Greenhouse gas (GHG) emissions from drained peatlands account for about 7% of the total anthropogenic GHG emissions in the European Union (EU). Yet, a lack of high-resolution spatial data hampers targeted mitigation. We combined soil and land use data to generate detailed maps of land use, GHG emissions, and emission hotspots for EU+ peatlands. Undrained peatlands and those drained for forestry dominate at high latitudes, while drained Grassland and Cropland prevail around latitudes 50°−55°. Four main emission hotspots emerge: the North Sea region, eastern Germany, the Baltics together with eastern Poland, and north Ireland. The North Sea region is the largest, accounts for 20% of EU+ peatland emissions on just 4% of the peatland area. Our findings highlight the urgency of reducing emissions from drained peatlands to meet EU climate targets and reveal substantial underreporting in National UNFCCC inventories, amounting to 59–113 Mt CO 2 e annually. Our analysis provides a robust and spatially explicit evidence base for policymakers to prioritize peatland rewetting to reduce GHG emissions.

This article presents the first published peatland map for Costa Rica. A probabilistic approach using vegetation, ecosystem, and soil datasets was used to predict the distribution and extent of peatlands found below 700 m in elevation. High-elevation sites found in the Talamanca Mountains were manually identified using satellite imagery; those peatlands are small in size (< 0.05 km2). Our analysis produced an estimated low-elevation peatland extent of 1433 km2 and a high-elevation peatland extent of 23.08 km2, yielding an estimated total extent of 1456 km2 for Costa Rica. This figure falls close to the middle of previously published extent estimates for this country, which vary widely (577-2670 km2). An agreement analysis between previously published maps and this new product is also presented. Plotting the peatland area of Costa Rica in a climate space (mean annual precipitation vs. precipitation seasonality) highlights key climatic differences between our peatland types/regions, hinting at broad-scale effects of climate-landscape interactions. As for the probability map therein, we stress that its accuracy is limited by data availability and quality, as well as ground-referencing information. Still, the new product can provide guidance for land management, policymaking, and future science endeavors.

The EU Nature Restoration Law (NRL) is critical for the restoration of degraded ecosystems and active afforestation of degraded peatlands has been suggested as a restoration measure under the NRL. Here, we discuss the current state of scientific evidence on the climate mitigation effects of peatlands under forestry. Afforestation of drained peatlands without restoring their hydrology does not fully restore ecosystem functions. Evidence on long-term climate benefits is lacking and it is unclear whether CO2 sequestration of forest on drained peatland can offset the carbon loss from the peat over the long-term. While afforestation may offer short-term gains in certain cases, it compromises the sustainability of peatland carbon storage. Thus, active afforestation of drained peatlands is not a viable option for climate mitigation under the EU Nature Restoration Law and might even impede future rewetting/restoration efforts. Instead, restoring hydrological conditions through rewetting is crucial for effective peatland restoration.

In July and August of 2023, we visited Costa Rica to examine some of the country’s peatlands. The purpose of our trip was to collect peat samples from a variety of wetland habitats from the coast to the highlands for future analysis. We summarize our observations in this short essay.

In spite of the worldwide largest proportional loss of mires, Europe is a continent with important mire diversity. This article analyses the condition and protection status of European mire ecosystems. The overview is based on the system of European mire regions, representing regional variety and ecosystem biodiversity. We combined peatland distribution data with land cover maps of the Copernicus Land Monitoring Service as well as with the World Database on Protected Areas to assess the extent of degraded peatlands and the proportion of peatlands located in protected areas in each European mire region. The total proportion of degraded peatlands in Europe is 25%; within the EU it is 50% (120,000 km2). The proportion of degradation clearly increases from north to south, as does the proportion of peatlands located within protected areas. In more than half of Europe’s mire regions, the target of at least 17% of the area located in protected areas is not met with respect to peatlands. Data quality is discussed and the lessons learned from Europe for peatland conservation are presented.

Summary Knowledge of a species’ ecological requirements is a prerequisite for effective conservation, particularly if the species is assumed to be declining due to modification of its primary habitats. Information about habitat suitability allows both the inference of specific habitat management measures as well as population size estimates which can facilitate the setting up of conservation priorities. As one of the least known Palaearctic breeding birds, the current knowledge of Baillon’s Crake Zapornia pusilla comprises only very general information about the species’ ecological requirements, habitat selection, extent and dynamics of home ranges or population densities within its Palaearctic-Afrotropical range. We used a multi-scale approach to assess the species’ habitat requirements in the Senegal River Delta, north-west Senegal. At the individual level, we calculated Manly selection indices for 17 radio-tracked Baillon’s Crakes, allowing for different levels of resource availability. Considering the entire Djoudj area including the Parc National des Oiseaux du Djoudj (PNOD), we modelled presence probability as well as population density of Baillon’s Crakes based on high-resolution satellite images and capture data from field surveys in 2009–2013. Using 95% kernels, home range size was on average 1.77 ± 0.86 ha with significant differences between habitats. Both at the individual as well as population level, Baillon’s Crakes preferred edge structures, selecting for trampling paths and edges along open water bodies as well as boundaries of specific vegetation stands while species composition was of less importance. Based on the regression models, we identified 9,516 ha of suitable habitat within the Djoudj area and a potential population size of 10,714 individuals (range 3,146–17,408). Although global population estimates are highly tentative, we assume the Senegal River Delta and the PNOD of outstanding significance for African and possibly also European populations of Baillon’s Crake.

Peatlands in the Nordic Baltic region and elsewhere in the world store large amounts of carbon and are at the same time important for conservation of biodiversity. Thus peatlands are space-effectiv ...

Peatlands in the Nordic Baltic region and elsewhere in the world store large amounts of carbon and are at the same time important for conservation of biodiversity. Thus peatlands are space-effectiv ...

The only well-studied wintering ground of the globally threatened Aquatic Warbler Acrocephalus paludicola is the ‘Djoudj area’ in Senegal. This study identifies potential Aquatic Warbler habitats within that area and gives an estimate of the size of the local wintering population. A land-cover map was generated by classifying high-resolution satellite images. Overlaying it with presence–absence data from field surveys and using logistic regression models (GLMM), we derived the presence probability of the Aquatic Warbler in the study area. Using presence probability as a proxy of habitat suitability we identified 4 729 ha of potential habitat. We calculated the population density of the Aquatic Warbler by applying a Poisson mixed model to our land-cover raster data and estimate a total population size of 776 individuals (range 260–4 057), i.e. 0.37–19.8% of the world population. However, this estimate is complicated by uncertainties including the unknown efficiency of the bird-catching method, clumped presence of individuals, the variability of water levels and other seasonal changes. An effective management of Aquatic Warbler habitats in the Djoudj area should include extensive grazing, the control of litter accumulation and shrub growth, and the removal of plant material from the channels to improve water circulation.

Knowledge of population-specific non-breeding areas in sub-Saharan Africa for the globally threatened Aquatic Warbler Acrocephalus paludicola is paramount for the implementation of successful conservation strategies that consider the species' entire annual range. This may be the case especially for declining marginal populations. Here we report on two Aquatic Warblers that were ringed in the Inner Niger Delta in Mali and in the region of the Djoudj National Park, Senegal. The first was recaptured in the Supoj mire, Ukraine, and the second observed in the Biebrza marshes in Poland. These records represent the first proof of connectivity between wintering areas and breeding sites for the species.

The globally threatened Aquatic Warbler Acrocephalus paludicola is a Palearctic–African long-distance migrant that undergoes a complete moult while wintering in Africa. Little is known about the timing of moult and the birds’ mobility during moulting periods. We conducted the first study on the moult of Aquatic Warblers, in the Djoudj area of Senegal, West Africa. Wing moult scores from 36 to 90 and raggedness scores from 0 to 25 were recorded in December and January. No moulting Aquatic Warblers were caught after January. Body-feather moult was observed during and shortly after wing moult until January. We conclude that Aquatic Warblers follow the typical sequence of passerine moult, with remige moult starting in October or November. To find out how moult affects their mobility, we measured the net distance that Aquatic Warblers equipped with radio transmitters travelled in 15-min intervals. In our small sample of eight birds, the mean path length was 34 m, and there was no obvious difference between the path lengths in moulting and non-moulting individuals. We conclude that, possibly, moult does not affect the mobility and flight ability of Aquatic Warblers in general. Further research is needed to locate other wintering grounds, e.g. in the Inner Niger Delta, and reproduce our study in other populations.

Stable isotope analysis of feathers can be useful in the study of seasonal interactions and migratory connectivity in birds. For the PalaearcticAfrican migration system, however, the lack of isotope data from feathers of known origin in Africa renders the geographic assignment of birds captured on European breeding grounds to potential wintering areas problematic. Rectrices of the threatened aquatic warbler Acrocephalus paludicola grown in Africa were sampled across six European countries to assess whether birds in different breeding populations shared similar isotopic signatures and so were likely to have wintered in the same region in Africa. Freshly grown feathers of aquatic warblers collected at the only known wintering site in Senegal showed high variation in carbon, nitrogen, and hydrogen isotope ratios. Due to similarly high variation in isotope ratios of African-grown feathers within all breeding populations, it was not possible to determine whether different populations wintered in different regions. However, isotope signatures of 20% of birds captured on European breeding grounds fell outside the range of those captured in Senegal, suggesting a wider wintering distribution than is currently known. We therefore assessed whether the origin of these feathers could be estimated by trying to establish isotopic gradients across sub-Saharan West Africa. Feathers of three ecologically similar surrogate species were sampled from wetlands across a 3000 km east-west and a 2000 km northsouth transect. Within-site variation in feather isotope ratios was frequently larger than the difference predicted by gradients across West Africa. Thus, predicting the origin of individual feathers using single-isotope gradients was not reliable. The large within-site variability of feather isotope ratios of a habitat specialist species like the aquatic warbler indicates that using feather isotope ratios will require large sample sizes from many locations, and may thus not be an efficient tool in identifying wintering areas of Palaearctic African migrants.

The Aquatic Warbler is a threatened Afro-Palaearctic migrant with a largely unknown distribution in the winter (non-breeding) season. Protection of wintering sites may be crucial for the conservation of the species. Previous studies have identified extensive areas of north-western sub-Saharan Africa that could potentially be occupied by the species during winter. However, these studies have not necessarily differentiated between potentially suitable and unsuitable habitat types at a spatial resolution appropriate for targeting field surveys. To identify specific sites that could be occupied by non-breeding Aquatic Warblers at a scale appropriate for targeted field surveys, we adopted a modelling approach that combined recent sightings from Djoudj, Senegal, with land cover and climate data. We produced maps of potential distribution using three maximum entropy models. While a paucity of sightings prevented a full test of these maps on independent records, the areas that were predicted to be potentially occupied included areas around which there are historical records. We suggest field surveys should be targeted towards sites in the Inner Niger Delta and a number of marshes along and away from the Niger River in Mali, and to sites in southern Mauritania.

The Aquatic Warbler Acrocephalus paludicola (AW) is the only globally threatened passerine species of continental Europe. The global population decreased by >90% during the 20th century. AWs breed in Palaearctic fen mires and sedge meadows and spend the non-breeding season in sub-Saharan Africa, but until 2007 no regular wintering site had been identified. To date, the only wintering grounds that have been discovered are in river floodplain marshes along the Senegal River in the Djoudj area, Senegal. Searches for additional wintering sites in south-western Mauritania, northern Senegal and Gambia have been unsuccessful. In Djoudj, AWs are found in extensive marshes dominated by Scirpus spp. or Sporobolus robustus, and favour shallow water and the occurrence of Eleocharis mutata and Sporobolus robustus on the microhabitat scale. Within these marshes, however, AW appear to avoid dense homogenous stands dominated by Scirpus maritimus. Estimates of the density of wintering AWs in suitable habitats range between 0.5 and 1.6 birds/ha. According to the estimated area of suitable habitat (4,000–10,000 ha with strong seasonal and inter-annual fluctuations), the Djoudj area may hold between 10 and >50% of the global population during the non-breeding season. Ringing, molecular studies and feather isotope ratios have failed to provide conclusive evidence for connectivity between the Djoudj area and particular Palaearctic breeding populations. Based on winter records, habitat data and satellite images, we speculate that the Inner Niger Delta in Mali could be another important wintering area. A pilot project that equipped 30 AWs in the Ukraine with geolocators in 2010 may reveal more details about migration routes and lead to the discovery of currently unknown wintering sites.

The Aquatic Warbler Acrocephalus paludicola was once a common breeding bird in mesotrophic fen mires all over Central and Western Europe. In the last century large parts of its habitat have been destroyed by wetland drainage and agricultural intensification. Besides protecting the remaining breeding habitats, it is of great importance to preserve suitable migration stopover habitats and wintering grounds to avert the extinction of the species.We determined home-range size and the use of vegetation associations of Aquatic Warblers on the wintering grounds in a flooded plain north of the Djoudj National Park in Senegal. Individual birds (11) were caught in mist nets and equipped with radio transmitters. Locations were assessed by radiotelemetry and a compositional analysis was conducted to determine which vegetation types were preferred within home ranges.Similar to their behaviour on the breeding grounds, the Aquatic Warblers showed no territorial behaviour in their winter quarters. They used home ranges that averaged 4 ha in size, which they shared with conspecifics and other warblers. The home ranges overlapped 54% on average, with a maximum of 90% in an area used by four individuals. The vegetation structure of the wintering habitat is similar to breeding grounds and stopover sites of the species. Preferential vegetation had 80% to 100% cover and consisted of 60 to 90 cm high stands of Oryza longistaminata, Scirpus maritimus or Eleocharis mutata. Most birds stayed more often near the edge of open water, probably for foraging. A constant inundation seems essential, because Aquatic Warblers never occurred in desiccated parts of the study site.

The Aquatic Warbler is the only globally threatened passerine bird species in Europe. Around 1900, it was one of the most abundant birds in European fen mires. The population severely decreased as a consequence of extensive wetland drainage. In recent years, it has been rather stable in key breeding sites but has decreased sharply in its westernmost occurrence Pomerania. Conservation of the Pomeranian birds is of key importance for conserving the intraspecific diversity of the species. Throughout 2004–2006 we studied all current breeding sites of the species in Pomerania. Two areas have been studied in more detail: Rozwarowo Marshes, the largest breeding site in Pomerania, and Lower Oder Valley National Park, the last breeding site in Germany. Data on vegetation composition and height, water level, site conditions, and land use were analysed. The sites near the coast and in small river valleys are characterised by sparse and low Phragmites australis stands with a well-developed lower sedge and herb layer. The sites in the Lower Oder Valley are more nutrient-rich and dominated by Carex acuta, Phalaris arundinacea, and other meadow grasses. In Rozwarowo Marshes, the birds inhabit sparse, short Phragmites australis and Thelypteris palustris vegetation that is maintained by winter reed cutting. In the Lower Oder Valley National Park, Aquatic Warblers shifted from Caricetum gracilis to other plant communities that continued to be mown frequently. Similar to the Lithuanian Aquatic Warbler habitats in the Nemunas Delta and in contrast to the predominantly mesotrophic habitats of the core population, the Pomeranian habitats are eutrophic and more influenced by inundation. Various rare and threatened plant communities occur here. The Aquatic Warbler can be regarded as an umbrella species for mesotrophic and slightly eutrophic peatlands for which this bird is a specialist. Conservation activities should focus on a site-specific management and the prevention of further eutrophication.