Chapter 7 Envi sci
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.
