 60,000 years
By doing so, they transformed the landscapes
environment of an entire continent
Fire-stick farming was also practiced by
foragers in Eurasia and the Americas
11
Controlling food stocks Megafaunal extinctions
c. 60 species of Australian megafauna went
extinct after humans arrived
Similar extinctions occurred in Siberia the
Americas
12
Pt. 2 The Agricultural Revolution
  • How does farming increase the energy available
    to humans?

www.historyforkids.org
13
Most of the energy that supports life on earth
comes from the Sun
14
Through photosynthesis, plants capture some of
the energy in sunlight, and store it in their
bodies
15
The Food Chain
Lions are rarer than antelopes because by this
stage in the food chain theres not much energy
left
16
Farmers and the Food Chain Farmers divert
energy to human use
Farmers remove crops they dont want
(weeds) animals they dont need (pests)
Result? Less food energy is produced But the
farmers get almost all of it
X
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17
Agriculture the Environment
  • When humans started to farm, their impacts on the
    environment increased in scale and variety
  • Population increase human numbers rose faster
  • Domestication Farmers altered some of the
    animals and plants around them through
    domestication
  • Transforming landscapes Farmers also altered the
    landscapes around them
  • Ploughing fields and weeding to remove unwanted
    plants
  • Killing off unwanted animals such as rats and
    wolves
  • Diverting rivers
  • Clearing forests
  • Cities The first cities were entirely
    constructed environments. Humans were beginning
    to reshape the environment.

18
Environmental impacts of the agricultural
revolution
19
As Farming SpreadHuman Impacts Increased
  • Over 10,000 years,
  • Agriculture spread over most of the world
  • Human populations rose by about 25 times (from c.
    10 million to c. 250 million)
  • The amount of energy
  • controlled by humans
  • increased
  • The impact of humans
  • increased!

www.tpwd.state.tx.us/.../ pages2/page26.html
20
Some examples 1) Irrigation
  • Through irrigation, farmers divert rivers to
    their own use
  • Just as they divert energy to their own use by
    growing crops

21
But The downside of irrigation
  • Over-used, irrigation can leach nutrients from
    the soil
  • Can use up precious supplies of water
  • Can leave deposits of salt which destroy the
    soils productivity Salinization!
  • Several civilizations declined because over-use
    of irrigation destroyed farm land
  • Including Sumer (c. 2,000 BCE)
  • Mayan civilization (c. 800 CE)

22
Ruined land and fisheries of the Aral Sea.
Satellite Image of one of the worst ecological
disasters of the 20th century
23
Example (2) Farming and over-grazing of
fragile soils
Desertification in Africa
  • Over-farming and over-grazing can destroy fragile
    soils
  • Leading to desertification
  • A big problem in China, Africa, Australia and the
    USA

www.acca21.org.cn/
Desertification in China
24
Over-farming and Desertification
A Modern example Ruined land in the Sahul
region, south of the Sahara
25
Example (3) Deforestation
  • Farmers also clear forests so they can farm
  • Result?
  • Much less photosynthesis occurs
  • But farmers can now use the products of
    photosynthesis
  • (i.e. we can eat corn, but we cant eat trees)
  • By 1850 c. 25 of all the worlds forests had
    been cleared
  • Today c. one and one-half acres of rainforest are
    being cut down or burned every second!

26
The Amazon Rain ForestBefore and After Clearance
www.chagres.com/AE-3.html
27
Pt. 3 The Modern Revolution
  • The Modern Revolution increased
  • Human population growth
  • The amount of land used for farming, roads and
    cities
  • The amount of water used for irrigation
  • The amount of energy used
  • It sharply increased human impacts on the
    environment

www.nipponroad.co.jp
28
In the 20th Century
  • Human impacts on the environment increased faster
    than every before

www.tnimc.org/feature
29
Some ecological changes of the 20th century
  • Paul Kennedy introduction to McNeill, Something
    New Under the Sun
  • The worlds population quadrupled The global
    economy expanded 14-fold, energy use increased 16
    times, and industrial output expanded by a factor
    of 40. But carbon dioxide emissions also went up
    13-fold and water use rose 9 times.

30
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31
More humans meant humans used more resources
  • The numbers of humans rose
  • But so too did the amount consumed by each person!

www.earthdayenergyfast
32
Consumption 1
33
Consumption 2
34
In some areas, consumption has reached critical
limits
  • Fresh water
  • Fish
  • Grazing land
  • Crop land

35
Increasing Energy Use
  • John McNeill Something New under the Sun, p.
    15
  • We have probably deployed more energy since 1900
    than in all of human history before 1900. My
    very rough calculation suggests that the world in
    the twentieth century used 10 times as much
    energy as in the thousand years before 1900 A.D.
    In the 100 centuries between the dawn of
    agriculture and 1900, people used only about
    two-thirds as much energy as in the twentieth
    century.

36
Satellite images of the earth at night In no
previous century would so much of the world have
been lit up. Can you tell from this map which
regions use the most energy?
www.livejournal.com
37
Transforming landscapesEngineering on an
entirely new scale
  • Humans have transformed environments on an
    unprecedented scale

www.transa.de
38
The Three Gorges Dam, China
The artificial lake behind the dam will displace
more than 2 million people
39
Diamond Mining in W. Australia
Diamonds are for ever not the landscapes they
come from!
40
The human impact on other species
  • As humans used more resources and energy
  • Less land, energy, and food was available for
    other species
  • So
  • As human numbers rose
  • The numbers of many other species fell
  • Nearly half of the world's species of plants,
    animals and microorganisms will be destroyed or
    severely threatened over the next quarter century
    due to rainforest deforestation alone
  • We are losing 137 plant, animal and insect
    species every single day due to rainforest
    deforestation (equates to 50,000 species a year)

41
Extinctions
42
Reconstruction of a Moa
www.onjix.com
Many species of flightless birds lived in New
Zealand before humans arrived, just over 1,000
years ago. Now, none survive.
www.usd.edu
43
Gorillas are close to extinction
Today, there are only 325 mountain gorillas and
150-200 Cross River gorillas left!
news.nationalgeographic.com
44
Endangered environments include coral reefs
A coral reef in the Red Sea
45
The pace of extinctions today
  • In the last billion years, there have been five
    or six periods of very rapid extinctions
  • One of those periods is today the cause is the
    activity of humans
  • The last great extinction
  • event was caused by the
  • asteroid that wiped out
  • most species of dinosaurs

www.ljn.brown.btinternet.co.uk
46
More humans and more consumption also
means more waste products
  • The waste produces from human societies pollute
  • The water
  • The air
  • The land

www.co.tompkins.ny.us/ solidwaste/
47
Some pollution affects small areas
In the 1970s, inhabitants had to evacuate Love
Canal, near Niagara Falls, as their lives were
threatened by toxic waste from a nearby waste
disposal facility.
www.michiganlcv.org/ about.htm
Pollution in Lake Michigan, summer 2006
48
In the 20th century, for the first time, human
pollution began to affect the entire planet
  • Global Warming
  • Increasing use of fossil fuels
  • Coal, oil, natural gas
  • Means more and more carbon
  • dioxide is pumped into the atmosphere
  • Which is leading to global warming
  • Perhaps the most serious environmental crisis you
    and your children will face!

49
Fossil Fuels and the Atmosphere
GR Press March 21 2005 Carbon dioxide, the gas
largely blamed for global warming, has reached
record-high levels in the atmosphere
GR Press Nov 10, 2006 Earth climate changes
from human activity are occurring particularly
intensely in the Arctic, evidenced by
widespread melting of glaciers
50
Increase in Carbon Dioxide in the Atmosphere
since Industrial Revolution
In two centuries, Carbon Dioxide levels almost
doubled
51
Should We Worry?
  • The Gaia Hypothesis
  • The British scientist, James Lovelock, has argued
    that the entire biosphere can be thought of as a
    single, complex system
  • He called that system Gaia, after the Greek
    goddess of the Earth
  • Gaia supports all life on earth


James Lovelock in his Lab
52
What Gaia Does
  • Lovelock pointed out that the activities of
    living creatures
  • Have created an oxygen rich atmosphere
  • Have made many rock forms
  • Have shaped the earth and seas in profound ways
  • He argued that, in a sense, living organisms
    maintain the earth as a habitable environment
  • But to do so, they have to work together!

53
Is the Earth a Single Organism?
James Lovelocks Gaia hypothesis suggests that
living organisms are so intertwined and so
interdependent that they function almost like a
single, huge life form.
54
Human Impacts on Gaia
Cancer cells in human lungs
oceanexplorer.noaa.gov
  • From the point of view of Gaia, humans are like
    cancer cells
  • Growing too fast
  • Taking too many resources
  • Starving other parts of Gaia of the energy and
    resources they need to survive
  • How much stress can Gaia take?
  • Most worrying of all, if change comes, it could
    be very sudden
  • Like the onset of disease

55
Humans and Planet Earth
Humans are now so powerful that they can
transform the earth For better or worse!
56
What does the future hold for human beings?
  • And what is your role in determining that future?
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