Land-use change in tropical peatlands substantially impacts peat emissions of methane (CH4) and nitrous oxide (N2O) in addition to emissions of carbon dioxide (CO2). However, assessments of full peat greenhouse gas (GHG) budgets are scarce and CH4 and N2O contributions remain highly uncertain. The objective of our research was to assess changes in peat GHG flux and budget associated with peat swamp forest disturbance and conversion to oil palm plantation and to evaluate drivers of variation in trace gas fluxes. Over a period of one and a half year, we monitored monthly CH4 and N2O fluxes together with environmental variables in three undrained peat swamp forests and three oil palm plantations on peat in Central Kalimantan. The forests included two primary forests and one 30-year-old secondary forest. We calculated the peat GHG budget in both ecosystems using soil respiration and litterfall rates measured concurrently with CH4 and N2O fluxes, site-specific soil respiration partitioning ratios, and literature-based values of root inputs and dissolved organic carbon export. Peat CH4 fluxes (kg CH4 ha−1 year−1) were insignificant in oil palm (0.3 ± 0.4) while emissions in forest were high (14.0 ± 2.8), and larger in wet than in dry months. N2O emissions (kg N2O ha−1 year−1) were highly variable spatially and temporally and similar across land-uses (5.0 ± 3.9 and 5.2 ± 3.7 in oil palm and forest). Temporal variation of CH4 was controlled by water table level and soil water-filled pore space in forest and oil palm, respectively. Monthly fluctuations of N2O were linked to water table level in forest. The peat GHG budget (Mg CO2 equivalent ha−1 year−1) in oil palm (31.7 ± 8.6) was nearly eight times the budget in forest (4.0 ± 4.8) owing mainly to decreased peat C inputs and increased peat C outputs. The GHG budget was also ten times higher in the secondary forest (10.2 ± 4.5) than in the primary forests (0.9 ± 3.9) on the account of a larger peat C budget and N2O emission rate. In oil palm 96% of emissions were released as CO2 whereas in forest CH4 and N2O together contributed 65% to the budget. Our study highlights the disastrous atmospheric impact associated with forest degradation and conversion to oil palm in tropical peatlands and stresses the need to investigate GHG fluxes in disturbed undrained lands.
Tag: peat
Where Policy and Culture Collide: Perceptions and Responses of Swidden Farmers to the Burn Ban in West Kalimantan, Indonesia
Catastrophic uncontrolled fires are a leading social-environmental challenge that now occur even in the humid tropics. In 2015 extensive Indonesian peatland fires commanded national and international attention and resulted in a ban on all burning in the country extending to traditional farmers practicing small-scale fire-based agriculture on mineral soils. However, the impacts of, and responses to the ban on these fire-dependent communities is not well understood. Understanding the mental models of communities exposed to environmental change and its corresponding policy responses can provide salient insights into the place-based experience of change to identify contested perceptions and serve to improve the distributional equity of associated impacts. We assessed the mental models of Dayak farmers in Kapuas Hulu, Kalimantan, in three distinct landscape contexts: i) oil palm (OP), ii) national park (NP), and iii) transition (T) sites. These locations enabled insights into how different contemporary landscape contexts and livelihood opportunities are related to experiences and coping strategies. We collected data using the Conceptual Content Cognitive Mapping approach in two communities in each landscape context (n = 24 participants per landscape), and 72 interviews in total. Results show that the NP and T sites were most similar, whilst the OP communities held distinct perceptions of fire. In addition to the agricultural value of fire, cultural and relational values are associated with fire use across sites and would be severed through fire prevention. Finally, we show that the burdens of the burn ban for farmers and forests were most pronounced in the NP and T sites where farmers are most reliant on traditional agriculture, have the fewest livelihood alternatives and least external support to fight uncontrolled fires.
Degradation increases peat greenhouse gas emissions in undrained tropical peat swamp forests
Tropical peat swamp degradation can modify net peat greenhouse gas (GHG) emissions even without drainage. However, current Intergovernmental Panel on Climate Change (IPCC) guidelines do not provide default emission factors (EF) for anthropogenically-degraded undrained organic soils. We reviewed published field measurements of peat GHG fluxes in undrained undegraded and degraded peat swamp forests in Southeast Asia (SEA) and Latin America and the Caribbean (LAC). Degradation without drainage shifted the peat from a net CO2 sink to a source in both SEA (− 2.9 ± 1.8 to 4.1 ± 2.0 Mg CO2–C ha−1 yr−1) and LAC (− 4.3 ± 1.8 to 1.4 ± 2.2 Mg CO2–C ha−1 yr−1). It raised peat CH4 emissions (kg C ha−1 yr−1) in SEA (22.1 ± 13.6 to 32.7 ± 7.8) but decreased them in LAC (218.3 ± 54.2 to 165.0 ± 4.5). Degradation increased peat N2O emissions (kg N ha−1 yr−1) in SEA forests (0.9 ± 0.5 to 4.8 ± 2.3) (limited N2O data). It shifted peat from a net GHG sink to a source in SEA (− 7.9 ± 6.9 to 20.7 ± 7.4 Mg CO2-equivalent ha−1 yr−1) and increased peat GHG emissions in LAC (9.8 ± 9.0 to 24.3 ± 8.2 Mg CO2-equivalent ha−1 yr−1). The large observed increase in net peat GHG emissions in undrained degraded forests compared to undegraded conditions calls for their inclusion as a new class in the IPCC guidelines. As current default IPCC EF for tropical organic soils are based only on data collected in SEA ombrotrophic peatlands, expanded geographic representation and refinement of peat GHG EF by nutrient status are also needed.