TRANSFORMATION OF MARITIME DESERT TO AN AGRICULTURAL CENTER — HOLOCENE ENVIRONMENTAL CHANGE AND LANDSCAPE ENGINEERING OF THE CHICAMA RIVER VALLEY, PERU

One of the longest-occupied human settlements along the Andean margin is located near the Chicama River mouth, where populations were supported primarily by abundant marine life despite having domesticated plant cultigens as early as ~10 ka. This maritime economy dominated until ~6 ka, after which agricultural production began to increase, accelerating rapidly into the late Holocene. The agricultural expansion was motivated in part by the development of arable fine-grained floodplains as a result of enhanced river floods, slowing sea-level rise, and the river’s unique basin lithology. Local populations made use of these stabilized floodplain and wetland settings to conduct small-scale raised-terrace farming. By ~3.5 ka, increasing fine-grained sediment delivery and a broadening floodplain promotes growing agricultural resources and major cultural developments, including the production of fired-ceramic pottery and adobe-brick monument construction. Coastal populations thereafter expand up valley, using small water-control structures to farm arid arroyos. These cultural and technological developments parallel natural environmental changes driven by increasing ENSO-related water and sediment discharge. After ~2 ka, the peak extent of agriculture and arable land was driven in large part by direct human manipulation of the environment. The construction of an ever-expanding network of irrigation canals diverted increasing volumes of water and sediment to distal reaches of the Chicama valley, supporting the great Moche and Chimu civilizations, and persisting through the Inka and Colonial periods. This history of the Chicama River valley traces strongly coupled interactions between the human and natural environments, supporting significant socio-cultural, economic, demographic, and technological advances.