This study examines the dynamics of aridity in Mexico in relation to El Niño–Southern Oscillation (ENSO) phases (El Niño, La Niña and neutral conditions) between 1999 and 2024. The aim is to identify ecosystems that are exposed to emerging aridification. Aridity was estimated using the Lang index at a resolution of 1 km across nearly two million grid cells. Aridity intensity and long-term trends were calculated and analysed by ENSO phase to identify areas of double exposure. Over 60% of Mexico is classified as arid or semi-arid. During El Niño, up to 100% of the central and southern regions exhibit increased aridity, affecting an area of 290,852 km2 (14.7%), where both the intensity and the trend are high. Although La Niña typically brings wetter conditions, 150,022 km2 (7.6%) still exhibit increasing aridity. Areas exposed to aridity under both ENSO phases cover 16,224 km2 (0.8%), particularly affecting cloud forests, secondary vegetation and agricultural landscapes. This suggests a process of persistent aridification. The average arid area was 64% ± 7.51% during El Niño, 67% ± 1.44% during La Niña and 64% ± 8.14% during neutral years, indicating substantial variability beyond phase dependence. These findings reveal a complex, non-linear ENSO influence and suggest chronic hydroclimatic stress in some regions. Understanding which ecosystems experience recurrent aridity is crucial for effective water management, biodiversity conservation, and climate adaptation planning.
López-Teloxa et al. (Sat,) studied this question.