Lecture 2_Population Growth and Broader Perspective_final

8/14/2019 Lecture 2_Population Growth and Broader Perspective_final

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EnvironmentalGeology

Dr Amanda DiochonDepartment of Geology


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Learning Outcomes (Part I)

Describe the Earth as a system, our roleand effectsExplain the concept of exponentialpopulation growth in the context ofgeologic hazards and resource

consumptionDefine sustainability in terms of humanimpact on the biosphere

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Earth as a System

Constantly changingand evolvingPrinciple ofenvironmental unityNeed to understandEarth from systemsperspective

Makes us goodstewards

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Population Growth

Linear Added, straight line

Slow and steady

(Non-linear)Exponential

Multiplied, nonlinearIncreases greatly overtime


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Population Growth and DoublingTime

Growth rate of 1%would suggest adoubling time of 100years (1% per year x100 yrs = 100%)

rule of 70 is a betterapproximation:

Population doubling time= 70 / growth rate (%)

So 2% growth rate =35 yr doubling time


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Doubling time & growth rate

Doubling time Growth rate

World 43 yrs 1.6% per yearN America 50 yrs 1.4% per yearS America 41 yrs 1.7% per year

Africa 26 yrs 2.8% per year

Asia 43 yrs 1.6% per yearEurope 346 yrs 0.2% per yearOceania 43 yrs 1.5% per year


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Global Population Growth

~ 200, 000 years 1billion peopleDoubled in 100 years(2 billion)Doubled again in 45years (4 billion)


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Limits to Growth?

Antoni van Leeuwenhoek (1687): upperlimit of 13.4 billionThomas Malthus (1798)

Population growth exponential, foodproduction linear

Food production controls populationCarrying capacity (1970s): finiteresources and computer models


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IPAT Equation

I=P+A+TI=impact

P=population A=affluenceT=technology


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Discussion Question

Can the exponential growth modelaccurately reflect the impact of populationgrowth on the planets resources andenvironmental health? Explain youropinion using at least one example


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Sustainability

Being able to maintain a system orprocess for an indefinite period of timeSustainable society

Lives within the Earths capacity to provideresources for future generations

Natural systems operate this way


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Ecological Footprint

Biologically productive land/sea areaneeded to support lifestyle of humansCertain portion of the biosphere forextracting resources and absorbing waste


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Human Impact and

ConservationDuring the Cretaceous, the extinction rateaveraged one species per 25 years. In 1991more than 1,700 species became extinct asa result of human activity.

Are we exceeding the limits of what theearth can support ?


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Easter Island

Dutch sailors (1722) 2000 inhabitants

Windswept, grasscovered wasteland No trees or native

animals 200 statues with 700 in

various stages ofdevelopment (>80tons, 10 km)


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Easter Island

Developed 400-700 AD 7 000-20 000 people

during peakconstruction

Palm trees and nativeflora 30 000 years prior

Abundant naturalresources

Dolphins, birds, nuts,timber


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What Happened?

800 AD charcoal1400 AD palms

extinctNo birds or dolphinsin diet after 1500 ADDeforestation andecosystem services

Food and watershortages

Collapse


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Small scale example of current

society? Not just aboutcaring. . .need afundamental

understanding ofhow the worldworks


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What could or should be doneto remedy the environmental

problems associated with such alarge human population?

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Describe the Earth as a system, our roleand effects

Explain the concept of exponentialpopulation growth in the context ofgeologic hazards and resource


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Learning Outcomes (Part II)

Describe our solar system and the size ofthe Earth relative to the solar system,

galaxy and universeUnderstand how the nebular hypothesisexplains the formation of the solar system

and the orbital characteristics of theplanets and moons

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Space?

Astronomicenvironment has

huge influence on theEarth systemSuns energy Moons gravitational

fieldOther planets

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The Solar System


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The Solar System

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The Sun

Average starNuclear fusion ofhydrogen and heliumto produce energyHot dense centersurrounded by anouter, less denseatmosphereReleaseselectromagneticradiation

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Pluto

Demoted as a planet in 2006

Rocky, cold and small

Very far away, last in solar system


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The Moon

Earths only satellite Gravity controlstides

Important for coastalprocesses

Gravity alsominimizes thewobble of the Earth


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Solar System: Observations

Formed around 4.6 billion years ago(common origin of bodies)Planets revolve around Sun incounterclockwise direction and haveregular, circular orbitsSun and most planets (except Venus) spin

on their axes in a counterclockwisedirection; Moons same

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Nebular Hypothesis


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Nebular Hypothesis and Our

Moon

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How Reliable is NebularHypothesis?

Most bodies rotate andrevolve counter-clockwise

All bodies in same plane withsolar equatorMost craters occurred earlyin the solar systems historySolidification around sametime

Accretion disks have beenfound around other stars(see photo)

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New stars forming in the gas and cloudsof the Eagle Nebula as seen from the

Hubble space telescope


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Other Stars in

the UniverseOur galaxy is theMilky Way

Most bright points inthe night sky aregalaxiesThe Big Bang Theoryexplains how theuniverse was formedfrom a centralexplosion

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Other Stars in the Universe

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Next Class

Finish Up Earth from a Larger PerspectiveStart Earth MaterialsWritten assignment 1 due at the beginningof class

Lecture 2_Population Growth and Broader Perspective_final

Documents

Transcript of Lecture 2_Population Growth and Broader Perspective_final