Between dunes and estuary: Forecasting mangrove forest change on primate culture and isolated livelihoods in Maranhão, Brazil

The unique ecological conditions of the mangrove forests in the Rio Preguiças Estuary, Maranhão, Brazil, support a culturally isolated population of bearded capuchin monkeys ( Sapajus libidinosus ) and contribute to the livelihoods and economy of the local community. In this location, the capuchins survive solely within the mangrove forests, primarily feeding on the mangrove crab ( Ucides cordatus ), often using wooden tools to crack them open. These mangrove forests serve as fish nurseries and support economically valuable crustaceans, sustaining local food resources and a thriving fishery. Given the multifaceted role of these mangrove forests as a habitat for this unique capuchin population and as a resource for the local community, our study assesses these forests' past, present and projected future status. We conducted a multiscale land‐use change analysis of the Rio Preguiças watershed and at the site of the isolated population of bearded capuchin monkeys. Using Sentinel imagery and high‐resolution images collected from unoccupied aerial vehicles, we tracked land cover changes from 2017 to 2023 and projected mangrove forest changes 5 years into the future. Remote sensing and GIS techniques revealed substantial and significant mangrove loss at the culturally important Capuchin mangrove site and substantial and significant forest transitions across the broader watershed. Both regions showed reduced natural land cover and increased human‐induced changes, which impacted the forests. Sand dune overwash in mangrove forests alters the mudflat dynamics, reshaping vegetation physiognomies within the mangroves and potentially leading to a decline in the crab population, a primary food source for capuchins and a source of protein and income for the local community. These findings underscore the need for conservation plans to ensure the long‐term survival of the mangrove forests, the local fisheries‐based livelihoods and the culturally unique isolated population of bearded capuchin monkeys at Morro do Boi.