Reducing natural vegetation loss in Amazonia critically depends on the formal recognition of indigenous lands

The Brazilian Amazon contains the world's largest tract of tropical forest, about 22 % of which is within demarcated indigenous territories. Formal governmental recognition of these traditional territories is often a critical deterrent to deforestation, but the relative conservation performance of Indigenous Lands (ILs) under different legal categories and geographic contexts remains poorly understood. We used 30-m resolution Landsat satellite imagery to quantitatively assess the land cover status and annual rates of natural vegetation loss between 1985 and 2020 for 381 indigenous territories amounting to ~115 million hectares. Using a comprehensive set of environmental and socio-economic covariates and a mixed-modelling approach, we found that all stages of formal IL recognition consistently inhibit natural vegetation loss throughout the Brazilian Amazon compared to adjacent unprotected areas. Formal physical demarcation and distance from roads were the main proximate drivers of avoided natural vegetation loss inside ILs. Forest loss associated with road access is substantially curbed by ILs, showing the importance of frontier expansion when assessing indigenous reserve performance in counteracting natural vegetation loss. Because loss of natural forest and savannah areas associated with agribusiness frontiers and infrastructure projects are likely to intensify, the importance of ecosystem services provided by ILs is expected to increase across the Brazilian Amazon. Cultural profile and human density exerted no impacts on IL effectiveness in precluding natural vegetation loss. Given widespread encroachment of timber extraction and agribusiness, formal recognition of indigenous territories is a critical factor in decelerating primary habitat conversion across the Amazon.