Time-series satellite image classification reveals comprehensive canopy loss of dense Thalassodendron ciliatum seagrass meadows at Cocos (Keeling) Islands

Seagrass meadows are among the most productive ecosystems on Earth and provide critical functions for marine life and associated fisheries. Yet, they are some of the most threatened ecosystems, mostly due to unregulated anthropogenic impacts and extreme climatic events associated with climate change. This study focuses on the seagrass ecosystems of the Cocos (Keeling) Islands in the eastern Indian Ocean, which have experienced a period of habitat loss. Through targeted assessment of satellite imagery and quantitative in situ habitat assessments, we demonstrate that the seagrass loss is more widespread than previously reported and includes the complete canopy loss of all described meadows of the dense, high-canopy seagrass species Thalassodendron ciliatum. Through support vector machine classification of a 14-year time series (2006-2020) of publicly available high-resolution satellite imagery, we demonstrate the temporal and spatial scale of the loss of the high-canopy seagrass meadows, which adds further evidence to the degradation of vegetated habitats at the Cocos (Keeling) Islands. We also discuss the potential drivers and the ecological and social implications arising from the degradation of complex seagrass habitats in a remote atoll.