Effects of Holocene climate change, volcanism and mass migration on the ecosystem of a small, dry island (Brava, Cabo Verde)
Effects of Holocene climate change, volcanism and mass migration on the ecosystem of a small, dry island (Brava, Cabo Verde)
Aim: palaeoecological data provide an essential long-term perspective of ecological change and its drivers in oceanic islands. However, analysing the effects of multi-scalar and potentially co-occurring disturbances is particularly challenging in dry islands. Here, we aim to identify the ecological consequences of the integrated impacts of a regional drying trend, volcanic eruptions and human mass migrations in a spatially constrained environment—a small, dry oceanic island in Macaronesia.
Location: Brava Island, Republic of Cabo Verde. Taxa: Terrestrial vegetation and fungi.
Methods: we use palaeoecological analyses applied to a caldera soil profile that dates back to 9700 cal yr BP (calibrated years before the present). Analyses include pollen (vegetation history), non-pollen palynomorphs (changes in fern and fungal communities), grain-size distribution, loss-on-ignition and geochemistry (sedimentology and erosion regimes), microscopic tephra shards (volcanic ash deposition) and charcoal (fire regime).
Results: a regional drying trend after c. 4000 cal yr BP caused increased erosion but had limited immediate impacts on highland grassland vegetation. The expansion of fern-rich woody scrubland was contemporaneous with significant deposition of volcanic ash and erosion between 1800 and 650 cal yr BP. About 300 cal yr BP, exogenous plants expanded, grazing and fires increased, and there was a decrease of native vegetation cover.
Main conclusions: throughout the Holocene, highland vegetation in Brava was characterized by the presence of open landscapes dominated by herbaceous species (e.g. Poaceae, Forsskaolea), with some presence of woody native taxa (e.g. Ficus, Dodonaea). A regional drying trend was a driver of erosion since the Mid Holocene but did not have an immediate influence on highland vegetation. Tephra deposition is a possible driver of vegetation change. Inter-island mass migration after volcanic events in Fogo Island c. 1680 CE potentially triggered land use change and intensification, causing a reduction of native vegetation in Brava.
African Humid Period, Anthropocene, Cape Verde, ecological change, environmental disturbances, Macaronesia, natural hazards, palaeoecology, tropical islands
1392-1405
Castilla-Beltrán, Alvaro
f5e694c1-0f7e-4263-8e94-a0fe932dafce
de Nascimento, Lea
1274af4c-1f12-45cf-82d1-b504d14ef163
Fernández-Palacios, José María
19ceeeb9-77d3-44b4-ac17-2e17eac71c3a
Whittaker, Robert J.
5578f7a4-02f9-4968-9acf-3c9445841af5
Romeiras, Maria M.
a2f04d16-d662-4b13-8ab4-8dd0b5f1b3de
Cundy, Andrew B.
994fdc96-2dce-40f4-b74b-dc638286eb08
Edwards, Mary
4b6a3389-f3a4-4933-b8fd-acdfef72200e
Nogué, Sandra
5b464cff-a158-481f-8b7f-647c93d7a034
June 2021
Castilla-Beltrán, Alvaro
f5e694c1-0f7e-4263-8e94-a0fe932dafce
de Nascimento, Lea
1274af4c-1f12-45cf-82d1-b504d14ef163
Fernández-Palacios, José María
19ceeeb9-77d3-44b4-ac17-2e17eac71c3a
Whittaker, Robert J.
5578f7a4-02f9-4968-9acf-3c9445841af5
Romeiras, Maria M.
a2f04d16-d662-4b13-8ab4-8dd0b5f1b3de
Cundy, Andrew B.
994fdc96-2dce-40f4-b74b-dc638286eb08
Edwards, Mary
4b6a3389-f3a4-4933-b8fd-acdfef72200e
Nogué, Sandra
5b464cff-a158-481f-8b7f-647c93d7a034
Castilla-Beltrán, Alvaro, de Nascimento, Lea, Fernández-Palacios, José María, Whittaker, Robert J., Romeiras, Maria M., Cundy, Andrew B., Edwards, Mary and Nogué, Sandra
(2021)
Effects of Holocene climate change, volcanism and mass migration on the ecosystem of a small, dry island (Brava, Cabo Verde).
Journal of Biogeography, 48 (6), .
(doi:10.1111/jbi.14084).
Abstract
Aim: palaeoecological data provide an essential long-term perspective of ecological change and its drivers in oceanic islands. However, analysing the effects of multi-scalar and potentially co-occurring disturbances is particularly challenging in dry islands. Here, we aim to identify the ecological consequences of the integrated impacts of a regional drying trend, volcanic eruptions and human mass migrations in a spatially constrained environment—a small, dry oceanic island in Macaronesia.
Location: Brava Island, Republic of Cabo Verde. Taxa: Terrestrial vegetation and fungi.
Methods: we use palaeoecological analyses applied to a caldera soil profile that dates back to 9700 cal yr BP (calibrated years before the present). Analyses include pollen (vegetation history), non-pollen palynomorphs (changes in fern and fungal communities), grain-size distribution, loss-on-ignition and geochemistry (sedimentology and erosion regimes), microscopic tephra shards (volcanic ash deposition) and charcoal (fire regime).
Results: a regional drying trend after c. 4000 cal yr BP caused increased erosion but had limited immediate impacts on highland grassland vegetation. The expansion of fern-rich woody scrubland was contemporaneous with significant deposition of volcanic ash and erosion between 1800 and 650 cal yr BP. About 300 cal yr BP, exogenous plants expanded, grazing and fires increased, and there was a decrease of native vegetation cover.
Main conclusions: throughout the Holocene, highland vegetation in Brava was characterized by the presence of open landscapes dominated by herbaceous species (e.g. Poaceae, Forsskaolea), with some presence of woody native taxa (e.g. Ficus, Dodonaea). A regional drying trend was a driver of erosion since the Mid Holocene but did not have an immediate influence on highland vegetation. Tephra deposition is a possible driver of vegetation change. Inter-island mass migration after volcanic events in Fogo Island c. 1680 CE potentially triggered land use change and intensification, causing a reduction of native vegetation in Brava.
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Effects of Holocene climate change
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Accepted/In Press date: 2021
e-pub ahead of print date: 22 March 2021
Published date: June 2021
Additional Information:
Funding Information:
We thank the Royal Geographic Society for funding our expedition, and NERC for radiocarbon support, which funded a set of six dates. This research was enabled by a Geography and Environment +3 Postgraduate Research Scholarship from the University of Southampton awarded to Alvaro Castilla‐Betrán (2017–2020, WRJB1B). MMR was funded by Aga Khan Development Network and Fundação para a Ciência e a Tecnologia (AKDN/FCT, CVAgrobiodiversity 333111699). We thank Sónia Araújo Lopes and the Serviço de Conservação da Natureza of Cabo Verde for helping to obtain the permits to carry out this research in Brava, and Christine Meynard, Carina Hoorn and two anonymous reviewers for comments on the manuscript. We are grateful for fieldwork assistance in Mato, Brava kindly provided by Roger Barros and Autylio Gonçalves, and permissions and help from Cova Galinha land owners. Laboratory support from Dr Ali Monteath in the identification of tephra shards was fundamental to the completion of this work. We thank Prof Paul Hughes and Dr Althea Davies for their constructive suggestions to improve this research article.
Publisher Copyright:
© 2021 The Authors. Journal of Biogeography published by John Wiley & Sons Ltd.
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
Keywords:
African Humid Period, Anthropocene, Cape Verde, ecological change, environmental disturbances, Macaronesia, natural hazards, palaeoecology, tropical islands
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Local EPrints ID: 448568
URI: http://eprints.soton.ac.uk/id/eprint/448568
ISSN: 0305-0270
PURE UUID: 25189f2a-2894-4589-b5af-29b34012dc5c
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Date deposited: 27 Apr 2021 16:39
Last modified: 18 Mar 2024 03:33
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Contributors
Author:
Alvaro Castilla-Beltrán
Author:
Lea de Nascimento
Author:
José María Fernández-Palacios
Author:
Robert J. Whittaker
Author:
Maria M. Romeiras
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