UCLA

Mangroves are critical tropical coastal ecosystems and provide essential ecological and societal services. Mangroves have been rapidly changing over the last fifty years, and geospatial technologies provide a tool to measure such changes around the world. As a response to climate change and rising temperatures, mangroves have been encroaching into salt marshes at many mangrove-salt marsh ecotones in sub-tropical areas, rapidly shifting their distributions poleward. Although mangroves have faced substantial degradation and deforestation due to human activity, we have seen a rise in anthropological efforts towards their preservation and reforestation in recent years. This dissertation examines both climatic and anthropogenic drivers of change for mangrove ecosystems, using a combination of remote sensing, climate modeling, and manipulative experiments. First, we investigate mangrove range limit dynamics on the Atlantic and Pacific coasts of North America, where the same three species of mangroves are found. Using gridded climate data, remote sensing and manipulative experiments, we compared the realized and fundamental niches of the Atlantic and Pacific mangroves, and found notably different responses to environmental conditions, resulting in contrasting range dynamics. We then focused specifically on the Pacific range limit, where further manipulative experiments on cold water temperatures and aridity highlighted the fact that mangroves’ response to changes in climate is highly species- and location-specific. Therefore, aspects particular to each range population must be taken into consideration to best understand and predict mangrove response to climate change. Lastly, we focused on anthropogenic impacts on mangrove ecosystems. Using the island of Madagascar - a major biodiversity hotspot - as a case study, we conducted a remote sensing analysis of mangrove dynamics over fifty years. Results show that mangroves have faced considerable loss. However, recent awareness arising over the last twenty years has led to better conservation and preservation efforts, resulting in an increase in overall mangrove cover during this period.