Regional Crop Diversity and Crop-Specific Productivity Following Wildfire Exposure: Evidence from Portuguese Agricultural Regions

Crop diversification is widely proposed as a resilience strategy, but whether regional crop diversity buffers crop-specific productivity after wildfire exposure remains uncertain. This study examines seven Portuguese agricultural regions using exposure years 2012–2024 and crop-specific productivity at t + 1. The primary sample comprises 972 Region × Crop × Year observations nested in 91 Region × Year cells. Pre-fire diversity is measured by a one-year-lagged Shannon index based on 11 crop groups. Models include Region × Crop and Year fixed effects, a lagged crop-area control, and few-cluster inference based on null-imposed wild cluster restricted bootstrap tests with Webb weights. Neither wildfire exposure nor crop diversity shows a statistically supported main association with subsequent productivity. The wildfire × diversity interaction is positive but unsupported at t + 1 (β = 0.0931; p = 0.491), t + 2 (β = 0.0623; p = 0.699), and t + 3 (β = 0.0348; p = 0.778). The interaction changes sign in a supplementary region-specific linear-trend specification (β = −0.0410), indicating sensitivity to regional trajectories; none of the preferred hypothesis tests support the proposed buffering mechanism. The results do not establish regional crop diversity as a wildfire-specific buffer for crop-specific productivity in this design, while remaining consistent with potential diversification benefits for other outcomes and spatial scales.