Prehistoric Vegetation and Environment at Chaco Canyon

Pollen analysis of woodrat (Neotoma) middens indicates that the local vegetation at Chaco Canyon and the regional vegetation of the San Juan Basin, northwestern New Mexico, have been shrub grassland since at least 10,600 years ago. Plant macrofossils in the same woodrat middens indicate that pinyon pine trees were present in the canyon during much of the Holocene, but low percentages of their pollen grains in both the middens and in adjacent alluvium suggest the trees were few, occurring as small stands or isolated individuals along canyon escarpments. The vegetation at Chaco Canyon during Anasazi times was an arid shrub grassland with a sparse escarpment population of pinyon and juniper. A climate-caused regional increase in pinyon at higher elevation sites occurred approximately at the time of Puebloan abandonment.