Rise and Fall of Caribbean Mangroves

Abstract

Tropical mangroves, one of the most important blue-carbon ecosystems, are among the world’s most threatened ecosystems and are in danger of disappearing within the next century, which may have a significant impact on coastal ecology and biodiversity, and also on the global capacity of climate change mitigation. The Caribbean region is one of the main mangrove hotspots on Earth. This paper is a thorough updated synthesis on the origin, evolutionary turnover, diversification and historical decline of the Caribbean mangroves, in relation to tectonic, climatic, eustatic and anthropogenic shifts. Neotropical mangroves originated in the Caribbean during the Middle Eocene, after the emergence of the first known mangrove-forming tree (Pelliciera). The abrupt cooling and sea-level fall of the Eocene-Oligocene transition (EOT) would have facilitated the replacement of the primeval mangroves by others dominated by Rhizophora. This was a major evolutionary disruption and gave rise to the modern Neotropical mangrove forests, still dominated by Rhizophora, with Pelliciera restricted to a relictual equatorial patch. The other extant mangrove-forming trees (Avicennia, Pelliciera) appeared in the Mio-Pliocene and the main diversification burst occurred in the Plio-Pleistocene, when 80% of extant genera emerged, with no extinctions documented. Pleistocene climatic and eustatic glacial cycles promoted recurrent spatial and compositional reorganizations. Natural drivers were the most influential until the Middle Holocene, when Amerindian cultures settled the whole Caribbean region and began to modify mangrove communities for agriculture and other activities using fire. During the last decades, deforestation has accelerated and the Caribbean mangrove cover has been reduced by >30%. A variety of conservation actions have been undertaken, but paleoecological and evolutionary knowledge remains to be fully incorporated into mangrove preservation. It is hoped that contributions like the present will help raising awareness on the importance of past records for conservation purposes.