TY - JOUR
T1 - Are Land-Use Change Emissions in Southeast Asia Decreasing or Increasing?
AU - Kondo, Masayuki
AU - Sitch, Stephen
AU - Ciais, Philippe
AU - Achard, Frédéric
AU - Kato, Etsushi
AU - Pongratz, Julia
AU - Houghton, Richard A.
AU - Canadell, Josep G.
AU - Patra, Prabir K.
AU - Friedlingstein, Pierre
AU - Li, Wei
AU - Anthoni, Peter
AU - Arneth, Almut
AU - Chevallier, Frédéric
AU - Ganzenmüller, Raphael
AU - Harper, Anna
AU - Jain, Atul K.
AU - Koven, Charles
AU - Lienert, Sebastian
AU - Lombardozzi, Danica
AU - Maki, Takashi
AU - Nabel, Julia E.M.S.
AU - Nakamura, Takashi
AU - Niwa, Yosuke
AU - Peylin, Philippe
AU - Poulter, Benjamin
AU - Pugh, Thomas A.M.
AU - Rödenbeck, Christian
AU - Saeki, Tazu
AU - Stocker, Benjamin
AU - Viovy, Nicolas
AU - Wiltshire, Andy
AU - Zaehle, Sönke
N1 - Publisher Copyright:
© 2021. American Geophysical Union. All Rights Reserved.
PY - 2022/1
Y1 - 2022/1
N2 - Southeast Asia is a region known for active land-use changes (LUC) over the past 60 years; yet, how trends in net CO2 uptake and release resulting from LUC activities (net LUC flux) have changed through past decades remains uncertain. The level of uncertainty in net LUC flux from process-based models is so high that it cannot be concluded that newer estimates are necessarily more reliable than older ones. Here, we examined net LUC flux estimates of Southeast Asia for the 1980s−2010s from older and newer sets of Dynamic Global Vegetation Model simulations (TRENDY v2 and v7, respectively), and forcing data used for running those simulations, along with two book-keeping estimates (H&N and BLUE). These estimates yielded two contrasting historical LUC transitions, such that TRENDY v2 and H&N showed a transition from increased emissions from the 1980s to 1990s to declining emissions in the 2000s, while TRENDY v7 and BLUE showed the opposite transition. We found that these contrasting transitions originated in the update of LUC forcing data, which reduced the loss of forest area during the 1990s. Further evaluation of remote sensing studies, atmospheric inversions, and the history of forestry and environmental policies in Southeast Asia supported the occurrence of peak emissions in the 1990s and declining thereafter. However, whether LUC emissions continue to decline in Southeast Asia remains uncertain as key processes in recent years, such as conversion of peat forest to oil-palm plantation, are yet to be represented in the forcing data, suggesting a need for further revision.
AB - Southeast Asia is a region known for active land-use changes (LUC) over the past 60 years; yet, how trends in net CO2 uptake and release resulting from LUC activities (net LUC flux) have changed through past decades remains uncertain. The level of uncertainty in net LUC flux from process-based models is so high that it cannot be concluded that newer estimates are necessarily more reliable than older ones. Here, we examined net LUC flux estimates of Southeast Asia for the 1980s−2010s from older and newer sets of Dynamic Global Vegetation Model simulations (TRENDY v2 and v7, respectively), and forcing data used for running those simulations, along with two book-keeping estimates (H&N and BLUE). These estimates yielded two contrasting historical LUC transitions, such that TRENDY v2 and H&N showed a transition from increased emissions from the 1980s to 1990s to declining emissions in the 2000s, while TRENDY v7 and BLUE showed the opposite transition. We found that these contrasting transitions originated in the update of LUC forcing data, which reduced the loss of forest area during the 1990s. Further evaluation of remote sensing studies, atmospheric inversions, and the history of forestry and environmental policies in Southeast Asia supported the occurrence of peak emissions in the 1990s and declining thereafter. However, whether LUC emissions continue to decline in Southeast Asia remains uncertain as key processes in recent years, such as conversion of peat forest to oil-palm plantation, are yet to be represented in the forcing data, suggesting a need for further revision.
KW - Dynamic Global Vegetation Models
KW - Southeast Asia
KW - atmospheric inversions
KW - book-keeping models
KW - forest area
KW - land-use changes
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U2 - 10.1029/2020GB006909
DO - 10.1029/2020GB006909
M3 - Article
AN - SCOPUS:85123680081
SN - 0886-6236
VL - 36
JO - Global Biogeochemical Cycles
JF - Global Biogeochemical Cycles
IS - 1
M1 - e2020GB006909
ER -