The carbon dynamics of peatlands are intricately linked to hydrology and microbial activity. Traditional drainage lowers the water table, exposing peat to oxygen, which accelerates microbial decomposition of organic matter, releasing large quantities of carbon dioxide. Rewetting peatlands by raising the water table is a recognized restoration practice that can slow down these processes. Yet, rewetting alone does not fully overturn the negative legacy effects; it faces challenges such as increased methane emissions, which are a potent greenhouse gas. This research pioneers the synergistic use of biochar and iron sulphate additions alongside water management to amplify carbon stabilization while mitigating methane release.

Conducted over a year in outdoor soil mesocosms designed to replicate agricultural peatland conditions, the experimental study meticulously tested several treatment combinations. The results strikingly show that when the water table is elevated in conjunction with biochar and iron sulphate amendments, carbon preservation is significantly enhanced compared to rewetting alone. Biochar, a stable carbon-rich material derived from pyrolyzed plant biomass, contributes persistent carbon directly to the soil matrix. More importantly, it alters microbial communities and soil biochemical processes, dampening the activity of enzymes responsible for organic matter breakdown.

Iron sulphate further intensifies carbon protection through complex mineral-organic interactions. The presence of iron fosters the formation of iron-bound carbon compounds, a phenomenon often called the “iron gate” effect, which immobilizes organic compounds by binding them to iron minerals. This mineral-carbon association effectively reduces the bioavailability of organic matter to decomposers. The combined treatment was found to suppress methane-producing archaea, which thrive under anaerobic conditions in rewetted peatlands, addressing a critical concern in peatland restoration where methane emissions can offset carbon sequestration gains.

Microbial hotspots in peat soils, areas of intense microbial metabolism, are phenotypically and functionally shifted due to the synergistic treatment. The study revealed that microbial community composition altered in ways that reduced decomposition rates without entirely hindering the necessary nutrient cycling that maintains soil health. Specifically, the suppression of soil enzymes like phenol oxidase and peroxidase that catalyze lignin and complex organic matter degradation was notable. This fine balance is vital, as overly inhibiting microbial activity can detrimentally affect peatland ecosystem functions.

The amendment synergy exerted by biochar and iron sulphate modulated redox conditions, crucial to the chemistry and biology of peat soils. Rewetting alone creates anaerobic environments conducive to methanogenesis but less favorable for oxidative enzyme activity. The presence of iron introduced microbially available iron phases that participate in redox cycling, effectively controlling electron flow and suppressing methanogenesis pathways. Simultaneously, biochar enhanced soil physical properties such as porosity and water retention, indirectly affecting microbial microhabitats and substrate accessibility.

The implications of this study extend beyond the immediate soil chemistry alterations to landscape-scale climate mitigation strategies. Peatlands represent a disproportionately large reservoir of terrestrial carbon, and restoring them as carbon sinks could significantly blunt anthropogenic carbon emissions. Integrating biochar and iron sulphate with rewetting provides a scalable and practical methodology for land managers, supplementing conventional restoration with nutrient and mineral amendments that buffer microbial carbon loss mechanisms.

Dr. Peduruhewa Jeewani, the study’s lead author, emphasized the ecological and climatological importance of the findings, stating that this synergistic approach “protects soil carbon and limits greenhouse gases” beyond what rewetting can achieve alone. This dual action—slowing decomposition and suppressing methane—addresses the complex trade-offs typically encountered in peatland restoration efforts. The controlled experimental setup allowed precise disentangling of these interactive effects, yielding insights crucial for informing future field-scale applications.

Biochar production methods, including slow pyrolysis of Miscanthus, were chosen for their ability to yield highly recalcitrant carbon forms that persist in soil. This stability ensures that carbon introduced via biochar remains sequestered for decades to centuries, contributing to long-term climate mitigation. Additionally, the influence of biochar on microbial nutrient cycling highlights its role as a soil amendment beyond carbon input—impacting nitrogen and phosphorus dynamics in peat soils prone to nutrient limitation.

Iron sulphate’s contribution is underscored by its promotion of iron redox cycling, which acts as an electron sink and mediates organic carbon stabilization in anaerobic conditions. This pathway of “mineral gating” organic carbon offers a promising avenue to reduce carbon mineralization rates in rewetted peatlands prone to rapid microbial processing. The coupling of iron chemistry with biochar’s structural and chemical properties elucidates a novel biogeochemical mechanism for enhancing peatland carbon retention.

Professor Davey Jones, co-author of the study, pointed out the broader significance for farming and climate resilience, “Healthy peatlands are critical for both farming and climate resilience.” Peatland degradation compromises both ecosystem services and agricultural productivity. Restoration techniques equipped with this emerging knowledge could promote sustainable land management practices that harmonize agricultural needs with climate objectives.

As global climate policy increasingly recognizes the importance of terrestrial carbon sinks, applying such integrative approaches to peatland restoration embodies a forward-looking strategy. This research not only advances the scientific understanding of peat soil microbial ecology and biogeochemistry but also provides actionable pathways to enhance carbon sequestration and greenhouse gas mitigation at landscape and regional scales.

This study, published in the journal Biochar, highlights a novel approach to tackling one of the most challenging climate mitigation issues—the restoration of degraded peatlands. It paves the way for future multidisciplinary research linking soil chemistry, microbial ecology, and environmental engineering to safeguard these vital ecosystems and their climate functions.

Subject of Research: Not applicable

Article Title: Restoring degraded agricultural peatlands: how rewetting, biochar, and iron sulphate synergistically modify microbial hotspots and carbon storage

News Publication Date: 10-Sep-2025

References: Jeewani, P.H., Brown, R.W., Rhymes, J.M. et al. Restoring degraded agricultural peatlands: how rewetting, biochar, and iron sulphate synergistically modify microbial hotspots and carbon storage. Biochar 7, 108 (2025). DOI: 10.1007/s42773-025-00501-y

Image Credits: Peduruhewa H. Jeewani, Robert W. Brown, Jennifer M. Rhymes, Chris D. Evans, Dave R. Chadwick & Davey L. Jones

Keywords: Soil chemistry, Environmental chemistry, Soil science

The workshops were orchestrated by leading environmental initiatives, including the EU-funded WET HORIZONS project, the United Nations Environment Programme’s Global Peatlands Initiative, Wetlands International, and Eurosite—the European Land Conservation Network overseeing the European Peatlands Initiative. This consortium reflects a comprehensive approach that bridges scientific research, governmental policy frameworks, and conservation practice, underscoring the complexity of effective peatland management in a rapidly changing climate context.

Participation predominantly featured researchers from diverse universities, research institutions, and federal agencies, representing an intersection of social and natural sciences. This multidisciplinary engagement fostered comprehensive dialogue encompassing ecological functions, socio-economic challenges, and governance dimensions critical to peatland restoration. Additionally, voices from environmental non-governmental organizations and a select group of private-sector entities contributed to enriching the discourse, facilitating a broader understanding of potential collaborative pathways.

A central focus of the workshops was identifying mechanisms to expedite the protection and restoration of peatlands within national contexts. Germany, the Netherlands, and Finland, each possessing distinct peatland landscapes and policy environments, offered unique challenges and opportunities. Collective discussions revealed converging priorities, such as reinforcing legal instruments for habitat preservation, leveraging ecological data for informed decision-making, and enhancing stakeholder engagement across sectors.

A key area of exploration centered on policy innovation and the harmonization of funding streams across diverse governance domains. The Nature Restoration Law emerging from European Union directives provides a timely framework within which integrated public funding can be aligned to maximize restoration outcomes. Workshop participants considered the strategic deployment of public capital to mitigate risk and attract private investment, notably through emerging carbon market instruments tailored for peatland ecosystems.

The national impact plans resulting from this process articulate precise objectives that intertwine policy effectiveness with operational accountability. By mapping clear tasks to overarching environmental goals, the plans aspire to drive coordination among governmental bodies, NGOs, and financing bodies. This structured approach also promotes transparency in funding allocation and progress tracking, thereby reinforcing a culture of shared ownership and sustained commitment to restoration targets across the participating countries.

Beyond strategy formulation, the workshops initiated active dialogues to facilitate knowledge transfer and reciprocal learning. Upcoming initiatives include targeted workshops designed to share empirical evidence and policy experiences among the three focus countries and with additional actors in the European peatland restoration community, including Scotland. This cross-border exchange fosters adaptive management practices, especially pertinent as Scotland pilots innovative funding blends that combine public funds with private capital to scale restoration.

The conversation also highlighted the potential for paludiculture—the cultivation of wetland crops on rewetted peatlands—as a nature-based solution that partners well with carbon market mechanisms. By valorizing ecosystem services through biochar production and carbon credits, paludiculture may offer a dual pathway to economic viability and ecosystem health. Workshop attendees underscored the need for coordinated research and policy frameworks to realize this potential at scale.

Emphasizing technological advancements, the gatherings spotlighted the integration of remote sensing technologies, particularly radar-based methods, to monitor peatland conditions accurately. Combining these insights with restoration practices like forest-to-bog transitions enhances the precision of carbon accounting in peatlands, thereby strengthening the credibility and robustness of carbon market participation. These technical innovations are essential for informing adaptive management and measuring the outcomes of restoration investments effectively.

The synergy generated by bringing together stakeholders actively engaged in peatland restoration fuels optimism for future collaborative ventures. Shared objectives and mutual recognition of challenges create fertile ground for joint learning and collective action, transcending national boundaries. Such partnerships will likely accelerate restoration pathways that reconcile ecological needs with socio-economic considerations.

Sustained momentum post-workshop is envisioned through ongoing engagement facilitated by the WET HORIZONS coordination team based at Scotland’s Rural College alongside UNEP’s Global Peatlands Initiative and Wetlands International. This continued support aims to underpin the implementation of impact plans and contribute substantive insights toward an internationally coordinated Peatland Breakthrough strategy—a concerted global effort targeting peatland conservation and restoration as a climate and biodiversity imperative.

Rooted in findings of the first UNEP Global Peatlands Assessment, the Peatland Breakthrough represents a landmark initiative that assembles public and private stakeholders to elevate peatlands’ role within climate policies and promote restorative land-use practices such as paludiculture. This collective action framework is critical for meeting ambitious climate mitigation and biodiversity conservation targets while safeguarding ecosystems and the livelihoods dependent on them.

Ultimately, this multi-layered approach integrating science, policy, funding innovation, and community engagement embodies a transformative step towards large-scale peatland restoration across Europe. By aligning diverse actors under a shared vision, the initiatives emerging from these workshops exemplify how coordinated international cooperation can translate ecological knowledge into tangible environmental outcomes, fostering resilience in the face of escalating global environmental challenges.

Image Credits: Louis Johansen Skovsholt, Aarhus University

Web References:

• WET HORIZONS
• Wetlands International LinkedIn
• Eurosite LinkedIn