population growth and its impact on the biosphere · 2005-05-19 · 1 population growth and its...

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Population Growth and its Impact on the Biosphere

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Source: Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat, World Population Prospects: The 2002 Revision and World Urbanization Prospects: The 2001 Revision, http://esa.un.org/unpp, 24 May 2004; 3:16:03 PM.

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Population 1950 - 2050

World PopulationBetween 1850 to 1950

Population doubled from 1.25 billion to approx. 2.5 billion

By 1987 it doubled again to 5 billion6th billion person was expected in October 1999Estimates for next 100 years range from 8 to 14 billion before leveling off

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Mortality rates can play a role in reducing population

HIVAIDSSarsExtreme climate changePollution related illness

World Population

Population IncreaseIncreased life expectancyImproved health careMore skills, ideas and labour required to add to social and economic resources

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Significance

Consequences: Social problems

"...democracy cannot survive over population. Human dignity cannot survive it. Convenience and decency cannot survive it. As you put more and more people into the world, the value of life not only declines, it disappears. It doesn't matter if someone dies. The more people there are, the less one individual matters.“

Isaac Asimov

SignificanceIn several countries around the developing world, abundant natural resources help fuel conflict, …. Prominent examples include Sierra Leone, Angola, Democratic Republic of the Congo, Sudan, and Afghanistan. Conflict has also erupted in several countries where the benefits of mining and logging projects—oil in Columbia and Nigeria, timber and natural gas in Indonesia, and copper in Bougainville/Papua New Guinea—accrue to a small elite while the social and environmental burdens are borne by local communities.—more than 5 million people killed during the 1990's, as many as 20 million driven from their homes, and considerable environmental destruction.

Consequences: Conflicts and Wars

Renner M. (2002) “The anatomy of resource wars” worldwatch paper #162http://www.worldwatch.org/pubs/paper/162/

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Significance

Consequences: Malnutrition

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Pimentel D. , et. al. (1999) Will limits of the earth’s resources control human numbers?, Environment, Development and Sustainability 1:19-39

Foods and feed grains supplied per capita (kg) per year

PovertyApprox. one fifth of the world population lives in absolute poverty

Approx. one billion people

841 million under nourished1.2 billion without access to safe drinking water

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Significance

Consequences: Diseases

Significance

Consequences

Lack of natural resources: Land Water EnergyBiological

Posted on the course website:Pimentel D. et. al. (1999) Will limits of the earth’s resources control human numbers?, Environment,

Development and Sustainability 1:19-39

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Resource DepletionLost of land for agriculture

Best farm land is being developed for urban developmentSoil erosionOver grazingClimate change

Grain Harvest

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Other Population ImpactsConversion of wetlands and valleys

Urban developmentWetlands lost:

Europe ~66%US ~50%ASIA ~25% mangrove swamp

Loss of coral reefs

Hydroelectric dams1950s approx 5,000 dams1980s approx 36,000 dams

Deforestation in Brazil

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Land Conversion

Other Population ImpactsDesertification and soil degradation

Drought caused by land mismanagementNorth Africa 1960 satellite photo

Salt intrusion and soil degradation40% world food production is on irrigated landPoor irrigation practices can lead to increased salt concentrations

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Other Population ImpactsUrbanization

More people living in citiesMore people to feedIncrease pollution

Air, water, soil

Other Population Impacts

Industrializationglobal manufacturing economy

Air, water, soil pollution and ill health

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Significance

Consequences: Social problems

"...democracy cannot survive overpopulation. Human dignity cannot survive it. Convenience and decency cannot survive it. As you put more and more people into the world, the value of life not only declines, it disappears. It doesn't matter if someone dies. The more people there are, the less one individual matters.“

Isaac Asimov

Vague; Not quantified

SignificanceIn several countries around the developing world, abundant natural resources help fuel conflict, …. Prominent examples include Sierra Leone, Angola, Democratic Republic of the Congo, Sudan, and Afghanistan. Conflict has also erupted in several countries where the benefits of mining and logging projects—oil in Columbia and Nigeria, timber and natural gas in Indonesia, and copper in Bougainville/Papua New Guinea—accrue to a small elite while the social and environmental burdens are borne by local communities.—more than 5 million people killed during the 1990's, as many as 20 million driven from their homes, and considerable environmental destruction.

Consequences: Conflicts and Wars

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Impact of Population Growth

Population growth

Urbanization & industrialization

Change in land use and land-cover

Global access

PovertyResource depletionGlobal climate changeResource depletion

Loss of rural landDeforestationDesertificationSoil loss, salinizationLoss of biodiversityLoss of cultural diversity

PollutionAir, fresh water, seas

Socio-economic trend Consequences

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Role of the Engineer

Role of the EngineerUse of problem solving skillsUse of analytical skills – honest broker

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California Population Impacts – Case Study

The Forty-niners (miners)

On January 24, 1848, James Marshall struck gold at Sutter’s Mill on the American River in Northern California.News spread quickly

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The Forty-niners (miners)Water rights “Prior Appropriation and Beneficial Use”.

Prior appropriation refers to the process by which water users acquire ownership of a water right simply by diverting it from a water source and putting it to a "beneficial use."

The Forty-niners (miners)During the 1800s, water uses included mining, ranching, farming, and manufacturing.

Users could divert the water to any necessary location, and could switch uses of the water, as long as all uses remained beneficial.

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Prior appropriation also means:that in times of drought or low stream flows, the oldest water right must be satisfied before junior rights’ holders can divert their water.

For ExampleIf five water users are diverting water from a stream and a drought diminishes the available amount of water, all five individuals do not have to conserve.

The individual with the most senior right can take his full amount, the individual with the second most senior right can do the same, and so on down the line. The individual with the most junior right is probably out of luck, as he can only divert water from what the first four users leave.

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From Mining to Agriculture While most settlers had come for the gold, most failed to strike it rich and therefore turned to farming.

Successful agriculture, however, depends on abundant water, and most areas of the state are quite arid, thus spurring new demand for irrigation.

Government SubsidyNot only did Californians need water, they wanted it as cheaply as possible and turned to government for a subsidy

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1887 Wright ActAuthorized the formation of public irrigation districts

Construction, maintenance, and operation of irrigation projects in these public districts were funded with tax dollars, and the districts were considered political subdivisions of the state.

California Factsagriculture uses 80 percent of the state’s water supply, while cities use about 20 percentin Southern California, population is expected to increase by 43% by 2020, for a total of 22.3 million people. California’s population continues to grow, increasing demand for urban water

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California FactsSouthern California’s two largest water suppliers are:Imperial Irrigation District (IID) Metropolitan Water District (MWD).

Imperial Irrigation Districtirrigation company that delivers 3.2 million acre-foot annually, all of which come from the Colorado River98 percent of water goes to agriculture.

One acres- foot of water is enough water for 2 to 4 houses per year

sells water to farmers at a cost of $14.06 per acre-foot.

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Metropolitan Water Districtconsortium of 27 cities and water agencies that provides water for more than 16 million people in six Southern California counties.In 1997, MWD sold 1.8 million acre-foot, which it received from the Colorado River and from Northern California sources via aqueducts

Metropolitan Water DistrictEach year, MWD spends $12.5 million on water conservation programs, such as water recycling, desalination, and storage programs. These high costs are reflected in the price of MWD’s water: $431 per acre-foot.

(30 times more than IID)

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CaliforniaNo water metersMonthly rate regardless of usage

$17.00 in Seattle area

Right to use as much water as neededFill pools, water lawns, etc.

The Colorado River 1922 Colorado River Compact

According to this agreement, California, Nevada, and Arizona share 7.5 million acre-foot that makes up the lower basin portion of the river.

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The Colorado River In a normal year (a year without drought)

California is entitled to 4.4 million acre-foot Nevada receives 300,000 acre-footArizona receives 2.8 million acre-foot

1.5 million of which the state diverts to Phoenix and Tucson through the Central Arizona Project (CAP) 336 miles of aqueducts

Environmental ImpactsLoss of fish habitat

1980 Chinook salmon listed as an endangered species

Fish restorationDry flows increasedCreation of new fish habitatRestocking program

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Environmental ConflictWater gains for fish have directly translated into water losses for California’s economyAction to protect fish are at odds with drinking water quality

Water pollution is increasing

Six year drought 1987 to 1992 put pressure on fish restoration program

SummaryVirtually all water in California is already spoken for by farms, cities, and environmental interests. With no new sources on the horizon, the challenge becomes one of reallocation.

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SummaryPopulation growth is increasingPressure to balance growth and resourcesMust balance economic, social and environmental issuesneed for political and social change

Engineering ApproachObserving and monitoring real behavior

Quantifying the problem(Parameters with specific ranges)

Defining or modifying mathematical models

Predicting the behavior of parameters

Planning

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Engineering Approach - Example

Average world wide soil erosion: 30 t/ha/yearSoil replacement rate: 1t/ha/year

15% to 30% reduction in world wide food production by 2020

Non sustainable agricultural systems

Learning ActivityTwo species of elephants left on the earth:

African elephantIndian Elephant

Question:If a population of 100 male and female breeding African elephants has unlimited resources, how many generations will it take them to multiply so that their combined total mass equals or exceeds the mass of Earth?

Source:http://www.studyworksonline.com

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Learning Activity

Required data:Earth’s mass: 5.976x1024 kgAverage mass of an African elephant: 7500 kgOriginal populationSize (OPS): 100Net reproductive rate:number of female offspring per female; 6 /per female/ per generation

Reproductive rate; mathematical model

Uncertainty

Initial condition:N1 = 50 females; R = 6 T = 24.45 generations

~ 1467 years

N1 = 55 females; R = 6 T = 24.4 generationsError = 0.2 %

10% uncertainty in OPS:

N1 = 50 females; R = 6.6 T = 23.2 generationsError = 5 %

10% uncertainty in R:

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Basic concepts (Reproductive rate, mathematical model, Original Population Size) were introduced

Effect of uncertainties on OPS and R were investigated

For controlling a population the value of R should be reduced

Conclusions

Population Growth Analysis

9,309,051,5392050

75,638,5401.186,386,542,8862004

72,049,4251.754,086,387,6651975

37,768,2371.472,555,982,6111950

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Growth Models1. Exponential2. Logistic3. Demographic

Population Growth Models

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Possible trajectories of population change

population growth and its impact on the biosphere · 2005-05-19 · 1 population growth and its...

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