290 cook: vegetation in southern peru 



cultivation. The growth of each native community means 

 that supplies of fire-wood have to be sought farther and farther 

 away. A large Indian town is usually surrounded by a broad 

 belt of denuded lands, no forest being allowed to remain within 

 two or three leagues. Judging the past by the present, a period 

 of denudation of all the neighboring slopes must have followed 

 the building of the extensive systems of terraces in the valleys 

 about Ollantaytambo, Torontoy, and Machu Picchu. The 

 country around these centers must have reached the same 

 treeless state as the districts that now have large agricultural 

 populations, such as the Vilcanota Valley and the slopes around 

 Lake Titicaca. 



reforestation prevented by fire 



In many localities cultivation is confined to the bottoms of 

 the valleys or to the lower slopes, while the higher slopes have only 

 a sparse covering of grass or low bushes. This gives the im- 

 pression that the interior of the country is naturally treeless, 

 like the desert regions along the coast. But the coast deserts 

 are explained by the rainless climate, whereas in the interior the 

 rainfall is sufficient to support forest growth. 



The former cultivation of many of the higher slopes is indi- 

 cated by the ridges and terraces that still remain. These show 

 in turn the previous existence of forests, since forests must have 

 preceded cultivation in order to accumulate soil and make it 

 possible to clear the land by the primitive method of burning. 

 This method is ineffective on grass lands, which have, to be re- 

 forested before they can be re-occupied by a primitive agricul- 

 tural people. At tfye higher altitudes grassy slopes are culti- 

 vated by spading, but this method is used only where turf is 

 formed. 



When treeless slopes are seen in tropical valleys meeting the 

 tropical forest vegetation, it is plain that some active enemy 

 of forest growth must be at hand, and this is fire. The fires that 

 are set to clear land for cultivation commonly escape and over- 

 run the slopes above. As the grass-covered slopes are used 

 only for grazing, no effort is made to protect them from fire. 



