Projecting Future Changes in Southeast Asia’s
Aboveground Forest Carbon Stock
Ronald C. Estoque

1,*12131
4
Makoto Ooba , Valerio Avitabile , Yasuaki Hijioka , Rajarshi DasGupta , Takuya Togawa , Yuji Murayama
1 National Institute for Environmental Studies, Japan; 2European Commission, Joint Research Centre, Italy; 3Institute for Global Environmental Strategies, Japan; 4University of Tsukuba, Japan* Corresponding author (estoque.ronaldcanero@nies.go.jp)

Forest cover loss and degradation in Sarawak, Malaysia due to logging

Introduction(Fieldwork photos by Ronald C. Estoque, September 2019 )While Southeast Asia’s forests play important roles in biodiversity
conservation and global carbon balance, the region is also a deforestation
hotspot. Here, we considered the five shared socioeconomic pathways (SSPs)
to portray a range of plausible futures for the region’s forests, employing astate-of-the-art land change modeling procedure and remotely sensed data.
More particularly, we focused on the spatial allocation of the projected
quantities of future forest cover changes in the region from 2015 to 2050
under the five baseline SSPs. The potential implications of these spatiallyallocated projected forest cover changes were examined by quantifying theirconsequent aboveground forest carbon stock (AFCS) changes at the countryand province levels.
SSP Database

Modeling and impact
analysis procedure

Spatially allocated future forest coverchanges and projected AFCS changes

ResearchFlowMethods
nLoss

AFCS LossY,V 2015−2050 = ෍ ACDi,2050 × Ai
i=1

where ACDi and Ai refer to the 2050 projected above ground carbon
density (Mg C ha−1) and the land area (ha), respectively, of pixel i; and n is
the number of pixels of the projected forest cover loss (2015–2050) withan ACD value within each country, Y, or province, V. Here, it is assumed
that deforestation will happen in 2050.

ACDjs,2050 = ACDjs + (CSR js × GP൯
where ACDjs and CSRjs refer to the 2010 aboveground carbon density (Mg Cha−1) and carbon sequestration rate (Mg C ha−1 yr−1), respectively, of pixel jwhich is a member of sub-class s of old growth forest and old secondary
forest; and GP refers to the growth period (40 years) for old growth forest
and old secondary forest from 2010 (the year of the ACD) to 2050 (the endyear of the projection).
mGain

AFCS GainY,V 2015−2050 = ෍ ACDq,2050 × Aq
q=1

where ACDq and Aq refer to the 2050 projected aboveground carbondensity (Mg C ha−1) and the land area (ha), respectively, of pixel q; and m isthe number of pixels of the projected forest cover gain (2015–2050) withineach country, Y, or province, V.

ACDqs,2050 = CSR qs × GP

Fig. 1. Flowchart of the spatially explicit land change modeling procedure developed and used in this study.

Fig. 2. Flowchart of geospatial approach developed and used in this study to reclassify the forest class by ecozones.

where CSRqs refers to the carbon sequestration rate (Mg C ha−1 yr−1) of
pixel q of the projected forest cover gain which is a member of sub-class sof the new young secondary forest; and GP refers to the growth period(17.5 years) for the projected young secondary forest with the assumptionthat trees would be planted not at one time, but rather across the 35-year
period (2015–2050).

Results and Discussion

Fig. 4. Country-level distribution of future forest and AFCS changes (2015-2050).

Fig. 5. Province-level distribution of future AFCS changes across the SSPs (2015-2050).

• We find that by 2050 under the worst-case scenario, SSP 3 (regional rivalry/a rocky road), the region’s forests
would shrink by 5.2 million ha. The region’s aboveground forest carbon stock (AFCS) would decrease by 790
Tg C, 21% of which would be due to old-growth forest loss. Conversely, under the best-case scenario, SSP 1(sustainability/taking the green road), the region is projected to gain 19.6 million ha of forests and 1651 Tg Cof AFCS.
• Translating these projected changes in AFCS into rates, the forest gaining scenarios suggest that Southeast
Asia would be able to sequester C at a rate ranging from 25 Tg C yr−1 (SSP 4) to 47 Tg C yr−1 (SSP 1). By
contrast, the forest-losing scenarios suggested that the region would be emitting C at a rate ranging from 14Tg C yr−1 (SSP 5) to 23 Tg C yr−1 (SSP 3).
• The choice of the pathway is thus critical for the future of the region’s forests and their ecosystem functions
and services. For the future directions of this study, its expansion to global scale and its relation with theforest transition theory and SDG 15 (Life on Land) are currently being considered.
More details can be found in:•Fig. 3. Maps of the spatially allocated projected forest cover changes under the five SSPs (2015-2050).

• Estoque RC, Ooba M, Avitabile V, Hijioka Y, DasGupta R, Togawa T, Murayama Y. 2019. The future of Southeast Asia’s forests. Nature Communinications 10:1829.