Influences of sea level changes and volcanic eruptions on Holocene vegetation in Tonga
Influences of sea level changes and volcanic eruptions on Holocene vegetation in Tonga
Here, we investigate Mid- to Late-Holocene vegetation changes in low-lying coastal areas in Tonga and how changing sea levels and recurrent volcanic eruptions have influenced vegetation dynamics on four islands of the Tongan archipelago (South Pacific). To investigate past vegetation and environmental change at Ngofe Marsh (‘Uta Vava’u), we examined palynomorphs (pollen and spores), charcoal (fire), and sediment characteristics (volcanic activity) from a 6.7-m-long sediment core. Radiocarbon dating indicated the sediments were deposited over the last 7700 years. We integrated the Ngofe Marsh data with similar previously published data from Avai’o’vuna Swamp on Pangaimotu Island, Lotofoa Swamp on Foa Island, and Finemui Swamp on Ha’afeva Island. Plant taxa were categorized as littoral, mangrove, rainforest, successional/ disturbance, and wetland groups, and linear models were used to examine relationships between vegetation, relative sea level change, and volcanic eruptions (tephra). We found that relative sea level change has impacted vegetation on three of the four islands investigated. Volcanic eruptions were not identified as a driver of vegetation change. Rainforest decline does not appear to be driven by sea level changes or volcanic eruptions. From all sites analyzed, vegetation at Finemui Swamp was most sensitive to changes in relative sea level. While vegetation on low-lying Pacific islands is sensitive to changing sea levels, island characteristics, such as area and elevation, are also likely to be important factors that mediate specific island responses to drivers of change.
Polynesia, Tonga, anthropogenic impacts, human impacts, paleoecology, pollen analysis, sea level, tephra
816-827
Strandberg, Nichola Ann
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Edwards, Mary
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Ellison, Joanna C.
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Steinbauer, Manuel J.
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Walentowitz, Anna
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Fall, Patricia L.
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Sear, David
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Langdon, Peter
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Cronin, Shane
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Castilla Beltran, Alvaro
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Croudace, Ian W.
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Prebble, Matiu
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Gosling, William D.
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Nogue, Sandra
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July 2023
Strandberg, Nichola Ann
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Edwards, Mary
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Ellison, Joanna C.
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Steinbauer, Manuel J.
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Walentowitz, Anna
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Fall, Patricia L.
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Sear, David
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Langdon, Peter
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Cronin, Shane
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Castilla Beltran, Alvaro
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Croudace, Ian W.
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Prebble, Matiu
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Gosling, William D.
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Nogue, Sandra
7e0d6d85-09b7-4dad-be61-3b95ca365287
Strandberg, Nichola Ann, Edwards, Mary, Ellison, Joanna C., Steinbauer, Manuel J., Walentowitz, Anna, Fall, Patricia L., Sear, David, Langdon, Peter, Cronin, Shane, Castilla Beltran, Alvaro, Croudace, Ian W., Prebble, Matiu, Gosling, William D. and Nogue, Sandra
(2023)
Influences of sea level changes and volcanic eruptions on Holocene vegetation in Tonga.
Biotropica, 55 (4), .
(doi:10.1111/btp.13231).
Abstract
Here, we investigate Mid- to Late-Holocene vegetation changes in low-lying coastal areas in Tonga and how changing sea levels and recurrent volcanic eruptions have influenced vegetation dynamics on four islands of the Tongan archipelago (South Pacific). To investigate past vegetation and environmental change at Ngofe Marsh (‘Uta Vava’u), we examined palynomorphs (pollen and spores), charcoal (fire), and sediment characteristics (volcanic activity) from a 6.7-m-long sediment core. Radiocarbon dating indicated the sediments were deposited over the last 7700 years. We integrated the Ngofe Marsh data with similar previously published data from Avai’o’vuna Swamp on Pangaimotu Island, Lotofoa Swamp on Foa Island, and Finemui Swamp on Ha’afeva Island. Plant taxa were categorized as littoral, mangrove, rainforest, successional/ disturbance, and wetland groups, and linear models were used to examine relationships between vegetation, relative sea level change, and volcanic eruptions (tephra). We found that relative sea level change has impacted vegetation on three of the four islands investigated. Volcanic eruptions were not identified as a driver of vegetation change. Rainforest decline does not appear to be driven by sea level changes or volcanic eruptions. From all sites analyzed, vegetation at Finemui Swamp was most sensitive to changes in relative sea level. While vegetation on low-lying Pacific islands is sensitive to changing sea levels, island characteristics, such as area and elevation, are also likely to be important factors that mediate specific island responses to drivers of change.
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Biotropica - 2023 - Strandberg - Influences of sea level changes and volcanic eruptions on Holocene vegetation in Tonga
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Accepted/In Press date: 18 April 2023
e-pub ahead of print date: 22 May 2023
Published date: July 2023
Additional Information:
Funding Information:
This work was supported by the Natural Environment Research Council PhD studentship [grant number NE/L002531/1] and NERC urgency grant NE/N006674/1. Radiocarbon dates from the Ngofe Marsh study were funded via the rangefinder grant (allocation number 2198.1019) and were processed at the SUERC facility (Scottish Universities Environmental Research Centre). Many thanks to Dr Katherine Holt from Massey University, New Zealand, for making John Flenley's 1999 report “Final report on the stratigraphy and palynology of swamps on the islands of Ha’afeva and Foa, Ha’apai, Tonga” available. We would like to acknowledge the late Arthur Whistler for his work on the botany and ethnobotany of Tonga and Samoa, much of this work would not have been possible without his contributions to the field. Permission to undertake research on Ngofe Marsh in 2017 was given by the Office of the Prime Minister of Tonga.
Funding Information:
This work was supported by the Natural Environment Research Council PhD studentship [grant number NE/L002531/1] and NERC urgency grant NE/N006674/1. Radiocarbon dates from the Ngofe Marsh study were funded via the rangefinder grant (allocation number 2198.1019) and were processed at the SUERC facility (Scottish Universities Environmental Research Centre). Many thanks to Dr Katherine Holt from Massey University, New Zealand, for making John Flenley's 1999 report “Final report on the stratigraphy and palynology of swamps on the islands of Ha’afeva and Foa, Ha’apai, Tonga” available. We would like to acknowledge the late Arthur Whistler for his work on the botany and ethnobotany of Tonga and Samoa, much of this work would not have been possible without his contributions to the field. Permission to undertake research on Ngofe Marsh in 2017 was given by the Office of the Prime Minister of Tonga.
Publisher Copyright:
© 2023 The Authors. Biotropica published by Wiley Periodicals LLC on behalf of Association for Tropical Biology and Conservation.
Keywords:
Polynesia, Tonga, anthropogenic impacts, human impacts, paleoecology, pollen analysis, sea level, tephra
Identifiers
Local EPrints ID: 477608
URI: http://eprints.soton.ac.uk/id/eprint/477608
ISSN: 1744-7429
PURE UUID: ce1e358c-67e2-4ca3-989e-61f737fa6f01
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Date deposited: 09 Jun 2023 16:49
Last modified: 17 Mar 2024 02:55
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Contributors
Author:
Joanna C. Ellison
Author:
Manuel J. Steinbauer
Author:
Anna Walentowitz
Author:
Patricia L. Fall
Author:
David Sear
Author:
Shane Cronin
Author:
Alvaro Castilla Beltran
Author:
Ian W. Croudace
Author:
Matiu Prebble
Author:
William D. Gosling
Author:
Sandra Nogue
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