Journal of Ethnobiology 33(2): 203–236
By: Rafael de Grenade and Gary Paul Nabhan
The oases of the Baja California peninsula, Mexico, harbor farming systems with crops first introduced by Jesuit missionaries during their political, economic, and ecclesiastical dominance from 1697–1768. The oases represent geographies of historic dissemination and hold assemblages of heirloom perennial crop species with origins in six of seven continents. The first Jesuit missionaries to the peninsula documented their agricultural introductions in detail, and these historic documents along with records from subsequent Franciscan and Dominican missionaries provide a benchmark by which to measure the persistence and/or loss of perennial crop species. Few other locations in the world have such complete historical records of the earliest agricultural transformations occurring with contact between hunter-gatherers and agricultural societies. Using original ethnohistorical manuscripts combined with thorough field-garden surveys and farmer interviews, we have attempted to measure modern species richness and characterize species persistence within and among the oases of the peninsula.
Studies in agricultural oases in Egypt, Oman, and on the Baja California peninsula show that oases, harboring complex species assemblages, provide unique sites for formal and informal in situ crop and traditional knowledge conservation (Hammer et al. 2009; Geubauer et al. 2007; Nabhan 2007; Nabhan et al. 2010; Routson 2012). In situ conservation maintains agricultural species within the biocultural systems in which they evolved and, especially applicable to oases agroecosystems, allows for continuing the adaptation of plants and animals within a social context (Brush 2000; Altieri and Merrick 1987; Nabhan 2007).
Traditional oasis agricultural systems support complex agroecosystems with higher levels of native biodiversity than surrounding environments or small household gardens (Nabhan et al. 1982; Pimentel et al. 1992; Thrupp 2000). The agrobiodiversity within these systems—diverse crop and livestock species, crop wild relatives other associated wild biodiversity, and traditional knowledge, are resources for the future of humanity and natural systems in the face of environmental degradation, climate variability and extreme events, crop disease outbreaks, and a growing world population (Frese et al. 2012; Hammer and Teklu 2008; Lenne´ 2011; Ortiz 2011).
These ‘‘islands’’ of agricultural diversity exist in broader landscapes where agriculture cannot be practiced, urban development has consumed agricultural production, or the systems have changed to large-scale crop monocultures. Oases, or other isolated pockets in the geographies of historical dispersal, however might only hold small representations of genetic diversity for each species, bottlenecked as many populations are through fragmentation, vicariance, or long-distance dispersal mechanisms. Associated farming and food processing knowledges and practices are equally fragmented and vulnerable to disappearance.