Seagrass losses since mid-20th century fuelled CO2 emissions from soil carbon stocks

Cristian Salinas; Carlos M Duarte; Paul S Lavery; Pere Masqué; Ariane Arias-Ortiz; Javier X Leon; David Callaghan; Gary A Kendrick; Oscar Serrano

doi:10.1111/gcb.15204

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Seagrass losses since mid-20th century fuelled CO2 emissions from soil carbon stocks

Journal article

Open access

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Seagrass losses since mid-20th century fuelled CO2 emissions from soil carbon stocks

Cristian Salinas, Carlos M Duarte, Paul S Lavery, Pere Masqué, Ariane Arias-Ortiz, Javier X Leon, David Callaghan, Gary A Kendrick and Oscar Serrano

Global Change Biology, Vol.26(9), pp.4772-4784

2020

DOI: https://doi.org/10.1111/gcb.15204

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Abstract

meadows

blue carbon

carbon sinks

climate change

conservation

erosion

eutrophication

seagrass

Seagrass meadows store globally significant organic carbon (C org) stocks which, if disturbed, can lead to CO2 emissions, contributing to climate change. Eutrophication and thermal stress continue to be a major cause of seagrass decline worldwide, but the associated CO2 emissions remain poorly understood. This study presents comprehensive estimates of seagrass soil C org erosion following eutrophication-driven seagrass loss in Cockburn Sound (23 km2 between 1960s and 1990s) and identifies the main drivers. We estimate that shallow seagrass meadows (<5 m depth) had significantly higher C org stocks in 50 cm thick soils (4.5 ± 0.7 kg C org/m2) than previously vegetated counterparts (0.5 ± 0.1 kg C org/m2). In deeper areas (>5 m), however, soil C org stocks in seagrass and bare but previously vegetated areas were not significantly different (2.6 ± 0.3 and 3.0 ± 0.6 kg C org/m2, respectively). The soil C org sequestration capacity prevailed in shallow and deep vegetated areas (55 ± 11 and 21 ± 7 g C org m−2 year−1, respectively), but was lost in bare areas. We identified that seagrass canopy loss alone does not necessarily drive changes in soil C org but, when combined with high hydrodynamic energy, significant erosion occurred. Our estimates point at ~0.20 m/s as the critical shear velocity threshold causing soil C org erosion. We estimate, from field studies and satellite imagery, that soil C org erosion (within the top 50 cm) following seagrass loss likely resulted in cumulative emissions of 0.06–0.14 Tg CO2-eq over the last 40 years in Cockburn Sound. We estimated that indirect impacts (i.e. eutrophication, thermal stress and light stress) causing the loss of ~161,150 ha of seagrasses in Australia, likely resulted in the release of 11–21 Tg CO2-eq since the 1950s, increasing cumulative CO2 emissions from land-use change in Australia by 1.1%–2.3% per annum. The patterns described serve as a baseline to estimate potential CO2 emissions following disturbance of seagrass meadows.

Details

Title: Seagrass losses since mid-20th century fuelled CO2 emissions from soil carbon stocks
Authors: Cristian Salinas (Corresponding Author) - Edith Cowan University
Carlos M Duarte (Author) - King Abdullah University of Science and Technology
Paul S Lavery (Author) - Edith Cowan University
Pere Masqué (Author) - Edith Cowan University
Ariane Arias-Ortiz (Author) - University of California Los Angeles
Javier X Leon (Author) - University of the Sunshine Coast, Queensland, School of Science and Engineering - Legacy
David Callaghan (Author) - The University of Queensland
Gary A Kendrick (Author) - The University of Western Australia
Oscar Serrano (Author) - Edith Cowan University
Publication details: Global Change Biology, Vol.26(9), pp.4772-4784
Publisher: Wiley-Blackwell Publishing Ltd.
Date published: 2020
DOI: 10.1111/gcb.15204
ISSN: 1365-2486; 1354-1013
Copyright note: Copyright © 2020 The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
Organisation Unit: School of Science and Engineering - Legacy; University of the Sunshine Coast, Queensland; School of Science, Technology and Engineering; Sustainability Research Cluster
Language: English
Record Identifier: 99465407802621
Output Type: Journal article

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Web Of Science research areas: Biodiversity Conservation; Ecology; Environmental Sciences

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