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 environmental problems we face in the world today may be 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 than ever before in human history. Both the number of people and the amount of overall consumption exert an impact on the environment. Wednesday Jan26

What is Earth’s Population Capacity

Population Trends over 200 yrs

Today 6.6B

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 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 Transition Calculating 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%. How long would it take to double the population? 70 years

Calculating % increase (Fertility Rates) and Doubling Times: Practice Calculate the Rates of increase and doubling times

Calculating % increase (Fertility Rates) and Doubling Times: Practice

End of WWII Demographic Transition Depression Baby Boom…………….. Echo Baby Boom…………

Age Structure Diagrams 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 that growing populations cause increased environmental stresses? –Infectious diseases –Biodiversity losses –Water shortages –Traffic congestion –Pollution of the seas –Climate change –Population Capacity 3 BBC Water UsePopulation Capacity 3

What is Earth’s Population Capacity Population Capacity 2 Population Capacity 3 Water UsePopulation Capacity 3 Population Capacity 4 Competition for scarce resourcesPopulation Capacity 4 Population Capacity 5 today’s populationPopulation Capacity 5 Population Capacity 6 Future EffortsPopulation Capacity 6

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 Earth will double again. Although the number of additional people on Earth continues to increase each year, the rate at which the population is growing each year, the growth rate, is slowing.

Infant Mortality: number of deaths by age 1 per 1000 live births in the population USA Average6.6 Sweden 2.4 France3.6 Afghanistan166

Infant Mortality (all values from 2005) USAAverage6.6 African-Americans 13.6 Native Americans8.9 Washington, D.C.11.4 Mississippi10.5 Louisiana9.8 Utah4.8 New Hampshire3.8 Singapore2.3 Sweden3.1 Bolivia54 Burundi106 Angola188

Age 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 Diagrams 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) CountryTotal Fertility Rate Doubling Time (Years) World2.854 Developing Countries Developed Countries

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 Population Causes MORE LESS deforestation resource depletion loss of agricultural land biodiversity disease pest resistance population migration irrigation wetlands

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 elderly population.

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 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 Population Causes MORE LESS deforestation resource depletion loss of agricultural land biodiversity disease pest resistance population migration irrigation wetlands