S12 - Session O3 - Impact of water availability on oases agro-biodiversity in Kebili region in southern Tunisia

Authors: Haifa Benmoussa, Nabila El Kadri, Nadhira BenAissa, Mehdi Ben Mimoun *

Poases 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 irrigation and water availability are key factors of 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 a drilling were mostly 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 4 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 and high gaps between irrigation are causing mortality for fruit trees and annual crops and therefore agro-biodiversity losses. These oases are heavily threatened and this situation can become more severe in the near future due to climate change, particularly the increase in temperatures that causes greater water demand due to an increase in ETP. Since spring 2021, monitoring of the irrigation strategy has been carried out in both a one-layer and three-layer oasis and a better irrigation schedule is discussed with growers to improve water use efficiency.