100 MAN ON THE LANDSCAPE 



scape which is swift enough to be noticeable in a human generation 

 must be classed as very violent. 



Violent reactions have been and are even now being brought about 

 6y: 



(1) Burning of forests, savannahs, grasslands and scrub 



(2) Careless lumbering operations which destroy young growth 

 (nd fail to provide for reseeding 



(3) Over-grazing of rangelands and farm pastures 



(4) Cultivating steep hillsides or long slopes 



(5) Continuous planting of the same crop year after year 



(6) Failure to return humus to the soil 



(7) Over-hunting and over-fishing 



(8) Unnecessary destruction of food and shelter for wildlife 



(9) Planned and sustained attacks on certain predatory animals, 

 such as hawks, owls, foxes, pumas. 



(10) Concentrating toxins in air and water sufficient to reduce life 

 processes 



(11) Interposing light-reducing obstacles between the sun and 

 chlorophyll 



(12) Withdrawing ground water faster than it can be replaced 



(13) Drainage of sub-marginal lands 



(14) Strip-mining 



(15) Destroying sod on dry and windy areas 



(16) Drawing on fertility faster than it is restored . 



The reaction of one or more of the above activities on the landscape 

 is in reality a complex of reactions. The complex involves two or 

 more reactions : on soil, water, light, temperature, air. The reactions 

 on soil, for example, may be classified as they relate to, or alter: (a) 

 the soil formation process, (b) soil structure, (c) soil texture, (d) 

 soil water, (e) soil solutions, (f ) soil gases. There are physical, chem- 

 ical and biologic reactions involved (one or more) in all the changes 

 mentioned. This highly intricate web of relationships has its weak 

 spots, and these offer opportunity for setting off a chain of reactions, 

 each of which may be minor, but which pile up a cumulative power 

 and violence sufficient to boot man off the landscape. 



Reserves Must Be Maintained. Climate is the long term charac- 

 teristics of weather. The weather averages commonly quoted are use- 

 less in providing a true picture of climate. We must know the daily, 

 monthly, annual and cyclical (if any) ranges of climatic factors in 

 order to understand the nature of such forces as they react on the 

 environment. (We will pass over the grand scale climatic shifts 

 which must be spoken of in terms of geologic time, such as those ac- 

 companying continental ice sheets.) Much study has been given to 

 finding some basis for forecasting climatic variations over a period of 

 years. The sunspot theory is current, and seems to offer some corre- 

 lation. Eleven years appears to be the time unit of cycles in both 

 climatic and sunspot activity. There also seem to be super-cycles, 



