THE ECOLOGICAL APPROACH TO THE STUDY OF THE HUMAN COMMUNITY
The young sciences of plant and animal ecology have become fairly well
established. Their respective fields are apparently quite well defined,
and a set of concepts for analysis is becoming rather generally
accepted. The subject of human ecology, however, is still practically an
unsurveyed field, that is, so far as a systematic and scientific
approach is concerned. To be sure, hosts of studies have been made which
touch the field of human ecology in one or another of its varied
aspects, but there has developed no science of human ecology which is
comparable in precision of observation or in method of analysis with the
recent sciences of plant and animal ecology.
I. THE RELATION OF HUMAN ECOLOGY TO PLANT AND ANIMAL ECOLOGY
Ecology has been defined as “that phase of biology that considers plants
and animals as they exist in nature, and studies their interdependence,
and the relation of each kind and individual to its environment.”[31]
This definition is not sufficiently comprehensive to include all the
elements that logically fall within the range of human ecology. In the
absence of any precedent let us tentatively define human ecology as a
study of the spatial and temporal[32] relations of human beings as
affected by the selective, distributive, and accommodative forces of the
environment. Human ecology is fundamentally interested in the effect of
_position_,[33] in both time and space, upon human institutions and
human behavior. “Society is made up of individuals spatially separated,
territorially distributed, and capable of independent locomotion.”[34]
These spatial relationships of human beings are the products of
competition and selection, and are continuously in process of change as
new factors enter to disturb the competitive relations or to facilitate
mobility. Human institutions and human nature itself become accommodated
to certain spatial relationships of human beings. As these spatial
relationships change, the physical basis of social relations is altered,
thereby producing social and political problems.
A great deal has been written about the biological, economic, and social
aspects of competition and selection, but little attention has been
given to the distributive and spatial aspects of these processes. The
plant ecologist is aware of the effect of the struggle for space, food,
and light upon the nature of a plant formation, but the sociologist has
failed to recognize that the same processes of competition and
accommodation are at work determining the size and ecological
organization of the human community.
The essential difference between the plant and animal organism is that
the animal has the power of locomotion which enables it to gather
nutriment from a wider environment, but, in addition to the power to
move in space, the human animal has the ability to contrive and adapt
the environment to his needs. In a word, the human community differs
from the plant community in the two dominant characteristics of mobility
and purpose, that is, in the power to select a habitat and in the
ability to control or modify the conditions of the habitat. On first
consideration this might seem to indicate that human ecology could have
nothing in common with plant ecology where the processes of association
and adjustment result from natural unmodifiable reactions, but closer
examination and investigation make it obvious that human communities are
not so much the products of artifact or design as many hero-worshipers
suppose.[35]
The human community has its inception in the traits of human nature and
the needs of human beings. Man is a gregarious animal: he cannot live
alone; he is relatively weak and needs not only the company of other
human associates but shelter and protection from the elements as well.
Brunhes says there are three essentials to the inception of the human
community: the house, the road, and water.[36] Food may be transported
more easily than shelter or water; the latter two therefore constitute,
even under the most nomadic conditions, the essential elements in giving
a location and a spatial fixity to human relations.[37] This is
exemplified under our present régime of automobile tourist life, where
water and shelter become the determining factors in the location of the
camp.
The size and stability of the human community is however a function of
the food supply and of the rôle played in the wider ecological process
of production and distribution of commodities. When man makes his living
from hunting or fishing, the community is small and of but temporary
duration; when agriculture becomes the chief source of sustenance, the
community is still small but assumes a more permanent character; when
trade and commerce develop, larger communities arise at points of break
in conveyance, that is, at the mouths of rivers, junctions of streams,
at waterfalls, and shallows where streams are forded. As new forms of
transportation arise, new points of concentration occur and old points
become accentuated or reduced. Again, as goods for trade are made in
communities, still other points of concentration come into existence,
determined largely by sources of power and raw material.[38]
II. ECOLOGICAL CLASSIFICATION OF COMMUNITIES
From the standpoint of ecology, communities may be divided into four
general types: first, the primary service community, such as the
agricultural town, the fishing, mining, or lumbering community which
serves as the first step in the distributive process of the outgoing
basic commodity and as the last stage in the distributive process of the
product finished for consumption. The size of such communities depends
entirely upon the nature and form of utilization of the extractive
industry concerned, together with the extent of the surrounding trade
area. The community responds in size to any element that affects the
productivity of the economic base or the extent of the area from which
it draws its sustenance. But, in any event, so long as such a community
does not assume any other function in the larger ecological process, it
cannot grow in population beyond a few thousand inhabitants.
The next type of community is the one that fulfils the secondary
function in the distributive process of commodities. It collects the
basic materials from the surrounding primary communities and distributes
them in the wider markets of the world. On the other hand, it
redistributes the products coming from other parts of the world to the
primary service communities for final consumption. This is commonly
called the commercial community; it may, however, combine other
functions as well. The size of this type of community depends upon the
extent of its distributive functions. It may vary from a small wholesale
town in the center of an agricultural plain to that of a great port city
whose hinterland extends halfway across the continent. Growth depends
upon the comparative advantages of the site location.
The third type of community is the industrial town. It serves as the
locus for the manufacturing of commodities. In addition it may combine
the functions of the primary service and the commercial types. It may
have its local trade area and it may also be the distributing center for
the surrounding hinterland. The type is characterized merely by the
relative dominance of industry over the other forms of service. There is
practically no limit to the size to which an industrial community may
develop. Growth is dependent upon the scope and market organization of
the particular industries which happen to be located within its
boundaries. Industrial communities are of two general types: first,
those that have diversified and multiple industries organized on a local
sale of products, and, second, those that are dominated by one or two
highly developed industries organized on a national or world-sale of
products.
The fourth type of community is one which is lacking in a specific
economic base. It draws its economic sustenance from other parts of the
world, and may serve no function in the production or distribution of
commodities. Such communities are exemplified in our recreational
resorts, political and educational centers, communities of defense,
penal or charitable colonies. From the standpoint of growth or decline
such communities are not subject to the same laws that govern the
development of towns that play a part in the larger productive and
distributive processes.[39] They are much more subject to the
vicissitudes of human fancies and decrees than are the basic types of
human communities. Of course, any community may and usually does have
accretions added to its population as a result of such service. It may,
for instance, be the seat of a university, of a state prison, or it may
be a recreational resort for at least certain seasons of the year.
III. DETERMINING ECOLOGICAL FACTORS IN THE GROWTH OR DECLINE OF
COMMUNITY
The human community tends to develop in cyclic fashion. Under a given
state of natural resources and in a given condition of the arts the
community tends to increase in size and structure until it reaches the
point of population adjustment to the economic base. In an agricultural
community, under present conditions of production and transportation,
the point of maximum population seldom exceeds 5,000.[40] The point of
maximum development may be termed the point of culmination or climax, to
use the term of the plant ecologist.[41] The community tends to remain
in this condition of balance between population and resources until some
new element enters to disturb the _status quo_, such as the introduction
of a new system of communication, a new type of industry, or a different
form of utilization of the existing economic base. Whatever the
innovation may be that disturbs the equilibrium of the community, there
is a tendency toward a new cycle of adjustment. This may act in either a
positive or negative manner. It may serve as a _release_ to the
community, making for another cycle of growth and differentiation, or it
may have a retractive influence, necessitating emigration and
readjustment to a more circumscribed base.
In earlier conditions of life, population was kept down to the community
balance by variations in the death-rate, or, as in the case of Greek
cities, the surplus population emigrated in groups to establish new
colonies—offshoots of the mother-city. Under modern conditions of
communication and transportation, population adjustment is maintained by
a ceaseless process of individual migrations. As a result of the dynamic
conditions prevailing throughout the civilized world during the last
fifty years, many communities have passed through swift successive
cycles of growth or decline, the determining factors being changes in
forms and routes of transportation and communication and the rise of new
industries.
Some advantage in transportation is the most fundamental and most
important of the causes determining the location of a distributing
center. It may almost be said to be the only cause for the formation
of such centers. For some reason or reasons a particular place is more
conveniently and cheaply reached by many people than any surrounding
point; and, as a result, they naturally exchange commodities there.
The country store is located at the crossing of roads. There also is
the village. In a mountain country the market town is at the junction
of two, or, still better, of three valleys. Another favorite location
is the end of a mountain pass, or a gap that is a thoroughfare between
two valleys. If rivers are difficult to cross, settlements will spring
up at the safest ferries or fords. In a level plain, a town will be
near its center, and a focus of roads or railroads in such a plain,
fertile and populous, will almost surely make a city.[42]
It is the railroad and the steamship that determine where a new
business shall be developed, quite as often as the government policy.
The grant of special rates and privileges to shippers is nowadays the
most efficient kind of protection.
It is this quickening and cheapening of transportation that has given
such stimulus in the present day to the growth of large cities. It
enables them to draw cheap food from a far larger territory and it
causes business to locate where the widest business connection is to
be had, rather than where the goods or raw materials are most easily
produced. And the perfection of the means of communication, the
post-office and the telegraph, intensifies the same result.[43]
The entire net increase of the population of 1870 to 1890 in Illinois,
Wisconsin, Iowa, and Minnesota was in cities and towns possessing
competitive rates, while those having non-competitive rates decreased
in population, and in Iowa it is the general belief that the absence
of large cities is due to the earlier policy of the railways giving
Chicago discriminating rates.[44]
The advent of the trolley line and more recently of the automobile has
produced still further disturbing elements in the growth of human
communities. Their effect has been chiefly to modify the life of the
small town or village, causing the decline of some and the sudden growth
of others. The introduction of these two forms of transportation, more
particularly of the automobile, has been the most potent force in our
recent American history in affecting redistribution of our population
and in the disorganization of our rural and small-town institutions
which grew up on the basis of a horse-and-vehicle type of mobility.[45]
The evolution of new types of industry is another feature that becomes a
determining factor in the redistribution of the country’s population. As
we review our census reports we see the emergence each decade of one or
more important industries; first, the textile industry causing
concentrations of population in the eastern states, then the development
of the iron and steel industry with its center of operations gradually
shifting farther and farther west, and more recently the advent of the
automobile and oil industries making for enormous concentration of
population in certain states of the Union, also the motion picture
industry with its concentrated center in southern California. The
emergence of a new industry has a far-reaching effect in disturbing the
_status quo_ of communal life. Competition soon forces the new industry
to concentrate its productive enterprises in one or two communities;
these communities then serve as great magnets drawing to themselves the
appropriate population elements from communities far and near.
IV. THE EFFECT OF ECOLOGICAL CHANGES ON THE SOCIAL ORGANIZATION OF
COMMUNITY
Population migrations resulting from such sudden pulls as are the
outcomes of unusual forms of release in community growth may cause an
expansion in the community’s development far beyond the natural
culmination point of its cyclic development, resulting in a crisis
situation, a sudden relapse, disorganization, or even panic. So-called
“boom towns” are towns that have experienced herd movements of
population beyond the natural point of culmination.
On the other hand, a community which has reached the point of
culmination and which has experienced no form of release is likely to
settle into a condition of stagnation. Its natural surplus of population
is forced to emigrate. This type of emigration tends to occasion
folk-depletion in the parent community. The younger and more
enterprising population elements respond most sensitively to the absence
of opportunities in their home town. This is particularly true when the
community has but a single economic base, such as agriculture,
lumbering, mining. Reformers try in vain to induce the young people to
remain on the farms or in their native villages, little realizing that
they are working in opposition to the general principles of the
ecological order.
Again, when a community starts to decline in population due to a
weakening of the economic base, disorganization and social unrest
follow.[46] Competition becomes keener within the community, and the
weaker elements either are forced into a lower economic level or are
compelled to withdraw from the community entirely. There are, of course,
periodic and temporary fluctuations in the economic balance, due either
to circumstances which affect the entire economic order or to the
vicissitudes of the particular industry from which the community draws
its sustenance. These temporary fluctuations, however, while important
from the standpoint of social well-being, do not comprise the basic
determinants of community development.
The introduction of an innovating element into the adjustment of a
community may be designated as the initial stage of an invasion which
may make for a complete change in the structure and organization of the
community. The introduction of a new mode of transportation, for
instance, may transform the economic organization of a community and
make for a change in population type.
Thus the Harlem Railroad transformed Quaker Hill from a community of
diversified farming, producing, manufacturing, selling, consuming,
sufficient unto itself, into a locality of specialized farming. Its
market had been Poughkeepsie, twenty-eight miles away, over high hills
and indifferent roads. Its metropolis became New York, sixty-two miles
away by rail and four to eight miles by wagon-road.
With the railroad’s coming, the isolated homogeneous community
scattered. The sons of the Quakers emigrated. Laborers from Ireland
and other European lands, even negroes from Virginia, took their
places. New Yorkers became residents on the Hill, which became the
farthest terminus of suburban travel.[47]
The establishment of a new industry, especially if it displaces the
previous economic base, may also make for a more or less complete change
of population without greatly modifying the size of the community. This
condition is exemplified in many of the small towns of the state of
Washington which have changed from lumbering to agriculture or from one
type of agriculture to another. In many cases few of the previous
inhabitants remained after the invasion of the new economic base.
As a community increases in size, however, it becomes better able to
accommodate itself to invasions and to sudden changes in number of
inhabitants. The city tends to become the reservoir into which the
surplus population drains from the smaller communities round about.
V. ECOLOGICAL PROCESSES DETERMINING THE INTERNAL STRUCTURE OF COMMUNITY
In the process of community growth there is a development from the
simple to the complex, from the general to the specialized; first to
increasing centralization and later to a decentralization process. In
the small town or village the primary universal needs are satisfied by a
few general stores and a few simple institutions such as church, school,
and home. As the community increases in size specialization takes place
both in the type of service provided and in the location of the place of
service. The sequence of development may be somewhat as follows: first
the grocery store, sometimes carrying a few of the more staple dry
goods, then the restaurant, poolroom, barber shop, drug store, dry-goods
store, and later bank, haberdashery, millinery, and other specialized
lines of service.[48]
The axial or skeletal structure of a community is determined by the
course of the first routes of travel and traffic.[49] Houses and shops
are constructed near the road, usually parallel with it. The road may be
a trail, public highway, railroad, river, or ocean harbor, but, in any
case, the community usually starts in parallel relation to the first
main highway. With the accumulation of population and utilities the
community takes form, first along one side of the highway and later on
both sides. The point of junction or crossing of two main highways, as a
rule, serves as the initial center of the community.
As the community grows there is not merely a multiplication of houses
and roads but a process of differentiation and segregation takes place
as well. Residences and institutions spread out in centrifugal fashion
from the central point of the community, while business concentrates
more and more around the spot of highest land values. Each cyclic
increase of population is accompanied by greater differentiation in both
service and location. There is a struggle among utilities for the
vantage-points of position. This makes for increasing value of land and
increasing height of buildings at the geographic center of the
community. As competition for advantageous sites becomes keener with the
growth of population, the first and economically weaker types of
utilities are forced out to less accessible and lower-priced areas. By
the time the community has reached a population of about ten or twelve
thousand, a fairly well-differentiated structure is attained. The
central part is a clearly defined business area with the bank, the
drugstore, the department store, and the hotel holding the sites of
highest land value. Industries and factories usually comprise
independent formations within the city, grouping around railroad tracks
and routes of water traffic. Residence sections become established,
segregated into two or more types, depending upon the economic and
racial composition of the population.
The structural growth of community takes place in successional sequence
not unlike the successional stages in the development of the plant
formation. Certain specialized forms of utilities and uses do not appear
in the human community until a certain stage of development has been
attained, just as the beech or pine forest is preceded by successional
dominance of other plant species. And just as in plant communities
successions are the products of invasion, so also in the human community
the formations, segregations, and associations that appear constitute
the outcome of a series of invasions.[50]
There are many kinds of intra-community invasions, but in general they
may be grouped into two main classes: those resulting in change in use
of land, and those which introduce merely change in type of occupant. By
the former is meant change from one general use to another, such as of a
residential area into a business area or of a business into an
industrial district. The latter embraces all changes of type within a
particular use area, such as the changes which constantly take place in
the racial and economic complexion of residence neighborhoods, or of the
type of service utility within a business section. Invasions produce
successional stages of different qualitative significance, that is, the
economic character of the district may rise or fall as the result of
certain types of invasion. This qualitative aspect is reflected in the
fluctuations of land or rental values.
The conditions which initiate invasions are legion. The following are
some of the more important: (1) changes in forms and routes of
transportation;[51] (2) obsolescence resulting from physical
deterioration or from changes in use or fashion; (3) the erection of
important public or private structures, buildings, bridges,
institutions, which have either attractive or repellent significance;
(4) the introduction of new types of industry, or even a change in the
organization of existing industries; (5) changes in the economic base
which make for redistribution of income, thus necessitating change of
residence; (6) real estate promotion creating sudden demands for special
location sites, etc.
Invasions may be classified according to stage of development into (_a_)
initial stage, (_b_) secondary or developmental stage, (_c_) climax. The
initial stage of an invasion has to do with the point of entry, the
resistance or inducement offered the invader by the prior inhabitants of
the area, the effect upon land values and rentals. The invasion, of
course, may be into an unoccupied territory or into territory with
various degrees of occupancy. The resistance to invasion depends upon
the type of the invader together with the degree of solidarity of the
present occupants. The undesirable invader, whether in population type
or in use form, usually makes entry (that is, within an area already
completely occupied) at the point of greatest mobility. It is a common
observation that foreign races and other undesirable invaders, with few
exceptions, take up residence near the business center of the community
or at other points of high mobility and low resistance. Once established
they gradually push their way out along business or transportation
thoroughfares to the periphery of the community.
The commencement of an invasion tends to be reflected in changes in land
value. If the invasion is one of change in use the value of the land
generally advances and the value of the building declines. This
condition furnishes the basis for disorganization. The normal
improvements and repairs are, as a rule, omitted, and the owner is
placed under the economic urge of renting his property to parasitic and
transitory services which may be economically strong but socially
disreputable and therefore able and obliged to pay higher rentals than
the legitimate utilities can afford. It is a well-known fact that the
vices under the surveillance of the police usually segregate in such
transitional areas.[52]
During the course of development of an invasion into a new area, either
of use or type, there takes place a process of displacement and
selection determined by the character of the invader and of the area
invaded. The early stages are usually marked by keenness of competition
which frequently manifests itself in outward clashes. Business failures
are common in such areas and the rules of competition are violated. As
the process continues, competition forces associational groupings.
Utilities making similar or complementary demands of the area tend to
group in close proximity to one another, giving rise to subformations
with definite service functions. Such associations as amusement areas,
retail districts, market sections, financial sections, and automobile
rows are examples of this tendency.
The climax stage is reached in the invasion process, once the dominant
type of ecological organization emerges which is able to withstand the
intrusions of other forms of invasion. For example, in the development
of a residential district, when it is not controlled in advance by
building restrictions, the early stages of growth are usually marked by
wide variations in the type and value of buildings constructed. But, in
the process of development, a uniform cost type of structure tends to
dominate, gradually eliminating all other types that vary widely from
the norm, so that it is customary to find a considerable degree of
economic homogeneity in all established residential districts. The same
process operates in areas devoted to business uses, competition
segregates utilities of similar economic strength into areas of
corresponding land values, and at the same time forces into close
proximity those particular forms of service which profit from mutual
association such as financial establishments or automobile
display-rooms. Once a dominant use becomes established within an area,
competition becomes less ruthless among the associational units, rules
of control emerge, and invasion of a different use is for a time
obstructed.
The general effect of the continuous processes of invasions and
accommodations is to give to the developed community well-defined areas,
each having its own peculiar selective and cultural characteristics.
Such units of communal life may be termed “natural areas,”[53] or
formations, to use the term of the plant ecologist. In any case, these
areas of selection and function may comprise many subformations or
associations which become part of the organic structure of the district
or of the community as a whole. It has been suggested that these natural
areas or formations may be defined in terms of land values,[54] the
point of highest land value representing the center or head of the
formation (not necessarily the geographic center but the economic or
cultural center), while the points of lowest land value represent the
periphery of the formation or boundary line between two adjacent
formations.
Each formation or ecological organization within a community serves as a
selective or magnetic force attracting to itself appropriate population
elements and repelling incongruous units, thus making for biological and
cultural subdivisions of a city’s population. Everyone knows how racial
and linguistic colonies develop in all of our large cities, but the age
and sex segregations which take place are not quite so obvious to common
perception. In the city of Seattle, which has in general a sex
composition of 113 males to 100 females, the downtown district,
comprising an area inscribed by a radius of half a mile or so, has from
300 to 500 males to every 100 females. But in the outlying districts of
the city, except in one or two industrial sections, these ratios are
reversed. Females predominate in numbers over males in all the
residential neighborhoods and in the suburbs of the city. This same
condition is true with regard to the age distribution of population. The
school census shows an absolute decline in the number of children of
school age in the central districts of the city although the total
population for this area has shown an increase for each decade. It is
obvious, then, that the settler type of population, the married couples
with children, withdraw from the center of the city while the more
mobile and less responsible adults herd together in the hotel and
apartment regions near the heart of the community.
This process of population-sifting produces not only increasing mobility
with approach from the periphery to the center of the formation, but
also different cultural areas representing different mores, attitudes,
and degrees of civic interest. The neighborhoods in which the settler
type of population resides, with their preponderance of women and
children, serve as the custodians of the stabilizing and repressive
mores. It is in the Seattle neighborhoods, especially those on the
hill-tops, that the conservative, law-abiding, civic-minded population
elements dwell. The downtown section and the valleys, which are usually
industrial sites, are populated by a class of people who are not only
more mobile but whose mores and attitudes, as tested by voting habits,
are more vagrant and radical.
R. D. MCKENZIE