Read pages 14-16, and 23-37 of Chapter 2.

Humans have transformed the earth by making various sues of its surface and resoruces, for:

• Agriculture (crops and pastoralism or animal grazing)

• Settlement (low density rural)

• Settlement (high density urban)

• Infrastructure (roads, dams, etc.)

• Industry

• Recreation (ski areas, etc.)

Book talks about "disturbance" , I tend to use the word "transformation" instead.

Either depend on technology, intensity of land and resource uses, etc.

Also, the book in this introductory chapter just refers to Rural and Urban land uses.

Agriculture is the largest land use, the most widespread human transformation of the earth. It is both cultivation (crops) and pastoralism (grazing). More land is use din grazing than cropping, but the book only gives the cultivated land in Fig. 2.12. You cans assume that most all of the "grasslands" are used at some level of intensity for domestic grazing, though this would exclude nature preserves that harbor native grazing species.

The extent and intensity of agricultural use for cultivation varies among nation-states. For example, as given in the book, the US has a much greater proportion of its land area in crops than does China, even though we are not considered an agrarian society.

China: 96 m ha (230 m acres)—area is 3.7 sq mi, 9.6 sq km

US: 185 m ha (450 m acres)—3.5 sq mi, 9.2 sq km

We also do this with far fewer people actually involved in agriculture (due to higher technology):

China has a population of 1.34 billion; With 500 m in agriculture

US pop is 281 million; US has maybe 20 m in agriculture

This raises a quality of land use and types of human transformations of the earth: how intensive vs how extensive—as we’ll see in the agriculture chapter, the US produces more crop yield per unit of land area than does China----by virtue of larger inputs of technology, energy, and fertilizers and pesticides.

Urbanization plus infrastructure is the other main human transformation of the land surfaces of the earth.

Compared to a "natural" or baseline earth, we have dramatically increased the amount of land covered in crops and settlement. We did this by clearing forests and cultivating natural grasslands.

• Forests (clearing caused forest cover to go from 40 to 30% of land sfc in last couple of centuries---but note there that some areas have net re-forestation)
• Grassland (25%, roughly stable, because some forest land cleared to grassland, and some grassland cultivated to crops and lost to settlement)
• Cultivation 11-12%
• Urbanization 5-6%
• Other: 27% tundra, ice, bare sand/rock (all of which cans till be in some form of human use that changes some aspect of the environment---hunting/gathering; nature preservation, etc.)

Along with any change in land use comes dozens of other changes, in, for example:

• Terrain/roughness (cut trees down and roughness declines; add buildings and it increases)
• Biodiversity (species per area) (added and subtracted, native and exotic)
• Hydrology (runoff vs. infiltration)
• Radiation/thermal properties (more of less solar radiation absorbed or reflected by the surface, this affects the thermal regime);
• Bio-geochemical cycles, like carbon absorption or emission from the vegetation and soil; the cycling of nutrients like nitrogen and phosphorous.

Various qualities and intensities of these changes occur when, for example:

We transform:

Forests into croplands

Grasslands into housing subdivisions (suburbs)

Croplands into suburbs

Etc.

As we’ll discuss in class, the changes are both overt and subtle, and complex: changes that maybe subtract some species actually bring in others, so biodiversity defined at number of species in an area may not change as much as you might think. Consequences of those changes can also be anticipated or unanticipated.