The Atlantic Forest extends from northeastern Brazil along the Atlantic coast and inland into northeastern Argentina and eastern Paraguay, encompassing 15 ecoregions that include tropical and subtropical rain forests, coastal forests, mangroves, and Araucaria moist forests. Ranking among the world’s top biodiversity hotspots, the forest also plays a vital role in climate regulation. Once spanning more than 350 million acres, the Atlantic Forest has lost ~88% of its original vegetation to human activity, leaving it one of the most endangered biomes on the planet. Although much of this deforestation occurred over the last century, the process began with the colonisation of the region by the Spanish and Portuguese during the 16th–19th centuries, with early colonial settlement patterns, commodity frontiers and and key transport routes influencing the spatial distribution of deforestation in the region.

Recent studies have begun to recognise contemporary Indigenous territories as critical spaces for forest conservation, but less attention has been paid to the historical impacts of colonial-era Indigenous resistance on present-day deforestation patterns. To address this gap, we first generated forest cover maps for the Atlantic Forest from declassified CIA satellite imagery (c. 1965) and collated a database of geolocated sites of historically documented Indigenous resistance (c. 1500-1800) events from national archives. Next, we calculated the impact of Indigenous resistance on probable colonial routes through the forest using a least cost path based approach that incorporated topography, river direction and flow speed, the presence of rapids and waterfalls, and the cost of portage. Finally, distances from both sites of Indigenous resistance and disrupted colonial routes were incorporated into a an explanatory spatial Random Forest model as predictors, alongside other key anthropogenic and environmental covariates. Model evaluation revealed that Indigenous resistance was the top-ranked predictor of forest survival in the region and a counterfactual simulation predicted that resistance reduced forest cover loss by 20 to 22% between the colonial period and the 1960s. These results highlight the historic importance of Indigenous resistance and indicate that researchers and policy makers should allocate more attention to the conservation effects of historical Indigenous actions.