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Climate warming is leading to permafrost thaw in northern peatlands, and current predictions suggest that thawing will drive greater surface wetness and an increase in methane emissions. Hydrology largely drives peatland vegetation composition, which is a key element in peatland functioning and thus in carbon dynamics. These processes are expected to change. Peatland carbon accumulation is determined by the balance between plant production and peat decomposition. But both processes are expected to accelerate in northern peatlands due to warming, leading to uncertainty in future peatland carbon budgets. Here, we compile a dataset of vegetation changes and apparent carbon accumulation data reconstructed from 33 peat cores collected from 16 sub-arctic peatlands in Fennoscandia and European Russia. The data cover the past two millennia that has undergone prominent changes in climate and a notable increase in annual temperatures towards present times. We show a pattern where European sub-Arctic peatland microhabitats have undergone a habitat change where currently drier habitats dominated by Sphagnum mosses replaced wetter sedge-dominated vegetation and these new habitats have remained relatively stable over the recent decades. Our results suggest an alternative future pathway where sub-arctic peatlands may at least partly sustain dry vegetation and enhance the carbon sink capacity of northern peatlands.

This article introduces Corpus PalaeoHibernicum (CorPH), a corpus currently consisting of 78 texts in Early Irish (c. 7th–10th cent.) created by the ERC-funded Chronologicon Hibernicum (ChronHib) project by bringing together pre-existing lexical and syntactic databases and adding further crucial texts from the period. In addition to being annotated for POS, morphological and syntactic information, another layer of annotation has been developed for CorPH – ‘Variation Tagging’, i.e. a tagset that numerically encodes synchronic language variation during the Early Irish period, thus allowing for much improved research on the chronological variation among the material. Another new pillar of studying linguistic variation is Bayesian Language Variation Analysis (BLaVA), in order to address the challenge that “not-so-big data” poses to statistical corpus methods. Instead of reflecting feature frequencies, BLaVA models language variation as probabilities of variation.

Annually laminated lake sediment can track paleoenvironmental change at high resolution where alternative archives are often not available. However, information about the chronology is often affected by indistinct and intermittent laminations. Traditional chronology building struggles with these kinds of laminations, typically failing to adequately estimate uncertainty or discarding the information recorded in the laminations entirely, despite their potential to improve chronologies. We present an approach that overcomes the challenge of indistinct or intermediate laminations and other obstacles by using a quantitative lamination quality index combined with a multi-core, multi-observer Bayesian lamination sedimentation model that quantifies realistic under- and over-counting uncertainties while integrating information from radiometric measurements (210Pb, 137Cs, and 14C) into the chronology. We demonstrate this approach on sediment of indistinct and intermittently laminated sequences from alpine Columbine Lake, Colorado. The integrated model indicates 3137 (95 % highest probability density range: 2753–3375) varve years with a cumulative posterior distribution of counting uncertainties of −13 % to +7 %, indicative of systematic observer under-counting. Our novel approach provides a realistic constraint on sedimentation rates and quantifies uncertainty in the varve chronology by quantifying over- and under-counting uncertainties related to observer bias as well as the quality and variability of the sediment appearance. The approach permits the construction of a chronology and sedimentation rates for sites with intermittent or indistinct laminations, which are likely more prevalent than sequences with distinct laminations, especially when considering non-lacustrine sequences, and thus expands the possibilities of reconstructing past environmental change with high resolution.

Mining has been a major contributor to economic development in Australia since British arrival in the late 1700s, with little to no thought regarding the long-term environmental consequences. This study assesses the metal pollution legacy caused by different smelting methods and mining activities during the British colonialism in western Tasmania. This region was the largest copper producer in the Southern Hemisphere during the 20th century. Lake sediments from Basin Lake and Owen Tarn, 12 and 5 km from Queenstown’s mines, respectively, were used to reconstruct historical metal contamination. Temporal changes in metal concentrations (iron, copper, arsenic, selenium and lead) were assessed in relation to the scale of mining activities and the technologies used. Sedimentation rates and metal influxes increased from 1900, reflecting the beginning of copper mining in Mount Lyell. Observed metal concentrations peaked after 1930, coinciding with the introduction of large-scale open-cut operations and an expansion of the mining machinery used. All elements underwent at least minor enrichment (EF 1-3) during the lifespan of the mine, with lead and copper undergoing extremely severe enrichment (EF > 50). Although smelters contributed to metal increases in the lakes, large open-cut large operations in the 1930s contributed most to metal contamination. Local metal deposition from mining-related activities decreased significantly once operations decreased, with selenium and arsenic decreasing nearly to background levels within 50 years. Lead and copper, the elements which underwent major enrichment, have not yet reached background values. The ecological consequences include the current degraded local landscape, poor water quality and disrupted local biota. Knowledge about the environmental impacts of mining in western Tasmania is less known compared to other sites around the world with a similar history. Our results demonstrate the urgent need to develop better policies and remediation programs that can mitigate the consequences of metal pollution from abandoned mines in Australia.

A 39-cm sediment core from Castle Lake, California (USA) spans the last ~ 450 years and was analyzed for diatoms and organic geochemistry (δ15N, δ13C, and C:N), with the goal of determining sensitivity to natural climate variation and twentieth century anthropogenic effects. Castle Lake is a subalpine, nitrogen-limited lake with ~ 5 months of annual ice cover. Human impacts include light recreational use, past fish stocking, and experimental use by the Castle Lake Research Station. The base of the core (below 32 cm; pre mid-1700s) represents the period of maximum ice cover. In contrast, the end of the Little Ice Age (mid 1700s–early 1800s) is dominated by cyclotelloids (mostly Discostella stelligera), indicating significant open-water periods, a condition that persisted into the early 1900s. Cyclotelloids began to decline in the 1960s and were replaced by the Fragilaria tenera grp. (peak in 1970s), succeeded by Asterionella formosa (peak ~ 2010), and accompanied by a reduction in δ15N values and a decrease in C:N that may represent increased atmospheric nitrogen deposition. Another anthropogenic signal was discerned in the core and was interpreted to be the result of an ammonium nitrate fertilization experiment of the epilimnion that was conducted in 1980 and 1981. This signal was manifested in the core largely by a negative excursion in δ15N, possibly caused by fractionation during denitrification in surface sediment. A phytoplankton monitoring dataset collected by the Castle Lake Research Station from 1967 to 1984 corroborates the timing of increased araphid euplanktonic species in the 1970s, and increases in two benthic diatoms (Staurosirella pinnata and Tabellaria fenestrata), entrained in the phytoplankton tows during the experimentation years. Both ice cover and nitrogen addition appear to be strong drivers that affected the lake diatoms, although additional drivers, such as fish stocking and associated cascade effects need further exploration. These data will be helpful for interpreting longer core records from Castle Lake, should the opportunity arise, as well as cores from similar systems in the region.

Radiometric dating methods are essential for developing geochronologies to study Late Quaternary environmental change and 210Pb dating is commonly used to produce age-depth models from recent (within 150 years) sediments and other geoarchives. The past two centuries are marked by rapid environmental socio-ecological changes frequently attributed to anthropogenic land-use activities, modified biogeochemical cycles, and climate change. Consequently, historical reconstructions over this recent time interval have high societal value because analyses of these datasets provide understanding of the consequences of environmental modifications, critical ecosystem thresholds, and to define desirable ranges of variation for management, restoration, and conservation. For this information to be used more broadly, for example to support land management decisions or to contribute data to regional analyses of ecosystem change, authors must report all of the useful age-depth model information. However, at present there are no guidelines for researchers on what information should be reported to ensure 210Pb data are fully disclosed, reproducible, and reusable; leading to a plethora of reporting styles, including inadequate reporting that reduces potential reusability and shortening the data lifecycle. For example, 64% of the publications in a literature review of 210Pb dated geoarchives did not include any presentation of age uncertainty estimates in modeled calendar ages used in age-depth models. Insufficient reporting of methods and results used in 210Pb dating geoarchives severely hampers reproducibility and data reusability, especially in analyses that make use of databased palaeoenvironmental data. Reproducibility of data is fundamental to further analyses of the number of palaeoenvironmental data and the spatial coverage of published geoarchives sites. We suggest, and justify, a set of minimum reporting guidelines for metadata and data reporting for 210Pb dates, including an IEDA (Interdisciplinary Earth Data Alliance), LiPD (Linked Paleo Data) and generic format data presentation templates, to contribute to improvements in data archiving standards and to facilitate the data requirements of researchers analyzing datasets of several palaeoenvironmental study sites. We analyse practices of methods, results and first order interpretation of 210Pb data and make recommendations to authors on effective data reporting and archiving to maximize the value of datasets. We provide empirical evidence from publications and practitioners to support our suggested reporting guidelines. These guidelines increase the scientific value of 210Pb by expanding its relevance in the data lifecycle. Improving quality and fidelity of environmental datasets broadens interdisciplinary use, lengthens the potential lifecycle of data products, and achieves requirements applicable for evidenced-based policy support.

Annually laminated lake sediment can track paleoenvironmental change at high-resolution where alternative archives are often not available. However, information about both paleoenvironmental change and chronology are often affected by indistinct and intermittent varves. We present an approach that overcomes these and other obstacles by using a quantitative varve quality index combined with a multi-core, multi-observer Bayesian varve sedimentation model that quantifies realistic under- and over-counting uncertainties while integrating information from radiometric measurements (210Pb, 137Cs, and 14C) into the chronology. We demonstrate this approach on thin sections of indistinct and intermittently varved sequences from alpine Columbine Lake, Colorado. The integrated model indicates 3137 (95 percentile highest density probability range: 2753–3375) varve years with a cumulative posterior distribution of counting uncertainties of −13/+7 % indicative of systematic observer undercounting. The sedimentary features of the thin and complex varves shift through time, from normally graded couplets to couplets interrupted with coarser sub-laminae, to inversely graded couplets. We interpret the normal grading couplets as spring nival discharge followed by winter settling, the coarser sub-laminae as high rainfall events, and the inverse grading as hyperpycnal flows and/or pulses of dust related to human impact changing the varve formation mechanism. Our novel approach provides a realistic constraint on sedimentation rates and quantifies uncertainty in varve counts by quantifying over- and under-counting uncertainties related to observer bias and the quality and variability of the sediment appearance. The approach permits the construction of a varve chronology and sedimentation rates for sites with intermittent or indistinct varves, which are likely more prevalent than sequences with distinct varves, and thus, expands the possibilities of reconstructing past environmental change with high resolution.

Dating with 210Pb has been instrumental in providing chronologies for sedimentary deposits back to around 100-150 years ago — a key period for recent environmental events such as increased pollution caused by industry developments. However, currently available 210Pb age-models often disagree with and/or cannot incorporate other types of dates, depend highly on the correct estimation of background 210Pb, often underestimate uncertainties and are limited by unrealistic assumptions of sediment accumulation over time. Plum is open-source Bayesian age-modelling software that solves the above problems. It can integrate other dates, produce realistic uncertainty estimates, and extend 210Pb chronologies several decades further back in time. Our method thus enables much more robust chronologies for studies of recent environmental change.

Permafrost peatlands are found in high-latitude regions and store globally-important amounts of soil organic carbon. These regions are warming at over twice the global average rate, causing permafrost thaw, and exposing previously inert carbon to decomposition and emission to the atmosphere as greenhouse gases. However, it is unclear how peatland hydrological behaviour, vegetation structure and carbon balance, and the linkages between them, will respond to permafrost thaw in a warming climate. Here we show that permafrost peatlands follow divergent ecohydrological trajectories in response to recent climate change within the same rapidly warming region (northern Sweden). Whether a site becomes wetter or drier depends on local factors and the autogenic response of individual peatlands. We find that bryophyte-dominated vegetation demonstrates resistance, and in some cases resilience, to climatic and hydrological shifts. Drying at four sites is clearly associated with reduced carbon sequestration, while no clear relationship at wetting sites is observed. We highlight the complex dynamics of permafrost peatlands and warn against an overly-simple approach when considering their ecohydrological trajectories and role as C sinks under a warming climate.

Mountain ecosystems are sensitive to environmental changes and are affected by direct and indirect anthropogenic activities. This study sought to understand the impacts of human occupation, environmental and climate change on the Great Hinggan Mountains (GHM) in Northeastern China. The last 200 years of environmental changes are reconstructed by analyzing sediment cores from five small mountain lakes. Cores were dated using ²¹⁰Pb and ¹³⁷Cs radioisotopes, microscopic charcoal identified regional fire activity and fossil pollen analysis reconstructed temporal and spatial changes in vegetation. Peaks in ¹³⁷Cs, ²²⁶Ra and microscopic charcoal flux were found to follow similar trends between sites. The radioisotope records reflect redistribution processes, such as erosion and fire events, which overwhelm the atmospheric fallout signal in the GHM. Microscopic charcoal increased from 1950 CE and peaked at all sites after 2000 CE suggesting that current fire management, coupled with a warmer climate due to global warming, may be leading to more wildfire events in the region. Pinus, Quercus and Betula declined at all sites as human occupation occurred in the early 1900s. Initially, open forest and grassland expanded in response to overexploitation of forests, followed by arboreal pollen reaching maximum values after 2000 CE. This study concludes that the present‐day mixed coniferous broad‐leaved forest dominating the southern region of the GHM is a product of changing fire activity, excessive logging and, more recently, forestry management and vegetation regeneration. Results suggest further management strategies are needed to address land degradation and wildfire events in mountain regions of Northeastern China.

Chronologies are an essential tool to place natural archives of environmental changes on a calendar scale. Because of this, studies that compare and assess the accuracy and precision of available dating models are essential. 210Pb is a radioactive isotope which is used to date recent sediments (210Pb dating models: the Constant Flux model (also known as the Constant Rate of Supply model) and the recently developed Bayesian Plum model. This comparison was implemented by using four sediment cores from contrasting environmental settings, and showed several benefits of using a Bayesian approach. This allows to infer variables, such as the supported levels of 210Pb, crucial to the chronology and commonly estimated through either samples where an asymptotic behaviour is observed or through 226Ra measurements, which themselves contain some level of uncertainty. Another step of traditional methods is the selection of the equilibrium depth in order to calculate total inventories, which carries strong consequences for the resulting age depth model. Plum, on the other hand, infers the 210Pb flux, which eliminates the need to select an equilibrium depth and allows for dating cores with incomplete inventory. When traditional methods address cores with missing inventory, 137Cs time markers are commonly used to correct the chronology, but Plum can use these time markers to improve the chronology and to reduce the uncertainty. These aspects show that the Bayesian approach results in more robust and objective chronologies, and thus in better reconstructions of environmental change over the past centuries.

In studies of environmental change of the past few centuries, $$^{210}$$ Pb dating is often used to obtain chronologies for sedimentary sequences. One of the most commonly used approaches to estimate the age of material at different depths in a sequence is to assume a constant rate of supply (CRS) or influx of ‘unsupported’ $$^{210}$$ Pb from the atmosphere, together with a constant or varying amount of ‘supported’ $$^{210}$$ Pb. Current $$^{210}$$ Pb dating models do not use a proper statistical framework and provide poor estimates of the uncertainties. Here, we develop a new model for $$^{210}$$ Pb dating, where ages and values of supported and unsupported $$^{210}$$ Pb form part of the parameters. We apply our model to a case study from Canada as well as to some simulated examples. Our model can extend beyond the current CRS approach, deal with asymmetric errors and mix $$^{210}$$ Pb with other types of dating, thus obtaining more robust, realistic and statistically better defined age estimates.

Mining causes extensive damage to aquatic ecosystems via acidification, heavy metal pollution, sediment loading, and Ca decline. Yet little is known about the effects of mining on freshwater systems in the Southern Hemisphere. A case in point is the region of western Tasmania, Australia, an area extensively mined in the 19th century, resulting in severe environmental contamination. In order to assess the impacts of mining on aquatic ecosystems in this region, we present a multiproxy investigation of the lacustrine sediments from Owen Tarn, Tasmania. This study includes a combination of radiometric dating (14C and 210Pb), sediment geochemistry (XRF and ICP-MS), pollen, charcoal and diatoms. Generalised additive mixed models were used to test if changes in the aquatic ecosystem can be explained by other covariates. Results from this record found four key impact phases: (1) Pre-mining, (2) Early mining, (3) Intense mining, and (4) Post-mining. Before mining, low heavy metal concentrations, slow sedimentation, low fire activity, and high biomass indicate pre-impact conditions. The aquatic environment at this time was oligotrophic and dystrophic with sufficient light availability, typical of western Tasmanian lakes during the Holocene. Prosperous mining resulted in increased burning, a decrease in landscape biomass and an increase in sedimentation resulting in decreased light availability of the aquatic environment. Extensive mining at Mount Lyell in the 1930s resulted in peak heavy metal pollutants (Pb, Cu and Co) and a further increase in inorganic inputs resulted in a disturbed low light lake environment (dominated by Hantzschia amphioxys and Pinnularia divergentissima). Following the closure of the Mount Lyell Co. in 1994 CE, Ca declined to below pre- mining levels resulting in a new diatom assemblage and deformed diatom valves. Therefore, the Owen Tarn record demonstrates severe sediment pollution and continued impacts of mining long after mining has stopped at Mt. Lyell Mining Co.

The Hunter and Latrobe Valleys have two of the richest coal deposits in Australia. They also host the largest coal-fired power stations in the country. We reconstructed metal deposition records in lake sediments in the Hunter and Latrobe Valleys to determine if metal deposition in freshwater lakes have increased in the region. The current regulatory arrangement applied to metal emissions from coal-fired power stations in Australia are presented, discussing their capacity to address future increases in metal deposition from these sources. Sediment records of spheroidal carbonaceous particles (SCPs), a component of fly-ash, were also used as an additional line of evidence to identify the contribution of industrial activities related to electricity generation to metal deposition in regions surrounding open-cut coal mines and coal-fired power stations. Sediment metal concentrations and SCP counts in the sedimentary records, from the Hunter and Latrobe Valleys, both indicated that open-cut coal mining and the subsequent combustion of coal in power stations has most likely resulted in an increase in atmospheric deposition of metals in the local region. In particular, the metalloids As and Se showed the greatest enrichment compared to before coal mining commenced. Although the introduction of bag filters at Liddell Power Station and the decommissioning of Hazelwood Power Station appear to have resulted in a decrease of metal deposition in nearby lakes, overall metal deposition in the environment is still increasing. The challenge for the years to come will be to develop better regulation policies and tools that will contribute to reduce metal emissions in these major electricity production centres in Australia.

Palaeoecologists use sequences of fossils within deposits from continents and oceans all over the world in order to produce time-series of past environmental dynamics over decades to millennia or longer. Such information can place current and future environmental change into context, for example by showing how climate, environments, ecosystems and humans interacted during past events, and by enabling verification of climate models through ‘hind-casting’ of such events. Through a meta-analysis and focused literature review of currently used statistical approaches in palaeoecological research, we highlight potential pitfalls and suggest ways forward to a fuller statistical understanding of the possibilities and limitations of palaeoecological studies. Statisticians or at least statistical reasoning should be involved in order to quantify uncertainties across the full analytical pipeline of obtaining, analysing and interpreting fossil time-series and could help optimizing the analytical decisions taken at all these steps. Supplementary materials accompanying this paper appear online.

ResumenEl artículo analiza los cambios político electorales en León, Guanajuato, a partir de cómo se fue configurando el desplazamiento del Partido Revolucionario Institucional (PRI) por el Partido Acción Nacional (PAN) en este ayuntamiento en el año 1988, hasta el cambio de correlación de fuerzas en el año 2012. Ello da pauta para analizar los escenarios que podrían caracterizar las próximas elecciones de este año. Con este objetivo se propone un modelo estadístico para dicho estudio: el modelo de regresión Dirichlet, el cual permite considerar la naturaleza de los datos electorales.AbstractThe article analyzes the electoral changes in León, Guanajuato, based on how it was setting the displacement of the Institutional Revolutionary Party (PRI) by the National Action Party (PAN) in this council in 1988, until the change of correlation forces in 2012, which gives guidelines to analyze the scenarios that could characterize the upcoming elections this year. With this aim the authors proposed a statistical model for the study: the Dirichlet regression model, which allows to consider the nature of electoral data.