Chapter 7 Envi sci

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Urban Area

contains more than 386 people per square kilometer (1,000 people per square mile) 75% of the population of developed countries lives in urban areas

Global human population growth trend: past and modern

past: deaths and births used to occur in roughly equal #'s modern: every 5 days the global population increases by more than a million lives The human population began to increase drastically 400 years ago when agricultural output increased and sanitation began to improve. Better living conditions caused death rates to fall, but birth rates remained relatively high.

Family planning

regulation of the number or spacing of offspring through the use of birth control As education improves fertility decreases When women have the option to use family planning, crude birth rates tend to drop.

Population Pyramid

Age structure diagram that is widest at the bottom and narrowest at the top (more younger people than older people) Typical of developing countries, such as Venezuela and India The wide base of the graph indicates that the population will grow because a large number of females aged 0-15 have yet to bear children

Thomas Malthus

One of the first to suggest that the human population could exceed Earth's carrying capacity. He observed that Earth's population was growing exponentially while the food supply was only growing linearly. Malthus concluded that the population size would eventually exceed the food supply

Current human population

Over 7 billion

Phase 4 (Declining growth)

Phase 4 is characterized by declining population size and often by a relatively high level of affluence and economic development. Japan, the United Kingdom, Germany, Russia, and Italy are phase 4 countries. CBR is below CDR. Less young people, more older people

Influences on population growth

1. Population size 2. birth and death rates 3. fertility 4. life expectancy 5. migration

By 2100 demographers believe that the population will stabilize between...

6.8 and 10.5 billion

Therefore a population growing at 2 percent per year will double every 35 years

70/2= 35

By 2050 demographers believe the population will be somewhere between...

8.1 and 9.6 billion

Developing country

A country with relatively low levels of industrialization and incomes of less than $3 per person per day. A TFR of greater than 2.1 is needed to achieve replacement level fertility. Replacement level fertility is higher in developing countries because mortality among young people tends to be higher.

IPAT equation

An equation used to estimate the impact of the human lifestyle on the environment Developed by Barry Commoner, Paul Ehrlich, and John Holdren Impact= Population x affluence x technology Although it is written mathematically, the IPAT equation is a conceptual representation of the three major factors that influence environmental impact Higher population=higher environmental impact Higher affluence=higher environmental impact

Total fertility rate (TFR)

An estimate of the average number of children that each woman in a population will bear throughout her childbearing years (between the onset of puberty and menopause)

Theory of Demographic Transition

As a country moves from a subsistence economy to industrialization and increased affluence, it undergoes a predictable shift in population growth. The theory of demographic transition models the way that birth, death, and growth rates for a nation change with economic development. PHASE 1: pre-industrial period characterized by high birth rates and high death rates PHASE 2: as the society begins to industrialize death rates drop rapidly, but birth rates do not change. Population growth is greatest at this point. PHASE 3: birth rates decline PHASE 4: the population stops growing and sometimes begins to decline as birth rates drop below death rates

Developed country

Countries with relatively high levels of industrialization and income, typically, with a replacement level fertility of about 2.

How do demographers determine yearly birth and death rates?

Crude birth rate and crude death rate

Doubling time can be approximated mathematically using a formula called the rule of 70

Doubling time (years) = 70/% growth rate

Changes in population size

If there are more births than deaths, there are more inputs than outputs and the system expands. When demographers look at population trends in individual countries, they take into account inputs and outputs.

Net migration rate equation

Net migration= # of immigrants per year/# of people in the population

Replacement-level fertility

The TFR required to offset the average number of deaths in a population so that the current population size remains stable.

Life expectancy

The average number of years that an infant born in a particular year in a particular country can be expected to live, given the current average life span and death rate in that country.

Net migration rate

The difference between immigration and emigration in a given year per 1,000 people in a country

Infant mortality rate

The number of deaths of children under 1 year of age per 1,000 live births

Child mortality rate

The number of deaths of children under age 5 per 1,000 live births

Phase 1 (slow growth)

The size of the population will not change very quickly because the high birth and death rates offset each other. In other words, CBR = CDR. This pattern is typical of countries before they begin to modernize. In these countries, life expectancy for adults is short due to poor working conditions. The infant mortality rate is also high because of disease, lack of health care, and poor sanitation (in a subsistence economy where most people are farmers, having children is an asset) Today, crude birth rates exceed crude death rates in almost every country, so even the poorest nations have moved beyond phase 1.

Affluence

The state of having plentiful wealth including the possession of money, goods, or property

Some scientists argue that the carrying capacity will not be reached.

They argue that the growing population of humans provides an increasing supply of intellect that leads to increasing amounts of innovation. For example, in the past whenever the food supply seemed small enough to limit the human population, major technological advances increased food production. (1. Arrows made hunting more efficient, which allowed hunters to feed a larger number of people - 2. Early farmers increased crop yields with hand plows and later with oxen or horse-driven plows. ^Each of these inventions increased the planet's carrying capacity for humans

Phase 3 (stable growth)

a country enters phase 3 when its economy and education system improve. As family income increases, people have fewer children. As a result, the CBR begins to fall. ^^ as societies transition from subsistence farming to more complex economic specializations, having large numbers of children may become a financial burden rather than an economic benefit Population growth levels off during this phase, and population size does not change very quickly, because low birth rates and low death rates cancel each other out. Phase 3 is typical of many developed countries such as the United States and Canada

Population momentum

continued population growth after growth reduction measures have been implemented It occurs because there are relatively large numbers of individuals at reproductive maturity in the population Population momentum is the reason why a population keeps on growing after birth control policies or voluntary birth reductions have begun to lower the CBR of a country. Eventually, over several generations, those actions will bring the population to a more stable growth rate but the momentum of all the individuals who have recently reached child-bearing age will carry the population forward for a number of years.

Phase 2 (rapid growth)

death rates decline while birth rates stay high modernization, better sanitation, clean drinking water, increased access to food and goods, access to health care, including childhood vaccinations, all reducing the infant mortality rate and CDR. India is in phase 2

Output

decreases population size Examples: emigration and deaths

Input

increases population size Examples: immigration and births

Human population growth

the global human population has grown more rapidly in the last 400 years than at any other time in history

immigration

the movement of people into a country or region from another country or region

emigration

the movement of people out of a country or region

Crude birth rate (CBR)

the number of births per 1,000 individuals per year

Crude death rate (CDR)

the number of deaths per 1,000 individuals per year

Doubling time

the number of years it takes for a population to double

demography

the study of human populations and population growth Demographers analyze the influences on population growth (Population size, birth and death rates, fertility, life expectancy, migration) and offer insights into how and why human populations change and what can be done to influence rates of change

Gross Domestic Product (GDP)

the value of all products and services produced in one year in one country. GDP consists of four types of economic activity: consumer spending, government spending, investments, and exports minus imports A country's GDP often correlates with its pollution levels (high pollution=high GDP; low pollution=low GDP) As a nation's GDP increases further, it may reach a turning point. It can afford to purchase equipment that burns fossil fuels more efficiently and cleanly, which helps to reduce pollution levels. Most commonly used measure of a nation's wealth

Local and Global Resources

two commonly overused local resources are the land itself and woody biomass from trees and other plants Global impacts are more common in affluent or urban societies because they tend to specialize production in the industrial and high technology sectors. For example, more than half the ecological footprint of the United States comes from its use of fossil fuels, of which approximately 50 percent are imported. Families in suburban areas of developed countries consume far fewer local resources than rural families in developing countries. When families are affluent they are more likely to use imported goods

Age structure diagram

visual representations of the number of individuals within specific age groups for a country, typically expressed for males and females. Each horizontal bar of the diagram represents a 5-year age group. The total area of all the bars in the diagram represents the size of the whole population.


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