Urban boundaries are an underexplored frontier for ecological restoration.

The restoration of degraded ecosystems is crucial for addressing climate, biodiversity, and health challenges. The benefits of these restorations are amplified when implemented closer to urban populations, particularly for climate adaptation and human health. This study investigated the potential of urban areas for forest restoration, introducing a novel distinction between dense urban areas and urban boundaries (peripheral zones of urban centers), and comparing their dynamics to rural areas. We analyzed three decades of deforestation and regeneration dynamics in Brazil, quantifying and mapping land-use transitions to assess restoration potential. Results show that forest transition has already occurred across all the different types of areas considered. Urban boundaries exhibited highly dynamic land use and high regeneration rates despite limited policy support. The landscape dynamics and the presence of environmentally risky areas reveal that urban boundaries contain significant areas that hold potential for restoration, which could significantly contribute to achieving national or subnational restoration targets. Integrating restoration into urban boundary planning offers both ecological and social benefits to a substantial portion of the population. Our findings reveal a missed opportunity to extend restoration efforts beyond the traditionally targeted rural areas, positioning urban boundaries as key areas for innovative land-use strategies and restoration initiatives.