how many people can the earth support? we do not know how long we can continue increasing the...
TRANSCRIPT
How Many People Can the Earth Support?
• We do not know how long we can continue increasing the earth’s carrying capacity for humans without seriously degrading the life-support system for humans and many other species.
Environmental science
is the study of how the natural world works, and what is happening to it as the human population expands. It includes all of the natural sciences and sometimes economics and a few other social sciences.
• Major topics can be boiled down to:– Human population– Energy & all implications of its use
including air pollution– Resources-biological, water, mineral
What is environmental science?
Knowing where your water/food/energy come
from and where your waste
goes
The single driving mechanism for all The single driving mechanism for all the environmental problems we the environmental problems we face in the world today may be face in the world today may be exponential growth.exponential growth.
Key Concepts
• Humans are subject to natural laws and ecological processes such as limiting factors.
• Significant differences in developed vs. developing worlds
• Unlimited use of natural resources is unsustainable
• There are a number of tools to understand populations project future outcomes
There are more people living on Earth today There are more people living on Earth today than ever before in human history. than ever before in human history.
Both the number of people and the amount Both the number of people and the amount of overall consumption exert an impact on of overall consumption exert an impact on the environment. the environment.
Wednesday Jan26Wednesday Jan26
What is Earth’s Population Capacity
Population Trends over 200 yrs
www.prb.org
Today6.6B
What Factors Influence the Size of the Human
Population? • Population size increases because of
births and immigration and decreases through deaths and emigration.
• The average number of children born to women in a population (total fertility rate) is the key factor that determines population size.
Population SizePopulation Size• Natality
– Number of individuals added through reproduction
– Crude Birth Rate - Births per 1000– Total Fertility Rate – Average number of
children born alive per woman in her lifetime
• Mortality– Number of individuals removed through death– Crude Death Rate Deaths per 1000
Calculating Population Change,
= (Births + Immigration) – ( Deaths +
Emmigration)
Demographic TransitionCalculating the % increase or
decrease of a population
(CBR – CDR)/10 = Rate of increase or decrease in population per 1,000 per year
Number of births or deaths/1000 so countries can be compared.Crude because no consideration of who is old or young
Calculating Doubling Times
70/Rate of Increase = Doubling Time
The world rate of population increase is 1%. The world rate of population increase is 1%. How long would it take to double the How long would it take to double the population?population?
70 years70 years
Calculating % increase (Fertility Rates) and
Doubling Times: PracticeCountry CBR CDR Rate of
Increase Doubling Time
Kenya 33 13 2.0 35
Mexico 27 5 2.2 32
USA 15 9 0.6 116
Denmark 13 11 0.2 431
Calculate the Calculate the
Rates of Rates of increase and increase and doubling doubling timestimes
Calculating % increase (Fertility Rates) and
Doubling Times: PracticeCountry CBR CDR Rate of
Increase Doubling Time
Kenya 33 13 2.0 35
Mexico 27 5 2.2 32
USA 15 9 0.6 116
Denmark 13 11 0.2 431
End of WWIIEnd of WWII
Demographic Demographic TransitionTransition
DepressionDepression
Baby Baby Boom……………..Boom……………..
Echo Baby Boom…………Echo Baby Boom…………
Age Structure Age Structure DiagramsDiagrams
Positive Growth Zero Growth Negative Growth (ZPG)Pyramid Shape Vertical Edges Inverted Pyramid
Population Profiles of the United
States
Human Population Growth Continues but It Is Unevenly
Distributed
• Population growth in developing countries is increasing 15 times faster than developed countries
• By 2050, 97% of growth will be in developing countries
• Should the optimum sustainable population be based on cultural carrying capacity?
• Major concers thatgrowing populations cause increased environmental stresses?– Infectious diseases– Biodiversity losses– Water shortages– Traffic congestion– Pollution of the seas– Climate change
– Population Capacity 3 BBC Water Use
What is Earth’s Population Capacity• Population Capacity 2• Population Capacity 3 Water Use• Population Capacity 4 Competition
for scarce resources• Population Capacity 5 today’s
population• Population Capacity 6 Future Efforts
Women Having Fewer Babies but Not Few Enough to Stabilize the World’s
Population
• Fertility rate – Replacement-level fertility rate– Total fertility rate (TFR)
Several Factors Affect Death Rates (1)
• Life expectancy & Infant mortality rate
• Why are people living longer and fewer infants dying?– Increased food supply and distribution– Better nutrition– Medical advances– Improved sanitation
Several Factors Affect Death Rates (2)
• U.S. infant mortality rate high due to– Inadequate health care for poor
women during pregnancy and their infants
– Drug addiction among pregnant women
– High birth rate among teenagers
Migration Affects an Area’s Population Size
• Economic improvement• Religious freedom• Political freedom• Wars• Environmental refugees
No one knows if the population on No one knows if the population on Earth will double again.Earth will double again.
Although the number of additional people Although the number of additional people on Earth continues to increase each year, on Earth continues to increase each year, the rate at which the population is the rate at which the population is growing each year, growing each year, the growth ratethe growth rate, is , is slowing.slowing.
Infant Mortality:Infant Mortality:number of deaths by age 1 per 1000 number of deaths by age 1 per 1000 live births in the populationlive births in the population
USA AverageUSA Average 6.66.6SwedenSweden 2.42.4FranceFrance 3.63.6AfghanistanAfghanistan 166166
Infant Mortality (all values from 2005)USA Average 6.6
African-Americans 13.6Native Americans 8.9
Washington, D.C. 11.4Mississippi 10.5Louisiana 9.8Utah 4.8New Hampshire 3.8
Singapore 2.3Sweden 3.1Bolivia 54Burundi 106Angola 188
Age StructureAge Structure• The age structure of a population
is usually shown graphically• The population is usually divided
up into prereproductives, reproductives and postreproductives
• The age structure of a population dictates whether is will grow, shrink, or stay the same size
Age Structure Age Structure DiagramsDiagrams
Positive Growth Zero Growth Negative Growth (ZPG)Pyramid Shape Vertical Edges Inverted Pyramid
Disparities
• Developed countries– 16% of the world’s population– Control 81% of the world’s wealth
• Low-income developing countries– 41% of the world’s population– Control 3.4% of the world’s gross national
income
• Difference in per capita income: 62 to 1!
Population Increase in Developed and Developing
Countries
Population Data for Selected Countries (Table 5-3)
Country Total Fertility Rate
Doubling Time (Years)
World 2.8 54
Developing Countries
3.5 37
Developed Countries
1.5 700
Different Populations, Different Problems
• Human pressure on the environment caused by three factors– Population size– Affluence– Technology
Ecological Footprints by World Region
• The average American places at least 20 times the demand on Earth’s resources as does an average person in Bangladesh
Fig. 5.7 here
Global Conditions for a Sustainable Population
• Lower fertility rates (stabilize population)
• Consumption must decrease• Protect the environment
(stewardly action must increase)
Consequences of Population Growth and Affluence
• The developing countries• Affluence
Developing or Developed Nations?
• High fertility rates• High consumptive lifestyles: use
80% of world’s wealth• Intense poverty• Eat high on the food chain
Developing or Developed Nations?
• Long doubling times• High environmental degradation• Twenty percent of the world’s
population
Basic Human Needs
• Drinkable Water• Edible Food• Safe Housing• Health Care• An Education• A Job
Growing Cities
Consequences of Exploding Populations in the Developing World
Consequences of Exploding Populations
More PopulationCauses
MORE
LESS
deforestationresource depletionloss of agricultural landbiodiversitydiseasepest resistancepopulation migrationirrigationwetlands
Affluence in the United States
• Consume the largest share of 11 of 20 major commodities
• Eat more than three times the global average in meat
• Lead the world in paper consumption
• Environment improves with increasing affluence
Affluence in the United States
• Enables wealthy to clean up immediate environment by transferring waste to more distant locations.
• Affluent isolate themselves and unaware of the environmental stresses caused by their consumptive lifestyles.
Dynamics of Population Growth
• Population profiles• Future populations• Population momentum• The demographic transition
Population Profiles of the United States
Population Profile for United States
Note increasing elderlypopulation.
Future World Populations
Future United States Populations
Projecting Future Populations: Developed
Countries
Population Projections: Developing Nations
Comparing Projected Populations (see Fig. 5-17)
Fertility Rate> 2
Fertility Rate< 2
Population Momentum
• Countries like Iraq will continue to grow for 50–60 years even after the total fertility rate is reduced to replacement level.
The Demographic Transition
Demographic Transition Comparisons
By the Year 2000
• 65 out of 117 countries will not be able to feed their own people
• One billion people will be living in cities that cannot support its inhabitants
• 400 million more women will be in need of child spacing services
Basic Human Needs
• Drinkable Water• Edible Food• Safe Housing• Health Care• An Education• A Job
The Developing Countries• Reform the system of land ownership• Intensify cultivation of existing land
to increase production per unit area• Open new land to farm• Move to cities and seek employment• Engage in illicit activities for income• Move to other countries
How do these “solutions” aggravate the problems?
Growing Cities
Consequences of Exploding Populations in the Developing World
Consequences of Exploding Populations
More PopulationCauses
MORE
LESS
deforestationresource depletionloss of agricultural landbiodiversitydiseasepest resistancepopulation migrationirrigationwetlands