precipitation [2]. Furthermore, the frequency and intensity of droughts are dramatically increasing due to global warming [3]. Extreme drought events adversely affect water resources, leading to excessive evapotranspiration and moisture deficiency [4; 5; 6]. Several studies have shown that drought can result in socioeconomic losses, reduced agricultural productivity, and ecosystem degradation [7; 8; 9; 10]. Regionally, the temperature rise has had catastrophic spatial consequences in the Middle East [11; 12], leading to increased evaporation demand, changes in precipitation patterns, and, consequently, intensifying drought and impacting snowpack and mountain glacier melt [13]. Moreover, droughts significantly affect terrestrial ecosystems, economies, and societies in the Middle East [14; 15], including food security [16], hydrological processes [17], vegetation growth, and the extinction of plant species [18]. Droughts in the Middle East have also led to a sharp decrease in carbon fluxes [19; 20] and agricultural crop yields [21]. Ecological programs and efforts have been implemented to mitigate ecosystem degradation and increase vegetation coverage in drought-prone areas [22; 23], but extreme drought reduces the effectiveness of such projects by restricting the dynamic growth of vegetation ecosystems [24]. The changes induced by climate change and drought are expected to have influenced the ecological dynamics of terrestrial ecosystems and vegetation communities. These alterations may impact the coupling relationship between terrestrial carbon and water fluxes. Gross primary productivity (GPP) represents the highest flux of carbon into terrestrial biomass from the atmosphere and plays a critical role in the global carbon cycle. Climatic conditions exert a more substantial influence on GPP dynamics than human activities [25; 26]. Drought events, such as the European drought spell in 2003 and the northwest USA drought of 2000-2004, have led to declines in GPP and carbon sink capacity [27; 28]. Conversely, water use efficiency (WUE), an integrated physiological indicator measuring the tradeoff between carbon gain and water loss during photosynthesis [29], offers insights into ecosystem adaptability to varying climate conditions [30; 31; 32; 33; 34]. Hydroclimatic conditions significantly influence WUE spatiotemporal variation by affecting evaporation, transpiration, and carbon uptake in ecosystems [35; 36; 37]. However, the response of WUE to drought indices varies, with different indices showing divergent responses in ecosystem productivity [38; 39; 40; 41]. In recent years, numerous studies have investigated the effects of drought on the coupling between carbon and water cycles [42; 43; 44; 45; 46; 47; 48]. However, the associations between ecosystem WUE and drought exhibit considerable variability across various vegetation types and climatic conditions, warranting further research for a comprehensive understanding. The West Asia region, classified as a transitional climate pattern between hot-dry and cold-humid climates, is highly susceptible to drought events due to water shortages [49; 50]. With limited agreement on GPP, actual evapotranspiration (AET), and WUE responses to extreme droughts in different climates and vegetation types, there is a need to understand the impacts of drought intensification in the region. This study investigates the responses of AET, GPP, and WUE to drought events in the northern part of West Asia. The research aims to answer critical questions, including differences in ecosystem responses to extreme droughts among climate patterns and biomes, variation in drought effects on AET, GPP, and WUE with different drought severities, and the most effective factor controlling WUE during severe droughts. Herein, we examine how AET, GPP, and WUE responded to drought events over the northern part of West Asia. We strive to treat the following questions: (a) How do ecosystems' AET, GPP, and WUE responses to extreme drought differ among climate patterns and biomes?