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Review

Issues of Peatland Restoration Across Scales: A Review and Meta-Analysis

by
Rinda Kustina
*,
Jessica Canchig Pilicita
and
Mateusz Grygoruk
*
Centre for Climate Research, Warsaw University of Life Sciences-SGGW, ul. Nowoursynowska 166, 02-787 Warsaw, Poland
*
Authors to whom correspondence should be addressed.
Water 2025, 17(16), 2428; https://doi.org/10.3390/w17162428 (registering DOI)
Submission received: 9 June 2025 / Revised: 10 August 2025 / Accepted: 14 August 2025 / Published: 17 August 2025
(This article belongs to the Section Biodiversity and Functionality of Aquatic Ecosystems)
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Abstract

Although peatland restoration has been widely promoted as a strategy for reducing carbon emissions and restoring hydrological function, its effectiveness remains context-dependent and highly variable across regions and methods. This study presents a systematic review and meta-analysis of 52 peer-reviewed studies from 2014 to 2024, synthesizing the ecohydrological impacts of restoration across multiple spatial scales and implementation types. In tropical peatlands, restoration frequently reduced CO2 emissions by more than 65,000 kg·ha−1·yr−1 and increased carbon sequestration up to 39,700 kg·ha−1·yr−1, with moderate CH4 increases (~450 kg·ha−1·yr−1). In boreal sites, CO2 reductions were generally below 25,000 kg·ha−1·yr−1, with long-term carbon accumulation reported in other studies, typically around 2–3 tCO2·ha−1·yr−1. Higher values in our dataset likely reflect the limited number of boreal studies and the influence of short-term measurements. Across all regions, restoration was also associated with an average rise in WTD up to 10 cm. These averages were derived from studies conducted across diverse climatic zones, showing high standard deviations, indicating substantial inter-site heterogeneity. These differences emphasize the need for region-specific assessments rather than global generalizations, highlighting the importance of adaptive restoration strategies that balance carbon dynamics with hydrological resilience in the face of climate change.
Keywords:
wetlands; water level; mires; fen; bog

1. Introduction

Peatlands are significantly harmed by human activities such as drainage, land use change, and deforestation. Approximately 12% of global peatlands are damaged or dried out [1,2], seriously threatening local ecosystems and rates of accelerating greenhouse gas emissions (GHG) worldwide [3]. Drainage is a primary driver of degradation, as it lowers the water table and initiates peat oxidation, leading to substantial carbon loss. Combined with agricultural conversion and fire, these pressures accelerate peatland collapse and biodiversity decline [4]. In response, various international and national policy frameworks, such as the UNFCCC commitments and the Global Peatlands Initiative, have recognized peatland protection and rewetting as urgent climate mitigation strategies [5]. Peatlands can be one of the most effective carbon sinks in their natural condition, which holds carbon that makes up 20% of the total carbon in the world’s soils and 60% of the carbon present in the atmosphere [6,7]. Moreover, peatland is the only home to the survival of endangered animals such as the orangutan and Sumatran tigers [8], which rely on the dense forest structure and constant moisture found only in intact peatlands. These saturated, carbon-rich soils help maintain the vegetation they depend on for food and shelter. Conserving peatlands, therefore, goes hand in hand with protecting biodiversity, not just carbon stocks. However, the ineffective protection of peatlands over the past two centuries has resulted in their degradation [9]. Now, in the 21st century, the essential goal of peatlands protection is the need to restore their umbrella functions (proper moistening of the topsoil, restoration of peat-forming processes), which may consequently allow the restoration of these ecosystems and the restoration of the numerous other functions they perform in the landscape (e.g., increasing carbon sequestration in the soil) [10,11,12]. Therefore, recovery initiatives are critically important and must be prioritized.
Restoring peatlands is an urgent task that society must address to bring back their functional state [13,14]. One of the main goals of this restoration effort is to preserve the water balance [15,16,17], which can be achieved by blocking drainage canals and enhancing water retention within the soil [18]. With stable hydrological conditions and high groundwater levels (GWL), the risk of further degradation can be reduced [19], as peatlands that are re-saturated with water will be more resistant to fire [14,20]. In addition, high water levels will stop further carbon loss by slowing down the decomposition of organic matter (OM), thus controlling carbon emissions [21,22]. This directly contributes to climate change mitigation by maintaining the function of peatland as a carbon sink [23,24]. Conversely, if peatland is allowed to dry out, peat oxidation releases large amounts of emissions [6,25], especially carbon dioxide.
Moreover, restoration also enables the recovery of peatland vegetation and wildlife [1]. With hydrological conditions maintained, regeneration of plant communities, e.g., the ones hosting Sphagnum sp., and Carex sp. [12], can take place optimally and create habitats that support the survival of peatland wildlife. Many peatland restoration initiatives have been undertaken in different parts of the world in recent decades. In Europe, for example, the projects are funded by the LIFE Peat Restore Project [26] and a range of other EU LIFE programs [27]. At the international level, the Global Peatlands Initiative continues to promote peatland protection and restoration as part of urgent climate change mitigation measures [2]. However, the effectiveness of peatland restoration is often debated, particularly regarding the resulting ecohydrological impacts [28,29].
Peatland restoration requires significant investments and long lead times of decades to restore hydrological function and carbon storage capacity [30], but it also relies on continuous monitoring and adaptation to environmental dynamics. Additionally, some studies reveal that despite the multitude of restoration actions taken to restore peatlands, their ecological status after these actions is far from their original and desired state [31]. Other studies reveal that hydrological indicators of peatland restoration success require a long time to reach a significant level [14,32]. These facts raise substantial concerns about the extent to which peatland restoration can stabilize and bring back these ecosystems so that the ecohydrological functions of these ecosystems are sustained. This study seeks to critically analyze the literature on the ecohydrological effects of peatland restoration across different scales, locally and globally.
This paper serves as a review that explores the challenges that must be overcome to understand the post-restoration ecohydrodynamics. By applying an approach from the general to the more specific, this paper aims to provide a comprehensive understanding of the impact of peatland restoration on selected ecohydrological features of these ecosystems, namely, water table depth, carbon sequestration, and greenhouse gas emissions (CO2 and CH4) across scales.

2. Materials and Methods

2.1. Justification and Scope of the Review

We started the literature identification by applying keywords in a title search ranging from 2014 to 2024. The 10 years were deliberately chosen to ensure the inclusion of the latest and relevant advancements in peatland restoration research. Previous studies, such as [8], revealed that restoration efforts in Indonesia were often fragmented, small in scale, and constrained by ecological degradation and policy inconsistency, yet lacked quantitative synthesis on their actual ecohydrological impacts. Similarly, ref. [29] documented North America’s shift from trial-based efforts to larger-scale, multidisciplinary restorations, but focused more on describing methodologies than evaluating their effectiveness across scales. Ref. [33] outlined ongoing anthropogenic and economic barriers to peatland restoration, especially in Southeast Asia but offered limited integration of hydrological data and emission outcomes. These studies were critical in identifying practical and governance-level challenges, yet they did not consolidate or statistically assess restoration effects on key ecohydrological metrics. However, over the past decade, the growing global attention on climate change mitigation has seen a surge in high-quality publications focused on the ecohydrological functions of peatland restoration.

2.2. Systematic Search Design

To fill this gap, we searched the systematic literature using the Scopus database. A Boolean strategy was applied to ensure high relevance, using search phrases such as “Peatland AND Restoration,” “Water AND Level AND Peatland,” “Peatland AND Ecohydrology,” “Peatland AND Biodiversity,” “Peatland AND Carbon AND Sequestration,” and “Peatland AND Hydrological AND Impacts.” The focus of these search terms was to capture both empirical and experimental research addressing ecohydrological restoration functions, including water table regulation, greenhouse gas emissions, and carbon sequestration. These keywords were purposefully designed to reflect the scope of ecohydrological parameters affected by peatland restoration. However, we acknowledge that our keyword selection may not have captured all relevant studies, as we used specific terms without broader wildcard or synonym expansion. This is a potential limitation, and we recommend that future reviews consider a wider range of search terms.

2.3. Screening and Eligibility Criteria

The search was conducted using the Scopus database, resulting in 566 potentially relevant papers. After the removal of duplicates, ineligible publication years, and journals not meeting quality criteria, 356 records proceeded to title screening. Following multiple stages of screening, title review, retrieval check, and eligibility assessment based on abstract and content relevance, a total of 52 peer-reviewed articles were included in the final analysis (Figure 1). These studies focus on the ecohydrological impacts of peatland restoration and form the empirical foundation of this review.

2.4. Meta-Analysis Approach

RStudio version 2024.09.1+394 (Posit Software, Boston, MA, USA) running R version 4.2.1 was used to calculate selected indicators for the meta-analysis of the ecohydrological impacts of peatland restoration (Table 1). The RStudio script for the meta-analysis, available through the meta package (installable via install.packages(“meta”)), allowed us to generate outputs such as I2, standard deviation (SD), and average values for the data. Data corresponding to the analyzed parameters—CO2, CH4, carbon sequestration, and WTD—were collected from the selected studies. Due to inconsistencies in units across these studies, the units were standardized to ‘kg·ha−1·year−1’ for emissions and ‘cm’ for WTD. Emission data originally reported in different units (e.g., g·m−2·day−1, mg·m−2·h−1) were converted to a common unit of kg·ha−1·year−1 using standard dimensional conversions. This involved scaling by area (1 ha = 10,000 m2), time (e.g., 365 days or 8760 h per year). All conversions were performed consistently across studies, and where unit information was ambiguous or missing, those data points were excluded to preserve reliability. Thus, although forest plots are typically used in meta-analyses to visually display effect sizes and confidence intervals across studies, they were not included in this study due to the limited number of studies per parameter with consistently reported variance estimates. For WTD variables, up to 8 studies were available for graphical synthesis, and the forest plots thus generated would not have been of interpretive utility. We, therefore, opted to present the principal results in the Table 1, which reveals summary statistics and shows heterogeneity across studies.

3. Results

3.1. Spatial and Temporal Patterns

The number of publications has fluctuated throughout the decade, reflecting variations in research focus, funding availability, and global interest in peatland conservation. In addition, Figure 2 illustrates the diversity of restoration methods used over the period, including rewetting (e.g., through the ditch blocking), revegetation (e.g., through the hay transfer), water management (e.g., change in river/canal discharge regime), soil removal (e.g., partial mechanic extraction of the drained topsoil), reforestation, and soil treatment (e.g., using specific chemical substances to increase water retention of the soil). Rewetting, as the most consistently applied restoration method, has been implemented yearly throughout the decade, compared to other techniques, highlighting its central role in restoring peatland hydrological conditions. This means peatland restoration research has developed over the past decade in terms of the number of publications and the variety of methods used. Thus, 2017 and 2022 show significant spikes in the number of studies, while 2021 has the lowest number of studies. The complexity and long-term nature of peatland restoration projects likely influence this irregularity. Research by [17] shows that CO2 emissions dominate the long-term climate impacts of restored peatlands, surpassing CH4 emissions. Although restored peatlands can be long-term carbon sinks, they still emit CH4, especially in the first 20 years after restoration. This shows that the peatland restoration process takes a long time (between 2 to more than 10 years) until the results can be published scientifically.
The number of locations presented on the map (Figure 3) does not represent how many restorations were described in each study. Still, it illustrates a representation of the restorations applied, so it is possible that more than one restoration could be carried out in one location. It was found that most studies were conducted in Canada for the North American region. In addition, Peru occupies the leading position in the South American region compared to Colombia. For the European region, the UK is the country that has carried out the most restoration. In the Asian region, Indonesia ranks at the top compared to China. Based on ref. [34] IPCC 2006 climate zone classification, the mapped studies span across boreal (e.g., Canada, Scandinavia), temperate (e.g., UK, USA, China), and tropical zones (e.g., Indonesia, Colombia, Peru), highlighting the importance of climatic context in shaping restoration outcomes.

3.2. Averaged Indicators of Peatland Restoration

A total of 52 studies met the inclusion criteria for this meta-analysis, covering peatland restoration efforts across Europe, North America, and Southeast Asia. The aggregated data show that restoration, on average, results in a substantial decrease in CO2 emissions. However, this reflects large regional contrasts, with tropical peatlands often exceeding 65,000 kg·ha−1·yr−1 and boreal sites generally below 25,000 kg·ha−1·yr−1 (Table 1). Carbon sequestration showed a mean increase of ~23,000 kg·ha−1·yr−1. Yet, the responses were highly variable and often modest in boreal systems due to slower peat growth and nutrient limitations. CH4 emissions increased by ~480 kg·ha−1·year−1 on average, consistent with enhanced anaerobic activity under elevated water levels. Meanwhile, WTD increased on average by 10 cm post-restoration, with study-level values ranging from minor increases of 2 cm to over 40 cm in high-intervention sites. The heterogeneity (I2) for most parameters was consistently high, over 66%, suggesting strong contextual variability in restoration outcomes. Given this high heterogeneity, we report mean values to indicate general trends, but we acknowledge that these averages should be interpreted with caution. The high I2 values reflect substantial contextual differences across studies, and as such, the reported means are intended to summarize typical outcomes, not to imply consistent effects across all settings. Thus, forest plots were not used in this study because several studies provided compatible variance estimates. Instead, we summarized the meta-analysis results using mean values, standard deviations (SD), and heterogeneity scores (I2), which are presented in Table 1. Among restoration techniques, rewetting was by far the most applied approach (appearing in more than 70% of studies), often in combination with revegetation or drainage blocking. Geographically, Europe dominated the sample, particularly the UK, followed by Canada and Indonesia. These patterns reflect both ecological suitability and national-level policy commitments.
Figure 4 describes the outputs of the different peat restoration methods analyzed from the 52 papers included in the study. The rewetting method was the most widely used, with 42 total discussions of its outputs. It focused on significantly reducing carbon sequestration, GHG emissions, groundwater table stabilization, and fire risk. The water management method discusses water quality improvement, flood control, and nutrient retention. The revegetation method discusses native vegetation restoration and support, ecosystem support, biodiversity enhancement, and habitat improvement. Other methods, such as reforestation, soil removal, biodiversity enhancement, and soil treatment, were only recorded in a few cases (1–2 cases each). Discussions of these methods, such as soil retention, nutrient cycling support, or carbon storage enhancement, tend to be more specific. Still, they do not receive the same attention in broader literature.
Table 2 summarizes the impacts of peatland restoration found in our research. These impacts include environmental changes such as changes in the water table, carbon sequestration, vegetation restoration, nutrient balance, and soil quality. Observed increases in water table depth following restoration were linked to improvements in carbon sequestration, soil moisture, and organic matter based on reviewed studies. This process also moderates peak flow events and mitigates fire risk, thereby supporting the re-establishment of a more stable and resilient hydrological cycle.

4. Discussion

Over the last ten years, researchers have shown both optimism and caution when evaluating the effects of peatland restoration. Our analysis supports this mixed picture: although rewetting often improves water levels and reduces CO2 emissions, the outcomes vary considerably, especially in sites with differing peat conditions, drainage history, or climate regimes. We observed substantial heterogeneity in outcomes (I2 > 50%), indicating that peatland restoration does not deliver consistent results across sites. The effectiveness of interventions appears closely tied to local conditions, particularly peat composition, prior drainage, and climatic factors such as rainfall variability. For example, in wetter climates, rewetting often raises the water table more rapidly and consistently than in drier regions, where water retention can be limited. While restoration often results in increased CH4 emissions, the broader climate implications depend on how these fluxes are evaluated. When converted into CO2-equivalents (CO2e) using GWP from IPCC AR6, methane emissions (~480 kg·ha−1·yr−1) amount to approximately 13,056 kg CO2e·ha−1·yr−1 under the 100-year time horizon (GWP100 = 27.2). In contrast, the large global average CO2 reduction (~54,000 kg·ha−1·yr−1) observed in this meta-analysis should, therefore, be interpreted with caution, as it reflects a mix of high-performing tropical sites and lower-performing boreal and temperate systems, with substantial variation (SD = 26,408). However, if assessed under a short-term lens using GWP20 (CH4 = 82.5), CH4 emissions rise to ~39,600 kg CO2e·ha−1·yr−1, partially offsetting the CO2 reductions. This reflects a short-term offset in benefits that diminishes over time: rewetting raises the water table, limiting aerobic decomposition of peat and, thus, suppressing CO2 release [3,59]. The rise in WTD following rewetting directly alters the oxygen dynamics within peat layers. Higher WTD reduces the thickness of the aerobic zone, thereby slowing microbial oxidation and lowering CO2 emissions. However, these saturated conditions promote anaerobic microbial processes, particularly methanogenesis, leading to an increase in CH4 emissions. Additionally, WTD influences vegetation composition and root activity, both of which affect organic matter input and long-term carbon sequestration. In a system with sustained WTD recovery and appropriate vegetation, conditions can gradually favor net peat accumulation, although this process may be delayed due to initial methane fluxes and hydrological instability [60]. However, the resulting anoxic conditions favor methanogenesis, increasing CH4 production by methanogenic archaea in saturated zones [24]. The delicate balance between CO2 suppression and CH4 release may also help explain why gains in carbon sequestration are not always immediately evident following restoration. While rewetting can theoretically enhance long-term peat accumulation, initial increases in methane emissions, particularly in saturated systems, can offset these benefits in the short term. In such conditions, the ecosystem may require more time to shift back into a net accumulating carbon state, especially if the vegetation or hydrology is not yet optimized for efficient carbon capture. However, as CH4 emissions tend to stabilize or decline over time and CO2 reductions remain substantial, the long-term climate benefit of restoration is likely to outweigh the short-term warming effects [61]. The magnitude of CH4 release is influenced by factors such as peat temperature, vegetation type, and microbial community structure. Studies included in our analysis show that while CH4 emissions may spike shortly after rewetting, they often stabilize or decline over time, particularly when sedges and other CH4-conducting vegetation are absent. Therefore, evaluating the climate benefit of restoration requires a temporal perspective that accounts for both short-term CH4 pulses and long-term CO2 mitigation. Although rewetting often results in clear reductions in CO2, the overall impact on greenhouse gases becomes more complex when the GWP of methane is taken into account. Specifically, when using a 20-year GWP, CH4 emissions, despite their smaller volume, can temporarily offset the climate benefits of CO2 reductions. Over longer time horizons (e.g., GWP100), restoration tends to be more climate-beneficial; however, the balance remains dependent on site conditions [61]. Regional variation in greenhouse gas responses was evident across the studies reviewed. Tropical peatlands tended to exhibit higher reductions in CO2 emissions, with reported values ranging from approximately 65,000 to 72,000 kg·ha−1·yr−1, and moderate increases in CH4 emissions (170 to 450 kg·ha−1·yr−1) [62,63,64]. Carbon sequestration in these systems reached up to 39,700 kg·ha−1·yr−1 in some cases [3,33]. In contrast, boreal peatlands in our subset mean was ~23,600 kg·ha−1·yr−1, higher than many long-term boreal reports where annual peat accumulation rates historically average only 1 mm (~2–3 t CO2·ha−1·yr−1) [65], and relatively higher CH4 emissions (~800 kg·ha−1·yr−1), suggesting a narrower net climate benefit in the short term [66,67]. Our findings suggest that restoration strategies should be tailored to account for the varying ecohydrological responses observed across sites. In particular, approaches that manage methane dynamics, such as selecting vegetation types that limit CH4 transport or fine-tuning water table levels, may help optimize both climate mitigation and hydrological recovery.
Regional differences in restoration outcomes reflect not only ecological variation but also divergent governance structures, institutional capacity, and historical land use. In the United Kingdom, restoration efforts are supported by strong policy instruments such as the Environmental Land Management Scheme (ELMS) and a legally binding net-zero commitment by 2050 [68,69], leading to widespread implementation of rewetting and revegetation. In Canada, where peatland restoration remains an inherent element of, e.g., peat harvesting projects, many restoration projects benefit from strong collaboration among government agencies, Indigenous communities, and environmental organizations, an approach that seems to improve both implementation and public acceptance [70]. Indonesia, meanwhile, has shown strong ambition through the creation of the Peatland Restoration Agency (BRG) in 2016 and a two-million-hectare target, but progress on the ground has been uneven due to coordination gaps, spatial mismatches, and limited local enforcement [8,71,72]. These discrepancies suggest that technical interventions alone are insufficient. For peatland restoration to work in practice, ecological design alone is not enough. Governance must support it through consistent policy, stable funding, and active involvement of local communities. Our review makes this clear: restoration outcomes are highly variable, and the interaction between ecological responses and implementation challenges remains complex, making a one-size-fits-all model unsuitable. Successful programs tend to emerge when governance capacity, policy frameworks, and local institutional contexts are thoughtfully aligned with ecological strategies. These approaches to peatland restoration are unlikely to yield consistent benefits. Instead, to be effective in the long term, restoration efforts must go beyond rewetting alone. Regular monitoring of water levels and greenhouse gases is essential; however, the ability to adapt to the weather by adjusting hydrological controls or rethinking vegetation choices can lower CH4 emissions. Just as important, the broader policy environment matters. Without stable funding, clear leadership, and buy-in from local communities, well-designed projects are likely to fall short. Future research should move beyond binary metrics of “success” or “failure” and instead focus on building adaptive frameworks that align ecological processes with climate goals and local realities. While this study focused on CO2, CH4, carbon sequestration, and WTD as core indicators of ecohydrological impact, we acknowledge that factors such as nutrient availability, biomass allocation, and vegetation productivity can influence these outcomes. Due to inconsistencies in how such variables were reported across studies, we did not attempt to directly model these relationships while recognizing them as important directions for future research.

5. Conclusions

Restoration of peatlands is frequently promoted as a climate mitigation strategy; however, in practice, its outcomes are unforeseen and fall short of expectations. The evidence treated here does not suggest a lack of effort, but instead, an inconsistency between ecohydrological, implementation, and the policy. While reductions in CO2 emissions and rises in water tables are frequently reported, increases in CH4 emissions still remain an inconvenient yet essential part of the story that is often sidelined in restoration discourse. More critically, the influence of scale, central to this study, is insufficiently considered in both practice and research. Local initiatives tend to be experimental and underfunded, national programs often politically driven and inconsistent, while global assessments remain too coarse to inform actionable policy. Yet across all levels, there is a shared over-reliance on rewetting, with little adaptation to the specific conditions that determine success or failure. Peatland restoration is not failing, but the field risks stalling if it continues to chase universal models over context-aware strategies. The efforts must confront complexity, investing in long-term monitoring, and aligning ecohydrological design with governance realities. Unless challenges related to implementation and context-specific design are addressed, the benefits of peatland restoration will remain largely unrealized.

Author Contributions

R.K.: conceptualization, investigation, methodology, formal analysis, visualization, writing—original draft, writing—review and editing; J.C.P.: review and editing; M.G.: review and editing, supervision. All authors have read and agreed to the published version of the manuscript.

Funding

This research was carried out in the framework of the European Union’s Horizon Europe WET HORIZONS project, grant agreement no. 101056848.

Data Availability Statement

Data sharing is not applicable to this article as no new data were created or analyzed in this study. All data were obtained from the published literature reviewed in the included studies.

Conflicts of Interest

The authors declare no competing interests.

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Water 17 02428 g001
Figure 1. PRISMA flow diagram outlining the literature screening and selection process for this systematic review.
Figure 1. PRISMA flow diagram outlining the literature screening and selection process for this systematic review.
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Figure 2. Number of selected studies and type of restoration methods every year on 52 papers between 2014 and 2024. 1—Rewetting, 2—Revegetation, 3—Water management, 4—Topsoil removal, 5—Reforestation, 6—Soil treatment, 7—Biodiversity.
Figure 2. Number of selected studies and type of restoration methods every year on 52 papers between 2014 and 2024. 1—Rewetting, 2—Revegetation, 3—Water management, 4—Topsoil removal, 5—Reforestation, 6—Soil treatment, 7—Biodiversity.
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Figure 3. Geographic distribution of peatland restoration studies across selected countries, categorized by intervention type: rewetting (blue), water management (red), revegetation (green), reforestation (yellow), soil removal (orange), biodiversity enhancement (dark blue), and soil treatment (purple).
Figure 3. Geographic distribution of peatland restoration studies across selected countries, categorized by intervention type: rewetting (blue), water management (red), revegetation (green), reforestation (yellow), soil removal (orange), biodiversity enhancement (dark blue), and soil treatment (purple).
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Figure 4. Sankey diagram showing the distribution of 52 studies across different peatland restoration methods and the ecohydrological outcomes reported for each method. The size of each block and the width of the connecting flows represent the number of studies linking a specific restoration method, such as rewetting, water management, revegetation, and others to outcomes like increased water table depth, reduced CO2 emissions, enhanced carbon sequestration, or changes in CH4 emissions. Numbers inside the blocks indicate the study count. The figure highlights that rewetting is the most frequently used method and is associated with a broad range of ecohydrological impacts.
Figure 4. Sankey diagram showing the distribution of 52 studies across different peatland restoration methods and the ecohydrological outcomes reported for each method. The size of each block and the width of the connecting flows represent the number of studies linking a specific restoration method, such as rewetting, water management, revegetation, and others to outcomes like increased water table depth, reduced CO2 emissions, enhanced carbon sequestration, or changes in CH4 emissions. Numbers inside the blocks indicate the study count. The figure highlights that rewetting is the most frequently used method and is associated with a broad range of ecohydrological impacts.
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Table 1. Meta-analysis of the ecohydrological impact of peatland restoration on the reduction of CO2, release of CH4, a non-significant rise in carbon sequestration, and WTD. I2 was included to assess heterogeneity among studies, indicating how much variability is due to differences across studies rather than chance. p-values test the statistical significance of the pooled effects, identifying whether the observed impacts are likely to be real. SD captures the data spread, reflecting variability in restoration outcomes, while the average provides a central estimate of effect size for each parameter.
Table 1. Meta-analysis of the ecohydrological impact of peatland restoration on the reduction of CO2, release of CH4, a non-significant rise in carbon sequestration, and WTD. I2 was included to assess heterogeneity among studies, indicating how much variability is due to differences across studies rather than chance. p-values test the statistical significance of the pooled effects, identifying whether the observed impacts are likely to be real. SD captures the data spread, reflecting variability in restoration outcomes, while the average provides a central estimate of effect size for each parameter.
ParameterCO2CH4Carbon SequestrationWTD
(kg·ha−1·Year−1)(kg·ha−1·Year−1)(kg·ha−1·Year−1)(cm)
I266.67%75.10%50.05%85.71%
p-value0.0490.0070.157<0.0001
SD26 40825723 5748.44
Average53 85748623 03010.45
Table 2. Key findings of studies.
Table 2. Key findings of studies.
Peatland Restoration ConsequencesFindingsRefs.
Water Table (WT) ChangesRestoration appeared to enhance carbon sequestration in many areas, though not always consistently or significantly. A recurring pattern was the reduction of CO2 emissions after rewetting, but this was often offset, at least partially, by a rise in CH4, especially in persistently saturated conditions. Methane variability also depended on plant type and water level stability[3,8,14,19,24,35,36,37,38,39]
Carbon Sequestration and GHG EmissionsRestoration appeared to enhance carbon sequestration in many areas, though not always consistently or significantly. A recurring pattern was the reduction of CO2 emissions after rewetting, but this was often offset, at least partially, by a rise in CH4, especially in persistently saturated conditions. Methane variability also depended on plant type and water level stability[16,17,36,38,40,41,42,43,44]
Vegetation RecoverySome restored peatlands showed clear signs of vegetation returning, particularly mosses like Sphagnum and sedges such as Carex. However, in several cases, the pace of recovery was slower than expected. Factors like site history and soil chemistry likely played a role in shaping these outcomes.[1,3,19,24,26,43,45,46,47,48]
Nutrient Dynamics (N, P, DOC)The effects of restoration on nutrients such as nitrogen and phosphorus were mixed. Some studies reported a rise in nutrient concentrations, while others observed declines. Similarly, dissolved organic carbon (DOC) quality improved in some sites; however, it remained variable elsewhere, suggesting the response is not universal.[6,36,38,39,49,50,51,52]
Soil Properties and HydrologyChanges to soil characteristics post-restoration were generally positive, with increases in organic matter and moisture retention in many cases. Bulk density decreased slightly in some locations, though not all studies reported structural improvements. There was also some evidence of surface emission reductions, but again, this varied by site.[22,37,38,44,45,50,53]
Hydrological Flows and Ecological ImprovementsFlood attenuation was reported in multiple cases, with some sites showing up to a 49% reduction in peak discharge. Seasonal water balance seemed to normalize over time, although responses varied depending on topography and rewetting method. Fire risk tended to drop where rewetting succeeded, and some signs of improved biodiversity were noted.[32,54,55,56,57]
Climate and Temperature EffectsIn some studies, the cooler surface temperatures were observed after restoration, especially in wetter sites. However, these patterns were not consistent across all sites and may be linked to increased soil moisture levels post-rewetting. A few observations also mentioned brighter, more reflective surfaces after rewetting, possibly due to vegetation changes, which could affect how much heat is absorbed.[22,44,58]
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Kustina, R.; Pilicita, J.C.; Grygoruk, M. Issues of Peatland Restoration Across Scales: A Review and Meta-Analysis. Water 2025, 17, 2428. https://doi.org/10.3390/w17162428

AMA Style

Kustina R, Pilicita JC, Grygoruk M. Issues of Peatland Restoration Across Scales: A Review and Meta-Analysis. Water. 2025; 17(16):2428. https://doi.org/10.3390/w17162428

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Kustina, Rinda, Jessica Canchig Pilicita, and Mateusz Grygoruk. 2025. "Issues of Peatland Restoration Across Scales: A Review and Meta-Analysis" Water 17, no. 16: 2428. https://doi.org/10.3390/w17162428

APA Style

Kustina, R., Pilicita, J. C., & Grygoruk, M. (2025). Issues of Peatland Restoration Across Scales: A Review and Meta-Analysis. Water, 17(16), 2428. https://doi.org/10.3390/w17162428

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