Spatial Distribution of Relict Inland Mangrove (Rhizophora mangle L.) in the San Pedro River Basin: A Transboundary Analysis between Mexico and Guatemala

Inland mangroves represent a unique ecosystem that develops away from coastal areas in response to specific environmental changes. Despite their ecological value, these ecosystems are often underestimated globally. Remote sensing (RS) techniques are widely used for large-scale monitoring of mangroves worldwide. This study aims to map mangrove relicts (Rhizophora mangle L.) in the Transboundary San Pedro River Basin (TSPRB), which spans Mexico and Guatemala, using RS and geographic information system (GIS) techniques. Field surveys were conducted to collect 419 ground points, distributed across the control (274 points) and verification (145 points), ensuring accurate classification of mangrove areas. To evaluate the performance of mangrove forest classification, we used composite images created from the red (B2), green (B3), blue (B4), and near-infrared (NIR) bands, along with the Normalized Difference Mangrove Index (NDMI). For this purpose, we applied the maximum likelihood classification (MLC) method, which effectively combines spectral information from composite images to achieve precise mangrove detection. The land cover classification was performed using Sentinel-2 from 2023 and the NDMI, achieving an accuracy of 80% and a Kappa Index of 0.73. The results show 2130.69 ha of mangroves along the San Pedro River. It includes 1868.38 ha in Mexico and 262.31 ha in Guatemala. In addition, areas were identified in Guatemala, where relict island mangroves are located the greatest distance from the coast worldwide (approximately 250 km). These findings highlight the ecological importance of mangrove ecosystems in this region and provide critical information for their management, conservation, and protection in the TSPRB.