AN EVALUATION OF THE CONCEPT OF CARRYING CAPACITY
John M . Street
University of H m a i i
T H E calculation of the carrying capacity
of the environment of some particular
primitive society and the improvisation of
formulae for the determination of carrying
capacities have been fairly common objectives of anthropologists and cultural geographers in recent years. According to
William Allan, a student of African husbandry, whose definition of carrying capacity seems to have the greatest currency
among anthropologists and geographer investigators of primitive agriculturalists, it
is “the maximum number of people that a
given land area will maintain in perpetuity
under a given system of usage without land
degradation setting in.” (I) L. G. Loffler,
(2) H. C. Conklin, (3) H. C. Brookfield (4)
and others imply that “a given system of
usage” involves: unvarying technology and
crop patterns; qualitatively and quantitatively constant per capita food consumption.
Conklin and Brookfield to name but two
out of many, fail to make any serious effort
t o determine whether land degradation is
setting in.
Unfortunately, the assumptions of technological and gastronomic stagnation mentioned above depart so markedly from
reality as to seriously diminish the utility
of the computed population density values.
Not only do primitive peoples readily adopt
new crops, new tools, new techniques-as
is attested by the rapid diffusion of maize,
Xanthosoma spp., and steel in New Guinea,
of watermelons, horses, and bananas in the
New World, of maize, manioc and papayas
in Africa-under
the pressure of circumstances, they may practice techniques already known, but not previously utilized.
W e may cite a number of examples: Allan,
in describing the intensive agriculture of
Wakara Island, Lake Victoria wrote, “faced
with the problem of maintaining permanent
cultivation-the
Kara adopted the expedient of manuring. There is nothing remarkable in this; it is a mistake to suppose
that African people are ignorant of the use
of manure or that its value as a soil fertilizer is beyond their understanding.” (5) At
first hand, I have observed in the Bismarck
Mountains of New Guinea, a t the village of
Kompiai, war refugees, whose traditional
system was slash and burn, busily spading
sod. Though they prefer the ancestral
system, circumstances obliged them to employ another well-known, but laborious
and distasteful system. (6) Ester Boserup
deals at length with the topic of agrarian
change under population pressure. “Thus
the new approach to agricultural development which is signalled by the concept of
frequency of cropping draws the attention
to the effects upon agricultural technology
which are likely to result from population
changes. This is a sharp contrast to the
usual approach which takes agricultural
technology as a largely autonomous factor
in relation to population changes.” (7)
The assumption of an unvarying crop
pattern which is implicit in “a given system
of usage” is clearly a t odds with empirical
fact. As people press upon their resources
they tend to raise those crops that give a
high yield as related to area available for
cropping-not
necessarily those that they
prefer to eat nor those that they formerly
ate. Many inhabitants of south China and
Okinawa who prefer rice and whose ancestors subsisted o n rice derive sustenance
from sweet potatoes which outyield other
upland crops. By the same token the quality
and quantity of per caput food consumption tend to decline with crowding upon
the land. The inhabitants of the limestone
country near Jogjakarta on Java have in
recent times changed their diet from rice
and maize to manioc and concurrently
have developed widespread protein deficiency symptoms. (8)
In most of the studies reviewed the criterion of the maintenance of the resource
base is treated perfunctorily. R. L. Carneiro, in a study of an Amazonian village
states that, “the number of years the plot
must lie fallow before it can be recultivated” is the equivalent of the length of
fallow required to prevent any long term
impairment of the soil. (9) I infer that he
determined “the number of years the plot
must lie fallow” simply by calculating the
104
VOL. XXI, NUMBER
2, MARCH,1969
average fallow practiced by his villagers.
There is no indication that he made any
serious effort to find out whether soil
degradation was occurring. R. F. Salisbury,
in a report on the Siane of the New Guinea
highlands, writes, “the technique of cultivation and the acreages used would support
an equilibrium analysis projecting the
present both forward and backward-.”
“The ratio of cultivation to fallow would
clearly indicate that no progressive impoverishment of the land need occur.” (10)
Alas, Salisbury fails to offer any evidence
to support his assertion that the land is
not being impoverished. I have the uneasy
feeling that he has simply equated contemporary fallowing practice with that requisite to soil conservation. H. C. Conklin, in
his treatise on Hanunoo agriculture on the
island of Mindoro in the Philippines works
out an “estimate of the critical carrying
capacity of the Yagaw area through time.”
(11) Again current fallowing practice is
equated with the ideal. True, he does state
that the community under study seems to
have been stable through time, through
references to erosion and the existence of
savannas suggest past, and possibly present,
instability. Harold Brookfield, in a study
on New Guinea’s upper Chimbu Valley, a
region of precipitous slopes where rural
population densities approach six hundred
per square mile, once more identifies
permissible fallowing practice with the
contemporary mean for purposes of estimating carrying capacity. He justifies this
procedure with the comment, “there is only
limited evidence to suggest that active soil
degradation is taking place in Chimbu today-.”
“We may thus assume, in the
absence of contrary data, that the values we
employ here are reasonable.” (12) In 1956,
seven years before Brookfield‘s book was
published, District Agricultural Officer J.
W. Barrie wrote of the Chimbu, “with
reference to the negative factor of diminishing land potential there is ample evidence
to illustrate that on the steeper slopes the
practice of shifting cultivation is resulting
in soil loss and soil nutrient depletion. Crop
yields are decreasing, denudation is apparent, loss and degradation of the soil is
(sic) widespread.” (13) I tramped the trails
of the Chimbu in October, 1964, and saw
numerous unmistakable signs of environmental deterioration, to wit: many land
105
slips, hard soil with poor structure, sediment-laden streams, rill wash, exposed subsoil.
In a recent commentary on the use of
the methods of ecological potential in
estimating the aboriginal American population, Peter Kunstadter states: “One underlying assumption of the whole argument is
that human populations will fill to the
point of equilibrium the ecological space
available to them.” “Finding that an isolated pristine human population did not
conform to the equilibrium model might
dispel some of the mysticism surrounding
the idea that primitive man is always in
balance with nature, while modern man
despoils and upsets that balance.” (14) Of
course we do have evidence of “pristine”
human populations having despoiled their
environment, for example, the Chimbu
discussed in this paper or the Kara referred
to in Allan’s 1965 work.
Determination of that fallow period
which allows maximum population density
consistent with maintenance of the soil
resource is difficult if not impossible.
Deterioration of the land is a cumulative
process and short term changes may be so
slight as to be exceeded by errors in measurement. Cowgill in a study of soil fertility
and the ancient Maya attempted to determine the rate of soil recovery under bush
fallow by means of chemical analyses of
randomly chosen fields which had been
under fallow for various lengths of time.
( 1 5 ) Not only did she not know the
nutrient status of these fields at the time
of garden abandonment, but the measurement of changes in available phosphorus
would be suspect even if the nutrient status
were known. Referring to the work of Nye
and Greenland on T h e Soil under Shifting
Cultiuation I found that “the value of soil
analysis as an index of fertility decline is
limited because of difficulties in interpretation. The conventional measurements-tell
us about the amounts of nutrients present,
but not directly about their ‘availability-.”
(16) “Changes in total soil phosphorus
during a period of cropping are relatively
so small that they cannot normally be
measured.” “These authors have not found
any generally valid method of estimating
the availability of soil phosphorus.” (I 7)
Further to confound the reckoner of the
soil fertility budget there exist only vague
106
THE PROFESSIONAL
notions of the rate of formation of most
tropical soils. And to quote once more
from Nye and Greenland, “Essential knowledge is also lacking on the extent of leaching losses particularly during the cropping
period.” ( I 8)
A deficiency common in calculations of
carrying capacity is the assumption that,
as the intensity of land use increases, the
incidence of weeds, diseases, harmful insects,
human and animal parasites will remain
constant, whereas there is a tendency for
pests to increase more rapidly than crop
acreage and human numbers. Propinquity
and long-continued cropping or residence
in a given place favor pests.
W e should not allow the elusiveness of
“long-term carrying capacity” to distract us
from a very proper concern with the
ecological soundness of the relationship
between our chosen people and the land.
Let us address ourselves to the question
posed by Spencer, “What does the practice
of shifting cultivation do to the landscape
and the environment?” (19)
Several investigators have approached
this problem in a most constructive manner.
I shall cite a few. J. D. Freeman in a
thorough and logical study of the Sea
Dayaks in Borneo ascertained that cropping
for two years in succession raised considerable hazards of erosion and of displacement
of forest by a highly combustible savanna
o f lmperuta cylindricu, whereas cropping
for but one year coupled with a fallow of
11-14 years markedly lessened these hazards. (20) L. G. Loffler working in the
Chittagong Hills assembled data on yields
per unit area, fallow land included, showing that o u t m t of a territorv rises then
with progressive shortening of the
GEOGRAPHER
fallow period. (21) David Simonett used
air photos to measure the incidence of landslides as a function of vegetation cover in
the eastern highlands of New Guinea, finding a higher frequency in anthropogenic
grasslands than in forests. (22)
A pitfall that often traps enquirers into
the ecology of shifting agriculturalists is
the tendency to become enamored of the
object of their scrutiny; the swiddeners
appear to be so self-sustaining, so well
integrated with their environment, so in
harmony with nature that it is hard to
believe that they may be damaging their
resource base. W. R. Geddes, who studied
the Mia0 of northern Thailand, staunchly
maintained that his people and primitives
in general would not fire the savannas
simply for pleasure. (23) Unfortunately,
my observations and those of many botanists and foresters are at variance with this
belief.
Much research is still needed to indicate
the effect of the shifting cultivator on his
environment: measurement of erosion,
measurement of leaching, measurement of
yields under diverse systems of land rnanagement and in various environments. T o
date anthropologists and geographers have
confined themselves to field studies with
relatively short periods of direct observation, while experimental studies of tropical
subsistence agriculture have been few and
often ill-structured. T o achieve progress it
is necessary to conduct experiments on
replicated plots, to control variables other
than those under investigation, to continue
observations over a long span of time, to
describe the experiments in sufficient detail
so that other workers in the field may
properly evaluate them.
* * *
Allan, William. “Studies in African
Land Usage in Northern Rhodesia.”
Rhodes Livingstone Papers, No. 15,
1949.
Loffler, Lorenz G. “Bodenbedarf
und Ertragsfaktor im Brandrodungsbau.” Tribus, Vol. 9, 1960, pp. 3943.
Conklin, Harold C. Hanumoo Agriculture. FAO, Rome, 1957, p. 146.
Brookfield, Harold C. and Paula
Brown. Struggle f o r Lund; Agriczcltiire und Group Territories among
(5)
(6)
(7)
the Chimbu o f the New Guinea
Highlands. Oxford University Press,
Melbourne, 1963.
Allan, William. The African Husbandmen. London, 1965, p. 200.
William Clarke discusses population
pressure and resulting technological
change in the general area of
Kompiai in “From Extensive to Intensive Cultivation: a Succession
from New Guinea.” Ethnology, Vol.
5 , 1966, pp. 347-359.
Boserup, Ester. T h e Economics o f
XXI, N U M I ~ E2,R MAIICH,1969
107
Agrarian Change Under Population
Pressure. Aldine Press, Chicago,
1765, p. 14.
Bailey, K. V. and Merle J. “Cause
and Effect of Soil Erosion in Indonesia.’’ Symposium on the lmpact of
Primitive Man on Humid Tropics
Vegetation. UNESCO, Goroka, Sept.
1960, p. 272.
Carneiro, Robert L. “Slash and
Burn Agriculture, a Closer Look at
its Implications for Settlement Patterns.” Selected Papers of the 5th
International Congress o f Anthropological and Ethnological Sciences.
University of Pennsylvania Press,
Philadelphia, 1960, p. 231.
Salisbury, R. F. “Changes in Land
Use and Tenure among the Siane
of the New Guinea Highlands (1952Pacific Viewpoint, Vol. 5,
1961)
No. 1, May, 1964, pp. 1-10, p. 10.
Conklin, op. cit., p. 146.
Brookfield and Brown, 09. cit., p.
123.
Barrie, J. W. “Population-Land
Investigation in the Chimbu District.” Papua and New Guinea Agricultural Journal, Vol. 11, No. 2,
October, 1956, p. 51.
Kunstadter, Peter. Current Anthropology. Vol. 7, No. 4, Oct. 1965, p.
437.
Cowgill, Ursula M. “Soil Fertility
of the Ancient Maya.” Trans. o f the
Conn. Acud. o f Arts and Sciences,
Vol. 42, October 1961, p. 45.
Nye, P. H. and D. J. Greenland. T h e
Soil under Shifting Cultivation.
Commonwealth Bureau of Soils,
Technical Communication No. 51,
1960, p. 98.
lbid., p. 112.
Ibid., p. 119.
Spencer, J. E. “Introduction.” Symposium: Effects of Shifting Agriculture on Natural Resources with
Special Reference to Problems in
Southeast Asia. Proceedings of the
9th Pacific Science Congress, Vol. 7,
Bangkok, 1759, p. 51.
Freeman, J. D. Ibun Agriculture.
London, 1955, p. 130.
Loffler, op. cit., p. 42.
Simonett, David S. “Soil Erosion in
the Eastern Highlands of New
Guinea.” Paper presented at the
national meeting of the Soil Science
Society of America, 1963.
Geddes, W. R. “Discussion.” S y m posium on the Impact o f Primitive
M a n on Humid Tropics Vegetation.
UNESCO, Goroka, Sept. 1963, pp.
135, 143.
The newest map title in the Bureau of
the Census GE-50 series, No. 24, is “Families in Poverty Areas for Selected Cities of
the United States: 1960.” Circle sizes show
the number of families in cities, and families in poverty and non-poverty city areas
expressed as portions of total numbers of
families in the city. The price of the map
at the Supt. of Documents is 50 cents.
ada: A Geographical Interpretation, edited
by John Warkentin.
.”
Frederick Watts, editor of the Canadian
Geographer and staff member at the University of Toronto, died on January 2.
After completing his M.A. degree at Syracuse University he lectured at the University
of Manitoba. His geographical interest
centered mainly on the field of climatology,
and he contributed the section on “Climate,
Vegetation, and Soil” to the volume, Can-
A recent newsletter announces that the
sixth international symposium on remote
sensing of environment is to be held at
the University of Michigan October 14-16,
1969. The registration fee, which includes
the cost of the published proceedings, will
be $30. Further information may be obtained from Extension Service, Conference
Department, University of Michigan, Ann
Arbor, 48104.
Leslie J. King of Ohio State University
is the director of a NSF grant to support a
summer institute for college teachers in the
social science fields during the summer of
1969.