Peatland Drainage Research Articles

Fate of methane in canals draining tropical peatlands.

Tropical wetlands and freshwaters are major contributors to the growing atmospheric methane (CH4) burden. Extensive peatland drainage has lowered CH4 emissions from peat soils in Southeast Asia, but the canals draining these peatlands may be hotspots of CH4 emissions. Alternatively, CH4 oxidation (consumption) by methanotrophic microorganisms may attenuate emissions. Here, we used laboratory experiments and a synoptic survey of the isotopic composition of CH4 in 34 canals across West Kalimantan, Indonesia to quantify the proportion of CH4 that is consumed and therefore not emitted to the atmosphere. We find that CH4 oxidation mitigates 76.4 ± 12.0% of potential canal emissions, reducing emissions by ~70 mg CH4 m-2 d-1. Methane consumption also significantly impacts the stable isotopic fingerprint of canal CH4 emissions. As canals drain over 65% of peatlands in Southeast Asia, our results suggest that CH4 oxidation significantly influences landscape-scale CH4 emissions from these ecosystems.

Ditch emissions partially offset global reductions in methane emissions from peatland drainage

Peatlands are globally important carbon sinks but are frequently drained. Drainage activities reduce overall methane emissions; however they are often accompanied by the construction of ditches, which are potential methane emission hotspots. Yet, the offsets of methane emissions from creating ditches in peatlands under different climate zones and land-use types remain unclear. Here we conducted a global meta-analysis by compiling annual methane emissions from paired near-pristine peatlands and terrestrial portion of drained peatlands and ditches to address this issue. Results showed that ditches occupy approximately 3.8 (95% confidence interval: 3.1~4.4)% of all drained peatlands. Ditches emit 695 (511~898) kg ha−1 yr−1 methane overall, with the highest emissions observed in (sub)tropics. Globally, ditch emissions offset approximately 12 (10~14)% for reductions in methane emissions from peatland drainage. Our findings demonstrate the importance of including ditch methane emissions to quantify emission factors for regional to global peatlands affected by drainage.

Application of SWAT to assess peatland forestry impacts on water quality

ABSTRACT Peatland drainage can affect the natural state of hydrological conditions and nutrient loading but is rarely included in catchment-scale models. To understand the gap, we aimed to use the soil and water assessment tool (SWAT) model to observe drained peatlands and their properties to predict nutrients and suspended solids (SS) in the peatland-dominated Simojoki catchment. We integrated drainage networks in SWAT to (i) identify the parameters for the drainage; (ii) determine annual loads and mean concentrations of SS, organic phosphorus (Org-P), total phosphorus (TP), organic nitrogen (Org-N), and total nitrogen (TN); (iii) understand spatial variation of nutrients and SS; and (iv) investigate the uncertainty ranges for the estimates. The calibrated SWAT model showed a 9.6% PBIAS between the simulated flow and the observations with low to medium loading variations for the water quality parameters. For Org-N and TN, the highest loading per year was at the downstream outlet, whereas for SS, Org-P, and TP, it was higher at the upstream outlet of the catchment. This approach of representing the drained peatland in SWAT indicated a maximum spatial distributed load in the peat soil in the clear-cut area and it can be beneficial in future hydrological modelling efforts in identifying the status of nutrients or SS.

Shallow drainage of agricultural peatlands without land-use change: have your peat and eat it too

IntroductionDrainage for agricultural purposes is one of the main drivers of peatland degradation, leading to significant greenhouse gas (GHG) emissions, biodiversity loss, and soil eutrophication. Rewetting is a potential solution to restore peatlands, but it generally requires a land-use shift to paludiculture or nature areas.MethodsThis study explored whether three different water level management techniques (subsoil irrigation, furrow irrigation, and dynamic ditch water level regulation) could be implemented on dairy grasslands to yield increases in essential ecosystem services (vegetation diversity and soil biogeochemistry) without the need to change the current land use or intensity. We investigated vegetation diversity, soil biogeochemistry, and CO2 emission reduction in fourteen agricultural livestock pastures on drained peat soils in Friesland (Netherlands).ResultsAcross all pastures, Shannon-Wiener diversity was below 1, and the species richness was below 5. The plant-available phosphorus (P) was consistently higher than 3 mmol L−1. None of the water level management (WLM) techniques enhanced vegetation diversity or changed soil biogeochemistry despite a notable increase in water table levels. The potential for CO2 emission reduction remained small or even absent. Indicators of land-use intensity (i.e., grass harvest and fertilization intensity), however, showed a strong negative correlation with vegetation diversity. Furthermore, all sites’ total and plant-available P and nitrate exceeded the upper threshold for species-rich grassland communities.DiscussionIn conclusion, our research suggests that incomplete rewetting (i.e., higher water tables while maintaining drainage) while continuing the current land use does neither effectively mitigate GHG emissions nor benefit vegetation diversity. Therefore, we conclude that combining WLM and reducing land-use intensity is essential to limit the degradation of peat soils and restore more biodiverse vegetation.

Examining the Ecosystem-Scale GHG Exchange Following the Acrotelm Harvesting Method (ACM) in Eastern Quebec

Traditional horticultural peat production involves the removal of vegetation and drainage of peatlands, resulting in significant ecological disturbances and greenhouse gas (GHG) emissions. The Acrotelm Harvesting Method (ACM) was developed as a more sustainable alternative, designed to reduce these impacts by allowing peat extraction without large-scale ecosystem alterations. However, the ACM still necessitates the passage of machinery over the peat, potentially disturbing surface vegetation and altering the carbon dynamics. My project, based at a field site near Baie-Comeau, QC, represents the first comprehensive assessment of the ACM’s impact on net ecosystem exchanges of main GHGs. I focused on evaluating the ecosystem-scale effects by analyzing data collected from paired eddy covariance towers installed at both the control (unharvested) and harvested sites. These towers provide temporally continuous, spatially integrated flux measurements. Preliminary findings indicate that the site subjected to ACM exhibits altered surface topography, leading to overall wetter conditions, compaction of hummocks, and vegetation damage. These changes have resulted in reduced carbon dioxide uptake and increased methane emissions at the harvested site. Through the analysis and interpretation of this data, my research contributes to a better understanding of the ACM’s environmental impact and its potential as a sustainable peatland management strategy. This research was conducted under the supervision of Dr. Ian Strachan in the Atmospheric Environmental Research (AER) lab.

Potential for large losses of carbon from non-native conifer plantations on deep peat over decadal timescales

Peatland drainage is a large source of anthropogenic CO2 emissions. While conversion to agriculture is widely acknowledged to lead to “irrecoverable” carbon (C) losses, in contrast the C impacts of peatland forestry are poorly understood, especially in intensively managed plantations. Losses of C from peat oxidation are highly variable and can be compensated for by gains of C in trees, depending on the lifecycle of the timber and timescale considered. Here, we used ITRAX scanning to enable rapid detection of the Hekla 4 cryptotephra layer as a reliable chronological marker above which peat properties and C stocks could be compared between open and afforested blanket bog cores in the Flow Country of Northern Scotland. At one site, Bad a’ Cheò, we combine replicated core pair comparisons (n = 19) with timber extraction data to derive net ecosystem C balance over the lifetime of the plantation. Here the reduction in peat C carbon storage above Hekla 4 in afforested samples (67 t C ha−1) is only partially compensated by tree C sequestration (47 t C ha−1), leading to a net ecosystem C balance indicating a loss of 20 t C ha−1 over the 50 years since the plantation was established. At that site, ∼65 % of tree C rapidly returned to the atmosphere, as it was primarily used for heat and power generation. Across the wider Flow country region, a simplified paired sampling method was adopted at eight further sites, finding a either a loss or negligible change in peat C storage above Hekla 4 in afforested samples with a mean loss of 86 t C ha−1 and median loss of 50 t C ha−1. This study suggests that potentially substantial C losses have been an unintended consequence of non-native conifer afforestation over deep blanket bogs.

Assessing the effects of drainage and forest structure on presence and absence of fledglings of boreal grouse

Anthropogenic factors threaten biodiversity of natural habitats globally, including boreal forest habitats of culturally important game species, such as grouse. Forestry and intense draining of wetlands have resulted in landscape fragmentation of the peatlands and the forests in terms of their structure (a mosaic of differently managed small stands), and the loss and alteration of natural grouse habitats, which impacts on fitness parameters are still partly unexamined. We used grouse brood location data from the Finnish wildlife triangle censuses from 2017 to 2020 to study how forest structure and drainage affect breeding success of four grouse species. We calculated environmental characteristics (forest and landscape structure, peatlands and their drainage status) around individual brood observations with different buffer sizes and used them to explain brood size variation and the probability of complete failure (female with no brood). While the most important buffer zones differed by species, brood sizes were generally linked to habitats that offer shelter and food. Black grouse brood size increased when the proportions of deciduous trees and xeric heath forests increased. Hazel grouse broods were largest in spruce-dominated mires and herb-rich forests. Willow grouse brood size decreased with increasing proportion of poorer barren heath forest habitat. Capercaillie brood size decreased as a function of drainage ditch length. In Capercaillie and Black grouse, females without broods were overrepresented (zero-inflation), and the zero excess was related to habitats that differed from those of brooded females. These results suggest that forest management methods and peatland drainage can have a negative effect on offspring production of boreal grouse species. Restoration of natural peatlands and less invasive management such continuous cover forestry should enhance environmental conditions for grouse.

Drainage induced carbon nitrogen loss and microbial community change were closely related and hard to be restored in subsurface peat

The artificial drainage and climate drying induced water table decline has resulted in large peat carbon and nitrogen (C&N) loss in peatlands, however, the effects of water table decline on C&N and microbe dynamics at different peat depths are not clear, as well as the effects of plant change and the restoration effects of rewetting. Here we selected a series of sites from undrained (NP), moderate-drained (MDP), deep-drained (DDP) to rewetted (RP) peatlands to study the variations in plants, C&N sequestration, stable isotopic abundances (δ13C and δ15N) and microbial communities at different depths. We found peatland drainage caused moderate degradation in the plant community, and litter greatly preserved the C&N in the 0–10/20 cm peat. Changes in C&N contents, δ13C and δ15N showed MDP had serious C&N loss in both the surface and part of subsurface peat (0-50 cm), and DDP caused more significant C&N loss in the subsurface peat (30-70 cm) than the surface peat (0-30 cm). Drainage changed the bacterial composition: oligotrophs (Acidobacteria) mostly increased, while copiotrophs (Proteobacteria and Bacteroidetes) mostly decreased. The stronger drainage the severer microbe changes, with serious changes in the subsurface peat rather than the surface peat; bacterial metabolic pathways exhibited similar patterns, and the changed pathways were mostly related to C&N metabolism. Long-term rewetting restored the surface C&N contents, δ13C and δ15N to the NP level with plant and litter recovery, whereas, the C&N contents and most of δ13C and δ15N in the subsurface peat were still significantly different from NP. RP had similar bacterial composition, diversity and metabolic pathways as NP in the surface peat, but the similarities between the subsurface microbes were very low. In addition, the taxonomic change, Shannon and Simpson indices of bacterial communities were significantly correlated with peat C&N dynamics during drainage and rewetting, and there were nine phyla dominantly relating to the peat C&N dynamics. Thus, the drainage caused C&N loss and microbial degradation were closely related, which were hard to be restored in the subsurface peat by the long-term rewetting. These indicated the peatlands with severe drainage or drying may consequently lose the stably restored subsurface C&N for a long-term and may have important implications with respect to climate change.

Mining impacts peatland hydrology reducing discharge and water storage volumes

Peatlands cover about 3% of the Earth’s land surface, but are the largest terrestrial carbon store and are important for freshwater storage. In Australia, nationally protected peatlands (called upland swamps) exist in the catchment headwaters for Sydney’s drinking water supply. In this region, longwall mining of underground coal seams can result in subsurface fracturing, land subsidence, and, potentially, peatland drainage. This study presents the water balance modelling results for an upland peat swamp before and after it was undermined in 2020. Following a detailed field campaign, a conceptual lumped hydrology model was developed to estimate the local water balance, with a Nash Sutcliffe Efficiency of 0.85 for the modelled storage of the intact swamp. After undermining, the water balance of the swamp changed, with higher deep seepage rates and reduced surface water discharge rates. For the first time, these findings detail the hydrologic effects of longwall mining on peatland environments. Based on these findings, broader catchment management initiatives are recommended to prevent or limit further water extraction from upland swamps, including incidental water losses associated with subsidence.

Green-house gas fluxes and soil microbial functional genes abundance in saturated and drained peatlands in South-West Iceland

The drainage of peatlands followed by land use conversion significantly impacts on the fluxes of green-house gases (GHGs, i.e. CO2, CH4, and N2O) to and from the atmosphere, driven by changes in soil properties and microbial communities.In this study, we compared saturated peatlands with drained ones used for sheep grazing or cultivated, which are common in South-West Iceland. These areas exhibit different degrees of soil saturation and nitrogen (N) content, reflecting the anthropic pressure gradient.We aimed at covering knowledge gaps about lack of estimates on N2O fluxes and drainage, by assessing the emissions of GHGs, and the impact of land conversion on these emissions. Moreover, we investigated soil microbial community functional diversity, and its connection with processes contributing to GHGs emission.GHGs emissions differed between saturated and drained peatlands, with increased soil respiration rates (CO2 emissions) and N mineralization (N2O), consistent with the trend of anthropogenic pressure. Drainage drastically reduced methane (CH4) emissions but increased CO2 emissions, resulting in a higher global warming potential (GWP). Cultivation, involving occasional tillage and fertilization, further increased N2O emissions, mediated by higher N availability and conditions favorable to nitrification. Functional genes mirrored the overall trend, showing a shift from prevalent methanogenic archaea (mcrA) in saturated peatlands to nitrifiers (amoA) in drained-cultivated areas.Environmental variables and nutrient content were critical factors affecting community composition in both environments, which overall affected the GHGs emissions and the relative contribution of the three gases.

Unlocking the potential of peatlands and paludiculture to achieve Germany’s climate targets: obstacles and major fields of action

Greenhouse gas emissions from drained peatlands must be substantially reduced to meet climate mitigation targets. In Germany, annual peatland emissions of 53 Mt CO2e account for more than 7% of total national GHG emissions. Peatland drainage and reclamation is traditionally considered as a symbol of progress and technical achievement, where agriculture has been the major driver. In Germany, an area of 1.3 million ha of drained peatlands used for agriculture ought to be rewetted by 2050 to meet the 1.5°C target of the Paris Agreement. Paludiculture allows a productive use of wet peatlands instead of abandonment following rewetting. This approach might therefore pave the way for voluntary large-scale peatland rewetting. However, implementation remains scarce. The long history and large extent of peatland drainage has shaped the political and legal framework as well as perceptions and attitudes, thus impeding rewetting and climate-friendly peatland use. This policy and practice review investigates the political, legal, economic and social aspects that hinder the implementation in Germany and derives approaches to overcome multifold restrictions. Finally, three major fields of action are identified: (1) To increase and accelerate rewetting, a consistent peatland mainstreaming approach is needed that overcomes structural barriers and adapts the policy and legal framework, e.g., the Common Agricultural Policy, planning law, water law and nature conservation law. (2) To motivate for a rapid transition, a system of immediate, comprehensive and attractive positive incentives is needed. This should be accompanied by early announcement and gradual introduction of negative incentives to set a clear course and provide planning certainty for farmers and landowners. (3) A just transition depends on empowering local communities to develop and pursue perspectives tailored to their peatland region. Future research of peatlands as social-ecological systems can help to identify region-specific drivers for sustainable peatland management.

Lowland Tropical Peatlands – A Brief Review of Their Important Role in the Global Carbon Cycle and Biodiversity Support

Tropical peatlands are crucial ecosystems, storing vast carbon reserves and supporting rich biodiversity. Despite covering a small land area, they play significant roles in global carbon cycling and climate regulation. However, these ecosystems face escalating threats from human activities, including agricultural expansion and peatland drainage. This paper provides a concise overview of tropical peatlands, focusing on their distribution, characteristics, and ecological importance in Southeast Asia, Africa, and South America. It highlights the diverse vegetation communities and notable animal species found in peat swamp forests, underscoring their conservation value. Peatland degradation leads to increased greenhouse gas emissions, land subsidence, and loss of traditional livelihoods for local communities. Addressing these challenges requires integrated approaches, including conservation efforts to protect and restore intact peat swamp forests, sustainable land-use practices, and policy interventions to regulate land management. Research collaboration between scientists, policymakers, and local communities is essential for developing evidence-based conservation strategies. By prioritizing the preservation of tropical peatlands, we can mitigate climate change impacts, conserve biodiversity, and safeguard the well-being of local communities.

Browning from headwaters to coastal areas in the boreal region: Trends and drivers

Browning of freshwaters, mainly caused by increased terrestrial organic carbon loading, has been widely studied during the last decades. However, there are still uncertainties regarding both the extent of browning in different aquatic ecosystems and the actual importance of different driving forces and mechanisms. To refine understanding of the extent and causes of browning and its temporal variation, we gathered a comprehensive dataset including 746 Finnish water quality monitoring stations representing various waterbody types: streams, rivers, lakes, and coastal waters. Monotonic trend analyses revealed that TOC concentrations increased in all waterbody types during the study period from 1990 to 2020, whereas non-linear trends indicated that upward trends in TOC concentrations have substantially decreased since the mid-2000s. However, despite the upward trends levelling off, non-linear analyses also indicated decreases in TOC concentrations at only a few stations. As a result, the TOC contents of the majority of Finnish waterbody types in 2020 were at a higher level than in 1990. To examine the driving forces of increasing TOC concentrations, we selected 100 riverine catchments and linked the detected trends to 24 different drivers, including both hydrometeorological and catchment characteristics. The increased TOC concentrations in surface waters could be connected to diverse human impacts: hydrometeorological variables impacted by climate change, decreased acidic deposition, and land use in terms of peatland drainage. The importance of increased temperatures was emphasized, and its role as a driver of increased leaching of organic carbon in the forthcoming years is expected to grow with climate change.

Value chain analysis for community livelihoods in peatlands: A case study in Southern Riau

Many of the Indonesian peatlands have been cleared of forest, then drained and burned for both large- and small-scale agricultural crop development. This has resulted in regular occurrences of haze from peatland fires during the dry season. Peatlands have long been a livelihood source providing up to 80% of earnings for nearby local communities. Nevertheless, many such communities apply unsustainable practices involving the use of fire for land preparation and drainage of wet healthy peatland ecosystems. For that reason, haze-free sustainable livelihoods need to be found immediately. This research analysed commodities traded in local markets as well as those with the potential for trade that could be grown in targeted villages. We collected data through market observations, focus group discussions and key informant interviews in nine targeted villages. Using Value Chain Analysis (VCA) methods, we analysed and assessed each commodity for their value chain distribution and governance, and power relations. The results of these assessments indicate that pineapple, areca nut, honey and fish are financially viable for generating income throughout the year and have fewer environmental impacts. These commodities have potential for consideration as alternatives in lieu of oil palm, which requires peatland drainage and often use of fire.

Response of C:N:P stoichiometry to long-term drainage of peatlands: Evidence from plant, soil, and enzyme

Drought induced by climate warming and human activities regulates carbon (C) cycling of peatlands by changing plant community composition and soil properties. Estimating the responses of peatlands C cycling to environmental changes requires further study of C: nitrogen (N): phosphorus (P) stoichiometric ratios of soil, plants, and enzyme activities. However, systematic studies on the stoichiometry of above-ground and below-ground ecosystems of peatlands post drainage remain scarce. This study compared stoichimetric ratios of plant and soil and stoichimetric ratios of enzyme activities with different functions in two different parts of a minerotrophic peatland, a natural undisturbed part and a part that had been drained for almost 50 years, in Northern China. For the shrub plants, the average C:N:P ratios of leaf in natural and drained peatland were 448:17:1 and 393:15:1, respectively. This indicated that the growth rate of shrub plants is higher in the drained peatland than in the natural peatland, which makes P element more concentrated in the photosynthetic site. However, from the perspective of the dominant plant, the mean C:N:P ratio of Carex leaf was 650:25:1 in the natural peatland, but was 1028:50:1 for Dasiphora fruticosa in drained peatland. This indicated that the intensification of P-limitation of plant growth after drainage. Soil C:N:P ratios of above water table depth (AWT) were 238:15:1 and 277:12:1, but were 383:17:1 and 404:19:1 for below water table depth (BWT) in the natural and the drained peatland, respectively. Soil C:P ratios were greater than the threshold elemental ratio of C:P (174:1), but the soil C:N ratios were less than the threshold elemental ratio of C:N (23:1), which suggested that P was the most limiting nutrient of soil. The soil microbial activities were co-limited by C&P in Baijianghe peatlands. However, the microbial metabolic P limitation was intensified, but the C limitation was weakened for the above water table depth soil after long-term drainage. There are connection between plant-microbe P limitation in peatlands. The P limitation of microbial metabolism was significant positively correlated with soil C:N but negatively with soil moisture. The increase in the lignocelluloses index suggested considerable decomposition of soil organic matter after peatland drainage. These results of stoichiometric ratios from above- to below ground could provide scientific base for the C cycling of peatland undergone climate change.

Influence of water color and catchment lake cover on stream macroinvertebrate communities: Ecological insights into browning effects

Browning of streams due to increased export of dissolved organic carbon (DOC) and iron has been observed in vast areas of the northern hemisphere with likely adverse ecological effects. Lake basins in stream catchments can moderate DOC export and influence stream communities, which complicates understanding of the effects of DOC. In this study, we explored the independent and interactive effects of water color (proxy for DOC and iron) and catchment lake cover on benthic macroinvertebrate communities in 94 medium-sized boreal forest streams. We first investigated the role of lake basins and other catchment characteristics in controlling water color. We then studied the effects of water color and catchment lake cover on macroinvertebrate community composition, biodiversity, and functional feeding traits. Water color correlated negatively with catchment lake cover, whereas the correlation with peatland cover and drainage intensity was positive. PERMANOVA and GLS analyses indicated that both color and catchment lake cover had a distinct independent effect on invertebrate community composition and community attributes, without significant interactions. Color had an independent negative effect on EPT (Ephemeroptera, Plecoptera, Trichoptera) taxa richness irrespective of lake cover. Increasing water color had negative effect on relative abundance of grazer, but no significant effect on shredder trait, while lake cover had a negative effect on both of the traits. Lake cover exhibited a negative influence on collector-gatherers, and a positive effect on filter feeders, while the predators were positively affected by both factors. The results highlight that water color influences the community structure of boreal stream ecosystems, and the effects are similar regardless of catchment lake cover. Mitigation measures should be emphasized, aimed at reducing DOC and iron runoff, in land use planning and river basin management.

Pengaruh Jarak Saluran Drainase Terhadap Suhu Dan Kelembaban Tanah Di Desa Teluk Empening Kecamatan Terentang Kabupaten Kubu Raya

Changes in land use in Teluk Empening have an impact on recovering infiltration capacity, loss of land cover, forest fires and drainage of peatlands, which can affect the climate. This research was conducted to determine the effect of drainage channels on the microclimate in rubber fields. The Mann Whitney test was carried out with the results that it can be concluded that there is no significant difference between the distance of the drainage canal and the high groundwater table in peatlands designated for rubber fields. Measurement of soil temperature and moisture showed that the temperature of the rubber plantation is close to drainage then the soil moisture is dry and if the measurement is far from drainage it indicates wet soil moisture. The ground water level obtained ranges from 29 – 64.5 cm which is influenced by the tides of the drainage channel in the morning and evening. At a distance of 20 m from the drainage canal, the groundwater level is higher than the measurements made at a distance of 100 m. This shows that the existence of drainage has a direct impact on changes in suhu and temperature of the soil

Sensitivity of varve biogenic component to climate in eastern and central Finland

Biogenic varves as well as the biogenic component of clastic–biogenic varves have great potential as climate and environmental proxies but the response of biogenic lamina thickness to variations in growing-season climate is not well known. The connection of biogenic lamina thickness with growing-season or open-water season climate has been the focus of a limited number of studies. We examined biogenic laminae deposited during the past 100 years in five Finnish lakes representing different catchment types. We compared variations in biogenic lamina thicknesses with growing-season temperature records and open-water-season precipitation records. Statistical analyses for the whole study period reveal that the studied lakes generally respond positively to variations in growing-season temperature and open-water season precipitation. This suggests that warm summers intensify primary production while precipitation enhances transportation of allochthonous biogenic material and nutrients into the lake. Both mechanisms lead to enhanced biogenic lamina thickness. Two lakes reveal a more complex relationship to climate. Biogenic lamina thicknesses record a distinguishable climate signal despite human activities in the catchments, such as peatland drainage and forest cutting. We conclude that variations in biogenic lamina thickness of such boreal (clastic)–biogenic varves show potential for growing-season climate reconstructions. However, the response of each lake to climate parameters should be tested and understood separately.

Downstream impacts of peatland drainage on headwater stream biodiversity and ecosystem functioning

Intensive peatland drainage alters the physico-chemical status of the recipient streams, potentially leading to the loss of biodiversity and impaired ecosystem functioning. However, the extent of these changes, and particularly their impacts on downstream ecosystems, remain poorly understood. We studied the downstream effects of peatland drainage on stream biodiversity (aquatic bryophytes and macroinvertebrates) and key ecosystem processes (primary productivity, organic matter (OM) decomposition and OM standing stock). Our survey design comprised upstream (directly below drainage network) and downstream (∼300 m downstream) locations in 18 boreal headwater streams encompassing an extensive gradient of peatland drainage intensity (0–48 %). Drainage modified environmental conditions, with nutrient (TP, TN) and dissolved organic carbon (DOC) concentrations and inorganic sediment cover increasing with intensifying drainage, in both upstream and downstream sites. Species richness of both benthic macroinvertebrates and bryophytes was strongly reduced with increasing drainage intensity. Upstream and downstream sites responded in a similar manner, suggesting wide-ranging impacts of drainage on stream biodiversity. Regardless of site location, ecosystem processes were unrelated to drainage intensity. Our results confirm that intense peatland drainage not only modifies environmental conditions and biodiversity in adjoining streams, but these impacts propagate further downstream in the stream network. To prevent further degradation of drainage-impacted freshwater ecosystems, large-scale peatland restoration is needed, with prioritization of sites with the greatest potential (least drainage-induced damage) for biodiversity recovery.

The role of peatland degradation, protection and restoration for climate change mitigation in the SSP scenarios

Peatlands only cover a small fraction of the global land surface (∼3%) but store large amounts of carbon (∼600 GtC). Drainage of peatlands for agriculture results in the decomposition of organic matter, leading to greenhouse gas (GHG) emissions. As a result, degraded peatlands are currently responsible for 2%–3% of global anthropogenic emissions. Preventing further degradation of peatlands and restoration (i.e. rewetting) are therefore important for climate change mitigation. In this study, we show that land-use change in three SSP scenarios with optimistic, recent trends, and pessimistic assumptions leads to peatland degradation between 2020 and 2100 ranging from −7 to +10 Mha (−23% to +32%), and a continuation or even an increase in annual GHG emissions (−0.1 to +0.4 GtCO2-eq yr−1). In default mitigation scenarios without a specific focus on peatlands, peatland degradation is reduced due to synergies with forest protection and afforestation policies. However, this still leaves large amounts of GHG emissions from degraded peatlands unabated, causing cumulative CO2 emissions from 2020 to 2100 in an SSP2-1.5 °C scenario of 73 GtCO2. In a mitigation scenario with dedicated peatland restoration policy, GHG emissions from degraded peatlands can be reduced to nearly zero without major effects on projected land-use dynamics. This underlines the opportunity of peatland protection and restoration for climate change mitigation and the need to synergistically combine different land-based mitigation measures. Peatland location and extent estimates vary widely in the literature; a sensitivity analysis implementing various spatial estimates shows that especially in tropical regions degraded peatland area and peatland emissions are highly uncertain. The required protection and mitigation efforts are geographically unequally distributed, with large concentrations of peatlands in Russia, Europe, North America and Indonesia (33% of emission reductions are located in Indonesia). This indicates an important role for only a few countries that have the opportunity to protect and restore peatlands with global benefits for climate change mitigation.