Geographical Analysis of Population
Even a brief glance at a global-scale population distribution map confirms
that people are spread very unevenly on Earthís surface. Approximately
75% of Earthís population occupies only about 5% of the land area, with
the largest concentrations being in East and South Asia, Western Europe,
and Northeastern North America.
Data gathered about populations is largely place-based. People are counted as individuals in specific places and then the data is aggregated to make general statements about large units. This basic process makes it necessary for all students of population to be constantly aware of the potential lack of precision in the numbers. For example, populations of houses are aggregated with other households to provide data about a census tract. Therefore much attention must be given to the areal unit being used. In addition the effect of boundaries must be considered. The census draws sharp boundaries between census tracts for example, but those boundaries are not significant in the behavior of people. Furthermore in the United States the Census counts people at their home (where the sleep) not where they work or spend most of their time. Thus all discussions of population geography must begin with some thought about the appropriate level of aggregation or areal units and the significance of the boundaries.
Because it is relatively simple to calculate, arithmetic density is widely used as a basis for comparison between countries and other places. When density is shown on small-scale maps, the degree of generalization can be misleading. Density is an abstract relationship, and does not describe actual distribution. An alternative measure of density is the ratio of people to cultivated land, or physiological density.
Scale and Process
A danger in population geography is the so-called "ecological fallacy."
This problem relates to scale and process. For example when a descriptive
statistic for an area is developed such as the median family income of
a census tract or country, one must not assume it would be possible to
find many families with that income. Put another way, you can not make
assumptions about individuals based on generalizations or statistical averages.
In addition a process may affect one part of a study area and not others.
For example there has been a large migration of people from Southeast Asia
into St. Paul, and so it is correct to say St. Paul has been greatly affected
by this migration. However, because the new arrivals live in a limited
number of neighborhoods, it is also possible to find areas in the city
with no evidence of any impacts of the new immigrants. Processes
not only work at different scales they impact the landscape and different
scales.
Population and Environment
The terms carrying capacity and sustainable use analyze of the relationship
between population and elements such air quality, safe water, food supply,
and biodiversity. Beginning in1798 with Thomas Malthus, scholars have discussed
impending crisis in the relationship between population growth and earthís
ability to maintain populations. The rise of the environmental movement
in the1960s and1970s was in large measure the result of gloomy predictions
about Earthís capacity to support life. In 1972 the Club of Rome published
a book called Limits to Growth which described a mathematical model using
variables of population, food production, industrialization, nonrenewable
resources, and pollution. The model and its advocates predicted an environmental
catastrophe that would lead to the collapse of Earth's systems. The simple
mathematical concepts in the model and lack of input from social science
in the development of the conclusions doomed the model to miscalculations.
The entire discipline of geography is focused on this question. The subsequent
sections of the course will also further inform students of the intricate
and every changing relationship between the environment at several scales
and the residents of Earth.
Population Distribution and Composition
The most superficial glance and a world map of human population reveals
the fundamental fact that the human population is not uniformly distributed
over the surface of the earth. The factors affecting the distribution are
quintessentially geographic. Some factors are place-based while others
have more to do with connections among places. All settlements are
in some way connected to the availability of resources or access to ways
of making a living.
It is important not to over-simplify explanations for the distribution of population. One cannot say this pace is too hot, too cold, too wet, or too dry because it seems that it is always possible to find a place to prove the counter point. However we do see broad patterns, for example, the Poles are devoid of human population although small groups do make their homes on the arctic fringe. Other places seem to be too dry but where humans practice irrigation it is possible to find large numbers of people. Some places have large numbers of people but low per capita GNPs. Others have small populations and are equally poor. Some populations live at high densities while others live in uncrowned conditions. Some of the worldís largest concertinos of people are rural with residents who are farmers. Other population concentrations are urban and industrial. One can easily see that global generalizations about population have limited value. Our scale of inquiry has great impact on the discussion of concentrations. At one scale a population may appear to be uniformly spread over an area but at closer examinations we see concentrations and empty areas.
The key questions in population geography are; why is population concentrated in some places and not in others? What will be the pattern in the years to come? How does this pattern of population distribution reflect a place's economy? How has it been influenced by changes in the economy? Encouraging students to exercise critical thinking skills such as questioning, evaluating, and analyzing patterns seen in maps or in the landscape enables the development of a geographic perspective.
Consequences of Particular Distributions
Not only do different levels of density impact the quality of human
life and social organizations, patterns are also important. The easiest
way to discuss this with students is to compare different travel costs
(time, money, impact on environment) for movement among people living along
a road and located one hundred miles apart versus a people living along
a road living one-mile apart. Compact and dispersed settlements will also
be discussed in other sections of the course.
Patterns of Age, Sex Race and Ethnicity
Patterns can also be observed in characteristics that define human
populations such as age, sex, race, ethnicity, and rural/urban distribution.
The composition of a population affords insight not only into present conditions
within the population, but also into the potential for change in the future.
For example, analysis of the age-sex distribution within a given population
reveals a demographic story - past, present, and future - about the place
in question.
The age-sex composition of a population can be represented graphically through a population pyramid, which shows the percent of total population in each age and sex cohort. Pyramids are commonly used to illustrate the populations of countries at different stages of both economic and demographic development. For example, the broad base of Ethiopiaís true pyramid reflects the countryís high total fertility rate of 7.0 and a young age structure that includes 46% of the population below the age of 15 years. Inferences can be made about future growth potential due to population momentum and economic conditions associated with a high dependency ratio resulting from the large population under the age of 15 years. In contrast, the almost column-like pyramid of Spain reflects this countryís more stable demographic situation.
Pyramids also reflect the demographic history of a country. For example, a series of pyramids for the United States from the mid-1950s to the present would reveal the progress of the baby-boom generation toward middle age, as well as the "echo" generation following in their wake. A pyramid for Germany would reveal the ravages of two world wars, as well as that countryís post-war baby boom.
At a different scale, comparison of pyramids for various states, Florida and Utah for example, reveals graphically just how diverse the U.S. population really is. Floridaís median age of 37.6 years becomes quickly apparent when the stateís pyramid is compared to that of Utah where the median age is only 26.8 years. Even a more local scale, pyramids tell an interesting story. For example, pyramids representing a transect from the central city into the distant rural-fringe suburbs traces the changing demographics a metropolitan area. What decision processes lie behind such very different demographic profiles in different locations within one metropolitan area? Examination of demographic patterns in local areas allows students to explore questions such as those raised above. Population pyramids are valuable tools for demographic analysis as long as students use them as a basis for inference, and not for absolute interpretation.
