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Funding: Leverhulme Trust (Grant Number(s): RPG-2018-306); UK Natural Environment Research Council (Grant Number(s): NE/R000751/1, NE/R016860/1, NE/V018760/1); Scottish Research Council/University of St Andrews. Tropical peatlands store globally significant quantities of carbon and are ecologically and culturally important, but little is known about their vulnerability to oil and gas exploration and extraction. Here, we analyse the exposure of tropical peatlands to the activities of the petroleum industry and review what is known about the sensitivity of peatlands to these activities. We find that 8.3% (107,000 km2) of the total area of tropical peatlands overlaps with a 30-km buffer area around oil and gas infrastructure. Major areas of overlap include the Sumatra Basin (Indonesia), the Niger Delta (Nigeria) and the Putumayo-Oriente-Marañón Basin (Peru/Ecuador/Colombia). Documented environmental impacts include deforestation and habitat loss associated with the exploration and development of oil fields, and contamination from spills of oil and produced water (well brine). Peatlands, and the ecosystem services they provide, are sensitive to these impacts due to unique aspects of their ecology and hydrology, the easy spread of contamination by flowing water, the long-term storage of contaminants in peat, and the slow degradation of oil under anoxic, waterlogged conditions. Given the potential negative consequences for human health, resource security, biodiversity, and carbon storage, we propose a research agenda to provide an improved evidence base to support effective governance. Publisher PDF

Over the past two decades, the existence of intact peatlands in lowland Amazonia has been demonstrated, including a vast area of potential peat-forming vegetation of around 43,617 km2 in the Pastaza-Marañón Foreland Basin (PMFB), in the Loreto Department of north-east Peru. Peat sampling and floristic assessments have revealed the presence of peat in four ecosystem types in the PMFB: palm swamps, peatland pole forests, open peatlands, and, more rarely, in seasonally flooded forests. However, recent field investigations and palynological studies show that temporal changes in vegetation in peatlands may have been driven by changes in the degree of flooding, suggesting greater complexity in the controls on peatland development and in the spatiotemporal relationships between ecosystems than current conceptual models allow. Here we present new high-resolution palynological, geochemical and radiocarbon data from an open peatland sampled in the PMFB near San Roque village on the Marañón river. Our study aims to: (1) reconstruct past vegetation changes; (2) investigate the interaction between the fluvial system and the peatland’s vegetation dynamics over time; (3) determine how patterns of ecological and fluvial change at San Roque compare with records from other peatland types in the wider PMFB. Downcore palynology on the dated SAR_T3_03_B peat core provides a vegetation record spanning the last 4,300 years documenting changes in ecological associations over time. Between 4,300 and 3,180 cal yr BP, prior to peat accumulation, our data shows pronounced fluvial influence with high amounts of inorganic material and pollen assemblages from taxa related to open water conditions. Since the beginning of peat accumulation around 3,180 Cal yr BP, palynological and geochemical data suggest conditions related to predominantly herbaceous communities. Core scanning micro-XRF provides proxy evidence for episodes of fluvially-derived minerogenic input during the period of peat accumulation (3,180–440 Cal yr BP). Simultaneous increases in flood-tolerant taxa (e.g. Symmeria paniculata, Alchornea sp., Myrtaceae) support the inference of intervals with increased frequency and depth of river flooding. From around 440 Cal yr BP, we infer the establishment of M. flexuosa palms linked to lower flooding, which persists today. Compared with other regional sequences, the San Roque record is distinctive because of this notable influence of flooding regime on the ecosystem, which impacted on the vegetation succession through changes in flood levels and nutrient inputs. The dynamics of the sediment-laden Marañón River therefore emerges as a major driver in vegetation change and trajectory of peatland development during the last four millennia.

The recently described peatlands of northern Peruvian Amazonia are relatively intact compared with peatlands elsewhere in the tropics. They make an important contribution to regional biodiversity and, by sequestering carbon, to climate change mitigation. Research to date has focused on their physical and biological aspects, but peatlands are not simply natural phenomena: they are used, valued and understood socially and culturally in profoundly different ways by different groups of people.This research project used an interdisciplinary participatory approach, working with peatland communities and stakeholders in Peru, to bring together the different perspectives needed to produce a comprehensive understanding which the natural sciences cannot achieve alone. The three central aims of the project were to 1) characterise the ecology and sociocultural values of the ecosystem types identified by local communities; 2) identify the strategies and challenges around community management of natural resources; and 3) identify opportunities for peatland conservation and maintenance of livelihoods. We worked with five peatland forest communities, three mestizo and two indigenous, in the Pastaza-Marañón Basin, which is the largest peat-forming area in lowland Peru. To address our aims we used a range of methods, both ecological (plot-based vegetation survey, measuring peat properties) and sociological (participatory mapping, interviews, focus groups).A key outcome of this work is a better understanding of the multifaceted importance of peatlands to local communities. The resources and spaces provided by peatland ecosystems were important culturally and socioeconomically to all five communities, but with pronounced differences relating to the communities’ different sociocultural and economic experiences and contexts. Another striking finding was that the nature of communities’ relationships with external actors, and their exposure to different opportunities and challenges, varied very markedly from one community to the next. For example, our study communities have experienced different interventions, some more successful and enduring than others, by government agencies and NGOs focusing mainly on biodiversity conservation; the success or otherwise of these past projects is likely to shape the willingness of communities to engage with future conservation efforts. Some communities have been more heavily influenced than others by the expansion of regional markets and value chains for timber and non-timber forest products into remote peatland areas over recent decades; other communities have been profoundly affected by activities of multinational extractive industries, including the oil industry and plantation agriculture.We conclude that future peatland conservation efforts and sustainable development projects in Peruvian Amazonia will need to recognize the significant variations from one community to the next in terms of the ways in which they use and value the peatlands, and in terms of their wider socio-economic and cultural contexts. Long-term protection of the peatlands will only be possible by engaging with communities individually, taking into account the concerns, needs, desires, threats, and opportunities particular to each one.

Funding: The work was funded by a NERC Large Grant to S.L.L. (‘CongoPeat’, NE/R016860/1), a NERC Doctoral Training Partnership award to B.C. (‘SPHERES DTP’, NE/L002574/1) and a Greenpeace Fund award to S.L.L. JAXA, NASA, METI, USGS, ESA, OSFAC and WWF are acknowledged for collecting and/or processing remote-sensing data. The world’s largest tropical peatland complex is found in the central Congo Basin. However, there is a lack of in situ measurements to understand the peatland’s distribution and the amount of carbon stored in it. So far, peat in this region has been sampled only in largely rain-fed interfluvial basins in the north of the Republic of the Congo. Here we present the first extensive field surveys of peat in the Democratic Republic of the Congo, which covers two-thirds of the estimated peatland area, including from previously undocumented river-influenced settings. We use field data from both countries to compute the first spatial models of peat thickness (mean 1.7 ± 0.9 m; maximum 5.6 m) and peat carbon density (mean 1,712 ± 634 MgC ha−1; maximum 3,970 MgC ha−1) for the central Congo Basin. We show that the peatland complex covers 167,600 km2, 36% of the world’s tropical peatland area, and that 29.0 PgC is stored below ground in peat across the region (95% confidence interval, 26.3–32.2 PgC). Our measurement-based constraints give high confidence of globally significant peat carbon stocks in the central Congo Basin, totalling approximately 28% of the world’s tropical peat carbon. Only 8% of this peat carbon lies within nationally protected areas, suggesting its vulnerability to future land-use change. Postprint Postprint

Funding: The core collection fieldwork was funded by the Royal Society, to S.L.L., Philip Leverhulme Prize to S.L.L. and a NERC CASE award to S.L.L. and G.C.D. The laboratory analysis, data analysis and write-up was funded by CongoPeat, a NERC Large Grant (NE/R016860/1) to S.L.L., I.T.L., A.B., S.E.P., P.G., supporting D.H., G.T., G.C.D., W.H., G.E.B., and Y.E.B.; and NERC Radiocarbon Facility grant (alloc. no. 1688.0313 and 1797.0414) to I.T.L., S.L.L. and G.C.D. Y. G. was supported by the Agence Nationale de la Recherche (ANR) grant ANR-19-CE01-0022. E.S. was supported by the Deutsche Forschungsgemeinschaft (DFG) grant SCHE 903/19–1 and the DFG-Cluster of Excellence ‘The Ocean in the Earth System’ at MARUM. The central Congo Basin contains the largest known peatland complex in the tropics. Here we present a detailed multi-proxy record from a peat core, CEN-17.4, from the centre of a 45 km wide interfluvial peatland (Ekolongouma), the first record of its kind from the central Congo peatlands. We use pollen, charcoal, sedimentological and geochemical data to reconstruct the site's history from the late Pleistocene to the present day. Peat began accumulating at the centre of the peatland ∼19,600 cal BP (∼17,500–20,400 cal BP, 95% confidence interval), and between ∼9500 (9430–9535 cal BP) and 10,500 (10,310–10,660 cal BP) cal BP towards the margins. Pollen data from the peatland centre show that an initial grass- and sedge-dominated vegetation, which burned frequently, was replaced by a Manilkara-type dominated flooded forest at ∼12,640 cal BP, replaced in turn by a more mixed swamp forest at ∼9670 cal BP. Mixed swamp forest vegetation has persisted to the present day, with variations in composition and canopy openness likely caused at least in part by changes in palaeo-precipitation. Stable isotope data (δDn-C29-v&icecorr) indicate a large reduction in precipitation beginning ∼5000 and peaking ∼2000 cal BP, associated with the near-complete mineralization of several metres of previously accumulated peat and with a transition to a drier, more heliophilic swamp forest assemblage, likely with a more open canopy. Although the peatland and associated vegetation recovered from this perturbation, the strong response to this climatic event underlines the ecosystem's sensitivity to changes in precipitation. We find no conclusive evidence for anthropogenic activity in our record; charcoal is abundant only in the Pleistocene part of the record and may reflect natural rather than anthropogenic fires. We conclude that autogenic succession and variation in the amount and seasonality of precipitation have been the most important drivers of ecological change in this peatland since the late Pleistocene. Publisher PDF

Funding: This work was funded by CongoPeat—a NERC large grant (NE/R016860/1) to S.L.L., I.T.L., S.E.P., A.B., A.J.B., P.J.M., P.G. and S.S. Natural Environment Research Council (CASE award to S.L.L. and G.C.D.), Leeds–York NERC Doctoral Training Partnership (‘SPHERES’) award to B.C. (NE/L002574/1), NERC Radiocarbon Facility NRCF010001 (alloc. no. 1688.0313, 1797.0414, 2222.1119, 14.108 and 2329.0920 to I.T.L., S.L.L., G.E.B., B.C., P.G. and G.C.D.), Wildlife Conservation Society – Congo (to G.C.D.), the Royal Society (to S.L.L.), Philip Leverhulme Prize (to S.L.L.), and a Greenpeace Fund award (to S.L.L.). E.S. was supported by the DFG–Cluster of Excellence ‘The Ocean in the Earth System’ at MARUM. C.H.V. publishes with permission of the Executive Director of the British Geological Survey, UKRI. The forested swamps of the central Congo Basin store approx. 30 billion metric tonnes of carbon in peat1,2. Little is known about the vulnerability of these carbon stocks. Here we investigate this vulnerability using peat cores from a large interfluvial basin in the Republic of the Congo and palaeoenvironmental methods. We find that peat accumulation began at least at 17,500 calibrated years before present (cal. yr BP; taken as AD 1950). Our data show that the peat that accumulated between around 7,500 to around 2,000 cal. yr BP is much more decomposed compared with older and younger peat. Hydrogen isotopes of plant waxes indicate a drying trend, starting at approx. 5,000 cal. yr BP and culminating at approx. 2,000 cal. yr BP, coeval with a decline in dominant swamp forest taxa. The data imply that the drying climate probably resulted in a regional drop in the water table, which triggered peat decomposition, including the loss of peat carbon accumulated prior to the onset of the drier conditions. After approx. 2,000 cal. yr BP, our data show that the drying trend ceased, hydrol. conditions stabilized and peat accumulation resumed. This reversible accumulation-loss-accumulation pattern is consistent with other peat cores across the region, indicating that the carbon stocks of the central Congo peatlands may lie close to a climatically driven drought threshold. Further research should quantify the combination of peatland threshold behavior and droughts driven by anthropogenic carbon emissions that may trigger this pos. carbon cycle feedback in the Earth system. Publisher PDF

This research was funded by the Gordon and Betty Moore Foundation, through grant #5349 ‘Monitoring protected areas in Peru to increase forest resilience to climate change’, and NERC standard grant ‘Carbon Storage in Amazonian Peatlands: Distribution and Dynamics’(NE/R000751/1). The peat-forming wetland forests of Amazonia are characterised by high below-carbon stocks and supply fruit, fibres and timber to local communities. Predicting the future of these ecosystem services requires understanding how hydrological conditions are related to tree species composition and the presence, or absence, of peat. Here, we use continuous measurements of water table depth over 2.5 years and manual measurements of pore-water pH and electrical conductivity to understand the ecohydrological controls of these variables across the large peatland complex in northern Peruvian Amazonia. Measurements were taken in permanent forest plots in four palm swamps, four seasonally flooded forests and four peatland pole forests. All trees ≥10 cm diameter were also measured and identified in the plots to assess floristic composition. Peat occurs in eight of these twelve sites; three seasonally flooded forests and one palm swamp are not associated with peat. Variation in tree species composition among forest types was linked to high flood levels (maximum flooding height) and pH: seasonally flooded forests experience high flood levels (up to 3.66 m from the ground surface) and have high pH values (6?7), palm swamps have intermediate flood levels (up to 1.34 m) and peatland pole forests experience shallow flooding (up to 0.28 m) and have low pH (4). In contrast, the presence of peat was linked to variation in maximum water table depth (ie the depth to which the water table drops below the ground surface). Surface peat is found in all forest types where maximum water table depth does not fall >0.55 m below the ground surface at any time. Peat formation and variation in tree species composition therefore have different ecohydrological controls. Predicted increases in the frequency and strength of flooding events may alter patterns of tree species composition, whereas increases in drought severity and declines in minimum river levels may pose a greater risk to the belowground carbon stores of these peatland ecosystems. Publisher PDF

Societal Impact Statement The approach that we take to our science is as important as the questions that we address if we would like our research to inform management. Here, we discuss our experience of using networks of permanent forest inventory plots to support sustainable management and conservation of intact tropical forests. A key conclusion is that to maximize the use of data from such large international networks within policymaking, it is crucial that leadership is widely shared among participants. Such an approach helps to address ethical concerns surrounding international collaborations and also achieves greater policy impact. Summary Long‐term data from permanent forest inventory plots have much to offer the management and conservation of intact tropical forest landscapes. Knowledge of the growth and mortality rates of economically important species, forest carbon balance, and the impact of climate change on forest composition are all central to effective management. However, this information is rarely integrated within the policymaking process. The problem reflects broader issues in using evidence to influence environmental management, and in particular, the need to engage with potential users beyond the collection and publication of high‐quality data. To ensure permanent plot data are used, (a) key “policy windows”—opportunities to integrate data within policy making—need to be identified; (b) long‐term relationships need to be developed between scientists and policy makers and policymaking organizations; and (c) leadership of plot networks needs to be shared among all participants, and particularly between institutions in the global north and those in tropical countries. Addressing these issues will allow permanent plot networks to make tangible contributions to ensuring that intact tropical forest persists over coming decades.

This work was funded by NERC (grant ref. NE/R000751/1) to I.T.L., A.H., K.H.R., E.T.A.M., C.M.A., T.R.B., G.D. and E.C.D.G.; Leverhulme Trust (grant ref. RPG-2018-306) to K.H.R., L.E.S.C. and C.E.W.; Gordon and Betty Moore Foundation (grant no. 5439, MonANPeru network) to T.R.B., E.N.H.C. and G.F.; Wildlife Conservation Society to E.N.H.C.; Concytec/British Council/Embajada Británica Lima/Newton Fund (grant ref. 220–2018) to E.N.H.C. and J.D.; Concytec/NERC/Embajada Británica Lima/Newton Fund (grant ref. 001–2019) to E.N.H.C. and N.D.; the governments of the United States (grant no. MTO-069018) and Norway (grant agreement no. QZA-12/0882) to K.H.; and NERC Knowledge Exchange Fellowship (grant ref no. NE/V018760/1) to E.N.H.C. Tropical peatlands are among the most carbon-dense ecosystems but land-use change has led to the loss of large peatland areas, associated with substantial greenhouse gas emissions. To design effective conservation and restoration policies, maps of the location and carbon storage of tropical peatlands are vital. This is especially so in countries such as Peru where the distribution of its large, hydrologically intact peatlands is poorly known. Here field and remote sensing data support the model development of peatland extent and thickness for lowland Peruvian Amazonia. We estimate a peatland area of 62,714 km2 (5th and 95th confidence interval percentiles of 58,325 and 67,102 km2, respectively) and carbon stock of 5.4 (2.6–10.6) PgC, a value approaching the entire above-ground carbon stock of Peru but contained within just 5% of its land area. Combining the map of peatland extent with national land-cover data we reveal small but growing areas of deforestation and associated CO2 emissions from peat decomposition due to conversion to mining, urban areas and agriculture. The emissions from peatland areas classified as forest in 2000 represent 1–4% of Peruvian CO2 forest emissions between 2000 and 2016. We suggest that bespoke monitoring, protection and sustainable management of tropical peatlands are required to avoid further degradation and CO2 emissions. Postprint

International audience

Funding from the Scottish Funding Council (Global Challenges Research Fund 2017–2018) and the Natural Environment Research Council (ref. NE/R000751/1) is gratefully acknowledged. Tropical peatlands play an important role in the global carbon cycle by acting as significant carbon stores. South America's largest peatland complex is located in the Loreto Region of the Peruvian Amazon. Here we present the first study of human relations with these peatlands, including their uses, cultural significance and current management, as well as implications for conservation, based on qualitative research with people living in two riverine rural communities. Our results indicate that peatlands are culturally ambiguous spaces, used mainly for hunting, palm fruit harvesting, and timber, but feared due to the dangers of getting lost, sinking into the ‘sucking’ ground, and being attacked by anacondas and/or mythical creatures. While the difficult terrain and remoteness of peatlands have thus far acted as natural barriers to their destruction through conversion to different land uses, overuse of natural resources is nevertheless a significant concern for people living in the peat-dominated landscape of the Peruvian Amazon, mixed with frustration about the lack of outside support to foster environmental conservation and economic opportunities. We explore how evaluations of the present situation differ across one indigenous and one mestizo community. We identify a range of nascent peatland conservation strategies, including seedling planting to regrow valuable (palm) trees, and the climbing of palm trees for harvesting fruit as opposed to felling them. We argue that peatland conservation could be combined with the development of sustainable management strategies, but that this would require sustained engagement by outside organisations with rapidly growing local communities in these areas. Postprint

This work was funded by the Wildlife Conservation Society, Gordon and Betty Moore Foundation (Grant #5439, MonANPeru network), NERC (Grant ref. NE/R000751/1), Concytec/British Council/Embajada Británica Lima/Newton Fund (Grant ref. 220-2018), Concytec/NERC/Embajada Británica Lima/Newton Fund (Grant ref. 001-2019), Leverhulme Trust (Grant ref. RPG-2018-306), Scottish Funding Council, and USAID/SWAMP program. Peatland pole forest is the most carbon-dense ecosystem in Amazonia, but its spatial distribution and species composition are poorly known. To address this knowledge gap, we quantified variation in the floristic composition, peat thickness, and the amount of carbon stored above and below ground of 102 forest plots and 53 transects in northern Peruvian Amazonia. This large dataset includes 571 ground reference points of peat thickness measurements across six ecosystem types. These field data were also used to generate a new land-cover classification based on multiple satellite products using a random forest classification. Peatland pole forests are floristically distinctive and dominated by thin-stemmed woody species such as Pachira nitida (Malvaceae), Platycarpum loretense (Rubiaceae), and Hevea guianensis (Euphorbiaceae). In contrast, palm swamps and open peatlands are dominated by Mauritia flexuosa (Arecaceae). Peatland pole forests have high peat thickness (274 ± 22 cm, mean ± 95% CI, n = 184) similar to open peatlands (282 ± 46 cm, n = 46), but greater than palm swamps (161 ± 17 cm, n = 220) and seasonally-flooded forest, terra firme, and white-sand forest where peat is rare or absent. As a result, peatland pole forest has exceptional carbon density (1,133 ± 93 Mg C ha−1). The new sites expand the known distribution of peatland pole forest by 61% within the Pastaza-Marañón Foreland basin, mainly alongside the Tigre river, to cover a total of 7540 km2 in northern Peruvian Amazonia. However, only 15% of the pole forest area is within a protected area, whilst an additional 26% lies within indigenous territories. The current low levels of protection and forest degradation but high threat from road paving projects makes the Tigre river basin a priority for conservation. The long-term conservation of peatland pole forests has the potential to make a large contribution towards international commitments to mitigate climate change. Publisher PDF

This work was funded by the NSF‐IPY (International Polar Year; ref 0732327), a Ph.D. studentship from the School of Geography and Sustainable Development, University of St Andrews, and the Quaternary Research Association. The settlement of Iceland is known to have had profound impacts on vegetation and landscape stability, but there remain uncertainties around the spatial variability and timing of environmental change, and the impacts of settlement on aquatic ecosystems. Here a new multiproxy palaeoenvironmental reconstruction spanning the last 3000 years is presented from Kalmanstjörn, a small lake in Mývatnssveit, northeast Iceland. Sedimentology, pollen and non‐pollen palynomorphs, and geochemical proxies, dated using tephrochronology, are used to reconstruct terrestrial vegetation, landscape stability and aquatic ecosystems. The data reveal complex environmental dynamics after settlement. At this site, substantial tree populations persisted until the late 15th century, in strong contrast to the rapid deforestation shown by almost all other records from Iceland. The eventual loss of woodland may have been caused by changes in direct human activity and the location of extensive grazing, in combination with Little Ice Age climatic cooling. The loss of woodland was accompanied by increased soil erosion. Conversely, the lake ecosystem showed an immediate response to settlement, becoming more productive for several centuries, perhaps in response to increased availability of nutrients from grazing herbivores. The late persistence of woodland in the Kalmanstjörn record adds to our understanding of the spatial variations in ecosystem responses to settlement in Iceland, while the evidence for decoupling of the aquatic and terrestrial systems suggests that palaeolimnological reconstructions focusing on aquatic ecosystem responses may be important new sources of information on the wider ecological consequences of human settlement. Publisher PDF

Volcanic ash (tephra) deposits are used to reconstruct past eruption parameters. The ways in which tephra deposits are modified between deposition and their long-term preservation in the stratigraphic archive are poorly understood. In particular, we don’t know if tephra layers preserved in lake sediments from small lakes accurately reflect the initial tephra fallout. We address this by re-surveying tephra deposits from the 1991 eruption of Volcán Hudson, Chile. We measured tephra thickness, mass-loading and grain-size distribution of tephra from multiple cores in six small (2) lakes at locations 76-110 km from the volcano and in areas of contrasting land cover and climate. We also measured tephra preservation in terrestrial sites within each lake catchment. These data were compared with measurements taken shortly (days to weeks) after the eruption to determine how the tephra deposits have changed in the 29 years since the eruption. Preservation is variable within and between lakes, and also varies with the vegetation cover at terrestrial sites adjacent to the lakes. Tephra thicknesses are broadly comparable to the original fallout, but the degree of similarity varied notably and is sensitive to preservation environment. These findings have implications for reconstructing eruption parameters from tephra deposits in small lakes, and where the fallout area crosses large environmental gradients and contrasting vegetation regimes.

This work was funded by CongoPeat, a NERC Large Grant (NE/R016860/1) to S.L.L. and E.T.A.M. (UAV data collection, I.J.D. time), a NERC Open CASE Studentship to S.L.L., I.L. and G.D. and a Phillip Leverhulme Prize to S.L.L. (peat depths). The world’s most extensive tropical peatlands occur in the Cuvette Centrale depression in the Congo Basin, which stores 30.6 petagrams of carbon (95% CI, 6.3–46.8). Improving our understanding of the genesis, development and functioning of these under-studied peatlands requires knowledge of their topography and, in particular, whether the peat surface is domed, as this implies a rain-fed system. Here we use a laser altimeter mounted on an unmanned airborne vehicle (UAV) to measure peat surface elevation along two transects at the edges of a peatland, in the northern Republic of Congo, to centimetre accuracy and compare the results with an analysis of nearby satellite LiDAR data (ICESat and ICESat-2). The LiDAR elevations on both transects show an upward slope from the peatland edge, suggesting a surface elevation peak of around 1.8 m over ~20 km. While modest, this domed shape is consistent with the peatland being rainfed. In-situ peat depth measurements and our LiDAR results indicate that this peatland likely formed at least 10,000 years BP in a large shallow basin ~40 km wide and ~3 m deep. Publisher PDF

The peatlands of the Cuvette Centrale depression in the Congo Basin store between 6.3 and 46.8 petagrams of carbon. To improve our understanding of the genesis, development and functioning of these peatlands, we need to know if their surface is domed. Past work using satellite-based instruments has established that if the peatland surface is domed, it is very shallow, below 2‑3 m over a distance of 26km. We used a laser altimeter mounted on an unmanned airborne vehicle (UAV) to measure peat surface elevation along two transects at the edges of a peatland to centimetre accuracy, and combined the results with an analysis of local ICESat and ICESat-2 returns. The LiDAR elevations show an upward slope inwards from both edges, and the ICESat and ICESat-2 returns suggest a peak around 1.8 m above the edges. This matches our expectations of a rainfed peatland and, combined with prior measurements of peat depth, indicates that this peatland formed in a 3 m-deep basin.

We gratefully acknowledge financial support from the Royal Geographical Society, and NERC (grant ref. NE/H011773/1 and a quota PhD studentship), including two radiocarbon allocations (refs. 1612.0312, 1558.0411). Amazonian peatlands sequester and store large amounts of carbon below ground and contribute to regional biodiversity. They also present an outstanding opportunity for palaeoecological research. This study uses multiple peat cores to improve our understanding of the long-term development of a peatland (Quistococha) in Peruvian Amazonia, by providing a reconstruction of the spatial patterns of vegetation change and peat accumulation over time across the site. Peat cores taken along transects totalling c. 5 km were used to establish the peat thickness and visible stratigraphy. Of 29 new peat cores, four were selected for pollen analysis, supported by 15 radiocarbon dates. These complement two existing published pollen records from the site, from a peat core and a lake sediment core. Our study shows that peat initiation occurred across the site in the form of primary mire formation between 2400 and 1900 cal yr BP. Following peat initiation, five broadly similar phases of vegetation development are recorded in all the pollen sequences: Amazon floodplain, herbaceous sedge fen, mixed angiosperm flooded forest, mixed palm swamp, Mauritia-dominated palm swamp. In detail, there are differences in the pattern and timing of vegetation change between the sequences. Much of this spatial variation is likely to be the result of the underlying substrate topography. In addition, we find that the difference in vegetation composition between core sites was greater during the early stages of peat accumulation at Quistococha than it is today. Such spatial and temporal variability has significant implications for computer modelling of carbon accumulation in tropical peatlands and, consequently, our understanding of their role in the global carbon cycle. Our findings highlight key challenges for numerical modelling on Holocene timescales, namely the difficulty in quantifying long-term variations in primary productivity, the variable influence of sediment input on carbon accumulation during the early stages of peatland formation, and the difficulty of modelling water tables in sites with variable underlying topography. Postprint

The work was supported by Historic Environment Scotland (Grant Title: ‘Final publication and archiving of Uig Landscape Project’; PI: MJC), Durham University and the University of Edinburgh. This paper considers the timing and mechanisms of deforestation in the Western Isles of Scotland, focusing in particular on the landscape around the Calanais stone circles, one of the best preserved late Neolithic/early Bronze Age monumental landscapes in north-west Europe. We present new archaeological and palaeoenvironmental evidence from a soil and peat sequence at the site of Aird Calanais, which spans the main period of use of the Calanais circles. We then draw on a new synthesis of archaeobotanical and palynological evidence from across the Western Isles and a review of comparable data from the wider North Atlantic zone, before assessing the role of early farming communities in clearing the wooded landscapes of the region. Pollen and radiocarbon dating at the site of Aird Calanais reveal that a layer of birch branches, dating to the late Neolithic (2912-2881 cal bc), was contemporaneous with a decline in woodland at the site, as well as with the major phase of Neolithic activity at the Calanais stone circle complex. However, our synthesis of the pollen and plant macrofossil evidence from across the Western Isles suggests that the picture across these islands was altogether more complex: woodlands declined both before, as well as during, the Neolithic and deciduous woodlands remained sufficiently abundant for Neolithic fuel procurement. Finally, we consider the implications of the results for understanding the interactions between first farmers and woodlands in the wider North Atlantic region. Publisher PDF

The concept of resilience has become increasingly important in ecological and socio-ecological literature. With its focus on the temporal behaviour of ecosystems, palaeoecology has an important role to play in developing a scientific understanding of ecological resilience. We provide a critical review of the ways in which resilience is being addressed by palaeoecologists. We review ~180 papers, identifying the definitions or conceptualisations of ‘resilience’ that they use, and analysing the ways in which palaeoecology is contributing to our understanding of ecological resilience. We identify three key areas for further development. First, the term ‘resilience’ is frequently defined too broadly to be meaningful without further qualification. In particular, palaeoecologists need to distinguish between ‘press’ vs ‘pulse’ disturbances, and ‘ecological’ vs ‘engineering’ resilience. Palaeoecologists are well placed to critically assess the extent to which these dichotomies apply in real (rather than theoretical) ecosystems, where climate and other environmental parameters are constantly changing. Second, defining a formal ‘response model’ – a statement of the anticipated relationships between proxies, disturbances and resilience properties – can help to clarify arguments, especially inferred causal links, since the difficulty of proving causation is a fundamental limitation of palaeoecology for understanding ecosystem drivers and responses. Third, there is a need for critical analysis of the role of scale in ecosystem resilience. Different palaeoenvironmental proxies are differently able to address the various temporal and spatial scales of ecological change, and these limitations, as well as methodological constraints on inherently noisy proxy data, need to be explored and addressed.

The impact of pre‐Columbian indigenous communities on forest cover in Amazonia is highly contentious, particularly for the wettest forests. To contribute to this debate, we studied the vegetation and fire history of a site, Quistococha, which lies within the aseasonal forests of the northern Peruvian Amazon and is associated with independently dated pre‐Columbian and recent human occupation. Paired cores from swamp and lake environments were used to distinguish landscape‐scale changes in vegetation from local‐scale succession. An increased abundance of disturbance‐adapted taxa in the pollen record from the lake, but not swamp, since c. AD 1860 probably reflects extensive deforestation related to the expansion of the nearby city of Iquitos. However, previous persistent occupation of the site by pre‐Columbian indigenous communities, indicated by the charcoal record from the lake site, is not associated with evidence for similarly extensive disturbance of the landscape. The unique features of this site therefore demonstrate that occupation by indigenous communities over thousands of years was not associated with large‐scale deforestation. These results support an emerging model of persistent but localized impacts by pre‐Columbian indigenous communities on aseasonal Amazonian forests.

FCD was supported by a NERC PhD Studentship (NE/ J50001X/1). Additional funding for the peatland fieldwork and floristic assessment was provided by a NERC Small Grant to KHR, TRB and IL (NE/H011773/1), The Royal Geographical Society, The Quaternary Research Association, The Anglo-Peruvian Society, the Earth and Space Foundation, and the Instituto de Investigaciones de la Amazonía Peruana. Plot installation, fieldwork and botanical identification in RAINFOR plots has been supported by several grants including a Gordon and Betty Moore Foundation grant to RAINFOR, the EU’s Seventh Framework Programme (283080, ‘GEOCARBON’) and NERC Grants to OLP (Grants NER/A/S/2000/0053, NE/B503384/1, NE/F005806/1, and a NERC Postdoctoral Fellowship), and a National Geographic Society for supporting forest dynamics research in Amazonian Peru (grant #5472-95). OLP is supported by an ERC Advanced Grant and is a Royal Society-Wolfson Research Merit Award holder. TRB acknowledges support from a Leverhulme Research Fellowship (RF-2015-653). Western Amazonia is known to harbour some of Earth's most diverse forests, but previous floristic analyses have excluded peatland forests which are extensive in northern Peru and are among the most environmentally extreme ecosystems in the lowland tropics. Understanding patterns of tree species diversity in these ecosystems is important both for quantifying beta-diversity in this region, and for understanding determinants of diversity more generally in tropical forests. Here we explore patterns of tree diversity and composition in two peatland forest types – palm swamps and peatland pole forests – using 26 forest plots distributed over a large area of northern Peru. We place our results in a regional context by making comparisons with three other major forest types: terra firme forests (29 plots), white-sand forests (23 plots) and seasonally-flooded forests (11 plots). Peatland forests had extremely low (within-plot) alpha-diversity compared with the other forest types that were sampled. In particular, peatland pole forests had the lowest levels of tree diversity yet recorded in Amazonia (20 species per 500 stems, Fisher's alpha 4.57). However, peatland pole forests and palm swamps were compositionally different from each other as well as from other forest types in the region. Few species appeared to be peatland endemics. Instead, peatland forests were largely characterised by a distinctive combination of generalist species and species previously thought to be specialists of other habitats, especially white-sand forests. We suggest that the transient nature and extreme environmental conditions of Amazonian peatland ecosystems have shaped their current patterns of tree composition and diversity. Despite their low alpha-diversity, the unique combination of species found in tree communities in Amazonian peatlands augment regional beta-diversity. This contribution, alongside their extremely high carbon storage capacity and lack of protection at national level, strengthens their status as a conservation priority. Postprint

The peatlands research was funded by Natural Environment Research Council Open CASE award (ref. no. 1087746) to S.L.L. and G.C.D.; NERC Radiocarbon Facility NRCF010001 (alloc. no. 1688.0313 and 1797.0414) to I.T.L., S.L.L. and G.C.D.), Phillip Leverhulme Prize (to S.L.L.) and the Wildlife Conservation Society-Congo (to G.C.D). The recent publication of the first spatially explicit map of peatlands in the Cuvette Centrale, central Congo Basin, reveals it to be the most extensive tropical peatland complex, at ca. 145,500 km2. With an estimated 30.6 Petagrams of carbon stored in these peatlands, there are now questions about whether these carbon stocks are under threat and, if so, what can be done to protect them. Here we analyse the potential threats to Congo Basin peat carbon stocks and identify knowledge gaps in relation to these threats, and to how the peatland systems might respond. Climate change emerges as a particularly pressing concern, given its potential to destabilize carbon stocks across the whole area. Socio-economic developments are increasing across central Africa and, whilst much of the peatland area is on paper protected by some form of conservation designation, the potential exists for hydrocarbon exploration, logging, plantations, and other forms of disturbance to significantly damage the peatland ecosystems. The low level of human intervention at present suggests that the opportunity still exists to protect the peatlands in a largely intact state, possibly drawing on climate mitigation funding, which can be used not only to protect the peat carbon pool but also to improve the livelihoods of people living in and around these peatlands. Publisher PDF

This research was undertaken while E.W. held a NERC-funded Doctoral Training grant (NE/K500847/1). This research was also supported by a Young Research Workers award to E.W. from the Quaternary Research Association.

Fine ash produced during volcanic eruptions can be dispersed over a vast area, where it poses a threat to aviation, human health and infrastructure. We analyse the particle size distributions, geochemistry and glass shard morphology of 19 distal (>1000 km from source) volcanic ash deposits distributed across northern Europe, many geochemically linked to a specific volcanic eruption. The largest glass shards in the cryptotephra deposits were 250 µm (longest axis basis). For the first time, we examine the replicability and reliability of glass shard size measurements from peatland and lake archives. We identify no consistent trend in the vertical sorting of glass shards by size within lake and peat sediments. Measuring the sizes of 100 shards from the vertical sample of peak shard concentration is generally sufficient to ascertain the median shard size for a cryptotephra deposit. Lakes and peatlands in close proximity contain cryptotephras with significantly different median shard size in four out of five instances. The trend toward a greater amount of larger shards in lakes may have implications for the selection of distal sites to constrain the maximum glass shard size for modelling studies. Although the 95th percentile values for shard size generally indicate a loss of larger shards from deposits at sites farther from the volcano, due to the dynamic nature of the controls on tephra transport even during the course of one eruption there is no simple relationship between median shard size and transport distance.

This work is funded by a Royal Society research grant to GTS (grant no. 481831). We acknowledge a quota PhD studentship, a radiocarbon facility grant (ref. 1747.1013) and a project grant (ref. NE/H011773/1) from the Natural Environmental Research Council (NERC). To date there have only been two studies using testate amoebae as palaeoecological indicators in tropical peatlands. Here we present a new ∼500-year testate amoeba record from San Jorge, a domed peatland in Peruvian Amazonia, which has a well-constrained vegetation history based on pollen analysis. We observe a major shift from Hyalosphenia subflava to Cryptodifflugia oviformis-dominated communities at ∼50 cm depth (c. AD 1760), which suggests a change to drier conditions in the peatland. The application of a statistical transfer function also suggests a deepening of the water table at this time. The transition in the microbial assemblage occurs at a time when pollen and geochemical data indicate drier conditions (reduced influence of river flooding), leading to an ecosystem switch to more ombrotrophic-like conditions in the peatland. Our work illustrates the potential of testate amoebae as important tools in tropical peatland palaeoecology, and the power of multiproxy approaches for understanding the long-term development of tropical peatlands. Postprint

Peatlands are carbon-rich ecosystems that cover just three per cent of Earth's land surface, but store one-third of soil carbon. Peat soils are formed by the build-up of partially decomposed organic matter under waterlogged anoxic conditions. Most peat is found in cool climatic regions where unimpeded decomposition is slower, but deposits are also found under some tropical swamp forests. Here we present field measurements from one of the world's most extensive regions of swamp forest, the Cuvette Centrale depression in the central Congo Basin. We find extensive peat deposits beneath the swamp forest vegetation (peat defined as material with an organic matter content of at least 65 per cent to a depth of at least 0.3 metres). Radiocarbon dates indicate that peat began accumulating from about 10,600 years ago, coincident with the onset of more humid conditions in central Africa at the beginning of the Holocene. The peatlands occupy large interfluvial basins, and seem to be largely rain-fed and ombrotrophic-like (of low nutrient status) systems. Although the peat layer is relatively shallow (with a maximum depth of 5.9 metres and a median depth of 2.0 metres), by combining in situ and remotely sensed data, we estimate the area of peat to be approximately 145,500 square kilometres (95 per cent confidence interval of 131,900-156,400 square kilometres), making the Cuvette Centrale the most extensive peatland complex in the tropics. This area is more than five times the maximum possible area reported for the Congo Basin in a recent synthesis of pantropical peat extent. We estimate that the peatlands store approximately 30.6 petagrams (30.6 × 10(15) grams) of carbon belowground (95 per cent confidence interval of 6.3-46.8 petagrams of carbon)-a quantity that is similar to the above-ground carbon stocks of the tropical forests of the entire Congo Basin. Our result for the Cuvette Centrale increases the best estimate of global tropical peatland carbon stocks by 36 per cent, to 104.7 petagrams of carbon (minimum estimate of 69.6 petagrams of carbon; maximum estimate of 129.8 petagrams of carbon). This stored carbon is vulnerable to land-use change and any future reduction in precipitation.

The chemical, physical and palaeobotanical composition of peat can be used to infer the history of a peatland and the processes presently operating within it. Here we present new data on the geochemistry of a peat sequence from a lowland palm swamp, Quistococha, in Peruvian Amazonia. We show, through comparison with subfossil pollen data from the same sequence, that changes in the depositional environment cause changes in peat properties including lignin content, C/N ratios, and the abundance of several metal cations, but that these properties are altered by post-depositional processes to a large extent. An upward trend in the top 1.5 m of the sequence in the concentrations of N, K, Ca, Mg and Na probably reflects nutrient uptake and cycling by the standing biomass. Upward trends in Mn and Fe concentrations suggest that limited oxygenation of the peat may occur to a similar depth. Comparison with other published records suggests that such deep biological alteration may be characteristic of tropical forested peats.

The volcanic ash or ‘tephra’ cloud resulting from the relatively small (volume and VEI) eruption of the Icelandic volcano Eyjafjallajokull in 2010 caused major air travel disruption, at substantial global economic cost. On several occasions in the past few centuries, Icelandic eruptions have created ash and/or sulphur dioxide clouds which were detected over Europe (e.g. Hekla in 1947, Askja in 1875, and Laki in 1783). However, these historical observations do not represent a complete record of events serious enough to disrupt aviation in Europe. The only feasible evidence for this is within the geological tephra record. Ash layers are preserved in bogs and lakes where tephra deposited from the atmosphere is incorporated in the peat/mud. In this article we: 1, introduce the analysis of the Northern European sedimentary tephra record; 2, discuss our findings and modelling results; 3, highlight how these were misinterpreted by the popular media; and 4, use this experience to outline several existing problems with current tephra studies and suggest agendas for future research.

Long (multi-millennial), continuous lake pollen records have provided insights into terrestrial ecosystem responses to orbital- and sub-orbital-scale climate forcing. By comparison, the potential of diatoms and stable isotopes to provide additional insights into limnetic response over comparable timescales has not been explored to the same extent, particularly in the Mediterranean region, even though such proxies are known to respond sensitively and rapidly to environmental change. Here we present a 19,000-year multiproxy record of limnetic change in the Ioannina basin, NW Greece, spanning the penultimate interglacial–glacial transition and the early penultimate glacial (c. 189–170 ka BP). The diatom record, the first from this interval in Southern Europe, reveals that lake conditions changed in concert with muted millennial-scale climate oscillations thought to originate in the North Atlantic, demonstrating clearly the sensitivity of diatoms to sub-orbital climate variability. Diatom and isotope-inferred changes in lake conditions coincided with the MIS 7/6 transition, whilst the new δ18O record suggests increased moisture availability in SE Europe during MIS 6.5, adding support for a Mediterranean-wide increase in precipitation. Comparison with pollen data from the same sequence demonstrates that lake and terrestrial ecosystems co-varied, with no delay in forest expansion in response to climate change during this interval. Substantial changes in lake conditions contrast with subdued changes in catchment vegetation during an 8000 year-long cold interval in the early penultimate glacial. This may reflect differences in limnetic and terrestrial thresholds of response to environmental change, and perhaps also the influence of site specific factors in modulating terrestrial ecosystem response.

Aim To characterize the changing fire regime of a Mediterranean landscape during the Holocene and the Last Interglacial and, by comparing the two periods, to improve our understanding of the extent and timing of human alteration of natural fire regimes. Location Lake Ioannina, north-western Greece (39°45′ N, 20°51′ E). Methods Using a long sequence of lake sediments, we measured the charcoal content of the sediment over the course of the Holocene and the Last Interglacial. We compared the charcoal data with pollen data for the same periods. Results Charcoal was present in all samples analysed. Charcoal influx was greater during interglacials, which at Ioannina were forested, than during glacials, when tree populations were small. Charcoal influx was greater and more variable during the Holocene than during the Last Interglacial. Main conclusions Fire was a persistent feature throughout the periods studied, under both glacial and interglacial conditions. Overall, more biomass was burned during interglacials than during glacials, and peak burning occurred at intermediate values of moisture availability. There is little evidence that the composition of forests significantly affected burning regimes. Enhanced burning during the Holocene relative to the Last Interglacial may reflect human impact, as well as climatic or vegetational differences between the two periods.

The form and functioning of peatlands depend strongly on their hydrological status, but there are few data available on the hydraulic properties of tropical peatlands. In particular, the saturated hydraulic conductivity (K) has not previously been measured in neotropical peatlands. Piezometer slug tests were used to measure K at two depths (50 and 90 cm) in three contrasting forested peatlands in the Peruvian Amazon: Quistococha, San Jorge and Buena Vista. Measured K at 50 cm depth varies between 0.00032 and 0.11 cm s−1, and at 90 cm, it varies between 0.00027 and 0.057 cm s−1. Measurements of K taken from different areas of Quistococha showed that spatial heterogeneity accounts for ~20% of the within-site variance and that depth is a good predictor of K. However, K did not vary significantly with depth at Buena Vista and San Jorge. Statistical analysis showed that ~18% of the variance in the K data can be explained by between-site differences. Simulations using a simple hydrological model suggest that the relatively high K values could lead to lowering of the water table by >10 cm within ~48 m of the peatland edge for domed peatlands, if subjected to a drought lasting 30 days. However, under current climatic conditions, even with high K, peatlands would be unable to shed the large amount of water entering the system via rainfall through subsurface flow alone. We conclude that most of the water leaves these peatlands via overland flow and/or evapotranspiration. Copyright © 2013 John Wiley & Sons, Ltd.

This research was undertaken while Elizabeth Watson held a NERC-funded Doctoral Training Grant (NE/K500847/1). GTS acknowledges support from the Dutch Foundation for the Conservation of Irish Bogs. IS and EJW thank CGS for generous support of the fieldwork in Sweden. Despite the widespread application of tephra studies for dating and correlation of stratigraphic sequences (‘tephrochronology’), questions remain over the reliability and replicability of tephra records from lake sediments and peats, particularly in sites >1000 km from source volcanoes. To address this, we examine the tephrostratigraphy of four pairs of lake and peatland sites in close proximity to one another (

The character and impact of climate change since the last glacial maximum (LGM) in the eastern Mediterranean region remain poorly understood. Here, two new diatom records from the Ioannina basin in northwest Greece are presented alongside a pre-existing record and used to infer past changes in lake level, a proxy for the balance between precipitation and evaporation. Comparison of the three records indicates that lake-level fluctuations were the dominant driver of diatom assemblage composition change, whereas productivity variations had a secondary role. The reconstruction indicates low lake levels during the LGM. Late glacial lake deepening was underway by 15.0 cal kyr BP, implying that the climate was becoming wetter. During the Younger Dryas stadial, a lake-level decline is recorded, indicating arid climatic conditions. Lake Ioannina deepened rapidly in the early Holocene, but long-term lake-level decline commenced around 7.0 cal kyr BP. The pattern of lake-level change is broadly consistent with an existing lake-level reconstruction at Lake Xinias, central Greece. The timing of the apparent change, however, is different, with delayed early Holocene deepening at Xinias. This offset is attributed to uncertainties in the age models, and the position of Xinias in the rain shadow of the Pindus Mountains.

We present distribution maps for all cryptotephras (distal volcanic ash layers) younger than 7 ka that have been reported from three or more lakes or peatlands in north-west Europe. All but one of the tephras originates from Iceland; the exception has been attributed to Jan Mayen. We find strong spatial patterning in tephra occurrence at the landscape scale; most, but not all of the tephra occurrences are significantly spatially clustered, which likely reflects atmospheric and weather patterns at the time of the eruptions. Contrary to expectations based on atmospheric modelling studies, tephras appear to be at least as abundant in Ireland and northern Scotland as in Scandinavia. Rhyolitic and other felsic tephras occur in lakes and peatlands throughout the study region, but andesitic and basaltic tephras are largely restricted to lake sites in the Faroe Islands and Ireland. Explanations of some of these patterns will require further research on the effects of different methodologies for locating and characterizing cryptotephras. These new maps will help to guide future investigations in tephrochronology and volcanic hazard analysis. Postprint

The ash cloud resulting from the A.D. 2010 eruption of Eyjafjallajokull in Iceland caused severe disruption to air travel across Europe, but as a geological event it is not unprecedented. Analysis of peats and lake sediments from northern Europe has revealed the presence of microscopic layers of Icelandic volcanic ash (tephra). These sedimentary records, together with historical records of Holocene ash falls, demonstrate that Icelandic volcanoes have generated substantial ash clouds that reached northern Europe many times. Here we present the first comprehensive compilation of sedimentary and historical records of ash-fall events in northern Europe, spanning the past 7000 yr. Ash-fall events appear to have been more frequent in the past 1500 yr. It is unclear whether this reflects a true increase in eruption frequency or dispersal, or is an artifact of the records or the way in which they have been generated. In the past 1000 yr, volcanic ash clouds reached northern Europe with a mean return interval of 56 ± 9 yr (the range of return intervals is between 6 and 115 yr). Probabilistic modeling using the ash records for the last millennium indicates that for any 10 yr period there is a 16% probability of a tephra fallout event in northern Europe. These values must be considered as conservative estimates due to the nature of tephra capture and preservation in the sedimentary record.

The vegetational history of the penultimate glacial period, Marine Isotope Stage (MIS) 6 (c. 185-135 ka), has remained relatively unexplored. Here we present a new record from the Ioannina basin, north-west Greece, which constitutes the highest-resolution terrestrial pollen record for this interval produced to date. It shows that the vegetation history of MIS 6 in this region can be divided into two parts: an early period (185-155 ka) with pronounced oscillations in tree population extent, and a later period (155 135 ka) with much smaller tree populations and subdued oscillations. This pattern is analogous to the MIS 3/MIS 2 division during the last glacial in the same sequence, although the early part of MIS 6 had larger Pinus populations and fewer temperate trees relative to the equivalent interval in MIS 3. This implies cooler and wetter conditions, which is somewhat counterintuitive given the high summer insolation during MIS 6e, but is in line with other palaeoclimatic evidence from the Mediterranean. Comparison with North Atlantic records suggests that despite the absence of pronounced iceberg discharges during MIS 6, North Atlantic millennial-scale variability had a significant downstream impact on tree populations in north-west Greece. Copyright (C) 2011 John Wiley & Sons, Ltd.

To elucidate the vegetation dynamics in the Aegean region during the last 20 kyr, we have studied terrestrial palynomorphs in marine core GeoTü SL152 (Mount Athos Basin, northern Aegean Sea) at centennial-scale (125 to 300 yr) resolution. The robust chronology of the core allows us to reliably date signals of short-term vegetation change in the Aegean region. For the Pleniglacial interval until ~14.6 kyr BP, our data document steppe vegetation, suggesting dry climatic conditions in the borderlands of the Aegean Sea. Subaerially exposed parts of the shelf were probably colonized by Pinus-dominated vegetation until shelf areas were flooded during Lateglacial sea-level rise. The final, rapid decrease of Pinus pollen percentages between ~14 and ~13 kyr BP appears to be connected to meltwater pulse MWP-1A. The Lateglacial interstadial complex (ie, Meiendorf, Bølling and Allerød) is characterized by the spread of oak trees, but also by the continuous presence of steppe elements, indicating only slightly increased humidity. The Younger Dryas chronozone was the driest interval of the past 20 kyr. Insufficient humidity was most likely also responsible for the ~2.0 kyr delay in Holocene reforestation in the Aegean region relative to western Greece. During the Holocene, the vegetation was repeatedly affected by centennial-scale episodes of reduced moisture availability. Radiocarbon-based age models of previously published pollen records imply strong discrepancies in vegetation development in the Aegean region, but there are reasons to doubt the accuracy of these age models. Here we use the well-dated pollen record from marine core SL152 and biostratigraphic correlation to propose revised chronologies for several published terrestrial pollen records. This re-assessment yields a spatiotemporally consistent pattern of vegetation dynamics in the borderlands of the Aegean Sea.

A new pollen record of the penultimate interglacial complex, corresponding approximately to marine isotope stage (MIS) 7 (ca 186,000–245,000 years before present), has been generated in core I-284 from the Ioannina basin in northwest Greece. It represents the highest resolution terrestrial record for this interval available to date, with a mean sampling interval of 200 years. The sequence records four forested intervals, correlated with MIS 7e, 7c, 7a and a sub-orbital-scale event following 7a but within MIS 7. The longest and most complete warm stage in terms of vegetational succession is MIS 7c, while the succession in MIS 7e appears to be truncated by a shift to colder, drier climatic conditions. The results of biomisation suggest that during all of these intervals winter temperatures in NW Greece remained lower than during the Eemian or Holocene, while smaller populations of sclerophyllous taxa indicate that summers may have been wetter. Intervening intervals of open vegetation are correlated with MIS 7d, 7b and an oscillation following 7a. Low tree pollen percentages during MIS 7d are interpreted as reflecting very cold and dry conditions, concomitant with a period of low northern hemisphere insolation which resulted from a rare combination of minimum obliquity and maximum precession. Higher tree pollen percentages throughout MIS 7b, by contrast, are indicative of relatively mild conditions, in agreement with marine temperature and ice volume records. Sub-orbital scale oscillations in tree population extent are also recorded in the new I-284 record suggesting that, just as in the last climatic cycle, NW Greece was affected by rapid climatic oscillations that are associated with changes in the North Atlantic.

Uncertainty as to the pattern of Lateglacial and early Holocene climate change in the western Balkans and Greece has persisted despite extensive investigation of the Ioannina I-284 lake–sediment sequence, northwest Greece. Here we present a new diatom record from I-284 for this time period. After dominance by eurytopic small Fragilariales, the Lateglacial Interstadial (ca 14.9–12.7 cal kyr BP) is marked clearly by a relative increase in planktonic Cyclotella ocellata. A return to small Fragilariales from ca 12.7 to 11.6 cal kyr BP approximately coincides with the Younger Dryas chronozone. It is followed by a major transition to dominance by Cyclotella spp. at the Pleistocene–Holocene boundary. We interpret these shifts as a response to both lake level and productivity change induced by shifts in effective moisture and temperature, demonstrating that the diatom record provides the first strong evidence for a Younger Dryas event in northwest Greece, and for both warming and wetting during the Lateglacial interstadial and early Holocene. We also present clear evidence for an abrupt phase of catchment instability during the early Holocene. In this case we must await the results of further research to test whether it was driven by climatic or tectonic forcing.

This work was funded by the Leverhulme Trust under the programme ‘Landscapes circum-landnam’

Chironomids were examined as part of a multiproxy palaeolimnological study of Gróthúsvatn, Sandoy, Faroe Islands. A total of 37 taxa was found in the top 1 m of the core. Chironomid-inferred total phosphorus and temperature reconstructions indicate that after landnám (the Norse settlement period) total phosphorus levels rose slightly, then peaked at a temperature minimum (interpreted as the `Little Ice Age'). Total phosphorus levels subsequently fell to only slightly above pre-settlement levels at the sediment surface. Little indication of increased erosion in the catchment after landnám was found, and it is likely that the impacts of human settlement on Gróthúsvatn and its catchment were slight. We therefore propose that the temperature decrease caused the increase in the lake's productivity.