Geography 2412 lecture Notes

Chap. 6: The Spread of Humanity, and Challenge of frontier Environments

Humans are an enormously successful species in terms of increasing their pop and diffusion across the globe.

Culture: all things invented, and passed on, by humans, such as our languages, tools, and ways of managing resources and producing and consuming goods and services. Our cultural "tool kit" separates us from other species and has allowed our success at inhabiting and transforming large areas of the earth for our benefit, including environments that seem inimical to human existence.

You could say, in an ecological sense, that culture enlarged our "tolerance thresholds" for "limiting factors" like climate, soils, etc.

Human diffusion: permanent move into new lands, originally quite slow and experimental, but widespread for 50K years; thin on the ground until ag/indus/urbanization)

Accompanied by adaptation to new environments, but also by transformation of those environments.

Covered the continents (except Antarctica) in 50,000 years thru diffusion from early human emergence in Africa. In at least a low density. (Fig. 6.1). One debate about this (and about the emergence of agriculture) has been how much was caused by environmental pressures or limits (e.g., a drought) on resources, with the idea that scarcity or necessity was the "mother of invention." Other social causes also make sense and the debate continues, even in our own Southwest where analysts try to explain the disappearance of the Anasazi (now called the ancestral Puebloans) either as a response to drought or to social forces (like war).

Agricultural revolution

By about 12K years ago a significant change in culture/technology had occurred and allowed further diffusion, intensified human occupance, and transformation of different environments.

Agriculture: the domestication and cultivation and husbandry of selected plants and animals for human consumption.

• Several ag cultures emerged independently: China, Mesopotamia (Iraq and Iran), Central and So. America. (Fig. 6.2)

• Asia, Meso-America: sedentization; pop growth; urban growth; increase environmental transformation (clearing forests, draining wetlands, irrigating land; promulgating some selecting species/reducing others; soil erosion; pollutants.

• Major agricultural centers by 6-7K BP

• Most of Europe, other mid-latitudes after 2K BP

• Then: North America, Australia, South America

Relied on innovations in cropping, animal domestication and breeding, moving and controlling water (irrigation), and food storage. We’ll examine agricultural systems in more detail in Chap. 8.

Emergence of global power and urban centers

• Shift in power form Asia to Europe (the “West”)

– Colonial powers

– Post-colonialism

• Global systems:

– Developed, developing, and deprived/poor

– Globalization along with uneven development

– Rise of new powers (China, India, Brazil), with uncertain, future environmental effects (e.g., China has lots of coal to burn)

Frontier Environments

Geographers have been long interested in this theme. Idea of "Frontier" is somewhat cultural-centric, especially Eurocentric, as noted in text, but used here as notion of mostly thinly-settled areas, often long settled by traditional or indigenous peoples, at low population densities and low impact, but also long seen as opportunity for expansion of "Western" or modern development, which brings tensions between land use and env, and among cultures. Often with resource limits, but also some rich resource endowments (e.g., timber and species in wet tropics; space for cropping/grazing in dry lands; wildlife and oil in cold regions).

Wet Tropics

Symbolized by the tropical rainforest of Asia, Africa and South America: difficult agriculture, isolated, travel, etc. but holding many resources that the developed countries want: tropical hard woods, places to grow coffee, oranges, etc, and often subject to pro-settlement policies by the local and national government. Key environmental effect is forest clearing and loss of species.

Tropical forests play role in global greenhouse gas budget (forest as store of carbon sequestered from the atmosphere at least temporarily), and regional to global hydrology (forests were storage of moisture, their loss means less evaporation , rainfall, and runoff.).

The Dry Zones

Many definitions: semi-arid, true desert, tropical wet/dry. Marked by relatively low precip, (less than 20 in/yr, often less than 10 in/yr) , and thus low primary productivity.

Include:

True deserts: very low precip (less than 12 in/yr; some places like the Atacama can go years withy no precip)), any precip mostly evaporates quickly rather than runoff or infiltrate. Little or no vegetation. Agr. Only where water sources are available: a river running from more humid climate thru the desert (the Nile) or groundwater.

Semi-arid or steppe lands: the great grasslands, for example the American Great Plains, the Sahel of Africa. No sufficient precept for trees, but grasses and shrubs; often good grazing lands, originally inhabited by herds of grazing animals (antelope; bison, etc.), now replaced in most places by domestic livestock.

Problems:

Moisture variability.— precipitation is not dependable seasonally and inter-annually (see 6.6a), so agriculture w/o irrigation is risky.

Note on statistical variability of precipitation: Some natural processes yield statistical distributions that are quite “normal”, the so-called bell curve. In this case the mean (or average: the sum of the observations divided by the number of observation) and the median (the most frequent value) are the same (or similar). But precipitation, especially in low precip settings, is often “skewed” so that the mean is higher than the median, or, put another way, while you may plan for the average precip, there is actually a better than 50/50 chance that in any given period (e.g., a year) you will have below average!

Desertification: the long-term degradation of land as a result of interaction of land use and climate leading to reduced plant cover, soil, and soil moisture reserves. Serious problems: in Sahel of Africa, Madagascar, also subject of a major UN conference last year.

Why does surface disturbance often result in reduced moisture holding capacity? Loss of organic matter in the soil profile. Organic matter absorbs and holds water, whereas the particles of mineralized soils cannot.

Cold/polar Lands, Mountains, and continental shelves (coming in next set of notes)