From closed canopy to cleared landscapes: Beetle remains reveal 6000 years of forest evolution and human impact on the French Atlantic coastline

The archaeological site of L'Amélie (Gironde department, southwestern France), exposed to ongoing shoreline retreat and coastal erosion, preserves a rare and invaluable record of millennia of human-forest interactions in a region where archaeological heritage is increasingly endangered. It provides an exceptional opportunity to reconstruct forest cover evolution through the analysis of forest beetle assemblages across numerous archaeological contexts dating from the Neolithic to Late Antiquity. Thirty-three forest beetle taxa were identified, representing key functional groups within forest ecosystems. Around 6000 years ago, a closed-canopy woodland with multiple microhabitats typical of ancient forests prevailed, but within a few centuries, extensive human clearance caused a strong collapse in forest beetle abundance and ecological diversity. Partial forest regeneration is apparent from the beginning of the Bronze Age, with pasture woodlands persisting until the Iron Age. Further deforestation during Antiquity led to a sustained opening of the landscape, with complete disappearance of saproxylic beetles. Despite subsequent intensive human modifications of forests in southwestern France, most forest beetle species identified in the archaeoentomological record are still present today in the Gironde department, demonstrating remarkable ecological resilience. Only one xylophagous species has disappeared, illustrating the replacement of native fauna by invasive species. This research represents the first archaeoentomological study in France documenting forest evolution over millennia, with only a few comparable studies worldwide, mainly from Great Britain. These findings provide unprecedented insight into long-term forest dynamics, the effects of human activity on insect communities, and a foundation for the sustainable management of forest ecosystems under growing anthropogenic pressures.