Humans are an enormously successful species in terms of increasing their pop and spread 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.

You could say that it enlarged our "tolerance thresholds" for "limiting factors" like climate, soils, etc.

Human diffusion: permanent move into new lands. 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. 4.1). 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 (ancestral puebloans) either as a response to drought or to social forces (like war).

By about 7K years ago a significant change had occurred to allow more dense human occupation of many areas.

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 America. (Fig. 4.2) . Relied on innovations in cropping, animal domestication and breeding, moving and controlling water (irrigation), and food storage.

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, but also long seen as opportunity for expansion of "Western" or modern development, which brings tensions between land use and env, and among cultures.

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.

Many definitions: semi-arid, true desert, tropical wet/dry. Marked by relaitveily low precip, and thus low primary productivity.

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

Desertification: the long-term degradation of land as a result of interaction of land use and climate. Serious problems: in Sahel of Africa, Madagascar, also subject of a major UN conference this year.

Polar lands: quite "harsh" conditions (temp limits on productivity, and some terrain limits like permafrost), but still home to long-term, thin, traditional settlement.

Now seen in various ways: energy; wildlife; new economic development desired by locals and by national governments (e.g., Canada)..

Boreal Forests: between mid-latitude and tundra: a rich forest env., thinly settled, and not yet greatly exploited for timber.

Access problems, slope making settlement and agriculture difficult; but often rich in resources. In US and elsewhere now more and more attractive as recreational areas.