A long-term perspective on biomass burning in the Serra da Estrela, Portugal

Fire is currently perceived as a major threat to ecosystems and biodiversity in the mountains of the Mediterranean region. Portugal's highest mountain range, the Serra da Estrela, is one of the country's most important protected areas and also the most fire-prone. We present a ∼14,000-year fire history based on microscopic charred particles in an infilled glacial lake to better understand the antiquity of biomass burning and its effects on Mediterranean vegetation at the Atlantic margin. Results indicate the continuous occurrence of fire in the Serra da Estrela over the period of the record. Two periods of increased fire activity – around 12,000–11,000 calendar years before the present (cal. a BP) and 3500–2500 cal. a BP – were accompanied by major vegetation changes and followed by long periods of vegetation stabilisation. Cross-correlation analyses reveal that post-fire succession consistently began with herbaceous vegetation, followed by forest and shrubland stages. Past successional trends were often markedly different to those observed at present. Holocene climatic changes, including shifts in the North Atlantic Oscillation, played a pivotal role in the vegetation development and fire history of the Serra da Estrela. In the late Holocene, human use of fire became a major agent of vegetation change, accelerating the Holocene decline of forests.

► High-resolution charred particle record from Portugal's highest mountain range. ► Evidence for continuous fire occurrence through last 14,000 years. ► Analysis of fire's effects on long-term ecological succession. ► Implications for understanding palaeoclimate and managing biodiversity.