A common-sense approach to tropical peat swamp forest restoration in Southeast Asia

Tropical peat composition may provide a negative feedback on fire occurrence and severity

Loss of peat through increased burning will have major impacts on the global carbon cycle. In a normal hydrological state, the risk of fire propagation is largely controlled by peat bulk density and moisture content. However, where humans have interfered with the moisture status of peat either via drainage, or indirectly via climate change, we hypothesise that its botanical composition will become important to flammability, such that peats from different latitudes might have different compositionally-driven susceptibility to ignition. We use pyrolysis combustion flow calorimetry to determine the temperature of maximum thermal decomposition (Tmax) of peats from different latitudes, and couple this to a botanical composition analysis. We find that tropical peat has higher Tmax than other regions, likely on account of its higher wood content which appears to convey a greater resistance to ignition. This resistance also increases with depth, which means that loss of surface peat in tropical regions may lead to a reduction in the subsequent ignitability of deeper peat layers as they are exposed, potentially resulting in a negative feedback on increased fire occurrence and severity.

Benefits of tropical peatland rewetting for subsidence reduction and forest regrowth: results from a large-scale restoration trial

Drainage and deforestation of tropical peat swamp forests (PSF) in Southeast Asia cause carbon emissions and biodiversity loss of global concern. Restoration efforts to mitigate these impacts usually involve peatland rewetting by blocking canals. However, there have been no studies to date of the optimal rewetting approach that will reduce carbon emission whilst also promoting PSF regeneration. Here we present results of a large-scale restoration trial in Sumatra (Indonesia), monitored for 7.5 years. Water levels in a former plantation were raised over an area of 4800 ha by constructing 257 compacted peat dams in canals. We find peat surface subsidence rates in the rewetted restoration area and adjoining PSF to be halved where water tables were raised from ~ - 0.6 m to ~ - 0.3 m, demonstrating the success of rewetting in reducing carbon emission. A total of 57 native PSF tree species were found to spontaneously grow in the most rewetted conditions and in high densities, indicating that forest regrowth is underway. Based on our findings we propose that an effective PSF restoration strategy should follow stepwise rewetting to achieve substantial carbon emission reduction alongside unassisted regrowth of PSF, thereby enabling the peat, forest and canal vegetation to establish a new nature-based ecosystem balance.

Streptomyces rugosispiralis sp. nov., a Novel Actinobacterium Isolated from Peat Swamp Forest Soil That Produces Ansamycin Derivatives and Nocardamines

Actinomycetes, especially the genus Streptomyces, are one of the most promising sources of bioactive natural products. In this study, a novel Streptomyces strain, RCU-064T, was isolated from a soil sample collected from a peat swamp forest in Thailand. Strain RCU-064T showed the highest 16S rRNA gene sequence similarity (99.06%) with Streptomyces malaysiensis NBRC 16446T. Based on a polyphasic approach, strain RCU-064T represents a novel species of the genus Streptomyces, for which the name Streptomyces rugosispiralis sp. nov. is proposed. The chemical isolation of the crude ethyl acetate extracts of the strain led to the isolation of six compounds: (1) geldanamycin, (2) 17-O-demethylgeldanamycin, (3) reblastatin, (4) 17-demethoxyreblastatin, (5) nocardamine, and (6) dehydroxynocardamine. These compounds were evaluated for their biological activities. All compounds showed no antimicrobial activity against tested microorganisms used in this study. Compounds (1)-(4) displayed cytotoxic activity against the NCI-H187 cell line, with IC50 values ranging from 0.045-4.250 µg/mL. Cytotoxicity against the MCF-7 cell line was found in compounds (1) and (3) with IC50 values of 3.51 and 1.27 µg/mL, respectively. Compounds (5) and (6) exhibited cytotoxicity only against Vero cells (IC50 of 16.57 µg/mL) and NCI-H187 cells (IC50 of 13.96 µg/mL), respectively. These results indicate that peat swamp forest soil remains a promising reservoir of novel actinomycetes capable of producing bioactive natural products.

The road to recovery: a synthesis of outcomes from ecosystem restoration in tropical and sub-tropical Asian forests

Current policy is driving renewed impetus to restore forests to return ecological function, protect species, sequester carbon and secure livelihoods. Here we assess the contribution of tree planting to ecosystem restoration in tropical and sub-tropical Asia; we synthesize evidence on mortality and growth of planted trees at 176 sites and assess structural and biodiversity recovery of co-located actively restored and naturally regenerating forest plots. Mean mortality of planted trees was 18% 1 year after planting, increasing to 44% after 5 years. Mortality varied strongly by site and was typically ca 20% higher in open areas than degraded forest, with height at planting positively affecting survival. Size-standardized growth rates were negatively related to species-level wood density in degraded forest and plantations enrichment settings. Based on community-level data from 11 landscapes, active restoration resulted in faster accumulation of tree basal area and structural properties were closer to old-growth reference sites, relative to natural regeneration, but tree species richness did not differ. High variability in outcomes across sites indicates that planting for restoration is potentially rewarding but risky and context-dependent. Restoration projects must prepare for and manage commonly occurring challenges and align with efforts to protect and reconnect remaining forest areas. The abstract of this article is available in Bahasa Indonesia in the electronic supplementary material. This article is part of the theme issue 'Understanding forest landscape restoration: reinforcing scientific foundations for the UN Decade on Ecosystem Restoration'.

Application of agroforestry business models to tropical peatland restoration

Indonesia is home to around 45% of the world's tropical peatlands which continue to be degraded on a large scale by deforestation, drainage and fire, contributing massively to global GHG emissions. Approaches to restoring the peat-water balance and reducing emissions in peat hydrological units, through managing them based either on full protection or large-scale commercial production, have generally failed to address environmental and local community needs. We present published and unpublished findings pointing to the need for an integrated peatland protection and restoration strategy based first on raising water levels in degraded (drained) peatlands and maintaining them in forested peatlands, thus, reducing GHG emissions. Second, the strategy incorporates ecologically sound agroforestry business models that strengthen livelihoods of smallholders and so sustain their interest in sustainably managing the peatlands. In this paper, we focus on the second element of this strategy in Indonesia. Eight agroforestry business models are proposed based on their merits to attract both smallholders and commercial investors as well as their compatibility with hydrological rehabilitation of the peatlands. While financial returns on investment will vary across sites and countries, our analysis indicates that some models can be profitable over both short and longer time periods with relatively low levels of investment risk.

Examining the Socio-Economic and Natural Resource Risks of Food Estate Development on Peatlands: A Strategy for Economic Recovery and Natural Resource Sustainability

Given the huge impact of the COVID-19 pandemic on the food and agriculture sectors, rapid measures are needed to reduce the risk of food crises, especially among the poor and the most vulnerable communities. The government of Indonesia planned to establish the Food Estate National Program to ensure food security. Most of the area will be on peatlands, and as such, the program still faces pros and cons as it might open up opportunities for deforestation, threats to biodiversity, and loss of community livelihoods. We conducted the present research in Central Kalimantan to formulate a food estate (FE) development strategy by taking into account the potential benefits and risks to ensure increases in the local community’s welfare and the sustainability of biodiversity. Data were collected through field surveys, interviews, focus group discussion (FGD), and literature studies. The results show that the operation of a food estate on degraded peatlands has a moderate to high level of risk of negative impacts. Community activities and changes in farming methods through using more inputs and mechanical equipment are the most risky activities in FE development. The low substitutability of peatlands requires mitigation efforts as part of risk management. The operation of food systems on peatlands must be based on a strong sustainability perspective with a main principle of complementary resources. The main strategy is to protect natural resources and replace cultivated exotic plants with potential native peat plants with minimal risk. In addition, the policy and capacity building of farmers towards a business-oriented direction will maximize socioeconomic benefits. Utilization of biodiversity and low-impact cultivation techniques can ensure sustainability.

Forty Years of Soil and Water Conservation Policy, Implementation, Research and Development in Indonesia: A Review

Dominated by mountainous topography, high rainfall, and erosion-sensitive soil types, and with the majority of its population living in rural areas as farmers, most of Indonesia’s watersheds are highly vulnerable to erosion. In 1984, the Government of Indonesia established 22 priority watersheds to be handled, which marked the start of formal soil and water conservation activities. Although it has not fully succeeded in improving watershed conditions from all aspects, something which is indicated by fluctuations in the area of degraded land, over the past 40 years the Indonesian government has systematically implemented various soil and water conservation techniques in various areas with the support of policies, laws and regulations, and research and development. These systematic efforts have shown positive results, with a 40% reduction in the area of degraded land over the last 15 years from 2004–2018. This paper reviews policy, implementation, and research and development of soil and water conservation activities in Indonesia over the last 40 years from the 1980s to 2020 and explores the dynamics of the activities.

Tropical Forest Landscape Restoration in Indonesia: A Review

Indonesia has the second-largest biodiversity of any country in the world. Deforestation and forest degradation have caused a range of environmental issues, including habitat degradation and loss of biodiversity, deterioration of water quality and quantity, air pollution, and increased greenhouse gas emissions that contribute to climate change. Forest restoration at the landscape level has been conducted to balance ecological integrity and human well-being. Forest restoration efforts are also aimed at reducing CO2 emissions and are closely related to Indonesia’s Nationally Determined Contribution (NDC) from the forestry sector. The purpose of this paper is to examine the regulatory, institutional, and policy aspects of forest restoration in Indonesia, as well as the implementation of forest restoration activities in the country. The article was written using a synoptic review approach to Forest Landscape Restoration (FLR)-related articles and national experiences. Failures, success stories, and criteria and indicators for forest restoration success are all discussed. We also discuss the latest silvicultural techniques for the success of the forest restoration program. Restoration governance in Indonesia has focused on the wetland ecosystem such as peatlands and mangroves, but due to the severely degraded condition of many forests, the government has by necessity opted for active restoration involving the planting and establishment of livelihood options. The government has adapted its restoration approach from the early focus on ecological restoration to more forest landscape restoration, which recognizes that involving the local community in restoration activities is critical for the success of forest restoration.

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.

Geographic Setting and Groundwater Table Control Carbon Emission from Indonesian Peatland: A Meta-Analysis

Peat restoration is a key climate mitigation action for achieving Indonesia’s Nationally Determined Contribution (NDC) emission reduction target. The level of carbon reduction resulting from peat restoration is uncertain, owing in part to diverse methodologies and land covers. In this study, a meta-analysis was conducted to assess the impact of rewetting on reduction of total CO2 in soil and heterotrophic emissions at the country level. The tier 2 emission factor associated with the land cover category in Indonesia was also calculated. The analysis included a total of 32 studies with 112 observations (data points) for total CO2 emissions and 31 observations for heterotrophic emissions in Indonesia. The results show that the land cover category is not a significant predictor of heterotrophic and total soil emissions, but the highest observed soil emissions were found in the plantation forest. Using the random-effects model, our results suggest that an increase in the water table depth of 10 cm would result in an increase in total CO2 emissions of 2.7 Mg CO2 ha−1 year−1 and an increase in heterotrophic emissions of 2.3 Mg CO2 ha−1 year−1. Our findings show that managing water table depth in degraded peatlands in various land cover types is important to achieve Indonesia’s emission reduction target by 2030.

Post-fire forest restoration in the humid tropics: A synthesis of available strategies and knowledge gaps for effective restoration

Humid tropical forests are increasingly exposed to devastating wildfires. Major efforts are needed to prevent fire-related tipping points and to enable the effective recovery of fire-affected areas. Here, we provide a synthesis of the most common forest restoration strategies, thereby focusing on post-fire forest dynamics in the humid tropics. A variety of restoration strategies can be adopted in restoring humid tropical forests, including natural regeneration, assisted natural regeneration (i.e. fire breaks, weed control, erosion control, topsoil replacement, peatland rewetting), enrichment planting (i.e. planting nursery-raised seedlings, direct seeding) and commercial restoration (i.e. plantation forests, agroforestry). Our analysis shows that while natural regeneration can be effective under favourable ecological conditions, humid tropical forests are often ill-adapted to fire, and therefore less likely to recover unassisted after a wildfire event. Active restoration practices may be more effective, but can be costly and challenging to implement. We also identify gaps in knowledge needed for effective restoration of humid tropical forests after fire, hereby taking into account the ecosystems and socio-economic conditions in which these fires occur. We suggest to incorporate fire severity in future studies, to better understand and predict post-fire ecosystem responses. In addition, as fire poses a recurring and intensifying threat throughout the recovery process, more emphasis should be placed on post-restoration management and the prevention of fire throughout the different phases of the restoration process. Furthermore, as tropical wildfires are increasing in scale, establishing collaborative capacity and setting priorities for efficient resource allocation should become a major priority for restoration practitioners in the humid tropics. Finally, as global fire regimes are changing and expected to intensify in the context of climate change, land use and land cover change, we suggest to put continuous effort into fire monitoring and modelling to inform the development of effective restoration strategies in the long-run.

Paludiculture as a sustainable land use alternative for tropical peatlands: A review

Peatlands cover approximately 4.2 million km² of terrestrial land surface and store up to 700 Pg of terrestrial carbon. Preserving the carbon stocks in peatland is therefore crucial for climate change mitigation. Under natural conditions, peatland carbon storage is maintained by moist peat conditions, which decreases decomposition and encourages peat formation. However, conversion of peatlands to drainage-based agriculture in the form of industrial plantations and smallholder farming has resulted in globally significant greenhouse gas emissions. Paludiculture, loosely conceptualized as biomass production on wet peatlands with the potential to maintain carbon storage, is proposed as a sustainable, non-drainage-based agriculture alternative for peatland use. However, while the concept of paludiculture was developed in temperate ecoregions, its application in the tropics is poorly understood. In this review, we examine common definitions of paludiculture used in literature to derive key themes and future directions. We found three common themes: ecosystem services benefits of paludiculture, hydrological conditions of peatlands, and vegetation selection for planting. Ambiguities surrounding these themes have led to questions on whether paludiculture applications are sustainable in the context of carbon sequestration in peat soil. This review aims to evaluate and advance current understanding of paludiculture in the context of tropical peatlands, which is especially pertinent given expanding agriculture development into Central Africa and South America, where large reserves of peatlands were recently discovered.

Smallholder perceptions of land restoration activities: rewetting tropical peatland oil palm areas in Sumatra, Indonesia

The Indonesian government committed to restoring over 2 million ha of degraded peatland by the end of 2020, mainly to reduce peat fires and greenhouse gas emissions. Although it is unlikely the government will meet this target, restoration projects are still underway. One restoration strategy involves blocking peatland drainage canals, but the consequences of this for smallholder farmers whose livelihoods are dependent on agriculture are unclear. This paper investigates perceived impacts of canal blocks on smallholder farmers and identifies factors that affect their willingness to accept canal blocks on their land. We use data from 181 household questionnaires collected in 2018 across three villages in Jambi province, Sumatra. We found that the majority of respondents would accept canal blocks on their farms, perceiving that the blocks would have no impact on yields or farm access, and would decrease fire risk. Respondents who would not accept blocks on their farms were more likely to use canals to access their farms and perceive that canal blocks would decrease yields. The majority of farmers unwilling to accept canal blocks did not change their mind when provided with an option of a block that would allow boat travel. Our results improve understanding of why some smallholders may be unwilling to engage with peatland restoration. Further research is needed to understand the impact of canal blocks on smallholders' yields. Engaging with stakeholders from the outset to understand farmers' concerns, and perceptions is key if the government is to succeed in meeting its peatland restoration target and to ensure that the costs and benefits of restoration are evenly shared between local stakeholders and other actors.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10113-020-01737-z.

Tropical peatlands and their conservation are important in the context of COVID-19 and potential future (zoonotic) disease pandemics

The COVID-19 pandemic has caused global disruption, with the emergence of this and other pandemics having been linked to habitat encroachment and/or wildlife exploitation. High impacts of COVID-19 are apparent in some countries with large tropical peatland areas, some of which are relatively poorly resourced to tackle disease pandemics. Despite this, no previous investigation has considered tropical peatlands in the context of emerging infectious diseases (EIDs). Here, we review: (i) the potential for future EIDs arising from tropical peatlands; (ii) potential threats to tropical peatland conservation and local communities from COVID-19; and (iii) potential steps to help mitigate these risks. We find that high biodiversity in tropical peat-swamp forests, including presence of many potential vertebrate and invertebrate vectors, combined, in places, with high levels of habitat disruption and wildlife harvesting represent suitable conditions for potential zoonotic EID (re-)emergence. Although impossible to predict precisely, we identify numerous potential threats to tropical peatland conservation and local communities from the COVID-19 pandemic. This includes impacts on public health, with the potential for haze pollution from peatland fires to increase COVID-19 susceptibility a noted concern; and on local economies, livelihoods and food security, where impacts will likely be greater in remote communities with limited/no medical facilities that depend heavily on external trade. Research, training, education, conservation and restoration activities are also being affected, particularly those involving physical groupings and international travel, some of which may result in increased habitat encroachment, wildlife harvesting or fire, and may therefore precipitate longer-term negative impacts, including those relating to disease pandemics. We conclude that sustainable management of tropical peatlands and their wildlife is important for mitigating impacts of the COVID-19 pandemic, and reducing the potential for future zoonotic EID emergence and severity, thus strengthening arguments for their conservation and restoration. To support this, we list seven specific recommendations relating to sustainable management of tropical peatlands in the context of COVID-19/disease pandemics, plus mitigating the current impacts of COVID-19 and reducing potential future zoonotic EID risk in these localities. Our discussion and many of the issues raised should also be relevant for non-tropical peatland areas and in relation to other (pandemic-related) sudden socio-economic shocks that may occur in future.

Fire Frequency and Related Land-Use and Land-Cover Changes in Indonesia’s Peatlands

Indonesia’s converted peatland areas have a well-established fire problem, but limited studies have examined the frequency with which they are burning. Here, we quantify fire frequency in Indonesia’s two largest peatland regions, Sumatra and Kalimantan, during 2001–2018. We report, annual areas burned, total peatland area affected by fires, amount of recurrent burning and associations with land-use and land-cover (LULC) change. We based these analyses on Moderate Resolution Imaging Spectroradiometer (MODIS) Terra/Aqua combined burned area and three Landsat-derived LULC maps (1990, 2007, and 2015) and explored relationships between burning and land-cover types. Cumulative areas burned amounted nearly half of the surface areas of Sumatra and Kalimantan but were concentrated in only ~25% of the land areas. Although peatlands cover only 13% of Sumatra and Kalimantan, annual percentage of area burning in these areas was almost five times greater than in non-peatlands (2.8% vs. 0.6%) from 2001 to 2018. Recurrent burning was more prominent in Kalimantan than Sumatra. Average fire-return intervals (FRI) in peatlands of both regions were short, 28 and 45 years for Kalimantan and Sumatra, respectively. On average, forest FRI were less than 50 years. In non-forest areas, Kalimantan had shorter average FRI than Sumatra (13 years vs. 40 years), with ferns/low shrub areas burning most frequently. Our findings highlight the significant influence of LULC change in altering fire regimes. If prevalent rates of burning in Indonesia’s peatlands are not greatly reduced, peat swamp forest will disappear from Sumatra and Kalimantan in the coming decades.

The Role of Ecological Linkage Mechanisms in Plasmodium knowlesi Transmission and Spread

Defining the linkages between landscape change, disease ecology and human health is essential to explain and predict the emergence of Plasmodium knowlesi malaria, a zoonotic parasite residing in Southeast Asian macaques, and transmitted by species of Anopheles mosquitos. Changing patterns of land use throughout Southeast Asia, particularly deforestation, are suggested to be the primary drivers behind the recent spread of this zoonotic parasite in humans. Local ecological changes at the landscape scale appear to be increasing the risk of disease in humans by altering the dynamics of transmission between the parasite and its primary hosts. This paper will focus on the emergence of P. knowlesi in humans in Malaysian Borneo and the ecological linkage mechanisms suggested to be playing an important role.