Title

Blue carbon drawdown by restored mangrove forests improves with age

Document Type

Journal Article

Publication Title

Journal of Environmental Management

Volume

306

Publisher

Elsevier

School

School of Science

Funders

HSBC in partnership with Deakin University’s Blue Carbon Lab and Earthwatch Institute Australia

Australian Research Council Discovery Grant (DP200100575)

Australian Research Council LIEF Project (LE170100219)

Deakin University’s ADPRF and Australian Research Council’s DECRA (DE210101029)

Institut de Ci`encia i Tecnologia Ambientals’ ‘Unit of Excellence’ Maria de Maetzu (CEX 2019-000940-M)

Grant Number

ARC Number : DP200100575, LE170100219, DE210101029

Comments

Carnell, P. E., Palacios, M. M., Waryszak, P., Trevathan-Tackett, S. M., Masqué, P., & Macreadie, P. I. (2022). Blue carbon drawdown by restored mangrove forests improves with age. Journal of environmental management, 306, 114301.

https://doi.org/10.1016/j.jenvman.2021.114301

Abstract

The restoration of blue carbon ecosystems, such as mangrove forests, is increasingly used as a management tool to mitigate climate change by removing and sequestering atmospheric carbon in the ground. However, estimates of carbon-offset potential are currently based on data from natural mangrove forests, potentially leading to overestimating the carbon-offset potential from restored mangroves. Here, in the first study of its kind, we utilise 210Pb sediment age-dating techniques and greenhouse gas flux measures to estimate blue carbon additionality in restored mangrove forests, ranging from 13 to 35 years old. As expected, mangrove age had a significant effect on carbon additionality and carbon accretion rate, with the older mangrove stands (17 and 35 years old) holding double the total carbon stocks (aboveground + soil stocks; ∼115 tonnes C ha−1) and double the soil sequestration rates (∼3 tonnes C ha−1 yr−1) than the youngest mangrove stand (13 years old). Although soil carbon stocks increased with mangrove age, the aboveground plant stocks were highest in the 17-year-old stand. Mangrove age also had a significant effect on soil carbon fluxes, with the older mangroves ( ≥ 17 years) releasing one-fourth of the CH4 emissions, but double the CO2 flux compared to young stands. Our study suggests that the carbon sink capacity of restored mangrove forests increases with age, but stabilises once they mature (e.g., > 17 years). This means that by using carbon sequestration and emissions from natural forests, mangrove restoration projects may be overestimating their carbon sequestration potential.

DOI

10.1016/j.jenvman.2021.114301

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