l- 2(1) human population

8/3/2019 L- 2(1) Human Population

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Human Population And EnvironmentHuman Population And Environment

Environmental degradation, hunger, persistent poverty, economicnvironmental degradation, hunger, persistent poverty, economicstagnation, urban deterioration, and health issuestagnation, urban deterioration, and health issues will continue to challengewill continue to challenge

us as our numbers increase during the 21st centuryus as our numbers increase during the 21st century

Demands of increasing population coupled with desire for a higheremands of increasing population coupled with desire for a higher

standard of l iving result worldwide pollution on a massive scaletandard of l iving result worldwide pollution on a massive scale



Human Population & EnvironmentHuman Population & Environment

Case Study: BangladeshCase Study: Bangladesh With aWith a growth rate of 1.67growth rate of 1.67 total population is over total population is over 155 million155 million

(March,2009)(March,2009)

Annual increase is over 2 million Annual increase is over 2 million Recently more than 100,000 died because of storm & tidal surgeRecently more than 100,000 died because of storm & tidal surge This tragedy is made even more tragic by the fact that this number wereThis tragedy is made even more tragic by the fact that this number were

replaced in 2 wksreplaced in 2 wks One of the poorest nations & this poverty affects human survivalOne of the poorest nations & this poverty affects human survival

Calories available per person is only 85% of the required for good healthCalories available per person is only 85% of the required for good health Less than half Less than half of the population has access to safe drinking water & lessof the population has access to safe drinking water & less

than a fifth has access to adequate sanitationthan a fifth has access to adequate sanitation With inadequate resource & rapid growth rate, Bangladesh struggles toWith inadequate resource & rapid growth rate, Bangladesh struggles to

maintain even its existing poor standard of livingmaintain even its existing poor standard of living

Low-lying coastal areas are fundamentally uninhabitable at high densitiesLow-lying coastal areas are fundamentally uninhabitable at high densitiesfor extended periodsfor extended periods Are inhabited now only because of huge numbers of people in the country Are inhabited now only because of huge numbers of people in the country For Bangladesh it is difficult to talk about solving environmental problems,For Bangladesh it is difficult to talk about solving environmental problems,

conserving biological diversityconserving biological diversity Growth of human population erases any advancesGrowth of human population erases any advances Already the land is overused for grazing & crop production Already the land is overused for grazing & crop production




►

Factors affecting population growthFactors affecting population growth

Populations grow or decrease through the interplay of threePopulations grow or decrease through the interplay of three

factors:factors: births, deaths, & migrationbirths, deaths, & migration

Population change = (Births + Immigration)Population change = (Births + Immigration)

– – (Deaths + Emigration)(Deaths + Emigration)

Annual rate of Birth rate – Death rate Annual rate of Birth rate – Death ratenatural change(%) = --------------------------- x 100natural change(%) = --------------------------- x 100

1,000 persons1,000 persons




► Growth depends on Social, political, economic, ethical factorsGrowth depends on Social, political, economic, ethical factors

Social FactorsSocial Factors ► TheThe major social factorsmajor social factors that determine family size are thethat determine family size are the status andstatus and

desirers of womendesirers of women in the culturein the culture

► As women become better educated and obtain higher paying jobs, they As women become better educated and obtain higher paying jobs, they

become financially independent and can afford to marry later, use birthbecome financially independent and can afford to marry later, use birth

control and consequently have fewer childrencontrol and consequently have fewer children

► What is most important is the desire of women to limit the size of their What is most important is the desire of women to limit the size of their

familiesfamilies

Political FactorsPolitical Factors

► Two other factors that influence the population growth rate of a country areTwo other factors that influence the population growth rate of a country are

government policies on population growth and immigrationgovernment policies on population growth and immigration► Birth rates are currently so low in several countries that these countries willBirth rates are currently so low in several countries that these countries will

likely have a shortage of those of working age in the near futurelikely have a shortage of those of working age in the near future

► One way to solve this problem is to encourage immigration from other partsOne way to solve this problem is to encourage immigration from other parts

of the worldof the world




Mini Glossary:Mini Glossary:

DemographyDemography – – The scientific study of human populations, their The scientific study of human populations, their

characteristics, how these characteristics affect growth, and thecharacteristics, how these characteristics affect growth, and theconsequences of that growth is known as demographyconsequences of that growth is known as demography

Population dynamicsPopulation dynamics ——the study of changes in populationthe study of changes in population sizessizes andand

thethe causescauses of these changesof these changes

PopulationPopulation ——Group of individuals of the same species living in theGroup of individuals of the same species living in the

same area capable of interbreeding and sharing genetic informationsame area capable of interbreeding and sharing genetic information

Species:Species: Group of organisms that resemble one another inGroup of organisms that resemble one another in

appearance, behavior, chemical makeup and processes, and geneticappearance, behavior, chemical makeup and processes, and genetic

structure, capable of interbreeding and producing fertile offspringstructure, capable of interbreeding and producing fertile offspring

A species is A species is made up of populationsmade up of populations

Doubling Time:Doubling Time: Time required for a population to double in sizeTime required for a population to double in size

► How rapidly a population changesHow rapidly a population changes dependsdepends on theon the growth rate, i.e.growth rate, i.e.

the difference between birth rate and the death ratethe difference between birth rate and the death rate



Exponential GrowthExponential Growth

It means that a population increases by a constant percentage in eachIt means that a population increases by a constant percentage in each

unit of timeunit of time

It occurs when resources are not limitingIt occurs when resources are not limiting

Exponential growth starts out slowly & then proceeds faster & faster as theExponential growth starts out slowly & then proceeds faster & faster as the

population increases; yields apopulation increases; yields a J-shapedJ-shaped exponential growth curveexponential growth curve

However, no population can sustain exponential rate of growth; eventuallyHowever, no population can sustain exponential rate of growth; eventually

population will run out of food and spacepopulation will run out of food and space

Logistic GrowthLogistic Growth

► It involves exponential growth followed by a steady decrease with time asIt involves exponential growth followed by a steady decrease with time as

the population encounters environmental resistance and approaches thethe population encounters environmental resistance and approaches the

carrying capacity of its environment & levels off carrying capacity of its environment & levels off

With this type of growth population typically fluctuates slightly above &With this type of growth population typically fluctuates slightly above &

below the carrying capacity; yields abelow the carrying capacity; yields a S-shaped curveS-shaped curve

Although logistic growth curve has been used frequently to project Although logistic growth curve has been used frequently to project

maximum population size it involves assumptions that aremaximum population size it involves assumptions that are unrealisticunrealistic for for

humans and other mammalshumans and other mammals

Especially unrealisticEspecially unrealistic if death rates continue toif death rates continue to decreasedecrease owing toowing to

improvements in health, medicine, and food suppliesimprovements in health, medicine, and food supplies



Exponential & Logistic Growth CurvesExponential & Logistic Growth Curves



Growth of Population—Different Societies & their Impacts onGrowth of Population—Different Societies & their Impacts on

EnvironmentEnvironment

Four major periodsFour major periods

11 Hunters and gatherersHunters and gatherers:: From evolution to beginning of agriculture;From evolution to beginning of agriculture;less than a few million; growth rate 0.00011%/yr; 1 person /130-260less than a few million; growth rate 0.00011%/yr; 1 person /130-260

kmkm22

► Environmental impact of early & advanced hunters—gatherers wasEnvironmental impact of early & advanced hunters—gatherers was

limited and local because of their small population sizes, low resourcelimited and local because of their small population sizes, low resource

use, migration, and lack of technologyuse, migration, and lack of technology

22 Early, Preindustrial AgricultureEarly, Preindustrial Agriculture::

Rise of agriculture allowed a much greater density of people; 1 or 2Rise of agriculture allowed a much greater density of people; 1 or 2

people/kmpeople/km22

; growth rate of 0.03%/yr ; growth rate of 0.03%/yr There have been many benefits from the development and spread of There have been many benefits from the development and spread of

agriculture but environmental degradation fromagriculture but environmental degradation from soil erosionsoil erosion, and, and

livestock overgrazinglivestock overgrazing was a factor in the downfall of great civilizationwas a factor in the downfall of great civilization




EnvironmentEnvironment

3.The Machine Age3.The Machine Age:: Growth rate actually increased during the 1Growth rate actually increased during the 1stst partpart

of the 20of the 20thth

century, peaking during 1965-70 at 2.1% owing tocentury, peaking during 1965-70 at 2.1% owing toimprovements in health, medicine, & food productionimprovements in health, medicine, & food production

Population increased to 900 million in 1800, almost doubling in thePopulation increased to 900 million in 1800, almost doubling in the

next century & again to 3 billion by 1960next century & again to 3 billion by 1960

Advances in medicine and health, agriculture, shelter and Advances in medicine and health, agriculture, shelter and

clothingclothing

4. The Modern Era4. The Modern Era

About About 6.7 billion as of April, 20096.7 billion as of April, 2009

Growth rateGrowth rate slowed in wealthy, industrializedslowed in wealthy, industrialized nations but continuesnations but continues

toto increase rapidly in poorer, less developedincrease rapidly in poorer, less developed nationsnations► Use of technology caused significant damage to the environmentUse of technology caused significant damage to the environment::

IncreasedIncreased Air pollution Air pollution,, Water pollutionWater pollution,, Waste productionWaste production,, SoilSoil

degradationdegradation,, Groundwater depletionGroundwater depletion,, Habitat destruction &Habitat destruction &

degradationdegradation,, Biodiversity depletionBiodiversity depletion




EnvironmentEnvironment Age structureAge structure

► Proportion of population in each age classProportion of population in each age class, a component of , a component of demography,demography, affectsaffects current and future birth rates, death rates, andcurrent and future birth rates, death rates, and

growth rates;growth rates; our impactour impact on the environment; and social andon the environment; and social and

economic statuseconomic status

Demographers construct age structure diagram using each of theDemographers construct age structure diagram using each of the

three age categoriesthree age categories:: prereproductiveprereproductive (ages 0-14),(ages 0-14), reproductivereproductive (ages 15-45), &(ages 15-45), & postreproductivepostreproductive (ages 45 & up)(ages 45 & up)

Future changes in population can be predicted from the diagramFuture changes in population can be predicted from the diagram

StructureStructure with a verywith a very high growthhigh growth rate is shaped like arate is shaped like a pyramidpyramid

Developing countriesDeveloping countries withwith 37%37% of the populationsof the populations belowbelow age 15age 15 have this type structurehave this type structure

Because when all these children mature, they will become theBecause when all these children mature, they will become the

parents of the next generation, & this group of parents will be larger parents of the next generation, & this group of parents will be larger

than the previous groupthan the previous group



•Age structureAge structure

Thus, even if theThus, even if the fertility ratefertility rate of such a countryof such a country declines to adeclines to a

Replacement-levelReplacement-level,, thethe populationpopulation will continue towill continue to growgrow for somefor some

timetime In countries withIn countries with stable population,stable population, tthe numbers of people athe numbers of people at pre-pre-

reproductivereproductive andand reproductive agesreproductive ages are approximatelyare approximately samesame

Also, Also, larger larger proportion of population isproportion of population is older older , i.e., i.e. post-reproductivepost-reproductive

In countries where population isIn countries where population is shrinkingshrinking, people at, people at pre-pre-

reproductivereproductive isis smaller thansmaller than either either reproductivereproductive or or post-post-

reproductivereproductive group (Russia)group (Russia)

Worldwide, 30% of the human population is under age 15Worldwide, 30% of the human population is under age 15

When these people enter their reproductive years, they have theWhen these people enter their reproductive years, they have the

potential to cause a large increase in the growth ratepotential to cause a large increase in the growth rate Most of the increase in population sinceMost of the increase in population since 1950 has taken place in1950 has taken place in

developing countries as a result of thisdeveloping countries as a result of this younger age structureyounger age structure andand

high fertility rateshigh fertility rates of their populationof their population



•Age structure DiagramAge structure Diagram



Demographic TransitionDemographic Transition The demographic transition is aThe demographic transition is a FOUR-stage patternFOUR-stage pattern of change in birth ratesof change in birth rates

and death rates as a country is transformed from undeveloped to developand death rates as a country is transformed from undeveloped to develop

► It leads to aIt leads to a declinedecline in population growthin population growth

►

InitiallyInitially, countries have a, countries have a stable populationstable population with a high birthrate and a highwith a high birthrate and a highdeath ratedeath rate

► Death rates often vary because of famine and epidemic diseaseDeath rates often vary because of famine and epidemic disease

► Improved economic and social conditions bring about a period of rapidImproved economic and social conditions bring about a period of rapidpopulation growth as death rates fallpopulation growth as death rates fall

► Birthrates remain highBirthrates remain high

► As countries become industrialized, the birthrates begin to drop because As countries become industrialized, the birthrates begin to drop becausepeople desire smaller families and use contraceptivespeople desire smaller families and use contraceptives

► Eventually, birthrates and death rates again become balanced, with lowEventually, birthrates and death rates again become balanced, with lowbirthrates and low death ratesbirthrates and low death rates

► It suggests that if a country can become industrialized, then social, political,It suggests that if a country can become industrialized, then social, political,

and economic processes will naturally cause its population to stabilizeand economic processes will naturally cause its population to stabilize► As a result of a common desire among parents for large families, as in the As a result of a common desire among parents for large families, as in the

case of case of BangladeshBangladesh,, the growth rate is so high that it outpaces increases inthe growth rate is so high that it outpaces increases ineconomic developmenteconomic development

► The key point here is that the demographic transition will only takeThe key point here is that the demographic transition will only take

place if parents come to believe that a small family size is to their place if parents come to believe that a small family size is to their benefitbenefit



Limiting FactorsLimiting Factors

Population thatPopulation that exceedsexceeds thethe carrying capacitycarrying capacity ((maximummaximum

population size that can be sustained indefinitely by thepopulation size that can be sustained indefinitely by theenvironmentenvironment) will) will change the environmentchange the environment in a way thatin a way that willwill

decreasedecrease future population sizefuture population size

Eventually the population will run out food and spaceEventually the population will run out food and space

Limiting factors include:Limiting factors include: local loss of current crops, energylocal loss of current crops, energyshortages that affect food production & disruption in theshortages that affect food production & disruption in the

distribution, abrupt change in weather, climatic changes, declinedistribution, abrupt change in weather, climatic changes, decline

in groundwater supplies, desertification, soil erosion, major in groundwater supplies, desertification, soil erosion, major

world catastrophes (outbreak of disease), acid rain, etcworld catastrophes (outbreak of disease), acid rain, etc



► Total Fertility Rate (TFR) and Replacement-Level Fertility (RLF)Total Fertility Rate (TFR) and Replacement-Level Fertility (RLF)

► An important factor that can delay changes in population growth is An important factor that can delay changes in population growth is

the average number of children expected to be born to a womanthe average number of children expected to be born to a woman

during her lifetime, known as theduring her lifetime, known as the total fertility ratetotal fertility rate, or , or TFRTFR► A population that maintained a TFR of 3.8 over a long time would A population that maintained a TFR of 3.8 over a long time would

increase rapidly, whereas a population that had a TFR of 2.0 over aincrease rapidly, whereas a population that had a TFR of 2.0 over a

long time would declinelong time would decline

Replacement-level fertilityReplacement-level fertility (RLF)(RLF) is the TFR required for ais the TFR required for a

population to remain constantpopulation to remain constant

A total fertility rate of 2.1, that is, A total fertility rate of 2.1, that is, RLFRLF will not necessarilywill not necessarily

immediately result in a stable population with zero growth for immediately result in a stable population with zero growth for

several reasonsseveral reasons

► A comparison of nations suggests that the TFR declines as income A comparison of nations suggests that the TFR declines as incomeincreasesincreases

► Bangladesh, which has an average income per person of a fewBangladesh, which has an average income per person of a few

hundred dollars per year, has a high fertility rate—approximatelyhundred dollars per year, has a high fertility rate—approximately

2.832.83 (In Sri Lanka it is 1.88) children born to each woman(In Sri Lanka it is 1.88) children born to each woman



Future Population TrendsFuture Population Trends

Mortality will fall everywhere and level off Mortality will fall everywhere and level off Fertility will reach replacement levels everywhere betweenFertility will reach replacement levels everywhere between

2005-20602005-2060

Equilibrium world population of 10.1 to 12.5 billionEquilibrium world population of 10.1 to 12.5 billion

Developing countries would increase from 4.5 billion to 9.6Developing countries would increase from 4.5 billion to 9.6

billionbillion

Bangladesh would reach 257 millionBangladesh would reach 257 million

Developed countries (from 1.2 billion today to 1.9 billionDeveloped countries (from 1.2 billion today to 1.9 billion

Developing countries contribute 95% of the increaseDeveloping countries contribute 95% of the increase



Slowing population growthSlowing population growth

Most effective is to delay the age of first childbearing by womanMost effective is to delay the age of first childbearing by woman Social pressures that lead to deferred marriageSocial pressures that lead to deferred marriage In Bangladesh, average age for marriage is 16 whereas in SriIn Bangladesh, average age for marriage is 16 whereas in Sri

Lanka it is 25Lanka it is 25 Increase in marriage age could account for 40-50% drop in fertilityIncrease in marriage age could account for 40-50% drop in fertility

required to achieve zero population growthrequired to achieve zero population growth Change in attitude, knowledge of means to control birth, and theChange in attitude, knowledge of means to control birth, and the

ability to afford these meansability to afford these means Increase in education and job opportunities for young women andIncrease in education and job opportunities for young women and

standard of livingstandard of living

Women empowermentWomen empowerment The best way is a combination of family planning, reducing poverty,The best way is a combination of family planning, reducing poverty,and elevating the status of womenand elevating the status of women



THANK YOUTHANK YOU

l- 2(1) human population

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