All human history has a natural context.  The essays in this section remind us that gila monsters, Sonoran Desert pronghorns, organ pipe cactuses, and pupfish were not created by people and have stories that have unfolded according to logics that do not always match human desires.  And yet our destinies are not entirely separate from theirs.  Cattle carrying diseases across the border, dwindling populations of endanger species, and the seasonal flowering of desert fruits–not to mention blistering temperatures, parched soils, and raging flash floods–have long shaped human understandings and actions in the Sonoran Desert.   At Organ Pipe, no less than anywhere else, history is the evolving outcome of the interactions between what humans do, what they think, and the natural context in which they do and think it all.  This entries in this section tell the region’s environmental history.