Managing Drought in Semi-Arid Regions through Improved Varieties and Choice of Species

Geographically dry lands (hyper-arid, arid, semi-arid, and dry sub-humid ecosystems) are demarcated by a water deficit with precipitation to potential evaporation ratio (also called the aridity index; AI) < 0.65 (Hassan et al. 2005; Cima et al. 2015; Plaza et al. 2018). The AI of humid drylands is > 0.65, arid areas are≥ 0.05 and < 0.2, and semi-arid regions are≥ 0.2 and < 0.5 (Abatzoglou et al. 2018; Figure 7.1).