Southeast Asia is rich in tropical forests and biodiversity but rapid deforestation and forest degradation have accelerated climate change and threatened sustainable development in the region. Carbon emission reductions through reducing deforestation and forest degradation, forest conservation, sustainable management of forests, and enhancement of forest carbon stocks (REDD+) have been a focal topic of the climate change mitigation since the Bali in 2007. However, only a handful of studies exist so far on this important issue that are suitable to inform the debate with estimates of carbon stocks and emission reductions or removals as a result of REDD+. Our study attempts to analyze the potential emission reductions and removals for a 35-year period under the REDD+ scheme. We start by developing land use change and forest harvesting models that are used to estimate carbon stock changes in natural forests and forest plantations in Southeast Asia. Carbon emissions from deforestation and forest degradation of natural forests were 1865.1, 1611.4, and 1300.4 TgCO2 year −1 , respectively. With a hypothetical carbon project of 35 years beginning from 2015, carbon emission reductions were estimated at 817.6 TgCO2 year −1 , of which about 10% was from reducing forest degradation. Carbon removals due to increase of forest plantations were 76.3 TgCO2 year −1 but the removals could be much higher if there is a new definition on the eligibility of forest plantations. Summing up together, about 893.9 TgCO2 of carbon credits could be achieved from implementing carbon project in Southeast Asia or about US $6.6 billion annually between 2015 and 2050 if carbon price in 2012 is used. In addition to reducing emissions, there are other benefits from carbon project implementation. This study suggests that REDD+ has great potential for reducing carbon emissions and enhancing carbon stocks in the forests. Without financial incentives, carbon project would not happen and therefore climate change will continue to threaten future development.

Carbon emissions from selectively logged forests in the tropics are strongly affected by logging practices. Although tropical forests are mainly managed under the concession system, only a handful of studies were done to assess the impact of logging practices on emission reductions and future timber supply. In this report, carbon stocks, timber supply, and carbon emission reductions under conventional logging (CVL), reduced-impact logging (RIL), and RIL with special silvicultural treatments (RIL+) were assessed in 3.4 million ha of concession forests for a 55-year project time span. Carbon emissions under a 25-year CVL practiced in Cambodia were estimated at 12.4 TgCO 2 year −1 for 55 years. We then tested four cutting cycles of selective logging and our results suggest that a 45-year selective cutting cycle was appropriate for managing concession forests in Cambodia in terms of maintaining commercial timber supply and reducing carbon emissions. By considering RIL or RIL+ as a new logging practice for improving forest management in the tropics, carbon credits from selective logging in Cambodia were estimated at 6.2-7.9 TgCO 2 or about $31.0-39.5 million annually if carbon is priced at $5. It is concluded that RIL or RIL+ should be adopted for "sustainable management of forests" element of the REDD+ scheme.

Selective logging creates a large amount of wood residues in forests in addition to producing a small amount of sawnwood for use as source of construction materials. Although accounting for carbon fluxes in harvested wood products (HWPs) becomes necessary in the fight against climate change, previous studies focused mainly on carbon fluxes in HWPs in temperate and boreal forests. This report attempts to analyze carbon fluxes in various wood components created by selective logging in production forest in Southeast Asia during a hypothetical period of carbon project implementation between 2015 and 2050 under conventional (CVL) and reduced-impact logging (RIL). Study results suggest that CVL produced about 146.6 (±5.4) million m 3 annually. Logging created annual carbon fluxes of about 0.23, 0.23, 0.20, 0.69, and 0.15 MgC ha −1 •year −1 in sawnwood, wood wastes at sawmills (SWW), wood product wastes due to logging damages remained in the forests (WPW), branches and top logs (BRA), and belowground dead root (BLD), respectively. Cumulative carbon fluxes were estimated at 281.0, 506.6, and 87.4 TgC year −1 in sawnwood, onsite (WPW, BRA, BLD), and offsite (SWW) pools, respectively. Except in SW, cumulative carbon fluxes in onsite and offsite pools showed a decline trend in about 10 years after logging. Switching from CVL to RIL could increase fluxes in sawnwood 60% higher than that under CVL, while reducing fluxes in short-lived onsite and offsite wood residues. Not only RIL can increase carbon fluxes in sawnwood, it can also increase production of sawnwood and retain more carbon in standing forests.