Alborz’s dry slopes face more days of fire-friendly weather
Weather favourable to burning increased across Iran’s Alborz mountains during 1980–2025, with stronger trends in dry, non-forested landscapes. A peer-reviewed analysis of daily climate data found substantial differences between southern slopes and humid forests. The measurements describe meteorological exposure; actual fire occurrence also depends on fuel, ignition and suppression.
Science··Morning
Dry southern landscapes have greater exposure
Dry, non-forested landscapes in the Alborz mountains in Iran experienced more days of weather favourable to burning than humid forests in a peer-reviewed study of 1980–2025. At the 21.3 fire-weather-index threshold, annual averages were 163.46 days in non-forest cells and 52.2 in forest cells. Summer concentrated the highest values. In ERA5, a reconstruction of past atmospheric conditions, the contrast spans the mountain range’s climatic divide between wetter northern forests on the Caspian side and the comparatively dry southern slopes.[1]
Daily weather data reveal uneven increases
The analysis used ERA5 atmospheric reanalysis, a reconstruction combining observations with a weather model, with a grid resolution of 0.25 degrees across 127 cells. Temperature, humidity, wind and rainfall supplied the index calculations. A fixed 2020 land-cover classification separated 83 forest cells from 44 non-forest cells. Increasing trends affected over 90 per cent of cells outside forests at the 21.3 threshold. At the extreme threshold of 50, the corresponding share exceeded 50 per cent.[1]
A statistical extension follows the historical series
For 2026–2035 estimates, researchers modelled annual observations in each cell with a random-forest approach, using calendar year as the sole predictor. The model used 46 annual observations and 80 decision trees, with five chronological validation folds. This extends historical statistical relationships rather than simulating future greenhouse-gas scenarios. The weather index describes potential burning conditions; fuel availability, ignition and firefighting were not directly modelled, and historical land-cover changes were not calculated.[1]
