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Methane and Nitrous Oxide Budgets for Australasia : A Regional Assessment of Natural and Anthropogenic Sources and Sinks

Villalobos, Yohanna LU orcid ; Canadell, Josep G. ; Keller, Elizabeth D. ; Briggs, Peter R. ; Ford, Phillip ; Harman, Ian N. ; Hilton, Timothy W. ; Hogikyan, Allison ; Lauerwald, Ronny and Maher, Damien T. , et al. (2025) In Global Biogeochemical Cycles 39(10).
Abstract

We present the CH4 and N2O budgets for anthropogenic and natural sources and sinks of Australasia (Australia and New Zealand) from 2010 to 2019 using bottom-up and top-down methods, in line with the RECCAP-2 initiative, with extensions to 2022. We show that the bottom-up CH4 budget for Australasia (2010–2019) was a net source of 14.1 ± 5.5 Tg CH4 yr−1, with Australia and New Zealand contributing 84% and 16%, respectively. Anthropogenic sources contributed 55% of all CH4 emissions, the rest coming from natural sources, primarily wetlands. The bottom-up N2O budget was a net source of 0.5 ± 0.3 Tg N2O yr−1, with Australia contributing the... (More)

We present the CH4 and N2O budgets for anthropogenic and natural sources and sinks of Australasia (Australia and New Zealand) from 2010 to 2019 using bottom-up and top-down methods, in line with the RECCAP-2 initiative, with extensions to 2022. We show that the bottom-up CH4 budget for Australasia (2010–2019) was a net source of 14.1 ± 5.5 Tg CH4 yr−1, with Australia and New Zealand contributing 84% and 16%, respectively. Anthropogenic sources contributed 55% of all CH4 emissions, the rest coming from natural sources, primarily wetlands. The bottom-up N2O budget was a net source of 0.5 ± 0.3 Tg N2O yr−1, with Australia contributing the majority (92%), mainly from natural sources (82%). Australasia top-down CH4 (10.4 ± 0.5 Tg CH4 yr−1) and N2O budgets (0.8 ± 0.5 Tg N2O yr−1) differ in magnitude from the bottom-up budgets but remain consistent within their uncertainties. Similar consistency is observed for Australia, while New Zealand shows significant discrepancies, particularly for N2O, where the bottom-up estimate is 71% higher than the top-down estimate. In terms of trends, bottom-up natural wetland CH4 emissions increased in both countries between 2010 and 2019. CH4 emissions from enteric fermentation slightly declined in Australia but increased in New Zealand. Soil N2O emissions from nitrogen additions increased in both countries, with a significant rise in New Zealand driving the overall positive trend in anthropogenic emissions. These findings highlight critical sectors with large mitigation potential and the significance of monitoring natural sources for possible biogeochemical-climate feedback.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
bottom-up, land ocean aquatic continuum (LOAC), methane budget, nitrous oxide budget, RECCAP-2, top-down
in
Global Biogeochemical Cycles
volume
39
issue
10
article number
e2024GB008484
publisher
Wiley-Blackwell
external identifiers
  • scopus:105018718559
ISSN
0886-6236
DOI
10.1029/2024GB008484
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2025. The Author(s).
id
7ddec59f-b8d0-4896-a16c-e4316ffd702b
date added to LUP
2025-12-18 10:44:56
date last changed
2025-12-18 14:26:33
@article{7ddec59f-b8d0-4896-a16c-e4316ffd702b,
  abstract     = {{<p>We present the CH<sub>4</sub> and N<sub>2</sub>O budgets for anthropogenic and natural sources and sinks of Australasia (Australia and New Zealand) from 2010 to 2019 using bottom-up and top-down methods, in line with the RECCAP-2 initiative, with extensions to 2022. We show that the bottom-up CH<sub>4</sub> budget for Australasia (2010–2019) was a net source of 14.1 ± 5.5 Tg CH<sub>4</sub> yr<sup>−1</sup>, with Australia and New Zealand contributing 84% and 16%, respectively. Anthropogenic sources contributed 55% of all CH<sub>4</sub> emissions, the rest coming from natural sources, primarily wetlands. The bottom-up N<sub>2</sub>O budget was a net source of 0.5 ± 0.3 Tg N<sub>2</sub>O yr<sup>−1</sup>, with Australia contributing the majority (92%), mainly from natural sources (82%). Australasia top-down CH<sub>4</sub> (10.4 ± 0.5 Tg CH<sub>4</sub> yr<sup>−1</sup>) and N<sub>2</sub>O budgets (0.8 ± 0.5 Tg N<sub>2</sub>O yr<sup>−1</sup>) differ in magnitude from the bottom-up budgets but remain consistent within their uncertainties. Similar consistency is observed for Australia, while New Zealand shows significant discrepancies, particularly for N<sub>2</sub>O, where the bottom-up estimate is 71% higher than the top-down estimate. In terms of trends, bottom-up natural wetland CH<sub>4</sub> emissions increased in both countries between 2010 and 2019. CH<sub>4</sub> emissions from enteric fermentation slightly declined in Australia but increased in New Zealand. Soil N<sub>2</sub>O emissions from nitrogen additions increased in both countries, with a significant rise in New Zealand driving the overall positive trend in anthropogenic emissions. These findings highlight critical sectors with large mitigation potential and the significance of monitoring natural sources for possible biogeochemical-climate feedback.</p>}},
  author       = {{Villalobos, Yohanna and Canadell, Josep G. and Keller, Elizabeth D. and Briggs, Peter R. and Ford, Phillip and Harman, Ian N. and Hilton, Timothy W. and Hogikyan, Allison and Lauerwald, Ronny and Maher, Damien T. and Martinez, Adrien and Pan, Naiqing and Poulter, Benjamin and Resplandy, Laure and Rosentreter, Judith A. and Saunois, Marielle and Tian, Hanqin and Yeo, Jacob and Zhang, Zhen}},
  issn         = {{0886-6236}},
  keywords     = {{bottom-up; land ocean aquatic continuum (LOAC); methane budget; nitrous oxide budget; RECCAP-2; top-down}},
  language     = {{eng}},
  number       = {{10}},
  publisher    = {{Wiley-Blackwell}},
  series       = {{Global Biogeochemical Cycles}},
  title        = {{Methane and Nitrous Oxide Budgets for Australasia : A Regional Assessment of Natural and Anthropogenic Sources and Sinks}},
  url          = {{http://dx.doi.org/10.1029/2024GB008484}},
  doi          = {{10.1029/2024GB008484}},
  volume       = {{39}},
  year         = {{2025}},
}