Plants of Casa Grande Ruins National Monument - NPS Inventory ...

and groundwater were used (Powell et al. 2006). By 1928, the construction of
Coolidge Dam ended the era of the Gila as a free-flowing river through the area.
The conversion of the landscape to agriculture continued unabated, and had
encircled the monument by 1932.
Agriculture in the Coolidge area suffered greatly from overpumping of the water
table, which was obvious as the water level of the park’s well dropped from
128 feet below the surface, in the early 1940s, to more than 300 feet below the
surface by 1956 (Clemensen 1992, Powell et al. 2006). This lowering of the water
table, combined with a widespread mistletoe infestation, contributed to a large
scale die-off of the Casa Grande Ruins mesquite population in the 1930s (Judd
et al. 1971). The decade of the 1930s also saw the bulk of the development at the
monument, with construction of the roof over the ruins in 1932 and, by the end
of the decade, the visitor center, paths, roads, and several outbuildings. These
are the same buildings that constitute the monument today. There has been only
one major excavation of the ruin complexes; at that time, vegetation was scraped
off the site entirely. Since the 1930s, little has been done to alter or manipulate
the vegetation at Casa Grande Ruins. Today, some studies have questioned
the negative effects of pesticide drift from neighboring agricultural land; this,
combined with the edge effects of rapidly urbanizing Pinal and Maricopa
counties, the continued decline of the water table, and active climate change, all
have serious ecological implications for Casa Grande Ruins NM.
Clemensen, A.B. 1992. A centennial history of the first prehistoric reserve:
1892-1992. United States Department of the Interior. National Park
Service, Washington, D.C.
Judd, B.I., J.M. Laughlin, H.R. Guenther, and R. Handegarde. 1971. The lethal
decline of mesquite on the Casa Grande Ruin National Monument.
Great Basin Naturalist 31: 152-159.
Powell, B. F, E. W. Albrecht, C. A. Schmidt, W. L. Halvorson, P. Anning,
and K. Docherty. 2006. Vascular Plant and Vertebrate Inventory of
Casa Grande Ruins Naitonal Monument. OFR 2005-1185. U.S.
Geological Survey, Southwest Biological Science Center, Sonoran
Desert Research Station, University of Arizona, Tucson, AZ.
Reichhardt, K. 1992. Natural vegetation of Casa Grande Ruins National
Monument, Arizona. Cooperative National Park Resources Studies
Unit. Technical Report NPS/WRUA/NRTR-92/45.
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