the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 05 Aug 2026
Ideas and perspectives: Rethinking climate mitigation of afforestation and rewetting of temperate and boreal degraded organic soils
Abstract. Degraded peatlands are among the largest land-based sources of greenhouse gas emissions in the European Union (EU). In response, the EU’s climate change mitigation targets are driving efforts to reduce emissions and enhance carbon sequestration within the land-use sector. A significant challenge is the high emissions from organic soils, particularly those degraded by peat extraction and agriculture. This has sparked discussions on appropriate mitigation strategies. Rewetting is gaining attention, and concerns persist that afforestation may hinder rewetting efforts, thereby reducing climate change mitigation potential. However, such concerns often oversimplify both measures. Though many perceive afforestation and rewetting as competing strategies, these measures should ideally and alternately be implemented based on distinct local conditions and goals in different regions. This perspective evaluates their advantages and limitations using evidence from boreal and temperate peatlands. The paper highlights underappreciated, evidence-based arguments to support more nuanced stakeholder discussions and promote complementary, context-appropriate implementation of the measures.
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Status: open (until 18 Oct 2026)
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CC1: 'Comment on egusphere-2026-4089', Normunds Stivrins, 14 Aug 2026
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AC4: 'Reply on CC1', Aldis Butlers, 24 Sep 2026
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Thank you for the suggestion. We agree that the figure could be made easier to read.
The land-use categories shown in the figure indicate the categories under which rewetting has been reported in national GHG inventories. Rewetting is reported under the respective land-use category in which it has occurred. We can clarify this in the figure caption.
Peat extraction sites are reported within the Wetlands land-use category in GHG inventories. Peat extraction sites are a separately reported land-use subcategory within Wetlands.
Citation: https://doi.org/10.5194/egusphere-2026-4089-AC4 -
AC5: 'Reply on CC1', Aldis Butlers, 24 Sep 2026
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Thank you for the suggestion. We agree that the figure could be made easier to read.
The land-use categories shown in the figure indicate the categories under which rewetting has been reported in national GHG inventories. Rewetting is reported under the respective land-use category in which it has occurred. We can clarify this in the figure caption.
Peat extraction sites are reported within the Wetlands land-use category in GHG inventories. Peat extraction sites are a separately reported land-use subcategory within Wetlands.
Citation: https://doi.org/10.5194/egusphere-2026-4089-AC5 -
AC6: 'Reply on CC1', Aldis Butlers, 24 Sep 2026
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Thank you for the suggestion. We agree that the figure could be made easier to read.
The land-use categories shown in the figure indicate the categories under which rewetting has been reported in national GHG inventories. Rewetting is reported under the respective land-use category in which it has occurred. We can clarify this in the figure caption.
Peat extraction sites are reported within the Wetlands land-use category in GHG inventories. Peat extraction sites are a separately reported land-use subcategory within Wetlands.
Citation: https://doi.org/10.5194/egusphere-2026-4089-AC6
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AC4: 'Reply on CC1', Aldis Butlers, 24 Sep 2026
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CC2: 'Comment on egusphere-2026-4089', Normunds Stivrins, 14 Aug 2026
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In Figure 3, agriculture and peat extraction are combined, although their emission factors differ substantially. For example, the reported CO₂ emission factor is 10.27 t CO₂ ha⁻¹ yr⁻¹ for peat extraction but considerably higher for cropland and most grasslands. Could these land uses be shown separately? Otherwise, the combined average may give a misleading impression of emissions from peat extraction sites.
Citation: https://doi.org/10.5194/egusphere-2026-4089-CC2 -
AC3: 'Reply on CC2', Aldis Butlers, 24 Sep 2026
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Thank you for the comment! Agricultural lands and peat extraction sites are shown separately in Figure A1; we can specify that in the caption of Figure 3.
Citation: https://doi.org/10.5194/egusphere-2026-4089-AC3
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AC3: 'Reply on CC2', Aldis Butlers, 24 Sep 2026
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RC1: 'Comment on egusphere-2026-4089', Anonymous Referee #1, 18 Sep 2026
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This manuscript addresses an important and timely question, and I agree that afforestation and rewetting should not be considered as universally applicable, one-size-fits-all measures. However, I have concerns about the central argument and, in particular, about how the evidence is selected and interpreted to support afforestation as a climate-mitigation strategy on drained agricultural organic soils.
My main concern is not simply that there are uncertainties. Rather, several of the key steps in the argument are not demonstrated by the evidence presented, while the comparison with rewetting is framed in a way that makes the potential benefits of rewetting appear narrower than they need to be. In several places, the manuscript also appears to transfer concepts from mineral-soil carbon dynamics to degraded organic soils without sufficiently demonstrating that the underlying mechanisms are applicable.
- The manuscript interprets lower emission factors for afforested organic soils relative to agricultural organic soils as evidence that afforestation reduces soil GHG emissions. However, this comparison does not demonstrate a causal effect of afforestation. The relevant question is whether converting a particular agricultural organic soil to forest reduces soil emissions, rather than whether established forest sites currently have lower emissions than agricultural sites.
The authors should distinguish much more clearly between observed emission factors for established forest and agricultural organic soils and evidence that afforestation causes a reduction in soil GHG emissions.
- A related concern is the use of literature on afforestation and SOC accumulation in agricultural/mineral soils to support the argument that afforestation of highly degraded organic soils will increase soil C inputs, reduce mineralization and potentially transform the soil into a C sink.
Drained peat and other organic soils cannot simply be treated as mineral agricultural soils with a large SOC stock. The dominant carbon pool is pre-existing, accumulated organic matter, and its persistence is strongly controlled by hydrology and oxygen availability. Increasing litter and root inputs therefore does not demonstrate that oxidation of the existing peat C has ceased, nor that the net soil-C balance has become positive.
I’ll make an example of the following statement from the article: Afforesting [implied organic] agricultural soils that have long been drained and are highly decomposed reduces mineralization promoted by cultivation (intensive and regular soil management) and increases soil carbon inputs (Hu et al., 2016; Lal, 2005; Feng et al., 2022). These studies provide evidence for mechanisms observed following afforestation of agricultural/mineral soils, but the manuscript does not sufficiently demonstrate that the same mechanisms can be assumed to operate in drained peat soils.
- I am concerned that individual studies are sometimes presented as supporting conclusions that they do not actually demonstrate, while evidence that complicates the proposed climate benefit of afforestation receives considerably less attention.
For example, Meyer et al. (2013) is cited in support of the conclusion that afforestation can transform areas with degraded organic soils into net GHG sinks. However, this study actually illustrates the difficulty of achieving a net climate benefit when soil GHG emissions offset tree carbon uptake, and the balance changes with forest development.
The use of Chiti et al. (2024) is also problematic. The 2–35 t CO₂ ha⁻¹ yr⁻¹ range should be clearly attributed to biomass accumulation across the afforestation systems represented in Chiti et al. (2024), rather than interpreted as a demonstrated net sequestration rate for forests established on degraded drained organic soils. The very high values appear to be from Eucalyptus plantations in the Mediterranean area.
Conversely, relevant evidence that directly complicates the manuscript's interpretation is not adequately discussed. For example, the modelling work of Escobar et al. 2025 (https://doi.org/10.5194/bg-22-2023-2025) indicates that substantial peat-C losses can persist through forest development and that the balance between forest uptake and soil-C loss changes over a forest rotation. This is directly relevant to the manuscript's argument that afforestation provides a predictable and sustained net climate benefit, yet it is not considered. Also, that paper acknowledges that even under a scenario with substantial tree growth and explicit accounting for HWP, the modelled peat soil continues to lose carbon, and the authors find that the cumulative climate effect can remain negative despite a positive end-of-period NCB.
- Tree biomass accumulation and harvested-wood-product effects may provide genuine mitigation, but these are distinct from avoiding oxidation of the existing peat C pool.
The key question is whether establishing forest on this particular drained organic soil provides additional climate mitigation compared with continued agriculture, rewetting, or producing equivalent forest biomass elsewhere. If the principal benefit of afforestation is biomass production, then the authors need to address the additionality of placing that forest on a large existing peat-C stock that remains exposed to aerobic decomposition.
- I agree with the manuscript that rewetting is not universally successful and that its effects on CH₄ emissions need to be considered. However, the discussion appears to mix rewetting as a hydrological intervention with ecological restoration of a peatland toward a particular wetland ecosystem.
Raising the water table does not require the immediate recreation of a pristine bog, fen or historically characteristic plant community. If the climate-mitigation objective is to reduce aerobic decomposition of existing organic soil C, then the relevant question is how changing water-table depth affects the CO₂–CH₄-N2O balance. The resulting vegetation and ecosystem may differ substantially from the original peatland and still provide an important reduction in soil-C loss.
This distinction matters because the manuscript uses the difficulty of achieving successful ecological restoration as part of the argument against rewetting.
The manuscript itself states that rewetting is more appropriately considered a strategy for reducing soil-C losses than as a reliable strategy for increasing carbon stocks. I agree with this distinction. However, if reducing soil-C losses is the objective, then rewetting may be particularly relevant on those agricultural organic soils that currently have the highest CO₂ losses.
- The manuscript places considerable emphasis on increased CH₄ emissions following rewetting, but does not adequately consider water-table depth as a continuous control of the combined CO₂–CH₄ climate balance.
Evans et al. (2021) demonstrated that effective water-table depth is a dominant control on the net climate impact of managed peatlands, with progressively shallower water tables generally reducing net warming over a substantial part of the hydrological gradient, until it is too high, resulting in excessive CH4. The relevant alternative to afforestation is therefore not necessarily “continued drainage” versus a highly flooded, CH₄-emitting peatland. Intermediate water-table regimes can substantially reduce aerobic peat oxidation without necessarily producing the highest CH₄ emissions.
This hydrological space is largely absent from the manuscript's comparison, despite the authors themselves identifying water table as an important determinant of GHG variability. A more appropriate comparison would therefore consider the CO₂–CH₄ balance across a range of water-table conditions rather than treating rewetting primarily as a discrete transition to a highly wet state.
- The manuscript states that peat-C loss after drainage “consistently decreases over time” and uses this to argue that land drained around the middle of the previous century has had time to stabilize and may therefore exhibit sustainable carbon stocks. I am not convinced that the available evidence supports such a general interpretation.
First, apparent declines in C loss with drainage age do not necessarily demonstrate that the remaining peat has become progressively less oxidizable or intrinsically more stable. It may reflect changes in peat depth and hydrology, subsidence, etc. This is particularly important because the highest emission rates reported in the literature are associated with intensively cultivated and highly degraded agricultural organic soils. It is therefore difficult to separate a true drainage-age effect from differences in land use and degree of degradation.
Second, the literature cited for this conclusion appears to be based on modelling rather than long-term empirical observations of individual drained peatlands. For example, Nguyen et al. (2025) provide a process-based modelling analysis of drainage-induced peat degradation, and their model is hard-coded to use progressively more recalcitrant C pools, causing less oxidation over time. They acknowledge this weakness in the paper after reviewers pointed out the issue. Similarly, Qiu et al. (2021) provide a modelling reconstruction of peatland carbon losses following conversion to cropland rather than a direct demonstration that emission rates from individual drained sites decline predictably with drainage age.
Sapir et al. (2026) (https://doi.org/10.5194/bg-23-1403-2026) is particularly relevant to this question. Their long-term reconstruction shows a substantial decline in SOM and modelled losses over several decades, but their respiration measurements do not demonstrate a substantially lower respiration rate per unit SOC in the long drained material. It is therefore my view that this question of a slowed-down oxidation rate with age is an open research question, deserving of attention.
In general, it is common to see studies draw on concepts of persistent and labile SOM pools and progressive stabilization that are well established in mineral-soil research. I would argue that such concepts cannot easily be transferred to peat without demonstrating that the relevant mechanisms apply.
The authors should therefore be much more cautious about presenting drainage age as an independent predictor of declining emission rates.
- There is also an internal tension between the evidence presented and the sites ultimately identified as suitable for afforestation.
The manuscript notes that cooler climates and, in particular, forested nutrient-poor drained organic soils can maintain or increase their carbon stocks. Yet the proposed priority areas for afforestation include highly degraded former peatlands with elevated pH and nutrient enrichment resulting from past fertilization. If nutrient status is an important determinant of the soil-C balance, evidence from nutrient-poor drained forest soils cannot simply be used to infer that nutrient-enriched agricultural organic soils will respond in the same way.
The authors should therefore provide much stronger evidence specifically for the class of sites they propose for afforestation.
- Interestingly, the manuscript does acknowledge that afforestation and rewetting can be combined. I think this is an important point and potentially a much more constructive direction for the paper.
However, this possibility is largely asserted rather than evaluated. The manuscript's main framework compares afforestation with continued drainage against rewetting, while the potentially interesting intermediate or combined management options receive little attention. If the authors intend to argue that afforestation and rewetting are complementary rather than competing measures, they should explain much more clearly what this means in practice and how the climate balance would change as water tables are raised under forest cover.
For example, the authors should distinguish between continued drainage for productive forestry, partial rewetting of forested sites, and deliberate establishment of wet forest systems. These are different management strategies with potentially very different CO₂, CH₄, biomass and soil-C outcomes.
Overall assessment
I find the perspective timely and potentially valuable, but the analysis stumbles. Unfortunately, I think the manuscript currently goes beyond what the evidence presented can support in several places. In particular, the case for afforestation as a climate mitigation measure on drained agricultural organic soils is stronger than the evidence synthesis appears to justify.
As an Ideas and Perspectives contribution, the manuscript is not expected to provide new empirical evidence, but its proposed perspective should nevertheless be clearly distinguished from conclusions that are supported by existing observations.
More generally, I would encourage the authors to distinguish more explicitly between (i) well-established effects of afforestation, such as biomass carbon accumulation, (ii) changes in the carbon balance of the pre-existing organic soil, and (iii) the net climate benefit of converting a particular drained agricultural organic soil to forest relative to realistic alternatives. These are related but not interchangeable questions. Strengthening this distinction would, in my view, make the perspective more balanced and would also clarify which conclusions are supported by the existing evidence and which represent the authors' interpretation.
Citation: https://doi.org/10.5194/egusphere-2026-4089-RC1 -
AC1: 'Reply on RC1', Aldis Butlers, 24 Sep 2026
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We thank the referee for their assessment and suggestions. Several questions raised have already been discussed in the manuscript, and in these cases, we tried to identify the relevant lines in our responses below. Some comments raise broader questions without identifying a specific claim or shortcoming in the manuscript. We respond to these questions as part of the discussion, but where we cannot identify a corresponding change that would improve the manuscript, we have included an explanation in this reply.
We also recognise points where the manuscript would benefit from clarification and specify the revisions we propose. To strengthen the Perspective and address the referee’s concerns, we consider the following manuscript revisions:
- Clarify the distinction between emission factors for established forests, afforested former agricultural soils, and evidence of changes caused by afforestation (Fig. A1; Table A1).
- Explain why findings from mineral soils may be relevant to some highly degraded organic soils
- Revise the wording to make it clearer that increased inputs do not reduce peat oxidation or nesessarily establish a positive net soil-carbon balance, but can offset all or part of losses by historical organic matter decomposition.
- Identify the range reported by Chiti et al. (2024) as biomass carbon accumulation across the studied afforestation systems, rather than sequestration on drained organic soils.
- Discuss Escobar et al. (2025) alongside contrasting measured and modelled outcomes, including continued soil-carbon loss and the importance of accounting boundaries (around lines 207–210).
- Clarify the distinction between raising the water table to reduce peat oxidation and restoring a particular peatland ecosystem. We will clarify why we consider restoration much more valuable than rewetting alone, and why rewetting should aim to restore the ecosystem.
- Revise claim that peat-carbon loss consistently declines with time since drainage, distinguishing modelled trends from direct observations.
- Revise the conclusions (lines 450–465) to clarify that, where afforestation reduces soil GHG emissions relative to continued previous land use, that reduction is itself a climate mitigation benefit, even if the site remains a net GHG source. Biomass accumulation and carbon stored in harvested wood products can provide additional benefits, as can substitution where wood use demonstrably avoids emissions. Within the ecosystem boundary, soil-carbon stock changes strongly influence the magnitude and long-term net balance. Across multiple rotations and a broader accounting boundary, the outcome also depends on harvested wood products and most importantly the extent of substitution effects. This way we will clarify what we meant by “predictable and reliable” afforestation, nevertheless we will revise this wording not to imply there are no uncertainties regarding afforestation.
This manuscript addresses an important and timely question, and I agree that afforestation and rewetting should not be considered as universally applicable, ‘one-size-fits-all' measures. However, I have concerns about the central argument and, in particular, about how the evidence is selected and interpreted to support afforestation as a climate-mitigation strategy on drained agricultural organic soils.
We welcome the referee’s agreement that neither measure is universally applicable. Our central argument is exactly that: the climate outcomes of both afforestation and rewetting depend on local conditions (including wide range soil charaacterisstics, hytrology, etc.) and should not be generalised across all drained agricultural organic soils (e.g. lines 18–20 and 89–91), and both should be considered case by case. We would welcome clarification of which aspect of this argument the referee disputes.
The referee raises a concern about our selection and interpretation of evidence, and identifies two specific references. We address both below and explain why we consider our use of them appropriate, but we still provide considered revisions. Our general reliance on existing syntheses as the principal basis for this perspective is explained in lines 76–78.
We do not claim that afforestation is suitable for every drained organic soil, considering alternatives. Throughout the manuscript, we argue that it should be considered as a potential mitigation option where site conditions warrant it, particularly where rewetting is less suitable (e.g. lines 18–20, 89–110 and 150–155; Fig. 2). We return to site selection in the conclusions (lines 450–465).
My main concern is not simply that there are uncertainties. Rather, several of the key steps in the argument are not demonstrated by the evidence presented, while the comparison with rewetting is framed in a way that makes the potential benefits of rewetting appear narrower than they need to be. In several places, the manuscript also appears to transfer concepts from mineral-soil carbon dynamics to degraded organic soils without sufficiently demonstrating that the underlying mechanisms are applicable.
Key steps of the argument are discussed below. Our emphasis on uncertainties associated with rewetting is deliberate and is explained in lines 66–80: we consider these uncertainties underrepresented in discussions that treat rewetting as broadly applicable. We discuss below our assumption that highly mineralised organic soils, on the threshold of mineral soil definitions, may act similarly to mineral soils.
- The manuscript interprets lower emission factors for afforested organic soils relative to agricultural organic soils as evidence that afforestation reduces soil GHG emissions. However, this comparison does not demonstrate a causal effect of afforestation. The relevant question is whether converting a particular agricultural organic soil to forest reduces soil emissions, rather than whether established forest sites currently have lower emissions than agricultural sites.
Our analysis does not rely solely on a comparison between agricultural land and established forestry-drained sites. Figure A1 and Table A1 separately identify forests established on former agricultural land (AF_AG) and peat extraction sites (AF_PE), using emission factors from Jauhiainen et al. (2023).
The authors should distinguish much more clearly between observed emission factors for established forest and agricultural organic soils and evidence that afforestation causes a reduction in soil GHG emissions.
Figure A1 shows that the mean soil CO2 emission factors for both categories (established drained forests with organic soils and afforested agriculture organic soils) are lower than the agricultural organic soil factors used in our comparison in boreal and temperate regions, although the temperate AF_AG factor is higher than that for established forests. We will make this distinction clearer in the main text.
- A related concern is the use of literature on afforestation and SOC accumulation in agricultural/mineral soils to support the argument that afforestation of highly degraded organic soils will increase soil C inputs, reduce mineralization and potentially transform the soil into a C sink.
The distinction between mineral and organic soils is important, but it is an operational classification rather than a sharp boundary in soil behaviour. Agricultural management and peat loss can produce soils with properties intermediate between organic soils and mineral soils, including soils close to the IPCC organic-soil threshold. We therefore consider mechanisms observed after afforestation of mineral soils potentially relevant to some such highly degraded organic soils. We do not assume that their magnitude or net soil-carbon response will be the same for organic soils. We can make this reasoning and its limits clearer in the manuscript.
Drained peat and other organic soils cannot simply be treated as mineral agricultural soils with a large SOC stock. The dominant carbon pool is pre-existing, accumulated organic matter, and its persistence is strongly controlled by hydrology and oxygen availability. Increasing litter and root inputs therefore does not demonstrate that oxidation of the existing peat C has ceased, nor that the net soil-C balance has become positive.
We would like to clarify that, as explained above, we do not consider all organic soils to be mineral soils with large C stocks. We do not assume or imply that increased litter stops oxidation of pre-existing peat carbon. As stated in lines 185–190, our argument concerns the net soil-carbon balance: additional inputs may offset some or, under suitable conditions, all of the continuing losses. We explicitly acknowledge the uncertainty of that balance and the risk of continued soil-carbon loss under drainage (lines 191–197 and 206–210). We can revise the wording to make it clearer that increased inputs do not reduce peat oxidation or necessarily establish a positive net soil-carbon balance, but can offset all or part of losses by historical organic matter decomposition.
I’ll make an example of the following statement from the article: Afforesting [implied organic] agricultural soils that have long been drained and are highly decomposed reduces mineralization promoted by cultivation (intensive and regular soil management) and increases soil carbon inputs (Hu et al., 2016; Lal, 2005; Feng et al., 2022). These studies provide evidence for mechanisms observed following afforestation of agricultural/mineral soils, but the manuscript does not sufficiently demonstrate that the same mechanisms can be assumed to operate in drained peat soils.
As explained above, we consider the mechanisms observed after afforestation of mineral agricultural soils potentially relevant to some highly degraded organic soils, particularly those approaching the organic-mineral soil classification threshold. This soil group should not be overlooked, as it is relatively widespread. We will add the explanation above to make the reasoning explicit.
- I am concerned that individual studies are sometimes presented as supporting conclusions that they do not actually demonstrate, while evidence that complicates the proposed climate benefit of afforestation receives considerably less attention.
We take the concern about how evidence is selected and interpreted seriously. We do not agree that we do not address limitations. The manuscript discusses several uncertainties relevant to afforestation: continued soil-carbon loss under drainage (lines 192–210), effects of forest operations on soil emissions (lines 265–274), disturbance effects on biomass accumulation (lines 327–330), and limitations in quantifying and retaining carbon in harvested wood products (lines 335–350). It also presents a range of estimates for substitution effects (lines 350–355). We address the two specific examples raised by the referee below. Our emphasis on rewetting reflects the manuscript’s stated aim of examining risks that we consider underrepresented (lines 66–75). Nevertheless, we agree that describing afforestation outcomes as “predictable and reliable” at line 461 overstates the certainty of the net climate outcome, and we will revise that wording.
For example, Meyer et al. (2013) is cited in support of the conclusion that afforestation can transform areas with degraded organic soils into net GHG sinks. However, this study actually illustrates the difficulty of achieving a net climate benefit when soil GHG emissions offset tree carbon uptake, and the balance changes with forest development.
Direct measurements by Meyer et al. (2013) identified the studied forest as a GHG sink. We therefore do not see the misuse of the reference: we use the study to show that an afforested organic-soil site can be a sink, as Meyer et al. observed. We cite it alongside other studies in lines 261–265, where we discuss evidence that drained organic-soil forests have been broadly shown to be carbon or GHG sinks; our argument does not rest on Meyer et al. alone.
The use of Chiti et al. (2024) is also problematic. The 2–35 t CO₂ ha⁻¹ yr⁻¹ range should be clearly attributed to biomass accumulation across the afforestation systems represented in Chiti et al. (2024), rather than interpreted as a demonstrated net sequestration rate for forests established on degraded drained organic soils. The very high values appear to be from Eucalyptus plantations in the Mediterranean area.
Chiti et al. (2024) synthesises afforestation in Europe and aligns with the manuscript-defined spatial scope; we cite its reported range to illustrate variation in biomass carbon accumulation, not to suggest that 35 t CO₂ ha⁻¹ yr⁻¹ should be expected on drained organic soils. We can add that, according to Chiti et al. (2024), excluding these very fast-growing species, afforestation promotes carbon sequestration in biomass in all biomes with an average rate of 5–10 Mg CO2 ha-1 yr-1.
Conversely, relevant evidence that directly complicates the manuscript's interpretation is not adequately discussed. For example, the modelling work of Escobar et al. 2025 (https://doi.org/10.5194/bg-22-2023-2025) indicates that substantial peat-C losses can persist through forest development and that the balance between forest uptake and soil-C loss changes over a forest rotation. This is directly relevant to the manuscript's argument that afforestation provides a predictable and sustained net climate benefit, yet it is not considered. Also, that paper acknowledges that even under a scenario with substantial tree growth and explicit accounting for HWP, the modelled peat soil continues to lose carbon, and the authors find that the cumulative climate effect can remain negative despite a positive end-of-period NCB.
We agree that Escobar et al. (2025) is relevant and can include it. Its contrasting results across system boundaries are particularly interesting: the model predicts continued peat-carbon loss and a negative time-integrated carbon-storage outcome, despite a positive end-of-period balance when harvested wood products are included. However, the outcome for one nutrient-rich former agricultural peatland should not be generalised to all afforested organic soils. Measurements at other sites range from a net ecosystem C sink (Bjarnadóttir et al., 2021) to a small annual CO₂ source (Lohila et al., 2007), while longer-term models are sensitive to assumptions about peat loss and harvested biomass (Cannell et al., 1993; He et al., 2016). We can discuss these contrasting findings alongside the uncertainty about continued soil-carbon loss already identified at lines 207–210.
However, focusing on source or sink categorisation distracts from what really matters. An afforested site need not become a net GHG sink to provide a climate benefit: reducing emissions relative to previous land use would itself constitute mitigation. The emission factors compared in Figures 3 and A1 support the potential for such a reduction, while also showing substantial variation and uncertainty. Carbon accumulation in living biomass and harvested wood products can add to this benefit, as can substitution where wood use demonstrably avoids emissions.
To address the issue, we can revise the conclusion’s claim of a predictable, sustained benefit: tree growth may be more predictable than the full soil and GHG balance, but the net climate outcome remains site-specific and is present as long as emissions are reduced compared to initial land use.
Tree biomass accumulation and harvested-wood-product effects may provide genuine mitigation, but these are distinct from avoiding oxidation of the existing peat C pool.
Biomass and harvested wood products definitely provide genuine mitigation as long as substitution occurs, because they reflect permanently avoided emissions, while biomass and harvested wood products are still subject to eventual oxidation. Biomass accumulation and the soil-carbon balance are biologically linked: greater plant productivity can increase litter and root inputs to soil. Decomposition continues even in wet soils, so maintaining soil carbon depends on the balance between continuing inputs and losses. We do not suggest that increased inputs stop oxidation of pre-existing organic matter; they may offset some or all of the gross soil carbon losses. The manuscript already discusses this distinction between inputs and losses. Nevertheless, we will check to clarify that increased litter input does not stop the oxidation of historical organic matter.
The key question is whether establishing forest on this particular drained organic soil provides additional climate mitigation compared with continued agriculture, rewetting, or producing equivalent forest biomass elsewhere. If the principal benefit of afforestation is biomass production, then the authors need to address the additionality of placing that forest on a large existing peat-C stock that remains exposed to aerobic decomposition.
Our perspective takes a broader view rather than assessing each carbon pool and source separately. As discussed throughout the manuscript, the synthesised soil emission factors suggest broadly similar soil GHG mitigation potential, expressed in CO2 equivalents, for afforestation and rewetting relative to continued agriculture (Figure 3, Figure A1). Afforestation can provide additional benefits through tree biomass, harvested wood products and substitution. Continued soil-carbon loss remains a risk under either measure and must be assessed for the site concerned. These points are already central to the manuscript.
- I agree with the manuscript that rewetting is not universally successful and that its effects on CH₄ emissions need to be considered. However, the discussion appears to mix rewetting as a hydrological intervention with ecological restoration of a peatland toward a particular wetland ecosystem.
Raising the water table does not require the immediate recreation of a pristine bog, fen or historically characteristic plant community. If the climate-mitigation objective is to reduce aerobic decomposition of existing organic soil C, then the relevant question is how changing water-table depth affects the CO₂–CH₄-N2O balance. The resulting vegetation and ecosystem may differ substantially from the original peatland and still provide an important reduction in soil-C loss.
This distinction matters because the manuscript uses the difficulty of achieving successful ecological restoration as part of the argument against rewetting.
Surely, raising the water table can reduce aerobic peat decomposition without recreating a pristine bog or fen. Our concern, however, is the longer-term ecosystem GHG balance in CO2 equivalents, which depends on CH₄ and N₂O emissions as well as continued carbon inputs from vegetation. Decomposition and CO₂ emissions do not cease in wet soils; if plant-derived carbon inputs are insufficient to offset soil-carbon losses, a rewetted soil may remain a net carbon source, even while losing carbon more slowly than under agriculture and drained forestry use. We believe rewetting should aim at soil C presevation whic is not posible without restoration. Otherwise, rewetting does not fully serve the purpose and soil C stock will be lost despite the efforts; in the longer term, CH4 emissions will likely remain elevated. We therefore emphasise vegetation development and argue that rewetting should aim to restore a functioning, carbon-accumulating ecosystem that can maintain its C stock where possible or even try to offset negative climate effects of CH4 emissions with C removals. This is relevant to aim for rewetting implementation where its climate benefits and co-benfits are maximised. Restoration may be desirable for ecological reasons even where its climate benefit is smaller than that of an alternative measure. We acknowledge this by identifying recoverable peatlands as candidates for restoration, while keeping the manuscript’s main comparison focused on climate outcomes. We will clarify why we consider restoration much more valuable than rewetting alone, and why rewetting should aim at restoration.
The manuscript itself states that rewetting is more appropriately considered a strategy for reducing soil-C losses than as a reliable strategy for increasing carbon stocks. I agree with this distinction. However, if reducing soil-C losses is the objective, then rewetting may be particularly relevant on those agricultural organic soils that currently have the highest CO₂ losses.
Largest potential reduction in soil-carbon loss does not necessarily identify the option with the greatest overall climate benefit. Large initial CO2 emissions can indicate increased GHG emissions also after rewetting. Our perspective calls for considering the full GHG balance in CO₂ equivalents, including CH₄ and N₂O, alongside tree biomass, harvested wood products and potential substitution effects.
- The manuscript places considerable emphasis on increased CH₄ emissions following rewetting, but does not adequately consider water-table depth as a continuous control of the combined CO₂–CH₄ climate balance.
Evans et al. (2021) demonstrated that effective water-table depth is a dominant control on the net climate impact of managed peatlands, with progressively shallower water tables generally reducing net warming over a substantial part of the hydrological gradient, until it is too high, resulting in excessive CH4. The relevant alternative to afforestation is therefore not necessarily “continued drainage” versus a highly flooded, CH₄-emitting peatland. Intermediate water-table regimes can substantially reduce aerobic peat oxidation without necessarily producing the highest CH₄ emissions.
This hydrological space is largely absent from the manuscript's comparison, despite the authors themselves identifying water table as an important determinant of GHG variability. A more appropriate comparison would therefore consider the CO₂–CH₄ balance across a range of water-table conditions rather than treating rewetting primarily as a discrete transition to a highly wet state.
We would like to kindly note that the hydrological aspects are addressed in the manuscript. We identify water-table level as a determinant of soil GHG emissions and discuss the need to maintain an elevated water table (lines 118–124), the effects of drought and water-table fluctuations (lines 230–247), and its role in site-specific emission estimates (lines 393–397). Our central question is whether a proposed water-table level can be achieved and maintained across a site, including during dry periods. A favourable CO₂–CH₄ balance at a specified depth does not establish the outcome of an intervention if water levels vary over time and space. In practice, some areas may become flooded while others remain more deeply drained than intended. In other words, if we have to struggle to control the water table, it undermines the relevance of water table control over GHG emissions. We can make this point more explicit, although the manuscript already discusses uncertainty in the hydrological response to rewetting.
- The manuscript states that peat-C loss after drainage “consistently decreases over time” and uses this to argue that land drained around the middle of the previous century has had time to stabilize and may therefore exhibit sustainable carbon stocks. I am not convinced that the available evidence supports such a general interpretation.
First, apparent declines in C loss with drainage age do not necessarily demonstrate that the remaining peat has become progressively less oxidizable or intrinsically more stable. It may reflect changes in peat depth and hydrology, subsidence, etc. This is particularly important because the highest emission rates reported in the literature are associated with intensively cultivated and highly degraded agricultural organic soils. It is therefore difficult to separate a true drainage-age effect from differences in land use and degree of degradation.
We reason that loss from a finite carbon stock cannot continue at its initial rate indefinitely after drainage. We do not know how quickly the loss rate changes, when it may stabilise, or what soil-carbon balance it may reach. Nevertheless, the rate cannot physically remain continuously elevated. The manuscript can emphasise this uncertainty more.
Second, the literature cited for this conclusion appears to be based on modelling rather than long-term empirical observations of individual drained peatlands. For example, Nguyen et al. (2025) provide a process-based modelling analysis of drainage-induced peat degradation, and their model is hard-coded to use progressively more recalcitrant C pools, causing less oxidation over time. They acknowledge this weakness in the paper after reviewers pointed out the issue. Similarly, Qiu et al. (2021) provide a modelling reconstruction of peatland carbon losses following conversion to cropland rather than a direct demonstration that emission rates from individual drained sites decline predictably with drainage age.
We did not attempt to establish a predictable decline in emissions at every drained peatland. We cite these studies to support the plausibility of our logic that losses from a finite carbon stock may change over time and naturally should decline, not to prove the mechanism or the time at which an individual site reaches a new balance. We apply the same caution to the modelled results of proposed Escobar et al. (2025): they are valuable for exploring a particular site and scenario but cannot, alone, establish the general outcome of afforestation. We therefore consider different model results as contributions to the discussion, subject to their assumptions and empirical support, but not as a necessary validated basis to prove a point.
Sapir et al. (2026) (https://doi.org/10.5194/bg-23-1403-2026) is particularly relevant to this question. Their long-term reconstruction shows a substantial decline in SOM and modelled losses over several decades, but their respiration measurements do not demonstrate a substantially lower respiration rate per unit SOC in the long drained material. It is therefore my view that this question of a slowed-down oxidation rate with age is an open research question, deserving of attention.
We agree that the mechanism behind declining peat-carbon losses deserves further study, and thank the referee for drawing our attention to Sapir et al. (2026). The study’s short-term aerobic incubations do not show lower respiration per unit SOC in the long-drained material. However, its historical reconstruction shows a substantial decline in SOM over 66 years, and its model estimates that total emissions were 60–85% lower after approximately 70 years. This supports our point that carbon loss should decline over time.
In general, it is common to see studies draw on concepts of persistent and labile SOM pools and progressive stabilization that are well established in mineral-soil research. I would argue that such concepts cannot easily be transferred to peat without demonstrating that the relevant mechanisms apply.
The authors should therefore be much more cautious about presenting drainage age as an independent predictor of declining emission rates.
Our argument does not require assuming that peat progressively stabilises through the same mechanisms proposed for mineral soils. It is simply that loss from a finite peat-carbon stock cannot continue at the same rate indefinitely. We agree that this does not tell us how the loss rate changes or when it changes; we can acknowledge this in the manuscript during revision.
- There is also an internal tension between the evidence presented and the sites ultimately identified as suitable for afforestation.
The manuscript notes that cooler climates and, in particular, forested nutrient-poor drained organic soils can maintain or increase their carbon stocks. Yet the proposed priority areas for afforestation include highly degraded former peatlands with elevated pH and nutrient enrichment resulting from past fertilization. If nutrient status is an important determinant of the soil-C balance, evidence from nutrient-poor drained forest soils cannot simply be used to infer that nutrient-enriched agricultural organic soils will respond in the same way.
The authors should therefore provide much stronger evidence specifically for the class of sites they propose for afforestation.
Our rationale for considering highly degraded, nutrient-enriched former peatlands for afforestation is already discussed in the manuscript (lines 99–110). Past fertilisation and elevated pH can hinder the recovery of certain peatland communities needed for C stock preservation, while conditions at nutrient-rich sites may favour forest succession despite rewetting. Rewetting nutrient-rich topsoil can also increase the risk of CH₄ emissions. Topsoil removal is sometimes proposed to address these problems, but the removal of soil must be accounted for when preserving the existing carbon stock is an objective.
These considerations make afforestation worth assessing at such sites; they do not imply that rewetting cannot reduce peat oxidation. The feasibility and total GHG balance of each option are ultimately more relevant to our climate comparison than soil-carbon preservation alone.
- Interestingly, the manuscript does acknowledge that afforestation and rewetting can be combined. I think this is an important point and potentially a much more constructive direction for the paper.
However, this possibility is largely asserted rather than evaluated. The manuscript's main framework compares afforestation with continued drainage against rewetting, while the potentially interesting intermediate or combined management options receive little attention. If the authors intend to argue that afforestation and rewetting are complementary rather than competing measures, they should explain much more clearly what this means in practice and how the climate balance would change as water tables are raised under forest cover.
For example, the authors should distinguish between continued drainage for productive forestry, partial rewetting of forested sites, and deliberate establishment of wet forest systems. These are different management strategies with potentially very different CO₂, CH₄, biomass and soil-C outcomes.
We use “complementary” primarily to mean applying afforestation and rewetting at different sites according to local conditions, not that they should routinely be combined on the same parcel. We mention wet forest establishment as a possibility, but the evidence is too limited for us to recommend a particular form of combined management or predict its GHG balance. We will leave detailed evaluation of paludisilviculture to future research rather than speculating beyond the available evidence.
Overall assessment
I find the perspective timely and potentially valuable, but the analysis stumbles. Unfortunately, I think the manuscript currently goes beyond what the evidence presented can support in several places. In particular, the case for afforestation as a climate mitigation measure on drained agricultural organic soils is stronger than the evidence synthesis appears to justify.
As an Ideas and Perspectives contribution, the manuscript is not expected to provide new empirical evidence, but its proposed perspective should nevertheless be clearly distinguished from conclusions that are supported by existing observations.
Our responses above show that the manuscript already discusses many of the issues raised, including conditions under which rewetting may be preferable. We have also identified passages that would benefit from clarification or revision. We recognise that the main issue is the statement that afforestation outcomes are “predictable and reliable”; we will revise it. We believe this and other revisions will address the referee’s principal concerns.
More generally, I would encourage the authors to distinguish more explicitly between (i) well-established effects of afforestation, such as biomass carbon accumulation, (ii) changes in the carbon balance of the pre-existing organic soil, and (iii) the net climate benefit of converting a particular drained agricultural organic soil to forest relative to realistic alternatives. These are related but not interchangeable questions. Strengthening this distinction would, in my view, make the perspective more balanced and would also clarify which conclusions are supported by the existing evidence and which represent the authors' interpretation.
We agree that these are distinct questions, and we believe the manuscript already treats them as such:
(i) We discuss carbon accumulation in tree biomass and harvested wood products as comparatively predictable and manageable, while identifying continued soil-carbon loss as an uncertainty relevant to both afforestation and rewetting.
(ii) We can clarify that the net soil-carbon balance includes inputs from new litter as well as losses of pre-existing organic matter and new litter. The available evidence does not allow these components to be quantified separately.
(iii) Estimating the climate balance of a specific site would require empirical research, which is beyond the scope of this article.
Citation: https://doi.org/10.5194/egusphere-2026-4089-AC1
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RC2: 'Comment on egusphere-2026-4089', Anonymous Referee #2, 24 Sep 2026
reply
In the manuscript, Butlers et al. aim to compare and evaluate afforestation and rewetting as climate change mitigation measures for peatlands previously drained for agriculture and peat extraction.
The work is motivated by the claim that so far rewetting has gained more attention and emphasis than afforestation and a more balanced evaluation of rewetting vs. afforestation is needed. While I pretty much agree with this claim, the authors unfortunately, instead of balanced evaluation, turn the situation around: every uncertainty concerning rewetting is seen as a problem, while every uncertainty concerning afforestation is seen as an opportunity to achieve even better results in the future. Further, as well explained with several examples by the anonymous reviewer 1, the major ideas that the authors present are not justified (neither by cited work nor by the authors’ own justifications). Instead of presenting good, theoretically sound, detailed enough mechanisms to justify their ideas, the authors rather superficially cite papers that often do not really support the ideas.
I think that reviewer 1 has convincingly enough and with several examples shown the rather fundamental problems that the manuscript has and what kind of approach could provide a way to rewrite the manuscript to answer the as such very good aims. It would be especially fruitful to really try to inspect to what extent rewetting and afforestation could be combined in the same peatland/site and in which cases they are mutually exclusive. Also it is necessary to notice that rewetting and (ecological) restoration can be different things, and rewetting is not a yes-no question but rather the intensity of rewetting could potentially be adjusted e.g. to try to support afforestation.
Below are some more specific comments (in addition to those presented by anonymous reviewer 1):
- Carbon storage in harvested wood products and substation effects are seen as game changers. While there certainly is potential to improve the current situation, there are also great challenges to improve the situation: Currently most of the harvested wood goes to short lived wood products and large proportion of wood never ends up to products but rather is lost / burned to energy during the processing (bark, saw dust, etc.). Also in the future short-lived products (like packaging) are needed and many wood fractions are hard to turn into long-lived products. And even wooden houses do not last forever, etc. Further, while wooden products can substitute e.g. steel and concrete (whose production causes large fossil emissions), wood products can also just add consumption instead of substituting other products. Also, the competing products likely can reduce their fossil footprint in the future, which can (and likely will) lead to reduced substitution effects of the wood products. Further, promoting wood produced on drained peatland has the fundamental problem that CO2 emissions due to loss of peat means that this wood has a considerable fossil carbon footprint. This means that e.g. fossil emission causing steel and concrete would be replaced by such wood that is also producing fossil-equivalent emissions. Wood grown on upland mineral soils (or on rewetted / naturally wet peatland) do not have this fundamental problem. So why produce wood on drained peatland, and especially why afforest more drained peatlands?
- Authors claim that afforestation does not promote drainage, as the targeted peat extraction areas and agricultural peatlands are already drained. While obviously this is true in the sense that currently undrained peatlands won’t be drained, typical afforestation and the following forestry strongly rely on ditch drainage to facilitate tree growth. Thus, if afforestation is encouraged/subsidized, many drained, open peatlands that otherwise might be let spontaneously rewet or would be actively rewetted, will stay drained or drainage will even be improved. Also, the tree stand itself through canopy interception and evapotranspiration substantially “biologically drains” the peatland. Thus, afforestation very likely promotes drainage and peat loss, and as explained by reviewer 1, the relatively fast cycling forest litter-derived soil carbon cannot prevent the loss of peat.
- Authors claim that afforestation and rewetting do not compete, as some sites suit well for afforestation and others well for rewetting. Surely there are sites where the only reasonable option would be afforestation (e.g. the peat layer already completely lost) or rewetting (e.g. topography prevents keeping the site dry enough for tree growth). But I would think that for most sites, both afforestation and rewetting are technically and economically possible and thus compete. E.g. in Finland so far, the vast majority of former peat extraction areas have been kept drained and quite successfully afforested (the authors claim these would rather be rewetted). Thus, if afforestation and rewetting should complement each other, I think evaluating to what extent afforestation and rewetting can co-exist on the same site would be the key question. For this evaluation, proper assessment of the (eco)hydrology of forest peatlands would be needed as a basis to address the potential of forestry in “forest paludiculture like” conditions.
Citation: https://doi.org/10.5194/egusphere-2026-4089-RC2 -
AC2: 'Reply on RC2', Aldis Butlers, 24 Sep 2026
reply
We thank Referee #2 for their assessment and valuable comments. We are pleased to note that neither referee has identified specific shortcomings in our discussion of rewetting, which is a central component of the manuscript. Regarding afforestation, we remain open to constructive suggestions for improving the presentation and interpretation of the available evidence. We believe that addressing the specific concerns raised by the referees will further strengthen the manuscript and its intended contribution .
We welcome critical feedback and remain open to suggestions that can help us improve the manuscript and strengthen its arguments. The main concern of Referee #2 appears to be the impression that we advocate afforestation even at sites where rewetting would provide greater climate mitigation benefits. This was not our intention. To resolve this misunderstanding, we propose to clarify explicitly in the manuscript that rewetting should be prioritised where it is expected to provide greater climate mitigation benefits, while afforestation should be considered where it is expected to provide a more favourable climate outcome.
We note that Referee #2 refers extensively to the concerns raised by Referee #1. We therefore kindly invite Referee #2 to consider our detailed responses to those comments, where we explain our reasoning and outline the revisions we propose. We did not interpret Referee #1's assessment as being as critical of the manuscript as Referee #2 appears to suggest. Rather, we considered many of the comments to be invitations for a scientific discussion, which we have addressed in our responses. We also recognise that Referee #1 raised several valid concerns requiring clarification or improvement, and we have proposed corresponding revisions.
Improvements identified in response to Referee #2’s comments
- Clarify that substitution benefits are conditional and may change over time.
- Clarify that where rewetting is expected to provide greater climate mitigation benefits, it should be prioritised.
- Clarify that the complementary implementation of afforestation and rewetting primarily refers to their application at different sites within the same landscape, according to site-specific conditions, rather than their coexistence on the same parcel.
- Introduce with the concept of paludisilviculture.
In the manuscript, Butlers et al. aim to compare and evaluate afforestation and rewetting as climate change mitigation measures for peatlands previously drained for agriculture and peat extraction.
The work is motivated by the claim that so far rewetting has gained more attention and emphasis than afforestation and a more balanced evaluation of rewetting vs. afforestation is needed. While I pretty much agree with this claim, the authors unfortunately, instead of balanced evaluation, turn the situation around: every uncertainty concerning rewetting is seen as a problem, while every uncertainty concerning afforestation is seen as an opportunity to achieve even better results in the future.
We thank the reviewer for this comment. As explained in the manuscript, starting from line 72, our approach deliberately places greater emphasis on aspects that we consider underrepresented in the existing discussion, particularly the uncertainties associated with rewetting. We believe that these uncertainties have received insufficient attention relative to the emphasis placed on rewetting as a climate change mitigation measure. Consequently, the manuscript devotes more space to discussing them. However, we do not believe that this constitutes an unbalanced evaluation, as the rationale for this approach is explicitly stated. Rather, our intention is to contribute to a more balanced discussion by placing greater emphasis on aspects that we consider insufficiently addressed in the existing literature and policy debate.
We would like to clarify that, in our view, not every uncertainty associated with afforestation is presented as an opportunity to achieve better results in the future. We do, however, identify areas where we consider there to be unused mitigation potential. These include improved accounting and tracking of harvested wood products, deliberate allocation of wood towards longer-lived products, improved processing efficiency, increased reuse and recycling, and reduced use of wood for short-lived energy purposes (lines 363–380).
At the same time, the manuscript identifies multiple uncertainties and limitations for which we do not propose that future developments will necessarily provide a benefit. We explicitly acknowledge the need to maintain drainage for productive tree growth and the associated concerns regarding soil-carbon loss (lines 43–49); the dependence of afforestation suitability on site-specific conditions (lines 89–110, Figure 2); uncertainties in quantifying soil-carbon stock changes, particularly the risk of continued carbon loss under maintained drainage and the greater risk associated with nutrient-rich organic soils (lines 192–210); the uncertain effects of forest operations on soil GHG emissions (lines 265–274); and the effects of natural disturbances on biomass accumulation (lines 327–330). Furthermore, we discuss limitations in quantifying and retaining carbon in harvested wood products, including uncertainties associated with their use, reuse and eventual oxidation (lines 335–350). We also acknowledge the wide range of substitution effects (lines 350–355) and the tendency of HWP carbon stocks to approach equilibrium under constant harvesting and wood-use practices (lines 363–365).
We therefore do not consider afforestation-related uncertainties exclusively as opportunities for greater future benefits. Rather, we distinguish between genuine limitations and risks, and areas where current management, accounting or wood-use practices leave scope for improvement.
Further, as well explained with several examples by the anonymous reviewer 1, the major ideas that the authors present are not justified (neither by cited work nor by the authors’ own justifications). Instead of presenting good, theoretically sound, detailed enough mechanisms to justify their ideas, the authors rather superficially cite papers that often do not really support the ideas.
Unfortunately, it is difficult to address this general concern without references to specific manuscript passages or claims that the referee considers insufficiently justified. Referee #1 identified two specific references whose use was questioned. We have addressed both concerns in our responses to Referee #1 and explained why we consider our interpretation and use of these references appropriate. We therefore kindly invite Referee #2 to consider those responses.
We recognise that not every element of our reasoning is supported by a specific reference. However, our arguments are grounded in the available scientific evidence and developed through theoretically sound reasoning based on established principles of ecosystem carbon dynamics. Or in referees' words, theoretically sound ideas are our own justification. As an Ideas and Perspectives contribution, the manuscript is also intended to stimulate scientific discussion and offer interpretations of the existing evidence, rather than merely summarise previously published conclusions.
We welcome specific examples of claims that the referee considers unsupported or theoretically unsound, so that we can assess whether additional references, clarification of the underlying mechanisms, or revisions to our arguments are necessary.
I think that reviewer 1 has convincingly enough and with several examples shown the rather fundamental problems that the manuscript has and what kind of approach could provide a way to rewrite the manuscript to answer the as such very good aims.
Referee #1 raised several concerns, which we have addressed individually (step by step) in our responses. We have also identified several valid points where the manuscript would benefit from clarification, additional evidence or revision, and have proposed corresponding improvements. However, we do not consider these concerns to challenge the fundamental arguments of the manuscript, as we believe they can be addressed through targeted revisions without substantially altering its structure or central message. We therefore kindly invite Referee #2 to consider our detailed responses and proposed revisions before concluding that the manuscript requires fundamental restructuring. We believe that the identified improvements can adequately address the concerns raised.
It would be especially fruitful to really try to inspect to what extent rewetting and afforestation could be combined in the same peatland/site and in which cases they are mutually exclusive.
We agree that combining afforestation and rewetting within the same site is an interesting possibility. However, paludisilviculture (https://urn.fi/URN:ISBN:978-952-419-167-8) is a relatively new concept, and we consider the available evidence insufficient for a detailed assessment of its climate mitigation potential under different site conditions. Nevertheless, we can introduce the concept of paludisilviculture in the manuscript and refer to the available literature, acknowledging its potential as an alternative management approach that combines forest establishment with elevated water-table conditions. A detailed evaluation of the hydrological requirements, forest productivity and associated GHG balance of such systems would require further research and is beyond the scope of this perspective.
Also it is necessary to notice that rewetting and (ecological) restoration can be different things, and rewetting is not a yes-no question but rather the intensity of rewetting could potentially be adjusted e.g. to try to support afforestation.
We agree with the referee that rewetting and ecological restoration are distinct interventions and that rewetting can be implemented to varying degrees, including in combination with afforestation. As discussed in our response to Referee #1, we have identified opportunities to clarify how we treat restoration within the scope of our perspective, and we proposed corresponding revision to the manuscript.
Below are some more specific comments (in addition to those presented by anonymous reviewer 1):
Carbon storage in harvested wood products and substation effects are seen as game changers. While there certainly is potential to improve the current situation, there are also great challenges to improve the situation: Currently most of the harvested wood goes to short lived wood products and large proportion of wood never ends up to products but rather is lost / burned to energy during the processing (bark, saw dust, etc.). Also in the future short-lived products (like packaging) are needed and many wood fractions are hard to turn into long-lived products. And even wooden houses do not last forever, etc. Further, while wooden products can substitute e.g. steel and concrete (whose production causes large fossil emissions), wood products can also just add consumption instead of substituting other products. Also, the competing products likely can reduce their fossil footprint in the future, which can (and likely will) lead to reduced substitution effects of the wood products. Further, promoting wood produced on drained peatland has the fundamental problem that CO2 emissions due to loss of peat means that this wood has a considerable fossil carbon footprint. This means that e.g. fossil emission causing steel and concrete would be replaced by such wood that is also producing fossil-equivalent emissions. Wood grown on upland mineral soils (or on rewetted / naturally wet peatland) do not have this fundamental problem. So why produce wood on drained peatland, and especially why afforest more drained peatlands?
The challenges associated with HWP carbon storage mentioned by the referee are acknowledged in lines 349–350, where we state that, depending on the life cycle, HWP carbon stocks are ultimately returned to the atmosphere and only a fraction accumulates in long-term sinks across multiple forest management cycles. We also discuss limitations in quantifying HWP carbon storage and tracking product use and reuse (lines 335–345). Regarding substitution effects, we present the range of estimated benefits in lines 350–355. We can expand this discussion to acknowledge explicitly that substitution benefits may decline as the carbon footprints of the products being substituted decrease.
The rationale for considering afforestation as a mitigation option is discussed throughout the manuscript, Briefly, agricultural organic soils and former peat extraction sites already exist, and different management options are available to reduce their associated GHG emissions. We discuss rewetting and afforestation because both may reduce emissions relative to the current land use, although their outcomes depend on site-specific conditions (lines 89–110 and 255–315). We consider afforestation a potentially reasonable option in specific cases, particularly where rewetting is not feasible or is unlikely to achieve its intended outcomes (lines 99–110 and 150–155; Fig. 2).
Authors claim that afforestation does not promote drainage, as the targeted peat extraction areas and agricultural peatlands are already drained. While obviously this is true in the sense that currently undrained peatlands won’t be drained, typical afforestation and the following forestry strongly rely on ditch drainage to facilitate tree growth. Thus, if afforestation is encouraged/subsidized, many drained, open peatlands that otherwise might be let spontaneously rewet or would be actively rewetted, will stay drained or drainage will even be improved. Also, the tree stand itself through canopy interception and evapotranspiration substantially “biologically drains” the peatland. Thus, afforestation very likely promotes drainage and peat loss, and as explained by reviewer 1, the relatively fast cycling forest litter-derived soil carbon cannot prevent the loss of peat.
Our argument is not that afforestation should be promoted at the expense of rewetting (we will highlight this when revising) or that maintaining drainage has no consequences for peat-carbon loss. Rather, we argue that afforestation and rewetting should be considered complementary measures at the regional scale, with their implementation depending on site-specific conditions (lines 89–96; Fig. 2). Where rewetting is the more appropriate measure, it should be implemented. Where rewetting is not feasible or is unlikely to achieve its intended outcomes, we consider afforestation a credible alternative (lines 99–110 and 150–155).
This consideration is particularly relevant to organic soils that have undergone long-term intensive agricultural cultivation and substantial degradation, resulting in the loss of peat and changes in soil properties (lines 99–105 and 165–190). In some cases, these soils may approach the classification threshold between organic and mineral soils. We consider it important to assess afforestation as a potential mitigation option for such sites rather than assuming that rewetting is necessarily the more appropriate intervention.
We acknowledge that afforestation may require continued drainage and that this can result in further peat-carbon loss. Indeed, the manuscript explicitly identifies continued soil-carbon loss under maintained drainage as the principal uncertainty associated with afforestation (lines 207–210). Our argument is therefore not that afforestation prevents peat oxidation, but that its overall climate mitigation potential should be assessed relative to the existing land use and other feasible management options, accounting for both soil GHG emissions and carbon accumulation in biomass and harvested wood products.
Authors claim that afforestation and rewetting do not compete, as some sites suit well for afforestation and others well for rewetting. Surely there are sites where the only reasonable option would be afforestation (e.g. the peat layer already completely lost) or rewetting (e.g. topography prevents keeping the site dry enough for tree growth).
We welcome the referee’s acknowledgement that there are sites where afforestation may be well suited. We were therefore somewhat surprised by the referee’s earlier question of why additional drained organic soils should be afforested, as the present comment recognises precisely the type of circumstances in which we consider afforestation a reasonable alternative.
But I would think that for most sites, both afforestation and rewetting are technically and economically possible and thus compete. E.g. in Finland so far, the vast majority of former peat extraction areas have been kept drained and quite successfully afforested (the authors claim these would rather be rewetted).
We agree that afforestation or reforestation may be technically feasible across much of the land area considered in our manuscript. However, technical feasibility alone does not establish which measure is more appropriate for a particular site. Our perspective invites to identify the conditions under which rewetting or afforestation may provide more suitable climate mitigation outcomes, rather than treating the technical possibility of implementing either measure as sufficient justification for its selection.
We recognise that our statement that afforestation and rewetting do not compete may be too categorical, since both measures can be technically feasible at the same site. Our intended argument is that they should be considered complementary at the regional scale, with site-specific conditions informing the selection of the more appropriate measure. In particular, we do not advocate afforestation at sites where rewetting is feasible and can achieve the intended climate mitigation objectives. Rather, we consider afforestation a potential alternative where rewetting is not feasible or is unlikely to achieve those objectives.
We can clarify what we mean by the complementary implementation of afforestation and rewetting.
Thus, if afforestation and rewetting should complement each other, I think evaluating to what extent afforestation and rewetting can co-exist on the same site would be the key question. For this evaluation, proper assessment of the (eco)hydrology of forest peatlands would be needed as a basis to address the potential of forestry in “forest paludiculture like” conditions.
We use the term complementary primarily to refer to the implementation of afforestation and rewetting at different sites within the same landscape, according to site-specific conditions, rather than their coexistence on the same parcel. This meaning is already stated in lines 89–96, where we refer to the complementary implementation of both measures at the regional scale. We recognise, however, that our wording could be clearer and will revise the manuscript to make this distinction explicit. The potential for combining forestry and rewetting on the same site, including under paludisilviculture-like conditions, is an interesting topic that we consider beyond the scope of a detailed assessment in this perspective, but mention such scenario.
Citation: https://doi.org/10.5194/egusphere-2026-4089-AC2
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Figure 5 contains relevant information, but the simultaneous use of stacked areas, colours for land-use categories and hatching for countries makes some of the individual contributions difficult to identify. The authors could consider presenting Denmark, Ireland and Latvia in separate panels (e.g. Fig. 5A–C), while retaining the same colours and y-axis scale to facilitate comparison.
It is also not entirely clear whether “Cropland”, “Forest Land”, “Grassland” and “Wetlands” refer to the land use prior to rewetting or to the land-use categories under which the rewetted areas are reported in the national GHG inventories. This distinction should be stated explicitly in the caption or accompanying text.
As the manuscript discusses both agricultural organic soils and former peat-extraction sites, could the authors clarify whether former peat-extraction areas can be identified separately in the underlying inventory data? If such separation is not possible, it would be useful to state this limitation and explain under which land-use category these areas are reported.