Use of an Adaptive-Vegetation Model to Restore Degraded Tropical Peat Swamp Forest to Support Climate Resilience

Abstract

Climate change poses significant challenges to ecosystems globally, demanding innovative methods for environmental conservation and restoration. Restoration initiatives require significant amounts of appropriate vegetation that is both adaptive and tolerant to the specific environmental factors. This study introduces an adaptive-vegetation model designed to support ecosystem resilience in the face of climate change. Traditional restoration methods often neglect dynamic environmental conditions and ecosystem interactions, but the model employs real-time data and predictive analytics to adapt strategies to evolving climate variables. The model takes a comprehensive approach, incorporating climate projections, soil health metrics, species adaptability, and hydrological patterns to inform restoration practices. By using a mix of adaptable native species, the model promotes biodiversity. In conclusion, according to the findings of our review, paludiculture and agroforestry could be implemented as models for improving climate resilience, particularly in tropical degraded peat swamp forests. These two models could improve the environment, the economy, and social functions. Finally, improving all three of these factors improves ecological stability. This adaptive-vegetation model represents a significant shift from static, uniform restoration approaches to dynamic, data-driven strategies tailored to specific environments. The future research directions underscore the need for ongoing innovation in conservation practices to safeguard ecosystems amid unprecedented environmental changes. Future efforts will focus on enhancing the model with advanced machine learning techniques and expanding its application to additional ecological contexts.

1. Introduction

Indonesia has around 13.43–14.90 Mha of tropical peatlands spread throughout Sumatra, Kalimantan, Papua, and Sulawesi, which contain 5.85 Mha, 4.54 Mha, 3.01 Mha, and 0.03 Mha, respectively [1,2]. These forests have significant ecological functions, as well as economic and social functions for people [3]. The ecological functions of tropical peat swamp forests include carbon storage, serving as unique biodiversity hosts, sustaining nutrients, and sustaining hydrological cycling systems [4]. In terms of economics, the peat swamp forests provide a variety of high-value timbers such as Gonystylus bancanus, Shorea spp., Palaquium spp., Calophyllum macrocarpum, Dyera lowii, and others [5]. It also produces a variety of non-timber forest products and raw materials for traditional medicines. With regards to social function, as a whole, the peat swamp forests provide an environment and resources for the livelihood of the local communities [6].

As the population of Indonesia grows at a rate of 1.17 percent per year [7], more land is required for shelter, food, and energy, leading to the conversion of peat swamp forests into land used for other purposes. Peat swamp forests are generally converted for other land uses that exceed their carrying capacity, resulting in degraded peatland. Logging due to high demand for timber, drainage activity, fires, and conversion for other land uses, especially plantation expansion, have caused significant deforestation and degradation in Indonesia’s peatlands [8,9]. According to the research [10], peatland deforestation from 2009 to 2019 amounted to 2.2% per year (142,492 ha/year). Rainforest Action Net Work’s Tropical Forest Program is tackling the two greatest drivers of rainforest destruction in Indonesia: industrial palm oil and pulp plantations [11]. However, other authors [12,13] mention that approximately 13 Mha of Indonesian peat swamp forests have been reported to be in degraded condition. Ref. [10] identified around 6 Mha of peatlands with the potential for restoration in Indonesia, specifically in Sumatra and the Kalimantan Islands. The majority of these areas of potential can be classified as areas of priority rewetting (5.3 Mha), with the size of areas of priority revegetation ranging from 0.5 to 1.1 Mha.

The consequences of peat swamp forest conversion, which include loss of pristine forest cover and changes in drainage, enhance the rate of peat decomposition and additionally increase carbon dioxide (CO₂) emissions, leading peat forests to change from a net carbon sink into a carbon source [14], as well as increasing the potential for wildfire [15]. Converting peat swamp forests into oil palm plantations and land used for pulpwood production leads to faster peat decomposition, as can be seen when mature oil palm plantations are compared to natural peat swamp forests. This is due to the lowered water table and increased litter supply resulting from this land-use change [16]. Draining peatlands increases soil oxygen levels and accelerates organic decomposition, leading to significant CO₂ emissions [17] and emissions of other greenhouse gases such as CH₄ and N₂O [18]. Therefore, the health of people, biodiversity, and the economy will all be impacted by the rise in greenhouse gases [19,20].

The issues affecting peatlands in Indonesia have prompted the Indonesian government to expedite peatland recovery through restoration efforts [10]. This is a crucial step to prevent further ecosystem loss [21]. In the end, Presidential Regulation 2016, which pertains to peat ecosystem protection and management (PP 2016), was issued by the Peatland Restoration Agency or Badan Restorasi Gambut (BRG) establishment, along with several program initiatives. The 3Rs program (rewetting, revegetation, and livelihood revitalization) is still ongoing [10,22], and a small amount of research has been done to delineate peat swamp forest restoration as the 4Rs strategy (rewetting, reduction of fire, revegetation, and revitalization) [23]. However, large-scale restoration efforts encounter numerous challenges, including ecological, economic, legal, social, logistical, research, and political issues [3].

Restoration initiatives for Indonesian peatland ecosystems commenced in the late 1990s (or early 2000s), following severe forest fires that occurred between 1997 and 1998 [24]. From 1997 to 2015, peatland ecosystem restoration efforts were primarily conducted through collaborations amongst universities and non-governmental organizations [24]. In 2016, the Peat Restoration Agency (Badan Restorasi Gambut) was established. This agency aims to coordinate actual restoration efforts. However, all peatland restoration is regulated by the Ministry of Environment and Forestry, Republic of Indonesia [25].

The loss of tropical forests and the destabilization of climate are moral issues exacerbated by a grave injustice: those who benefit the most from activities driving deforestation and climate change often remain insulated from the direct consequences of their actions, while the severe impacts disproportionately affect the world’s poorest and most marginalized communities. The profound ethical dimension of the climate and deforestation crisis demands attention and remediation, with attention to the fundamentally religious and spiritual aspects of these environmental and social issues as well [26]. To mitigate these adverse effects, it is necessary to implement conservation programs such as establishing protected areas, adopting sustainable land-management practices, preventing illegal timber extraction and land expansion, fostering global cooperation to tackle climate change and promote sustainable development, and restoring degraded peatlands through adaptive-vegetation models.

The existing gaps in the data and publications on adaptive-vegetation models developed so far remain inadequately addressed, particularly with regard to their effectiveness in enhancing resilience to climate change. In this review, we define the adaptive-vegetation model as a specific approach or strategy for planting tree/plant species (vegetation) that have the capability to survive and grow well in degraded tropical peatland and that have a positive impact on site quality and biodiversity. Furthermore, this vegetation also must have high economic value, giving it a positive role in increasing community welfare. Therefore, this vegetation will become the reference in initiatives to restore degraded tropical peat swamp forest while simultaneously enhancing climate resilience. As the main feature of forests is the presence of tree species, this review focuses on tree species.

2. Methods

The writing of this publication involved reviewing various references in the form of international journals, books/book sections, reports of activities of institutions in Indonesia authorized to carry out peatland restoration, and official data from government websites. The approach used ensured that the references used were of high quality and relevant. The process began by determining the aspects to be covered in the publication. A data-collection strategy was developed that included the use of major databases and search engines such as Google Scholar and Web of Science. The selection of relevant articles was carried out using specific keywords and phrases related to the scope of the article. Boolean operators (AND, OR, NOT) were used to ensure the return of broad but focused search results, as well as to increase search accuracy.

There are more than 100 references included in this article. The selection process involved several stages of screening. Initial screening based on the title and abstract was used to determine each paper’s relevance to the scope of the article. Furthermore, the full text was examined to ensure that the article met the inclusion criteria in terms of relevance, quality of research methodology, and significance of the findings. The topics of focus are reflected in the subchapter titles in this manuscript, as follows: A developed adaptive-vegetation model and its role in increasing resilience to climate change; Role of a developed adaptive-vegetation model in supporting biodiversity; Role of a developed adaptive-vegetation model in supporting plant growth; Role of a developed adaptive-vegetation model in supporting soil health; Role of a developed adaptive-vegetation model in sustaining the peat water-table level; Role of a developed adaptive-vegetation model in supporting microclimates; Role of a developed adaptive-vegetation model in supporting the value of benefits to community welfare.

3. A Developed Adaptive-Vegetation Model and Its Role in Increasing Resilience to Climate Change

What happens if the peat ecosystem has been severely damaged, with no forest remaining, due to recurring fires? Revegetation with native tree species has a strategic role in the restoration of peat swamp forests because it increases forest and land cover as well as biodiversity [27]. Additionally, throughout the recovery process, trees will continue to grow and absorb carbon dioxide from the atmosphere, storing it in their plant tissue and thereby enhancing resilience to climate change [28,29].

The effectiveness of carbon enhancement in peat-reforestation activities varies based on the species planted. Shorea balangeran, Dyera polyphylla, and Tetramerista glabra have demonstrated significant carbon sequestration. Over 20 years, the sequestration potential generated from planting activities can reach 106 thousand MgCO₂e, as determined based on a reference site of plants that have been established for 13 years under the ITTO Project in South Sumatra, Indonesia [30].

Apart from technical considerations, the selection of adaptive vegetation for peat swamp forest restoration must incorporate social and economic aspects. This holistic approach is essential for enhancing climate-change resilience. Peat swamp forest restoration efforts are anticipated to benefit local communities by improving socio-economic conditions through pathways including poverty alleviation. Additionally, local communities are encouraged to participate in the restoration program through activities such as post-planting care in the restored areas. Research highlighted by [31] identifies the local species Shorea balangeran and Dyera polyphylla as promising vegetation for peat swamp forest restoration given their economic value for timber and resin production, respectively. This economic value can contribute to local economic development through product processing and market sales. Thus, economic and social aspects of selecting adaptive vegetation for peat swamp forest restoration are as important as other aspects. Figure 1 illustrates the role of adaptive vegetation in enhancing climate-change resilience.

Peat swamp forest restoration requires long and sustained efforts compared to restoration of other forest ecosystems, necessitating contributions from various stakeholders, including local communities, to ensure the successful growth of restoration plants. Research highlighted by [32] identifies critical post-planting activities essential for supporting restoration programs, such as monitoring, replanting dead plants, and weed control. However, these activities are often neglected due to their high costs. Involving local communities can help mitigate these costs and enable them to derive economic benefits from restored plants. Thus, engaging them not only reduces post-planting expenses but also allows them to benefit economically from the restored plants.

While selecting adaptive vegetation for peat swamp forest restoration, it is important to consider their responsiveness to fire disturbances as part of enhancing resilience to climate change. Based on research conducted by [32], Campnosperma coriaceum, Combretocarpus rotundatus, and Alstonia pneumatophor are fire-tolerant native plant species with potential for use in peat swamp forest restoration. Ref. [33] reported that Eurya sp. and Ilex sp., are also considered fire-tolerant, while Arenga sp., Ficus sp., and Trema sp. can recover quickly after forest fires and are resistant to drought. Apart from that, the local community also needs to be involved in strategies for forest-fire mitigation as well as in ensuring the restoration of degraded peat swamp forests [34]. Adaptive vegetation with the specific characteristic of tolerance to flooding also needs to be considered as part of supporting the restoration of peat swamp forests and increasing their resilience to climate change. Research by [32] revealed that Alstonia spatulate, Diospyros gibbon, Cratoxylon glaucum and Eugenia spicata are categorized as flood-tolerant species, while Koompassia malaccensis is reported to be resistant to dry conditions, as well as to floods.

4. Role of a Developed Adaptive-Vegetation Model in Supporting Biodiversity, Plant Growth, Soil Health, Peat Water-Table Level, Microclimate, and the Value of Benefits for Community Welfare

4.1. Role of a Developed Adaptive-Vegetation Model in Supporting Biodiversity

Adaptive vegetation is vital for preserving biodiversity, as it maintains ecosystem health by providing habitat, food, and protection for various other vegetation species [34]. It fosters ecological balance and supports interactions among organisms, promoting ecosystem stability and richness [35]. By adjusting to environmental changes like climate shifts and soil variations, adaptive vegetation enhances ecosystem resilience against environmental challenges [36]. This resilience ensures biodiversity conservation for future generations. Ref. [37] emphasizes the need to conserve, manage, and restore peatlands globally. Peatlands are valuable nature-based resources crucial for addressing environmental threats. Investing in their conservation offers benefits for climate, biodiversity, and disadvantaged communities, including the poor, women, and children, who are vulnerable to resource depletion. Policymakers must prioritize peatland conservation for urgent action.

Adaptive vegetation significantly supports ecosystem sustainability amidst environmental changes. As climate change threatens biodiversity and ecosystem stability, plants that thrive in diverse conditions (temperature, precipitation, soil) are increasingly vital [38,39]. These resilient species act as buffers against extreme weather and habitat degradation, protecting biodiversity hotspots and sensitive ecosystems [40,41]. Their ability to regenerate and restore degraded habitats further aids in preserving and restoring ecosystems amid environmental challenges.

The utilization of components of biodiversity in recent decades has resulted in the destruction of habitats, the extinction of species, and the loss of genetic variation, threatening current and future means of subsistence [42]. Our understanding of the adaptive capability of species and populations will greatly benefit from research on interactions within and between species [43]. There is a strong correlation between vegetation and the presence of a diverse understorey, highlighting the importance of understorey cover for species richness [44]. Beside that, vegetation has a significant role in changing the global environment [45]. Vegetation can adjust to its environment thanks to a variety of changeable properties. Different adaptation scales can be distinguished using the vegetation-optimality model, which eliminates the need for parameterization based on observed responses. It accomplishes this by modeling the best possible adaptation to environmental conditions under the prediction that differences in vegetation features will maximize the net carbon profit over the long term [46].

Learning from community ecology, one can also apply next-generation dynamic global vegetation models (DGVMs). DGVMs could provide new perspectives on how vegetation might react to climate change, and they could encourage interactions between vegetation modelers and functional biologists [47]. In addition, an understanding of DGVMs is needed and can be applied to past and future conditions [48]. This is crucial, especially considering Indonesia’s status as a hotspot for peat swamp forests with rich biodiversity [49].

4.2. Role of a Developed Adaptive-Vegetation Model in Supporting Plant Growth

The model for peatland reforestation, focusing on maintaining or restoring wet conditions—as in the paludiculture concept—requires careful consideration and adaptation to local biophysical, meteorological, socio-economic, and regional conditions. This approach is crucial for ensuring that management choices support both socio-economic and ecological benefits [50,51]. To restore degraded peatlands, natural vegetation and species that can adapt to flooding due to re-watering, as well as to nutrient-poor and acidic peatland conditions are essential [52]. Rewetting activities at a trial-plot scale in peatland-restoration efforts can provide concrete evidence to support improvements to the biophysical characteristics of land and vegetation cover [53].

Ideally, restoration of degraded tropical peatlands is achieved through the paludiculture approach, using native species in their natural wet or rewetted peatland environments [54]. However, some compromises may be necessary, such as incorporating non-native species in combination with the native species in wet or rewetted peatland [55] or utilizing native species in drained peatlands [56,57]. It is important to note that in drained peatlands, the maximum water-table level is typically 40 cm below the soil surface [58].

Pure paludiculture requires several native tree species that are well adapted to wet or waterlogged environments, particularly during the seedling phase. One model of this type vegetation involves native species that develop adventitious roots, such as Shorea balangeran, Cratoxylon arborescens [59]. Other native species that can adapt to inundiation include Dyera polyphylla, Gonystylus bancanus, Shorea balangeran, Alseodaphne spp., Nothaphoebe spp., Melaleuca cajuputi, Shorea stenoptera, Alstonia pneumatophora, Adenanthera pavonina, Dacryodes rostrata, Lithocarpus dasystachys, Campnosperma coriaceum, and Combretocarpus rotundatus [55,60,61,62]. These species can also be selected for restoration in drained peatland where the water-table level is below 40 cm. Additionally, Mahang (Macaranga pruinosa) is another native species suitable for planting in drained peatland [57].

Native tree species are the best adaptive-vegetation model to choose for peatland restoration. Some previous studies showed that the performance growth of adaptive vegetation is better than that of introduction species [57,63] or at least comparable [64]. Despite some research indicating that the growth performance of native species may not surpass that of introduced species, their survivorship is generally better than that of exotic species [57]. Furthermore, using native tree species positively affects the growth of other native plants and helps restore the vegetation structure to a condition close to its original condition [65].

Theoretically, native vegetation is the vegetation that is most adaptive to peatland environments, particularly to wet or waterlogged conditions. Therefore, in wet or rewetted peatlands, the growth of adaptive-native tree species is expected to be better than that of introduced species. This was demonstrated by a study in Indonesia [65], which showed that the growth of native species such as Geronggang (Cratoxylum arborescens), Gelam (Melaleuca leucadendra), Balangeran (Shorea balangeran) was better than that of the exotic species Acacia crassicarpa.

Research has been more focused on the role of a developed adaptive-vegetation model in supporting plant growth than on its role in maintaining the peat water-table level. According to the results of a literature review by [31] on peatlands in Southeast Asia in the period 1988–2019, restoration was attempted at 94 sites, and 141 species of native tree species were planted. The average survival rate was 62%, with a half-life of 33 months, and Shorea balangeran, Dyera poliphylla, Alstonia pneumatophora, and Gonystylus bancanus were the most commonly planted species.

Planting native tree species in peat swamp forests after fire (specifically, planting Gonystylus bancanus, Tetramerista glabra, Fagraea fragrans, and Alstonia pneumatophora) in Sumatra produces a survival rate of 93–95%, height growth of 33–45 cm annually, and diameter growth of 0.87–1.21 cm annually, as shown in Figure 2 [28]. The history of peat formation in the areas cascades into the Sunda Self configuration and the age was estimated at 5000–6000 years. Some important physical characteristics of the peat are as follows: upper layer (0–100 cm) bulk density, 0.06–0.19 (gr/cc); lower layer (100–400 cm) bulk density, 0.05–0.13 (gr/cc); upper layers’ moisture content, 190–1700% gravimetric; and lower layer’s moisture content, 500–1900% gravimetric.

Revegetation of burned and drained peat lands can be done by selecting native tree species, such as Dyera poliphylla and Shorea balangeran. Land-cover changes 8 years after planting are presented in Figure 3 and Figure 4.

Meanwhile, for burned peatlands that have long durations and extreme depths of waterlogging, native tree species that are adapted to these conditions can be selected; one example is Shorea balangeran, which has a survival rate of 85%, height growth of 97 cm per year and diameter growth of 3.3 cm per year [67]. The growth until the age of 3.5 years is presented in Figure 5.

4.3. Role of a Developed Adaptive-Vegetation Model in Supporting Soil Health

Peatlands are drained through canal construction for various purposes, leading to land subsidence and the mineralization of organic carbon. This alteration affects the hydrophysical properties of peat [67]. Additionally, repeated burning impacts soil characteristics in wetlands by increasing soil specific gravity and reducing soil water content and temperature, particularly in moist conditions [68]. This process diminishes soil microbial abundance, thereby affecting soil fertility [69], and results in decreased levels of soil organic carbon, cation-exchange capacity, total nitrogen, and water-retention capacity [70]. Consequently, only a limited number of vegetation species can adapt to these unhealthy and nutrient-poor soil conditions.

Soil health, or soil quality, describes the capacity of soil to provide the resources required by plants and animals for their growth [71]. Simultaneously, soil health was determined by three categories of characteristics: its biological, chemical, and physical properties [72].

Vegetation plays a crucial role in influencing soil health [73]. Therefore, using an appropiate adaptive-vegetation model can have a positive effect on soil health. Due to the generally poor content of nutrients in tropical peatland, especially of P and available minerals [74], it is better if the restoration of degraded tropical peatland uses vegetation that can conserve P and mineral availability or that has relatively high nutrient-use efficiency. Vegetation associated with arbuscular mycorrhizal fungi (AMF) has high nutrient resorption; alternatively, vegetation with high litter quality is a good choice for the restoration of degraded peatland [16,75,76]. AMF can enhance phosphorus availability by working together with certain bacteria that increase alkaline phosphatase, an important enzyme in the mineralization of organic phosphorus. Vegetation with high nutrient resorption tends to have lower dependency on soil nutrient availability, so the impoverishment of soil health could be retarded. Furthermore, the main source of nutrient input in restoration is litterfall, so using vegetation that has higher litter quantity and quality will have a beneficial impact on soil health [77,78,79].

Several adaptive vegetation species in tropical peat swamp forests were identified as being associated with AMF, such as Cratoxylum arborescens, Campnosperma auriculatum, Gonystilus bancanus, and Dyera polyphylla [80]. However, research on the characteristics of litter quality and nutrient resorption (NR) in tree species native to tropical peatland is very rare. There was only one study on three native tree species; this study showed that the litter quality of Cratoxylum arborescens, Macaranga pruinosa, and Macaranga gigantea was low due to its high lignin content and low nutrient content [81], while the nutrient resorption of all those three native species lacked any correlation with soil properties [82]. Therefore, to increase scientific knowledge of the adaptive vegetation of tropical peatland, further study of litter quality and the resorption of nutrients in adaptive native species of tropical peatland was required.

Peat swamp forests, which tend to be harsh ecosystems, are found in tropical regions and are characterized by waterlogged (most of the time), acidic, and nutrient-poor peat soils [83]. When these forests undergo disturbances, they are degraded, whether through deforestation, drainage for agriculture or development, or fire [13]. This can have significant deteriorating impacts on soil health. Addressing soil health in tropical degraded peat swamp forests requires holistic approaches that consider the complex interactions involving soil conditions, vegetation performance, hydrological merit, and a broad array of human activities.

The development and implementation of adaptive-vegetation models has an important role to play in improving soil health in the tropical degraded peat swamp forests. These models integrate ecological principles with cutting-edge technology to guide the restoration and management of degraded peatland ecosystems. Adaptive-vegetation models such as Palaquium sumatranum and Callophylum lowii help to identify plant species that are well suited to the specific conditions of degraded peat swamp forests [82,84]. This includes species tolerant of acidic soils, waterlogged conditions, and low nutrient availability.

4.4. Role of a Developed Adaptive-Vegetation Model in Sustaining the Peat Water-Table Level

Research regarding the role of developing adaptive-vegetation models to support the maintenance of peat water levels remains limited. However, studies have extensively investigated the impact of rewetting on groundwater levels and its effects on the growth of the adaptive vegetation [85]. For instance, a study conducted in South Sumatra, Indonesia, involved rewetting an area of 4800 ha with 257 dams, resulting in a significant improvement in groundwater levels from 60 cm to 30 cm. This rise has proven effective in reducing carbon emissions. Additionally, the increased groundwater levels facilitated the spontaneous growth of 57 native tree species, predominantly Ridsdalea grandis, Timonius flavescens, and Syzygium incarnatum.

The practice of rewetting in peatland restoration uses vegetation adapted to wet conditions. Such plant traits are found in the native peat swamp plant. Paludiculture, or swamp cultivation, enables the massive use of rewetted peatland to produce food and other goods for human consumption [50,86]. Furthermore, Refs. [55,87] reported several native peatland species that developed well on degraded peatland in Ogan Komering Ilir District, South Sumatera, namely jelutung (Dyera polyphylla), belangeran (Shorea balangeran), pulai (Alstonia pneumatophore), ramin (Gonystylus bancanus), tembesu (Fragraea fragrans), and punak (Tetramerista glabra). The ability of native species to grow and thrive on wet and wetted land allows canal-blocking activity to be done on drained peatland without reducing plant productivity, and the peat water table can be maintained at higher levels [51]. It has been reported that the agrisilviculture project, which represents one form of paludiculture, experienced an increase in water-table level followed by increased growth of revegetation plants after a blocking canal was installed in the closest canal [56]. Improvement of peatland hydrology by canal blocking can be used as a long-term strategy for rehabilitation of degraded peatland [88].

Peatland drainage causes the water table to drop and increases CO₂ and CH₄ emissions [89,90]; the peat becomes dry and more susceptible to fire [88,91,92,93], subsidence, and flooding. A decrease in the water-table level of more than 40 cm causes a 40–70% increase in soil CO₂ flux [94].

Restoring degraded peat through hydrological and vegetation-based restoration methods is crucial. Hydrological restoration is carried out by rewetting through blocking of drainage canals [95]. Canal blocking can effectively elevate the water levels in peatlands, ensuring sustained wet conditions. Canal blocking at intervals of 100–200 m significantly influences peat water levels, reducing dependency on rainfall and preventing peatlands from drying out during dry seasons [96,97]. The lessons learned from the peat-restoration model with adaptive vegetation in several regions of Indonesia with diverse characteristics are presented in

Table 1. Lessons learned from the peat-restoration model with adaptive vegetation and its role in sustaining the peat water-table level.

No.	Restoration Models	Location and Characteristics of the Restoration Model	Brief Description of the Role of Peat Restoration on Peat Water-Table Level	Source
1.	Peatland restoration with Dyera lowii, Gonystylus bancanus, Shorea uliginosa, Mezettia parvifolia, Callopylum sumatranum, Cratoxylon arborescens, and Palaquium burckii.	The research plot is a 2 ha burnt oil palm plantation located in Tanjung Leban Hamlet, transition zone of Giam Siak Kecil Biosphere Reserve Bukit Batu, Riau.	After 3.5 years of restoration:	[98]
		In the research plots, peatland was moistened by blocking the canals around the demonstration plots.	The wetting has not succeeded in increasing the depth of the water table or soil moisture content. Average water-table level increased from −73.53 cm to −68.33 cm.
2.	Peatland restoration using paludiculture with sago as the main crop combined with oil palm, rubber and pineapple.	The 6-ha research plot is located in Siak District, Riau. It is divided into four plots spread across four villages. Peat depth varies from 500 to 750 cm. The peatland was moistened by blocking canals in the canals around the demonstration plots. In each plot, there are 2 to 3 canal blocks.	After one year of restoration:	[99]
			- Average water level from 36.25 cm to 22.6 cm.
			- Average subsidence from 5.5 cm/year to 1.4 cm/year. - Average carbon reduction of 37 tonnes CO2 eq/year/ha

.

4.5. Role of a Developed Adaptive-Vegetation Model in Supporting Microclimates

Adaptive vegetation species have a significant role in efforts to restore peat swamp forests by accelerating microclimate formation and increasing their resilience to climate change. In the context of forest ecosystems, the term “microclimate” refers to the distinct climatic conditions that develop within the forest and differ from those outside the forest area [100]. These climatic differences arise due to the forest canopy’s ability to reduce the intensity of radiated sunlight and wind speed, thereby directly impacting temperature and humidity within the forest environment. Other variables contributing to the microclimate include solar radiation and rainfall intensity due to the presence of forest vegetation [101]. Another definition of microclimate is the climate measured near the surface in a particular area, which is influenced by local climate characteristics and stand type [101].

The specific characteristic of adaptive vegetation that supports peat swamp forest restoration is their ability to maintain microclimate conditions. This means that these plants need to be able to survive external environmental changes while maintaining their internal microclimate. A review about peat swamp forest restoration efforts in 94 sites from the period 1988–2019 was conducted [31]. The review reported that 141 native plant species had been used for studies related to peat swamp forest restoration. However, instead of fast-growing plant species, the study suggested that slow-growing species such as Lophopetalum rigidum, Alstonia spatulate, and Madhuca motleyana had the capability to survive longer in the environment of a degraded peat swamp after planting. This indicated that more research should be conducted to examine plant species suitable for planting in specific locations for use in efforts to restore peat swamp forests.

The selection of species is an important factor in improving the microclimate, as well as in supporting the restoration of degraded peat swamp forest. Only specific species of plants can grow, survive, and create a microclimate in peat swamp forest ecosystems. A study was conducted that involved planting several adaptive species native to peat swamp forests in Central Kalimantan: Shorea balangeran, Dyera poyphylla, Calophyllum bifforum, and Callophyllum inophyllum [102]. The results showed that Shorea balangeran has the highest survival rate and growth rate 8 months after planting compared to the other three species. Other research by [31] revealed that there are other species with significant survival rates and growth rates: Lophopetalum rigidum, Cratoxylum arborescens, Alstonia spatulata, and Madhuca motleyana. These species are native to peat swamp forests in the tropical region. However, a significant number of adaptive vegetation species in peat swamp forests remain unexplored. It is estimated that only approximately 10% of these species have been investigated for use in rehabilitation, as well as in restoration projects [31].

The formation of microclimates in a degraded forest ecosystem is determined by several factors. Research conducted by [103] reported that the presence of intact forests near degraded peat swamp forests can increase forest recovery and support the regeneration of the microclimate in the degraded forests. The existence of intact forests in close proximity can accelerate the regeneration process of degraded forest ecosystems. Other research also confirmed that the presence of birds and mammals in intact forests can assist in the regeneration of degraded peat swamp forests [104].

However, topics related to microclimate in peat swamp forests are understudied. A study was conducted on features of microclimates occurring in various types of forest ecosystems [100]. However, there was limited discussion related to microclimate in peat swamp forests. On the other hand, research was conducted on the impact of the conversion of peat swamp forests to oil palm plantations on conditions of microclimates and soil [105]. It was revealed that the conversion caused significant changes in microclimate parameters, such as air temperature, wind speed, light intensity, and relative humidity. The temperature and intensity of sunlight in the oil palm plantations were higher, while the humidity was lower and the wind speed was higher compared to those in the peat swamp forest. The research concluded that changes in microclimate lead to accelerated soil acidification.

Incorporating adaptive-vegetation models to restore microclimate in degraded tropical peat swamp forests is critical. By developing adaptive-vegetation models that consider the species-specific needs of peat swamp forests, restoration initiatives can increase biodiversity and ecosystem resilience. A study conducted by [60] revealed that Shorea balangeran can survive relatively well in degraded peat swamp forest, as indicated not only by positive growth, but also with by its resilience to water-table fluctuations. In selecting adaptive plant species for peat swamp forest restoration, fire-disturbance responsiveness also needs to be considered in the interest of increasing resilience to climate change. Based on research conducted by [32], Campnosperma coriacea, Combretocarpus rotundatus, and Alstonia pneumatophore are fire-tolerant native plants species with potential for use in peat swamp forest restoration. Ref. [33] reported that the Eurya sp. and Ilex sp., are also species considered fire-tolerant, while Arenga sp., Ficus sp., and Trema sp. can recover quickly after forest fires and are resistant to drought. Furthermore, maintaining 50% forest vegetation cover on medium-depth peat and protecting very deep peat have the potential to reduce greenhouse gas emissions and increase forest carbon storage. This mitigation scheme is also believed to improve hydrological function and biodiversity [106].

Research by [100] employed various methods, including sensors and satellite data, to measure and analyze microclimate variations across different levels of canopy cover. The findings demonstrated that increasing forest canopy cover contributes to reducing temperature. The study by [107] further added to this concept by suggesting that certain crop-growth patterns can increase vegetation cover, thereby positively impacting soil moisture, ambient temperature, and peatland quality. The study also emphasized the potential of using native plant agroforestry practices for the improvement of degraded peatlands [107]. Another development associated with an adaptive-vegetation model is paludiculture, which has been proposed as a sustainable land use alternative for tropical peatland. The paludiculture concept, wet farming on peatlands, suggests managing vegetation while maintaining wet conditions. Wet environments can influence local temperature and humidity, suggesting a potential link to microclimate management. Given this, paludiculture is an example of vegetation management that has a secondary impact on microclimate. Several studies have suggested that paludiculture can help maintain carbon storage, promote native species, and ensure economic benefits, balancing ecological functions and socio-economic needs [50,55,108,109]. For example, the use of native species (such as jelutong, ramin, and balangeran) in paludiculture not only supports ecological integrity but also contributes to mitigating climate change by maintaining peatland carbon stocks [50,55].

Research conducted by [110] explored how soil and water conservation have improved the adaptation of native plants to conditions of local rainfall and soil, positively impacting biodiversity. Through vegetation-based techniques, soil and water conservation have contributed to lowering temperatures, increasing humidity, and reducing rainfall intensity levels, thereby improving microclimate conditions. Studies by [111] used a bioclimatic model incorporating topographic data to describe microclimate variations within forest ecosystems. Studies by [112,113] used models to analyze how vegetation characteristics and water conditions affect temperature and humidity in peatland and urban environments. These studies emphasize the importance of vegetation in mitigating urban heat-island effects and improving thermal comfort in tropical cities.

4.6. Role of the Developed Adaptive-Vegetation Model in Supporting the Value of Benefits for Community Welfare

Paludiculture is more effective in restoring degraded peat swamp forests compared to traditional drainage-based peat cultivation systems. A study by [114] emphasized the importance of paludiculture in restoring degraded peat areas and highlighted the need for community participation in species selection to ensure the sustainability of restoration efforts. Research by [51] highlighted the potential of paludiculture, a land-management practice that rewets degraded peatlands, to mitigate climate change, increase biodiversity, and offer economic potential, recognizing the economic potential of paludiculture under specific conditions [51]. This can help identify income-generating options for local communities engaged in restoration efforts, such as the production of specific materials from wetland plants.

A study by [115] demonstrated how communities can utilize innovative technologies in their home yards to manage degraded peatlands while improving livelihoods. They emphasize the potential for sustainable intensification practices that balance livelihood improvement with peatland conservation. Adaptive-vegetation models can predict the long-term impacts of various agroforestry and management strategies on peat hydrology, nutrient cycling, and crop productivity. Ref. [116] highlighted the economic benefits of agroforestry for local communities through diverse income sources. These models can also identify plant communities suitable for agroforestry on degraded peatlands, producing not only timber products, but also economically valuable non-timber forest products (NTFPs). This approach can improve sustainable livelihoods for communities involved in restoration efforts.

The restoration of degraded peatlands through paludiculture not only creates sustainable livelihood opportunities but also enhances ecosystem services and benefits for local communities [114]. There are around 1376 species of plants that can be developed on peatlands using the paludiculture concept, and only around 40 species have been developed in Indonesia using the social forestry scheme [117]. This indicates that there are numerous potential plant species that can be developed for peatland restoration and to strengthen the community’s economy. Paludiculture is a technology developed on peatlands to keep the peat wet and provide economic value to the community. The agroforestry approach, which combines multipurpose tree species (MPTS) with peat-endemic woody plants, offers a viable alternative. It provides various livelihood options, enhancing the community’s environmental and economic resilience against the impacts of climate change [118,119]. Enrichment of woody species that have peatland adaptability and have economic value in monoculture agricultural can increase environmental and community economic resilience to climate change [117].

In addition to paludiculture technology, communities utilize peatlands as a source of livelihood through various peatland-processing technologies aimed at facilitating plant growth and adaptation. These methods include creating mounds, raised beds, carrying out amelioration to reduce acidity, and carrying out polybag farming. This technology is carried out without drying out the peatland so that the peat remains wet and is protected from fires [120].

Thousands of villages in Indonesia are located on peatlands [121,122], both shallow peat and deep peat. The livelihoods of many people in these villages rely on land-based activities to support their families. Farming on peatlands presents numerous challenges, including biophysical issues, fires, floods [117], pests, and disease [123]. Additionally, farming is also expensive. Ref. [123] observed that villagers in Bram Itam Raya and Mekar Jaya, West Tanjung Jabung Regency, as well as those in Sidomukti and Pandan Sejahtera, East Tanjung Jabung Regency, Jambi Province, cultivate peatland to meet their families’ needs. They face various challenges and learn from the experiences that arise due to their limited knowledge of managing peatlands. After numerous trials with different farming technologies and various plant species in their yards and gardens, they identified several economically viable species: areca nut (Areca catechu), Liberica coffee (Coffea liberica), coconut (Cocos nucifera), and palm oil. The selection of these mainstay species is based on factors such as seed availability, peat thickness (shallow or deep peat), land preparation and maintenance costs, post-harvest handling, market demand, and market price. These four species, planted on shallow peatland, contribute 67.4% of total household income. Other plants cultivated on shallow peatland are sago [124], rattan [125], and rubber [126]. Sago is being primarily grown for use as food.

In deep peat swamps, there are various endemic species that have high commercial value, including Gonystylus bancanus, Dyera lowii, Shorea balangeran, Alstonia scholaris, and Melaleuca leucadendron. Some communities cultivate peat-swamp plants with high commercial value for several reasons: the trees will be rare in the future, they do not require intensive management, they provide a source of income while rehabilitating degraded peatlands, and they reduce the risk of fire. Increasing people’s income by improving the environment will reduce their vulnerability and increase their resilience to climate change.

5. The Way Forward

Adaptive-vegetation development models, such as paludiculture and agroforestry, are particularly relevant for the mitigation of degraded peat swamp forests [55,107], offering significant potential to restore these ecosystems and enhance their resilience to climate change. Both paludiculture and agroforestry, in the form of various combinations of perennial and annual crops, help restore degraded peat swamp forests, re-establishing their ecological functions and increasing their resilience to environmental stressors. These practices improve water retention and quality, which are crucial for coping with extreme weather conditions such as floods and droughts. Rewetting peatland and integrating trees into agricultural systems can enhance carbon sequestration and reduce the atmospheric concentration of greenhouse gases.

By estimating carbon stocks, increasing pollination services, and improving soil fertility, restoration initiatives have contributed to mitigating climate change, biodiversity protection, and agricultural productivity. In conclusion, adaptive-vegetation-development models such as paludiculture, agroforestry, and optimal reforestation programs are essential to achieving both environmental sustainability and community welfare in initiatives for the restoration of degraded peat swamp forests. These efforts not only restore ecosystems but also provide economic opportunities and social benefits for local communities, ensuring a harmonious relationship between nature and society.

Implementing these practices can turn degraded landscapes into productive and resilient ecosystems, showcasing a harmonious balance between human activities and nature conservation. Despite their potential, implementing developed adaptive-vegetation models in peatland-restoration projects poses challenges related to seed availability, site preparation, and long-term monitoring [49]. Addressing these challenges certainly requires collaboration among scientists, practitioners, policymakers, and local communities to develop innovative solutions and adaptive management strategies. Opportunities exist to leverage advances in remote sensing [127], genetic resources, and participatory approaches to improve the effectiveness of adaptive-vegetation models for peatland restoration.

6. Conclusions

Enhancing resilience to climate change in degraded peat swamp forests through the development of environmentally adaptive vegetation models represents an appropriate strategic approach in the context of climate-change adaptation. This is based on the consideration that environmentally adaptive vegetation models will provide benefits not only in biophysical aspects such as biodiversity, plant growth, soil health, peat water-table level, and microclimate, but also provide significant welfare benefits to local communities. By encompassing these comprehensive, multi-faceted benefits, environmentally adaptive vegetation models hold promise to substantially foster resilience to climate change in degraded peat swamp forests. According to the findings of this review, paludiculture and agroforestry could be implemented as models for improving climate resilience, particularly in tropical degraded peat swamp forests. These two models could improve the environment, the economy, and social functions.