^^m^^^*^] CLIMATE AND EVIDENCE OF CLIMATIC CHANGES 59 



Lewis ^ has investigated the plant remains in the peat bogs of Eng- 

 land and Scotland. In the lowest strata are arctic willows, above 

 these are forest remains, followed by the present-day peat mosses. 

 In the Cross FeU chain, peat beds having forest remains cover about 

 140 square miles; the present forest extends over only 11 square 

 miles. Lewis thmks that the destruction of these forests has been 

 due to ''climatic changes acting over very long periods of time." 

 Studies of forest successions in Europe indicate that they, too, are 

 due in some cases to climatic changes. 



As aheady said, botanical evidence of changes of chmate within 

 historic times is meager and not convincing. It is a field of study to 

 a large extent untouched, a study beset with difficulties. Methods 

 of investigation are not worked out. Successions of vegetation 

 have and are taking place, but the relative importance of climatic 

 and other operating factors is difficult of analysis. 



Any change of climate would be very slow.- The fact that meteor_ 

 ologic records fail to show such change is of little importance, for 

 such records extend over only a few centuries and accurate records 

 over only a very short period, during which the change, if in progress, 

 would be too slight to manifest itself in averages, besides being masked 

 by probably more or less periodic fluctuations, while the accumulated 

 change of 2,000 or 3,000 years, if records were available, might be 

 quite manifest. 



It is improbable that change of temperature has had any direct 

 bearing on the disappearance of the ancient dwellers from this region. 

 Present temperatures are suitable for agriculture and for comfortable 

 living However, if there has been an increase in the mean annual 

 temperature, as is not at all improbable, it would have increased the 

 evaporation, thus making greater precipitation necessary for agricul- 

 ture and in that way indirectly aiding in depopulating the area. 



vSpeaking of the region west of Albuquerque, Newberry ^ says: 



In all this region a fact was observed, to which our attention was first called on the 

 banks of the Little Colorado, viz: that the lower hills and the bases of the highlands 

 are covered with dead cedar trees, an apparent indication ^f the increasing dryness 

 of the climate. The timber in this country is confined to the more elevated surfaces, 

 where the precipitation of moisture is greatest, and the belts of deadened trees, cer- 

 tainly untouched by fire, prove fhat the conditions favorable to the growth of arbo- 

 rescent vegetation are becoming restricted to narrower limits. This fact is mentioned 

 merely as being confirmatory of the conclusion drawn from other data, that the amount 

 of rain on the table-lands west of the Rio Grande is now much less than formerly. 



Many dead cedars occur also on the mesas west of Santa Fe. Mistle- 

 toe is a pest there and may have caused their death, or it may, of 



' Lewis, Francis J., Plant Associations in Moorland Districts, in Nature, Lxxi, 257-58, 1905. 



2 See Sullivan, Richard H., The So-called Change of Climate in the Semiarid West, in Yearbook U. S. 

 Dept. Agric. for 1908, pp. 2S9-300, 1909. 



' Newberry, J. S., Geological Report, Report upon the Colorado River of the West, Explored in 1857 and 

 18o8 by Lieutenant Joseph C. Ives, pt. m, p. 96, 1861. 



