Impact of water availability on agro-biodiversity of oases in the Kebili region of southern Tunisia

Oases are fertile and cultivated lands in Sahara and dry areas due to the water source presence as rivers and deep aquifers. It was usually assumed that oases’ agro-biodiversity level is linked to their history, type of cropping system, and their governance. Nevertheless, data collected from a survey carried out in 2020 on a referenced random sampling of 52 plots of farmers in Kebili, a southern Tunisian region, showed that water availability and irrigation practice are key factors determining agro-biodiversity level. Our results showed that plots that were irrigated by water turn were mostly organized on one layer (only date palm) while plots having drilling were mostly organized on three layers (palm date, fruit trees, vegetables, and/or forage and cereals). The plots that were irrigated at least once a week are those that were planted by more than 3 species, while those that were irrigated less than 3 times per month had the lowest agrobiodiversity level and were grown mostly by palm date only. Low water availability due to low water resources and drought and high gaps between irrigation are causing mortality for fruit trees and annual crops and therefore agro-biodiversity losses. These oases are heavily threatened.