I = P * A * T

San fernando Valley

impacts of settlements on land, air, & water.


Environmental History is the study of how settlements alter ecological conditions and how those changes influence each era’s ideas about nature with respect to responsible resource use from one period to the next.


The impacts are on water, energy, air and land or WEAL.


Ideas meaning those concepts associated with the perception, ideology and values that contribute to methods of discovery with respect to our surrounding land, air and water when contrasted with an Earth’s eye view of the past.


Siry, Worster, Merchant

Perception, ideology, and values




Environmental history provides a double vision of human ambitions.



Beavers as a keystone species, water tables, reservoirs, forests.


Natives as diverse beyond our experience, farmers, horses.

Settlement of nationalities and churches from Europe.

         Revolution and nationalism: uniformity and commercial-agrarian tension.



America's watersheds are the engines of the ecological systems we need as we are all dwellers's downstream on round river.


Changes in scale with respect to means of altering surroundings


Economic patterns:                          impact quotient

Subsistence                                     1                      one

            Commercial                                      10                     10

Manufacturing                                  100                  102


Urban                                                 1000                103

Industrial                                           10000              104


Metropolitan (suburban)                 100000            105

Hyper-industrial                               1000000          106


Examples of the changes in landscape:




Jeffersonian Agrarianism


characteristics of the periods




River – based 1600-1900:

Fur trade



Planting - production oriented



Railroad – 1830-1950:




Urban concentration – production to consuming oriented




Roads –1917-2009:

            Birth of metro-areas SMSA

            Commercial centers

            Hyper-industrial (high water & electrical use)

            Consumption oriented


Changes in populations

population growth

                          Amount of people                           Year             Number of years elapsed


Population --                        3 million                              1790                base

                                            30 million                              1860                + 27

                                           100 million                              1900                + 70

                                           300 million                               2000                +200

in 2012 ? 


Impact = Population x Affluence x Technology                    I=PAT



Any impact is proportional to the number of people, their level of affluence, and the equipment they use to supply themselves and others with a means to make a living.

technological change, qualities of.


Preservation diverges from Conservation as protection.

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Emerson| Merchant | Worster | Cronin | Reisner | Jackson | Siry | Leopold | Diamond | Williams | Austin | Mumford | Marx




Siry II, Worster, Merchant, Emerson II, Olmsted, Mumford II, Egan, Rome