TRACKING CORAL LOSS AT A REFUGIUM IN BELIZE: A MULTITEMPORAL SATELLITE ASSESSMENT

Coral Gardens Belize, located off the coast of Ambergris Caye, has served as a critical refugium for endangered Staghorn coral (Acropora cervicornis) for decades, with live coral assessments conducted annually since 2011. The once-thriving reef suffered a mass mortality event in response to the anomalous 2023 marine heatwave, with live coral abundance at the site plummeting from ~30% live coral tissue to zero. In 2015 a previous study used supervised and unsupervised classification of multispectral satellite imagery to assess live coral abundance in the 25 km² area surrounding Coral Gardens. However, no previous efforts have focused on tracking the multiyear decline of live coral in the wider Coral Gardens areas to understand the long-term trends in coral health and resilience there. Here we expand on previous work to track live coral abundance in the wider area.This study aims to quantify the decline of live Acropora cervicornis populations along the Belizean Barrier Reef from 2011 to 2023, using advanced remote sensing and supervised classification techniques to understand the impacts of environmental stressors on a coral refugium. Using Geoeye-1 and Worlview-2 high resolution satellite imagery, a Random Tree supervised classification algorithm in ArcGIS Pro was developed to identify and monitor live coral populations along the reef. Mapped areas with live coral populations, identified through field surveys, were used to train the model and distinguish live coral from non-live coral in the satellite imagery. Satellite imagery from 2011, 2021, and 2023 were analyzed to track coral decline over the period of 13 years. Coral Gardens was used as the primary training area, due to its refugium status for A. cervicornis. Results showed live coral coverage declined from 155,825 m² in 2011, to 71,511 and 10,097 m² in 2021 and 2023 respectively. Our data indicate that the pattern of A. cervicornis loss at Coral Gardens is representative of coral loss in the wider area. Nine areas classified as containing live coral based upon satellite data from 2023 were visited and ground-truthed in December of 2024. Eight of the visited sites contained standing, recently dead Acropora sp. coral at that time, attesting to the veracity of the methodology. Furthermore, two sites still contained very small living specimens of Acropora sp. corals.