Socio-economic Study of Conservation and Rehabilitation of Tropical Peatland With Agroforestry Systems in Central Kalimantan, Indonesia

Current studies on tropical peatlands in Indonesia are mostly focused on the impacts of management practices on the environment. Studies on efforts to conserve and rehabilitate the degradation of tropical peatland involving farmers through agroforestry systems have been limited. By employing the qualitative survey with semi-structured interviews and field observations to agroforestry locations in two villages of Tumbang Nusa and Kalampangan, Central Kalimantan, Indonesia aims to fill those research gaps. The results showed that the main motivation of farmers in starting agroforestry activities was the understanding that there would be limited trees in the future, and planting trees with a combination of intercrops provided adequate income. Agroforestry farmers who devote considerable time to agroforestry can meet the family's economic needs. Although further guidance is not typically provided, government intervention through tree planting programs also stimulates agroforestry activities. Intensive management of intercrops in various types can provide a good income. For intensive intercropping options, farmers follow market demand, while less intensive farmers prefer plants that do not require intensive management. Trees planted in agroforestry systems are only given fertilizer at the initial planting stage. Some farms receive fertilizer subsidies from government support programmes, but fertilizers are obtained from intercropping at the following stage. The study results imply that the community needs to get knowledge and training on agroforestry, which can be a way of conserving and rehabilitating tropical peatlands and a source of income.

Peatlands Are More Beneficial if Conserved and Restored than Drained for Monoculture Crops

Peatlands are especially important but fragile tropical landscapes. The importance of peatlands is owing to their ability to 1) sequester a considerable amount of terrestrial carbon, 2) store freshwater, and 3) regulate floods during the rainy season. Nowadays, extensive peatland degradation occurs because of peatland utilization for agriculture purposes, causing severe environmental consequences such as carbon emission, loss of biodiversity, risk of flooding, and peat fire. Meanwhile, local planners and decision makers tend to overlook the long-term strategic function of peatlands for carbon storage and hydrological regulation, preferring peatland utilization for short-term economic benefits. The objective of our study is to quantify the total ecosystem services (except biodiversity) of a tropical peatland landscape in various peat-utilization scenarios to help build awareness among local planners and decision makers on the strategic tradeoff between peatland utilization and restoration. Studies on the total ecosystem services in a tropical peatland landscape involving hydrological regulation are still rare. Based on the net present value calculation, provisioning services, carbon regulation, and hydrological regulation in our study area account for 19, 70, and 11% of the total ecosystem services, respectively. Based on uncertainty analysis, at any combination of the social cost of carbon emission (within a range of USD 52.7–USD 107.4) and discount rate (within a range of 5–10%), the enrichment of peatlands with paludiculture crops (e.g., jelutong) shows superior ecosystem services compared to other peatland-utilization scenarios. Conversely, planting peatlands with monoculture crops, which are associated with peatland drainage, shows a rapid decrease in the total ecosystem services. The fluvial carbon export in our study, which is often neglected in a peatland carbon budget, increases the estimate of the total carbon budget by 8%. Restoring undrained peatlands with paludiculture crops such as jelutong contributes positively to carbon sequestration and potentially reduces carbon emissions by 11%. These quantitative findings can help local planners and decision makers in understanding the tradeoff between the long-term benefits of peatland restoration and the short-term economic benefits of peatland utilization for monoculture crops.

Comparing GHG Emissions from Drained Oil Palm and Recovering Tropical Peatland Forests in Malaysia

For agricultural purposes, the drainage and deforestation of Southeast Asian peatland resulted in high greenhouse gases’ (GHGs, e.g., CO2, N2O and CH4) emission. A peatland regenerating initiative, by rewetting and vegetation restoration, reflects evidence of subsequent forest recovery. In this study, we compared GHG emissions from three Malaysian tropical peatland systems under the following different land-use conditions: (i) drained oil palm plantation (OP), (ii) rewetting-restored forest (RF) and (iii) undrained natural forest (NF). Biweekly temporal measurements of CO2, CH4 and N2O fluxes were conducted using a closed-chamber method from July 2017 to December 2018, along with the continuous measurement of environmental variables and a one-time measurement of the soil physicochemical properties. The biweekly emission data were integrated to provide cumulative fluxes using the trapezoidal rule. Our results indicated that the changes in environmental conditions resulting from draining (OP) or rewetting historically drained peatland (RF) affected CH4 and N2O emissions more than CO2 emissions. The cumulative CH4 emission was significantly higher in the forested sites (RF and NF), which was linked to their significantly higher water table (WT) level (p < 0.05). Similarly, the high cumulative CO2 emission trends at the RF and OP sites indicated that the RF rewetting-restored peatland system continued to have high decomposition rates despite having a significantly higher WT than the OP (p < 0.05). The highest cumulative N2O emission at the drained-fertilized OP and rewetting-restored RF sites was linked to the available substrates for high decomposition (low C/N ratio) together with soil organic matter mineralization that provided inorganic nitrogen (N), enabling ideal conditions for microbial mediated N2O emissions. Overall, the measured peat properties did not vary significantly among the different land uses. However, the lower C/N ratio at the OP and the RF sites indicated higher decomposition rates in the drained and historically drained peat than the undrained natural peat (NF), which was associated with high cumulative CO2 and N2O emissions in our study.

Restoration of Degraded Tropical Peatland in Indonesia: A Review

Tropical peatlands are fragile ecosystems with an important role in conserving biodiversity, water quality and availability, preventing floods, soil intrusion, erosion and sedimentation, and providing a livelihood for people. However, due to illegal logging, fire and conversion into other land use, the peatlands in Indonesia are under serious threat. Efforts to restore Indonesia’s tropical peatlands have been accelerated by the establishment of the Peatland Restoration Agency in early 2016. The restoration action policy includes the rewetting, revegetation and revitalisation of local livelihood (known as the 3Rs). This paper summarises the regulatory, institutional and planning aspects of peatland restoration, in addition to the implementation of the 3Rs in Indonesia, including failures, success stories, and the criteria and indicators for the success of peatland restoration.

Effects of Long-Term Nitrogen Fertilization and Ground Water Level Changes on Soil CO2 Fluxes from Oil Palm Plantation on Tropical Peatland

A long-term study on the effect of nitrogen (N) fertilization on soil carbon dioxide (CO2) fluxes in tropical peatland was conducted to (1) quantify the annual CO2 emissions from an oil palm plantation under different N application rates and (2) evaluate the temporal effects of groundwater level (GWL) and water-filled pore space (WFPS) on soil organic carbon (SOC) and CO2 fluxes. Monthly measurement of soil CO2 fluxes using a closed chamber method was carried out from January 2010 until December 2013 and from January 2016 to December 2017 in an oil palm plantation on tropical peat in Sarawak, Malaysia. Besides the control (T1, without N fertilization), there were three N treatments: low N (T2, 31.1 kg N ha−1 year−1), moderate N (T3, 62.2 kg N ha−1 year−1), and high N (T4, 124.3 kg N ha−1 year−1). The annual CO2 emissions ranged from 7.7 ± 1.2 (mean ± SE) to 16.6 ± 1.0 t C ha−1 year−1, 9.8 ± 0.5 to 14.8 ± 1.4 t C ha−1 year−1, 10.5 ± 1.8 to 16.8 ± 0.6 t C ha−1 year−1, and 10.4 ± 1.8 to 17.1 ± 3.9 t C ha−1 year−1 for T1, T2, T3, and T4, respectively. Application of N fertilizer had no significant effect on annual cumulative CO2 emissions in each year (p = 0.448), which was probably due to the formation of large quantities of inorganic N when GWL was temporarily lowered from January 2010 to June 2010 (−80.9 to −103.4 cm below the peat surface), and partly due to low soil organic matter (SOM) quality. A negative relationship between GWL and CO2 fluxes (p < 0.05) and a positive relationship between GWL and WFPS (p < 0.001) were found only when the oil palm was young (2010 and 2011) (p < 0.05), indicating that lowering of GWL increased CO2 fluxes and decreased WFPS when the oil palm was young. This was possibly due to the fact that parameters such as root activity might be more predominant than GWL in governing soil respiration in older oil palm plantations when GWL was maintained near or within the rooting zone (0–50 cm). This study highlights the importance of roots and WFPS over GWL in governing soil respiration in older oil palm plantations. A proper understanding of the interaction between the direct or indirect effect of root activity on CO2 fluxes and balancing its roles in nutrient and water management strategies is critical for sustainable use of tropical peatland.

Water Table Fluctuation and Methane Emission in Pineapples (Ananas comosus (L.) Merr.) Cultivated on a Tropical Peatland

Inappropriate drainage and agricultural development on tropical peatland may lead to an increase in methane (CH4) emission, thus expediting the rate of global warming and climate change. It was hypothesized that water table fluctuation affects CH4 emission in pineapple cultivation on tropical peat soils. The objectives of this study were to: (i) quantify CH4 emission from a tropical peat soil cultivated with pineapple and (ii) determine the effects of water table depth on CH4 emission from a peat soil under simulated water table fluctuation. Soil CH4 emissions from an open field pineapple cultivation system and field lysimeters were determined using the closed chamber method. High-density polyethylene field lysimeters were set up to simulate the natural condition of cultivated drained peat soils under different water table fluctuations. The soil CH4 flux was measured at five time intervals to obtain a 24 h CH4 emission in the dry and wet seasons during low- and high-water tables. Soil CH4 emissions from open field pineapple cultivation were significantly lower compared with field lysimeters under simulated water table fluctuation. Soil CH4 emissions throughout the dry and wet seasons irrespective of water table fluctuation were not affected by soil temperature but emissions were influenced by the balance between methanogenic and methanotrophic microorganisms controlling CH4 production and consumption, CH4 transportation through molecular diffusion via peat pore spaces, and non-microbial CH4 production in peat soils. Findings from the study suggest that water table fluctuation at the soil–water interface relatively controls the soil CH4 emission from lysimeters under simulated low- and high-water table fluctuation. The findings of this study provide an understanding of the effects of water table fluctuation on CH4 emission in a tropical peatland cultivated with pineapple.