Quantifying the Causal Strength of Compound Drought–Heatwaves: Implications for Fire Events and Cropland Productivity

Serhan Yeşilköy 

Compound drought and heatwave (CDHW) events represent one of the most disruptive forms of climate extremes, as the simultaneous occurrence of dry and hot conditions signifies their impacts far beyond those of individual events. Yet, despite their increasing significance, the causal influence of CDHW frequency and severity on fire activity and crop yield variability remains poorly quantified, particularly in Mediterranean climate hotspots. This study provides a comprehensive assessment of long‑term CDHW climatology across Türkiye and quantifies their causal effects on burned areas and major crop‑yield anomalies through the complex causal networks based on the Peter and Clark Momentary Conditional Independence (PCMCI) framework. The findings reveal a clear intensification of CDHW conditions over recent decades, with significant upward trends in both event frequency (2.74 days/decade) and thermal severity (0.74°C/decade), particularly during winter and summer months. The causal strengths of CDHW events and severity on fire regimes explain up to 38.3% of burned‑area variability and crop yield reductions during critical phenological periods, affecting both rainfed winter wheat (up to 71.6%) and irrigated crops such as maize, rice, and soybean (up to 69.8%). The spatial causal signals demonstrate that CDHW events can be considered dominant climatic stressors across Türkiye’s agro‑ecosystems and fire‑prone landscapes. Overall, this work provides one of the first spatially explicit causal strengths of CDHW impacts on both agriculture and fire activity, indicating the importance of compound‑event‑aware early warning systems and climate‑resilient management strategies in regions facing intensifying hot‑dry extremes.