Tropical peatland carbon dynamics simulated for scenarios of disturbance and restoration and climate change

Tropical peatlands contain a globally significant carbon pool. Southeast Asian peatlands are being deforested, drained and burned at very high rates, mostly for conversion to industrial oil palm or pulp and paper plantations. The climate mitigation potential of tropical peatlands has gained increasing attention in recent years as persistent greenhouse gas emissions can be avoided or decreased if peatlands remain intact or are rehabilitated. In addition, peatland conservation or rehabilitation for climate mitigation also includes multiple co-benefits such as maintenance of ecosystem services, biodiversity, and air quality from reduced fire occurrence. Inventory guidelines and methodologies have only recently become available, and are based on few data from a limited number of sites. Few heuristic tools are available to evaluate the impact of management practices on carbon dynamics in tropical peatlands, and the potential climate mitigation benefits of peatland restoration. We used a process based dynamic tropical peatland model to explore the C dynamics of several peatland management trajectories represented by hypothetical scenarios, within the context of simulated 21st century climate change. All scenarios with land use, including those with optimal restoration, simulate C loss over the 21st century, with C losses ranging from 10% to essentially 100% of pre-disturbance values. Fire, either prescribed as part of a crop rotation cycle, or stochastic occurrences in sub-optimally managed degraded land can be the dominant C-loss pathway, particularly in the drier climate scenario we tested. A single 25-year oil palm rotation, with a prescribed initial burn, lost 40-50 kg C/m2, equivalent to accumulation during the previous 500 years, 10-30% of which was restored in 75 years of optimal restoration. Our results indicate that even under the most optimistic scenario of hydrological and forest restoration and the wettest climate regime, only about one-third of the carbon lost to the atmosphere from 25 years of oil palm cultivation can be recovered within the next 75 years. In addition, peat fire suppression is the most effective management tool to maintain peatland carbon stocks, and should be a high priority for climate mitigation efforts on peatlands