12 



In Cook County, according to Dr. Waterman, of Northwestern Uni- 

 versity, Department of Botany, out of 5,760 acres surveyed, only seven hun- 

 dred acres still bear original forest growth and of this only eighty acres 

 is virgin forest. The Cook County Forest Preserve Board, however, is 

 doing much to save these scattered bits of native forest for the people 

 of Cook County as a recreation ground and now has over 17,500 acres of 

 such forest under its jurisdiction. 



Forest Influences. Among the forest influences or forest reactions 

 which should be considered in Illinois are the effects of the removal of 

 the forest cover in causing irregularity of stream flow due to the drying up 

 of streams and springs, with destructive floods. Dr. Fernow says that the 

 stopping of floods is an engineering problem but that forests can be de- 

 pended upon to render the flow of water throughout the year more uniform. 

 Illustrations from remote regions lose their effect but we might take a 

 specific one from Jo Daviess County. One flood in a stream only five 

 miles long destroyed a stone mill dam and wrecked the large flouring mill. 

 Some fifteen feet of silt was deposited on the bed of the mill pond after 

 the flood had subsided, representing as Dr. Pepoon says, "one foot of 

 eroded soil from four acres of farm land." 



Another marked result of deforestation in this same county has been 

 the drying up of springs and brooks and the lowering of the water table. 

 This is quite in conformity with evidence cited by Greve, by McGee, Tourney 

 and Mead. Where originally there were 'six minor brooks and fifteen 

 springs in a certain map area, today none remain and the ground water has 

 been lowered from eight to twelve feet below its former level. This is not 

 the opinion of a casual visitor to the region but the observation of one 

 who has studied the same region for years. 



Erosion. It is stated on good authority that leaf mould will absorb 

 from two to four times its weight in water. Due to this large absorptive 

 capacity, measurements made in France show that surface run-off from 

 wooded slopes is only one-half of that from deforested slopes. Reduction 

 of run-off prevents erosion, so that one of the main remedies for badly 

 eroded and gullied land, according to the Illinois Soil Survey, is "to put 

 them back into forests as rapidly as possible." Their reports abound 

 with instances of where soil abandonment is taking place, but more espe- 

 cially in the seven southern counties and in those adjoining the Wabash, 

 Mississippi and Illinois rivers. The Illinois Geological Survey speaks of 

 deforestation as one of the agencies in causing erosion, with the attendant 

 evils of gullying and sheet washing. 



Let us take some specific examples. Dr. Fuller says of LaSalle county, 

 in the upper Illinois valley region, that "along many of the stream valleys 

 are slopes of such a character that the removal of the forest cover will 

 cause, and in some cases has already caused rather extensive gullying." 



In Union county, where the Dongola topographic sheet is being prepared, 

 many fields were seen, especially in yellow silt loam soil, where gullies 

 were forming and the owners of the farms were making unsuccessful 

 efforts to stop them with brush and straw. According to the- older resi- 

 . dents, these slopes had years ago been covered with a forest of tulip, white 

 pak and *ea Q&fc, B0. P$fc m$ sycamore seedlings, fUopg with sassafras 



