The impact of compound droughts and heatwaves on ecosystem carbon-water dynamics in Eurasia

Abstract

Climate change has been intensifying the occurrence of compound droughts and heatwaves (CDHW), seriously affecting the carbon and water cycles of terrestrial ecosystems. However, the understanding of the impacts of CDHW is still limited in Eurasia, with its complex terrain and diverse landscapes. This study used a high-precision carbon and water flux dataset from meteorological stations to examine the spatiotemporal patterns of CDHW in Eurasia during 1984−2018 and their effects on ecosystem carbon-water dynamics across various land cover types, in particular net ecosystem carbon exchange (NEE) and water fluxes (WF). The findings revealed a marked increase in CDHW frequency since 1984. Standardized anomalies for heatwaves seemed to be more severe than for droughts but the latter exhibited a greater spatial variability. CDHW generally demonstrated a negative impact on NEE and WF, with the magnitude of net carbon uptake decreases growing and the magnitude of WF increases diminishing since 1984. The grassland experienced the largest reduction in net carbon uptake, with a mean standardized anomaly (SA) of 0.53 for NEE, while the forest appeared to be the least affected. The wetland indicated the most pronounced WF response to CDHW, with a mean SA of 0.93, followed by the forest. Geographically, the effects of CDHW on NEE and WF varied along latitudes, with the strongest negative influences occurring in high-latitude regions. After CDHW, the average recovery times for most stations ranged from three to ten days, with the forest and shrubland illustrating the greatest resilience in NEE and WF, respectively. Understanding these dynamics is critical for designing targeted adaptation strategies—such as forest protection and afforestation to enhance ecosystem resistance, and precision irrigation to alleviate water stress—to mitigate the CDHW impact and sustain the ecosystem functions amidst the rising climatic extremes.