## 4 Discussion
### Implications for Tropical Peatland Management  
Tropical peat swamp forests sequester carbon because their high annual NPP exceeds their respiration rates. Degradation and conversion (land-use changes) of peat swamp forests significantly affected NPP. [10] stated that tropical peatland landscapes in Indonesia are now net sources of carbon as there is four times more degraded peat forest than the intact forest. Intact peat swamp forests now only comprise <7% of all peatland areas in Indonesia's main islands [7]. In 2015 there were more than three million hectares of oil palm estates and almost one million hectares of degraded grasslands/early seral (ES) in South East Asia [7]. Using our estimates of oil palm's NEP (\(-25.1\) Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\)), the 3 million ha of oil palm will emit significant amounts of CO\({}_{2}\) into the atmosphere, as much as 75 Tg CO\({}_{2}\) yr\({}^{-1}\). In addition, our results from the NEP of early seral sites (9.1 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\)) suggest that allowing grasses and ferns to regrow and cover the peat surface under 3 million ha of OP trees could reduce the emissions by about 27 Tg CO\({}_{2}\) yr\({}^{-1}\). Most ignitions in peatland landscapes are from humans and in contrast to early seral sites and logged forests, rarely are fuels dry enough to burn in natural forests [60]. However, our results show that land-use change significantly lowered the water table and increased soil temperatures, thus increasing fire susceptibility [61]. Fire is a significant threat to the production of peatland ecosystems. A single event of uncontrolled peat fire may emit as much as 416 Mg CO\({}_{2}\) ha\({}^{-1}\)[62]. This is a value equivalent to the NEP of peat forests for almost four decades. Logging and conversion to early seral communities and oil palm estate reduce potential carbon sequestration by 10.9, 1.7, and 35.9 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\), respectively. These are the differences in NEP between intact peat forest (10.8 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\)) and each of logged peat forest (\(-0.1\) Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\)), early seral (9.1 Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\)), and oil palm (\(-25.1\) Mg CO\({}_{2}\) ha\({}^{-1}\) yr\({}^{-1}\)). Logging and conversion of peat swamp forests have shifted the ecosystem from a carbon sink to a carbon emitter. The large carbon stocks and emissions arising from the land cover change in tropical peat forests and other ecosystem services of intact peat forests suggest that their conservation and restoration are of local and global importance for mitigating climate change. Figure 6: Net ecosystem production among wetland ecosystems. Data for mangrove are from [51; 53]. Shrimp pond is from [53]. Peat oil palm is from [56] and this study. Peat pine forest and drained peat forests are from [54; 58]. Peat shrub is from [59]. Peat forest, logged peat forest, oil palm, and early seral are from this study (bordered with black line). **Author Contributions:** Conceptualization, J.B.K., D.M., G.Z.A. and I.B. ; methodology, J.B.K., D.M., I.B. ; software, I.B. ; validation, J.B.K., D.M., G.Z.A., J.T.P. and I.B. (all authors); formal analysis, I.B., J.B.K. ; investigation, I.B., J.B.K. ; resources, J.B.K. ; data curation, I.B., J.B.K. ; writing--original draft preparation, I.B. ; writing--review and editing, all authors; visualization, I.B. ; supervision, J.B.K., D.M., G.Z.A. ; project administration, J.B.K. ; funding acquisition, J.B.K. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by the United States Agency for International Development (USAID). **Data Availability Statement:** The data presented in this study are available on request from the corresponding author. **Acknowledgments:** This study was part of the Kalimantan Wetlands Climate Change Study (KWACS) funded by the United States Agency for International Development (USAID).