Multiple asynchronous drought facets drive Mediterranean natural and cultivated ecosystems

Drought is a keystone constraint with far-reaching implications for agro-environmental threats. Yet, drought indices are mostly hydro-meteorological or agricultural, obscuring evidence of the key role agro-ecosystem diversity plays in buffering the consequences of regional climatic variability. We then question how contrasted drought facets could differentially drive the functioning of agro-ecosystems, and whether the interannual asynchrony of these facets might prevent multi-crisis events. Here, we examine how a multifaceted characterization of yearly drought events differentially relates to key agro-environmental sectors and test how these drought facets synchronize over Lebanon, a Middle Eastern drought-prone country grappling with socio-economic and political crises. Using parsimonious multiple linear regression (MLR) models, we captured the combined functional roles of six yearly drought facets (duration, onset, offset, drying rate, peak drought day, and mean intensity of episodic rainfall pulses) on major agro-environmental sectors, including winter wheat yield, tree-ring radial growth, and area burned by wildfires. Delayed drought offset and faster spring soil moisture drying rates appeared more closely associated to increased burned areas (R² = 0.25), while drought onset and autumn rainfall pulses from the previous year were negatively linked to winter wheat yield (R² = 0.12), and tree radial growth switched from a control by drought onset and to duration with increasing altitude (R² = 0.33). The observed asynchrony in agro-environmental response to climate variability over the 1960-2020 period appears to buffer the occurrence of concomitant extremes, a pattern that we could relate to the asynchrony in their controlling drought facets. By demonstrating the functional role of each drought facet, we conclude on the efficiency of a compound functionally-sound drought facets index for synchronous agro-environmental climate crisis warning.