Title: ERAs 7 and 8 Overview: TWENTIETH CENTURY 2 HUMANS AND THE EARTH
1ERAs 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?
2Humans 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
3In 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.
4A 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
5Pt. 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
6The 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
7Migrations Adapting within Africa
Learning to live in deserts
Learning to live in tropical forests
The human homeland Savanna lands
8Evidence of New Technologies
McBrearty Brooks, The Revolution that wasnt,
2000
9New 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
10Controlling 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
11Controlling food stocks Megafaunal extinctions
c. 60 species of Australian megafauna went
extinct after humans arrived
Similar extinctions occurred in Siberia the
Americas
12Pt. 2 The Agricultural Revolution
- How does farming increase the energy available
to humans?
www.historyforkids.org
13Most of the energy that supports life on earth
comes from the Sun
14Through photosynthesis, plants capture some of
the energy in sunlight, and store it in their
bodies
15The Food Chain
Lions are rarer than antelopes because by this
stage in the food chain theres not much energy
left
16Farmers 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
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17Agriculture 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.
18Environmental impacts of the agricultural
revolution
19As 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
20Some examples 1) Irrigation
- Through irrigation, farmers divert rivers to
their own use - Just as they divert energy to their own use by
growing crops
21But 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)
22Ruined 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
24Over-farming and Desertification
A Modern example Ruined land in the Sahul
region, south of the Sahara
25Example (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!
26The Amazon Rain ForestBefore and After Clearance
www.chagres.com/AE-3.html
27Pt. 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
28In the 20th Century
- Human impacts on the environment increased faster
than every before
www.tnimc.org/feature
29Some 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(No Transcript)
31More humans meant humans used more resources
- The numbers of humans rose
- But so too did the amount consumed by each person!
www.earthdayenergyfast
32Consumption 1
33Consumption 2
34In some areas, consumption has reached critical
limits
- Fresh water
- Fish
- Grazing land
- Crop land
35Increasing 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.
36Satellite 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
37Transforming landscapesEngineering on an
entirely new scale
- Humans have transformed environments on an
unprecedented scale
www.transa.de
38The Three Gorges Dam, China
The artificial lake behind the dam will displace
more than 2 million people
39Diamond Mining in W. Australia
Diamonds are for ever not the landscapes they
come from!
40The 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)
41Extinctions
42Reconstruction 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
43Gorillas are close to extinction
Today, there are only 325 mountain gorillas and
150-200 Cross River gorillas left!
news.nationalgeographic.com
44Endangered environments include coral reefs
A coral reef in the Red Sea
45The 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
46More 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/
47Some 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
48In 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!
49Fossil 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
50Increase in Carbon Dioxide in the Atmosphere
since Industrial Revolution
In two centuries, Carbon Dioxide levels almost
doubled
51Should 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
52What 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!
53Is 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.
54Human 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
55Humans and Planet Earth
Humans are now so powerful that they can
transform the earth For better or worse!
56What does the future hold for human beings?
- And what is your role in determining that future?