dr. stephen malcolm, department of biological sciences

BIOS 5445: Human Ecology Dr. S. Malcolm Week 10: Slide - 1

•  Week 10. Survivorship: resources:

–  Lecture summary: •  Resources. •  Resource gathering. •  Temporal resource

variation. •  Spatial resource variation. •  Group sizes. •  Human responses. •  “There should be no more

people in a country than could enjoy daily a glass of wine and a piece of beef for dinner”

–  Thomas Malthus (1798).

BIOS 5445: Human Ecology Dr. Stephen Malcolm, Department of Biological Sciences

American Gothic by Grant Wood, 1930


2. Resources:

•  Kinds of resources: –  Essential, Substitutable & Complementary resources

(sometimes antagonistic): •  Necessary.

–  Key resources: •  Scarce but valuable.

•  Supply of resources: –  Density-dependent when limited. –  Costs and benefits of gathering resources:

•  Economics (study of resource allocation) of: –  Renewable resources. –  Non-renewable resources.


3. Resource gathering:

•  Technology increases efficiency of resource gathering. •  Human subsistence patterns - food gathering:

–  Foraging, Pastoralism, Horticulture, Intensive Agriculture.

Spring turning by Grant Wood, 1936


4. Foraging:

•  Hunter-gatherer life style. •  Use of wild food resources. •  <12,000 BP all humans were foragers. •  Modern versions:

–  Inuit of Canadian Arctic – San of the Kalahari desert.

•  Small, mobile groups strongly influenced by their environment:

– Bands with high family kinship.


5. Pastoralism:

•  Herding domestic animals as major food & materials resource.

•  Mobile - seasonal movements. •  Low population density. •  Rudiments of social control over

behavior. •  Basically egalitarian society.


6. Horticulture:

•  Subsistence agriculture. •  Use of simple tools to grow crop plants without

complex irrigation and fertilizer use. •  Use of small garden plots and long fallow

periods. •  Sustainable with increased population

densities. •  Examples:

–  Floodwater farming –  Swidden or slash-and-burn agriculture, such as “milpa.”


7. Milpa agriculture:

•  Dominant throughout mesoamerica: –  “Traditionally, a "milpa"

plot (from the Nahuatl word for "corn field") is planted with maize, beans, and squash and might include a variety of other plants. These plots are planted for two or three years and then allowed to lie fallow for some years in order to restore the fertility of the soil.”

•  http://en.citizendium.org/wiki/Milpa_agriculture

Milpa plots are found from Chihuahua to Central

America. This one is in Oaxaca, Mexico. Squashes

are being grown between the rows of maize.

Photo: Joey Hipolito

Harvesting beans from a mountainside milpa in Chiapas, Mexico. Photo: Lorena Pajares


8. Domestication:

•  Means controlling reproduction of selected plants and animals:

–  “Domestication is probably the single greatest technical achievement in the human record, more important than the internal combustion engine or nuclear energy. It was, from the beginning and long before these other triumphs, a remarkable way to capture energy.”

•  Hirschoff & Kotler (1989) p 115-116.

•  Mutualisms with food plants and animals: –  Despite consumption of crops and livestock

harvested species benefit from the interaction with humans.


9. Intensive Agriculture: •  Technology & labor used to create artificial agroecosystems to

grow crops and raise livestock. •  Intensive use of fertilizers and irrigation systems and large-scale

monocultures. •  Two major types:

–  Labor-intensive agriculture: •  Use of human muscular effort.

–  Subsidized agriculture: •  Use of fossil fuels for energy - not sustainable indefinitely.

•  Supports very high population density & urbanization: –  Swidden rice = 12 people/Km2, intensive rice = 386 people/Km2.

•  People work longer & harder: –  Population increase drives intensification, or, –  Political pressure drives intensification, or, –  Intensification drives population increase?


10. Modern 4-crop rotation to sustain soil nutrient balance (Fig. 15.12, Bush 2002).


11. Population and agricultural intensification (Fig. 3.6, Livi-Bacci, 1997):


12. Seasonal variation in resources:

•  Almost all resources on Earth are derived from the fixation of solar energy by plants.

•  Solar energy varies systematically by location and time (Fig. 11-11).


13. Non-seasonal variation in resources through time:

•  Succession: – “the non-seasonal, directional and

continuous pattern of colonization and extinction on a site by species populations.” (Begon et al. 2006).

•  Successional changes allow for crop rotations.

•  Many crops are early successional, annuals, or mid-successional perennials.


14. Hypothetical succession by pioneer (pi), mid- successional (mi) and climax (ci) species. (Fig. 16.16, Begon et al. 2006).


15. Spatial variation in resources - patchiness

•  Group size is affected by spatial distribution of resources - patchiness.

–  In North American Indians group size was related to resource characteristics: •  Amount, mobility, predictability and distribution.

–  Large group size = resources mobile, unpredictable & clumped.

–  Small group size = resources stable & evenly distributed

•  Human behavior also influences group size.

– E.g. cooperative hunting with nets vs bow- and-arrow hunting in Mbuti pygmies.


16. Human responses to seasonal resource change:

•  Movement or migration: – Common among foragers & pastoralists but

not agriculturalists. – Examples:

•  Nomadism - the entire social group moves •  Transhumance - part of the social group moves to

follow herds. •  Migrant farm workers - seasonal work availability.


17. Annual cycle of Karimojong cattle herders in East Africa (Fig. 11-13):


18. Annual cycle of Quechua Indians in Peruvian altiplano (Fig. 11-14):


19. References: •  Begon, M., C.R. Townsend, & J.L. Harper. 2006. Ecology: From

individuals to ecosystems. 4th edition. Blackwell Science, Oxford, 738 pp.

•  Bush, M.B. 2002. Ecology of a changing planet. Prentice Hall, NJ. •  Cohen, J.E. 1995. How many people can the Earth support? W,W. Norton

& Co. New York, 532 pages. •  Hirschoff, P.M., & N.G. Kotler. 1989 (eds.). Completing the food chain:

Strategies for combating hunger and malnutrition. Smithsonian Institution Press, Washington, DC.

•  Hobhouse, H. 1985. Seeds of change. Five plants that transformed mankind. Harper Row, New York.

•  Kormondy, E.J., & D.E. Brown. 1998. Fundamentals of Human Ecology. Prentice Hall.

•  Livi-Bacci, M. 1997. A concise history of world population. 2nd edition. Blackwell, Oxford.

•  Milpa agriculture: http://en.citizendium.org/wiki/Milpa_agriculture –  Citizendium, the Citizen’s Compendium.

dr. stephen malcolm, department of biological sciences

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