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Tropical forests post-logging are a persistent net carbon source to the atmosphere

Lookup NU author(s): Professor Yit Arn TehORCiD



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Logged and structurally degraded tropical forests are fast becoming one of the most prevalent land-use types throughout the tropics and are routinely assumed to be a net carbon sink because they experience rapid rates of tree regrowth. Yet this assumption is based on forest biomass inventories that record carbon stock recovery but fail to account for the simultaneous losses of carbon from soil and necromass. Here, we used forest plots and an eddy covariance tower to quantify and partition net ecosystem CO2 exchange in Malaysian Borneo, a region that is a hot spot for deforestation and forest degradation. Our data represent the complete carbon budget for tropical forests measured throughout a logging event and subsequent recovery and found that they constitute a substantial and persistent net carbon source. Consistent with existing literature, our study showed a significantly greater woody biomass gain across moderately and heavily logged forests compared with unlogged forests, but this was counteracted by much larger carbon losses from soil organic matter and deadwood in logged forests. We estimate an average carbon source of 1.75 ± 0.94 Mg C ha-1 yr-1 within moderately logged plots and 5.23 ± 1.23 Mg C ha-1 yr-1 in unsustainably logged and severely degraded plots, with emissions continuing at these rates for at least one-decade post-logging. Our data directly contradict the default assumption that recovering logged and degraded tropical forests are net carbon sinks, implying the amount of carbon being sequestered across the world's tropical forests may be considerably lower than currently estimated.

Publication metadata

Author(s): Mills MB, Malhi Y, Ewers RM, Kho LK, Teh YA, Both S, Burslem DFRP, Majalap N, Nilus R, Huaraca Huasco W, Cruz R, Pillco MM, Turner EC, Reynolds G, Riutta T

Publication type: Article

Publication status: Published

Journal: Proceedings of the National Academy of Sciences

Year: 2023

Volume: 120

Issue: 3

Print publication date: 17/01/2023

Online publication date: 09/01/2023

Acceptance date: 16/11/2022

Date deposited: 23/01/2023

ISSN (print): 0027-8424

ISSN (electronic): 1091-6490

Publisher: National Academy of Sciences


DOI: 10.1073/pnas.2214462120

PubMed id: 36623189


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Funder referenceFunder name
DEB- 9107247
DEB- 9629601
Centre for Tropical Forest Science (CTFS)
HSBC Climate Partnership.
European Research Council
GEM-TRAIT (321131)
Malaysian Palm Oil Board (MPOB)
Natural Environment Research Council Human-Modified Tropical Forests Programme
NOMIS Foundation
Sime Darby Foundation