Dispersal and coastal geomorphology limit potential for mangrove range expansion under climate change

Jacqueline Raw, Tom Van der Stocken, Dustin Carroll, Linda Harris, Anusha Rajkaran, Lara Van Niekerk, Janine Adams

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2 Citations (Scopus)
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Latitudinal range limits for mangroves on high-energy, wave-dominated coasts are controlled by geomorphological features and estuarine dynamics. Mangroves reach a southern global range limit along the South African coastline, but the distribution is patchy, with stands occurring in only 16% of the estuaries in the region. Yet, the persistence of forests planted >50 years ago beyond the natural distribution limit suggests that additional estuaries could support mangroves. Understanding regional drivers is necessary to inform global-scale estimates for how this important ecosystem is predicted to respond to climate change. Here, we combine species distribution modelling (MaxEnt), Lagrangian particle tracking using an eddy- and tide-resolving numerical ocean model, and connectivity matrices, to identify suitable mangrove habitats along the South African coastline at present, as well as under the IPCC RCP4.5 and RCP8.5 climate scenarios. Within the current South African distribution range (±900 km), eight more estuaries were identified to be suitable under contemporary conditions. When considering potential range extension (±110 km), an additional 14 suitable estuaries were identified. Connectivity matrices suggest limited long-distance dispersal, stranding mostly at or near the release location, and a decreased probability of connectivity towards the range limit. Under both future climate scenarios, 30% of estuaries currently supporting mangroves are predicted to become unsuitable, while an additional six estuaries beyond the current distribution are predicted to become suitable. However, there is limited connectivity between these new sites and established forests. Synthesis. This study shows that dispersal substantially limits mangrove distribution at the southern African range limit and highlights the importance of including this process in species distribution models. Ultimately, our results provide new insight into mangrove conservation and management at range limits that are not controlled predominantly by temperature, as it has been assumed that mangroves will largely expand to higher latitudes under climate change.

Original languageEnglish
Pages (from-to)139-155
Number of pages17
JournalJournal of Ecology
Issue number1
Publication statusPublished - Jan 2023

Bibliographical note

Funding Information:
The authors thank the reviewers and associate editor for their valuable and helpful comments on this manuscript. This research received funding from the Water Research Commission (WRC) of South Africa (Project K5/2769), the South African Department of Science and Innovation (DSI)—National Research Foundation (NRF) Research Chair in Shallow Water Ecosystems (UID: 84375), and the Nelson Mandela University. High‐end computing resources were provided by the NASA Advanced Supercomputing (NAS) Division of the Ames Research Center. J.L.R. is supported by a DSI‐NRF Innovation Postdoctoral Fellowship (UID: 120701). T.V.d.S. is supported by the EU Horizon 2020 Framework Programme for Research and Innovation under the Marie Skłodowska‐Curie actions Individual Fellowship (MSCA‐IF) with grant agreement No. 896888 (GLOMAC). L.V.N. is supported by the DSI‐CSIR Parliamentary Grant. The funders played no role in the design of the study, collection or analysis of the data, writing the manuscript, or the decision to publish.

Publisher Copyright:
© 2022 The Authors. Journal of Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.

Copyright 2022 Elsevier B.V., All rights reserved.


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