Peatlands transformation in Indonesia has caused immense ecological and environmental degradation. Land use conversion has changed this natural carbon sink to a drought- and fire-prone ecosystem. Public awareness to tackle the drought and fire risk in peatlands has led to the development of drought-fire index. Current knowledge states that both climate and hydrology have a strong influence on drought-induced fire in tropical peatlands, yet the role of soil hydraulic properties in controlling the drying of peats remains unclear. This study develops an improved drought-fire index for tropical peatlands, called the Peat Fire Vulnerability Index, by incorporating groundwater and soil water retention information. We tested the new index on two peatland regions in Kubu Raya and Batanghari, Indonesia, to assess fire danger. We monitored daily rainfall, groundwater tables, and soil moisture from 2018 to 2019 on eight stations in the peatlands. Our model was calibrated against the observed drought index of two stations, and the results were verified with actual fire events through daily fire hotspots and fire burned areas in the other six stations. Results showed that soil-hydrological properties influenced the moistening and drying of peats through capillarity. Our model showed good performance in assessing fire danger during the calibration period, as indicated by three employed statistical metrics: the RMSE-standard deviation ratio (RSR = 0.57), Kling-Gupta Efficiency (KGE = 0.81), and percent bias (PBIAS = 1%). For verification, all observed fire events fell in high and extreme fire danger classes predicted by PFVI. Further, our findings revealed the importance of the groundwater table as a threshold of fire events. The high fire danger class was mostly found when groundwater table dropped below 40 cm, and burned areas only occurred when the groundwater table was below 60 cm. These findings suggest that our drought-fire index can be used as a peat fire risk management tool, and its application may minimize fire risks in tropical peatlands.
Tag: hydrology
Managing Water Regimes: Controlling Greenhouse Gas Emissions and Fires in Indonesian Tropical Peat Swamp Forests
Until recently, tropical peat swamp forests in Indonesia have been subject to increasing pressure from land-use change and excessive drainage. This has increased greenhouse gas (GHG) emissions and risk of fires. Five tropical peat landscapes under different management regimes were selected and assessed with regards to GHG emissions and vulnerability to fire. Converted peat swamp forest emitted CO 2 at a similar rate to primary and secondary peat swamp forests. Total emissions ranged between 41 and 52 Mg CO 2 /ha/yr, and 85% of this was from heterotrophic respiration. Managing groundwater levels (GWL) is crucial to GHG mitigation actions. Peatland fire risk is closely associated with GWL, and fire risk can be reduced by 30% when peat rewetting is prioritized in the most vulnerable areas. Lack of coordinated water management could lead to uncontrollable GWLs, peat subsidence, and fires, causing large GHG emissions and other environmental degradation. Government-initiated Forest Management Units could manage peatlands at a regional level. Compliance mechanisms need to be institutionalized to control emissions, land subsidence, and fire incidence.
Kaleka Agroforest in Central Kalimantan (Indonesia): Soil Quality, Hydrological Protection of Adjacent Peatlands, and Sustainability
Increased agricultural use of tropical peatlands has negative environmental effects. Drainage leads to landscape-wide degradation and fire risks. Livelihood strategies in peatland ecosystems have traditionally focused on transitions from riverbanks to peatland forests. Riparian ‘Kaleka’ agroforests with more than 100 years of history persist in the peatlands of Central Kalimantan (Indonesia), where large-scale open-field agricultural projects have dramatically failed. Our field study in a Dayak Ngaju village on the Kahayan river in the Pulang Pisau district involved characterizing land uses, surveying vegetation, measuring soil characteristics, and monitoring groundwater during a period of 16 months. We focused on how local practices and farmer knowledge compare with standard soil fertility (physical, chemical, biological) measurements to make meaningful assessments of risks and opportunities for sustainable land use within site-specific constraints. The Kaleka agroforests around a former settlement and sacred historical meaning are species-rich agroforests dominated by local fruit trees and rubber close to the riverbank. They function well with high wet-season groundwater tables (up to −15 cm) compatible with peatland restoration targets. Existing soil quality indices rate the soils, with low soil pH and high Alexch, as having low suitability for most annual crops, but active tree regeneration in Kaleka shows sustainability.
Modeling Non-Cooperative Water Use in River Basins
Conventional water use and management models have mostly emulated purposefully designed water use systems where centralized governance and rule-based cooperation of agents are assumed. However, water use systems, whether actively governed or not, involve multiple, independent decision makers with diverse and often conflicting interests. In the absence of adequate water management institutions to effectively coordinate decision processes on water use, water users’ behaviors are rather likely to be non-cooperative, meaning that actions by individual users generate externalities and lead to sub-optimal water use efficiency. The objective of this review is to evaluate the advantages and disadvantages of recently proposed modeling systems dealing with non-cooperative water use regarding their ability to realistically represent the features of complex hydrological and socioeconomic processes and their tractability in terms of modeling tools and computational efficiency. For that purpose, we conducted a systematic review of 47 studies that address non-cooperative water use in decentralized modeling approaches. Even though such a decentralized approach should aim to model decisions by individual water users in non-cooperative water use, we find that most studies assumed the presence of a coordinating agency or market in their model. It also turns out that most of these models employed a solution procedure that sequentially solved independent economic decisions based on pre-defined conditions and heuristics, while only few modeling approaches offered simultaneous solution algorithms. We argue that this approach cannot adequately capture economic trade-offs in resource allocation, in contrast to models with simultaneous solution procedures.
The Effect of Fire and Rewetting on the Groundwater Level in Tropical Peatlands
Hydrological system strongly influences the sustainability of peatlands. The drainage system in peatlands that is not designed appropriately will result in the drop of groundwater level (GWL), and thus, peat will be dried and become susceptible to fire. Efforts to restore peatlands have been carried out, one of which is peat rewetting through canal blocking. This study assessed the non-burnt and burnt peatland areas as well as an area with canal blocking to determine the effect of fire and canal blocking on the GWL for the foregoing variables. In each area, dipwells were established at a distance of 1 m (representing the canal water level), 10, 50, 100, 250, and 350 m from the canal. The study clearly showed a significant correlation between the average GWL and fire, and canal blocking as well as the distance from the canal. Fire resulted to an increase of the average GWL, from 61 cm to 50 cm below the ground. There were significant impacts on land use relevant to the average GWL. Canal blocking demonstrated its role in increasing GWL on drained peat areas by mimicking the average GWL on the reference site. This study concluded that constructing more canal blockings and planting more fire-resistant plants are critical to reduce the fire risks.
Canal blocking optimization in restoration of drained peatlands
Drained peatlands are one of the main sources of carbon dioxide (CO2) emissions globally. Emission reduction and, more generally, ecosystem restoration can be enhanced by raising the water table using canal or drain blocks. When restoring large areas, the number of blocks becomes limited by the available resources, which raises the following question: in which exact positions should a given number of blocks be placed in order to maximize the water table rise throughout the area? There is neither a simple nor an analytic answer. The water table response is a complex phenomenon that depends on several factors, such as the topology of the canal network, site topography, peat hydraulic properties, vegetation characteristics and meteorological conditions. We developed a new method to position the canal blocks based on the combination of a hydrological model and heuristic optimization algorithms. We simulated 3 d dry downs from a water saturated initial state for different block positions using the Boussinesq equation, and the block configurations maximizing water table rise were searched for by means of genetic algorithm and simulated annealing. We applied this approach to a large drained peatland area (931 km2) in Sumatra, Indonesia. Our solution consistently outperformed traditional block locating methods, indicating that drained peatland restoration can be made more effective at the same cost by selecting the positions of the blocks using the presented scheme.
The effect of water table levels and short-term ditch restoration on mountain peatland carbon cycling in the Cordillera Blanca, Peru
Many tropical mountain peatlands in the Andes are formed by cushion plants. These unique cushion plant peatlands are intensively utilized for grazing and are also influenced by climate change, both of which alter hydrologic conditions. Little is known about the natural hydroperiods and greenhouse gas fluxes of these peatlands or the consequences of hydrologic alteration for these fluxes. Therefore, our objectives were to assess how carbon dioxide (CO2) and methane (CH4) fluxes varied across a hydrological gradient caused by ditching and evaluate how short-term carbon cycling responds after rewetting from ditch blocking in a tropical mountain peatland. The study was carried out in Huascarán National Park, Peru using static chamber methods. Comparing reference to highly drained conditions, mid-day net ecosystem exchange (NEE) was higher (1.07 ± 0.06 vs. 0.76 ± 0.11 g CO2 m−2 h−1), and the light compensation point for CO2 uptake was lower. Gas fluxes were relatively stable in the rewetted and reference treatments, with small positive responses of NEE to rising water tables. CH4 emissions averaged 2.76 ± 1.06 mg CH4 m−2 day−1, with negative fluxes at water tables >10 cm below the soil surface, and positive fluxes at higher water levels. Our results indicate that undrained peatlands appear to be carbon sinks, highly drained peatlands were likely carbon sources, and rewetting of moderately drained peatlands increased NEE and the ability to store carbon to undrained reference conditions. Ditching of peatlands will likely increase their susceptibility to negative climate change impacts, and hydrologic restoration could moderate these impacts.
Provisioning of water ecosystem services in the Kapingazi River Basin in Kenya: can prospects of willingness to pay improve water quality and quantity?
The Kapingazi River Basin in Kenya is home to a range of ecosystem services. Agricultural and industrial activities have negatively impacted water quality and flows. This study assesses the willingness to pay for improving water service provision. Two-thirds of the respondents are willing to pay for improved water quality and quantity. The respondents were willing to pay an average of US$9.10 per annum for improved water services, not counting water connection fees. Logistic regression analysis revealed that age, education and household size were factors influencing respondents’ willingness to pay.