Andean Soils Struggle to Recover Four Years After Major Wildfire

A wildfire that burned nearly 2,000 hectares of shrubland on the Pichu Pichu volcano in southern Peru has led to severe and lasting soil degradation, according to a new study. Researchers from Miguel Hernández University of Elche (UMH) analyzed soil samples from the affected area four years after the fire and found significant losses in soil organic carbon (SOC), weakened soil structure and increased vulnerability to erosion. Their findings, published in the Spanish Journal of Soil Science, highlight the fragility of volcanic soils in arid environments when exposed to fire.

Soil carbon loss and post-fire erosion

Unlike Mediterranean ecosystems, where vegetation has evolved to withstand wildfires, the volcanic soils of Arequipa – one of the driest regions in the world  –lack fire adaptation mechanisms. The study found that the combination of vegetation combustion and subsequent erosion has led to a severe decline in SOC, which plays a key role in maintaining soil fertility.

“The Peruvian Andes are not prepared for wildfires,” said UMH professor Jorge Mataix Solera, an expert in post-fire soil recovery. The research team observed that the physical and chemical properties of the soil had been significantly altered, making ecosystem recovery difficult. Additionally, post-fire erosion has further reduced clay content, leading to weaker soil structure and greater susceptibility to degradation.

Water repellency increases fire-induced vulnerability

The study also identified persistent water repellency in the affected soils, a phenomenon influenced by organic matter composition and high sand content. In fire-affected areas, this repellency prevented water infiltration, leading to increased surface runoff and erosion.

“While well-structured and evolved soils, such as Mediterranean soils, have a high water-holding capacity, young volcanic Andean soils, which are naturally sandy, lose this ability after fire-induced organic matter loss.”

Dr. Minerva García Carmona.

This loss of water retention can delay vegetation regrowth, further slowing ecosystem recovery.

Vegetation type influences post-fire soil degradation

The researchers examined how different plant species contributed to soil degradation after fire exposure. Their analysis focused on two native shrub species – Berberis lutea ("palo amarillo del Perú") and Parastrephia quadrangularis ("tola"). The results showed that areas dominated by Berberis lutea experienced greater soil degradation, likely due to the species’ larger biomass, which intensified combustion effects.

While Mediterranean forests have developed resilience mechanisms due to frequent fire exposure, the findings from Pichu Pichu suggest that volcanic soils in Arequipa are highly susceptible to post-fire degradation. The study underscores the need for conservation efforts and fire prevention strategies in these vulnerable ecosystems.

The impact of wildfires on Andean ecosystems

Pichu Pichu is part of the Andean Volcanic Belt, where ecosystems are shaped by extreme climatic conditions. The study site, located at 3,700 meters above sea level, receives just 385 mm of annual precipitation, mostly concentrated over a few months. These cold desert conditions make the region highly sensitive to environmental disturbances.

Despite the arid climate, the region is an important water source, supporting diverse plant and animal life. While the upper slopes are dominated by shrubland, the foothills host endangered Polylepis (queñua) forests, which play a crucial role in local biodiversity. Wildfires threaten these fragile ecosystems, further exacerbating the challenges posed by climate change.

Rising wildfire frequency and climate change concerns

Wildfires are becoming more frequent in Peru, particularly between July and October. In September 2024, satellite monitoring recorded an all-time high of 7,037 wildfire hotspots across the country. The increasing occurrence of fires in desert environments like Arequipa raises concerns about long-term ecosystem resilience.

Conservation and fire management strategies

The study highlights the need for targeted fire prevention measures and soil restoration strategies in fire-prone areas of the Peruvian Andes. As climate change continues to alter fire regimes worldwide, lessons from regions like Arequipa can help inform broader conservation efforts.

Reference: Coaguila L, Mataix-Solera J, Nina S, García-Carmona M, Salazar ET. Soil degradation evidence following a wildfire in Arequipa’s Andean Region, Peru. Span J Soil Sci. 2025;15:13983. doi: 10.3389/sjss.2025.13983

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