Cactus on the Altiplano of South America contain an archive of useful climate, physiological and demographic information in the isotopes of their spines. As demonstrated on saguaro cactus in Tucson, Arizona, spines emerge from the apex of the cactus, cease growth, and then are retained in time-ordered sequence on the side of the cactus as the stem continues to grow upward. Thus, time ordered sequences of spines contain diurnal, seasonal, and annual information in the oxygen and carbon isotope ratios of the robust spine tissue.