B. P. I. — 417. 



VEGETATION AFFECTED BY AGRICULTURE 

 IX CENTRAL AMERICA. 



INTRODUCTION. «• 



That climate and other natural conditions of existence have had 

 their influences upon the development of civilization in different 

 parts of the world has often been recognized, but relatively little 

 study has been given to the corresponding influence of man on his 

 environment. The two questions are in many way- inseparable, for 

 we can hardly gain a correct idea of one without taking the other 

 into account. 



Savage who live by hunting and fishing or upon wild fruits, seeds. 

 and honey may occupy a tropical region without seriously disturbing 

 the previous balances of organic nature: but no careful observer of 

 the agricultural aborigines of the Central American countries can 

 doubt that they have had very definite influences upon their sur- 

 roundings, or that influences of the same kind have been exerted for 

 long periods of time. 



Humboldt and other geographical writers have reported the exist- 

 ence of very diverse types of vegetation in different parts of Central 

 America, and have proposed various geological and meteorological 

 explanations of the distribution of the different kinds of plant life, 

 the dense tropical forests, scattered growths of pine and oak, open 

 grass lands, and cactus deserts. (PL I.) 



As a matter of fact, these varied types of vegetation are not re- 

 stricted to particular altitudes or to particular geological forma- 

 tions. There are open fire-swept grass lands near sea level and at 

 many different elevations, and even on the upper slopes of the highest 

 volcanic peaks. Similar wide ranges of altitudes and conditions are 

 shared by the pines, oaks, and other trees which represent various 

 stages of a general process of reforestation. Cacti thrive in barren 

 places near the coast and also on the high interior plateaus. 



That the geological and meteorological influences are often very 

 important need not be denied, but their effects can be correctly esti- 

 mated only when the other factors of the problem are considered, 

 not by taking it for granted that the present conditions repre- 

 sent, or even approximate, the primeval state of the country. Unless 

 72058— Bull. 145—09 2 7 



