The UK Environmental Change Network after twenty years of integrated ecosystem assessment: key findings and future perspectives

The UK Environmental Change Network (ECN), the UK's Long-Term Ecosystem Research (LTER) network, has now been operating for over twenty years. It was established in 1992 as a set of terrestrial sites at which sustained observations relevant to a range of ecological indicators and environmental parameters could be made. An additional ECN freshwater network was launched in 1994. In this paper we provide a brief history of the network, and describe its current structure and role within a complementary wider range of UK environmental monitoring and observation programmes that are either more focussed on specific parameters or habitats, or operate at different temporal and spatial scales. We then provide a review of the other papers within this Special Issue, which exemplifies the broad range of environmental concerns that ECN data and sites are helping to address. These include network-wide summaries of environmental and biological trends over the first two decades of monitoring, more site-specific assessment of the ecological impacts of local pressures resulting from changes in management, biological and ecosystem service indicator development, and the testing of new monitoring technologies. We go on to consider: (i) future directions of network development and adaptation in light of recently emerging environmental concerns, dwindling financial resources and the consequent need for greater efficiency; (ii) the desire for tighter integration with other monitoring and observation programmes both nationally internationally; (iii) opportunities raised by recent technological developments; and (iv) the need to process and make available data more rapidly to increase the capacity of ECN sites as early warning systems. In its first two decades of operation the ECN has accumulated a robust set of baseline data that describe environmental and biological variability across a range of habitats in unprecedented detail. With appropriate, informed development, these should prove invaluable in discerning the causes and consequences of environmental change for decades to come

A Water Framework Directive-compatible metric for assessing acidification in UK and Irish rivers using diatoms

Freshwater acidification continues to be a major problem affecting large areas of Europe, and while there is evidence for chemical recovery, similar evidence for biological recovery of freshwaters is sparse. The need for a methodology to identify waterbodies impacted acidification and to assess the extent of biological recovery is relevant to the EUWater Framework Directive, which requires methods to quantify differences in biology between impacted and unimpacted or reference sites. This study presents a newWFD-compliant metric based on diatoms Diatom Acidification Metric: DAM) for assessing the acidification status of rivers. A database of 558 benthic diatom samples and associated water chemistry data was assembled. Diatom taxa were assigned to one of 5 indicator classes on the basis of their pH optimum, assessed using Gaussian logistic regression, and these indicator values used to calculate a DAM score for each site using weighted averaging. Reference sites were selected on the basis of their acid neutralising capacity (ANC) and calcium concentration, and a regression model developed to predict expected DAM for each site using pH and total organic carbon (TOC) concentration. Site-specific DAM scoreswere used to calculate ecological quality ratios ranging from≥1, where the diatom assemblage showed no impact, to (theoretically) 0, when the diatom assemblage was indicative of major anthropogenic activities. The boundary between ‘high’ and ‘good’ status was defined as the 25th percentile of Ecological Quality Ratios (EQRs) of all reference sites. The boundary between ‘good’ and ‘moderate’ status was set at the point at which nutrient sensitive and nutrient-tolerant taxa were present in equal relative abundance. The methodology was evaluated using long-term data from 11 sites from the UK UplandsWaters Monitoring Network and is shown to perform well in discriminating naturally acid from acidified sites

Development of a UV miniaturised Fourier transform spectrometer (MicroFTS) for the detection of dissolved organic carbon in water

Within the UK and overseas, there are increasing scientific and water industry needs to acquire spatially and temporally intensive measurements of levels and molecular character of dissolved organic carbon (DOC) in the aquatic environment. The need is particularly acute in upland catchments that are often crucial for drinking water supply, and where DOC concentrations are high and have been increasing in recent years. Spectrometer-based systems currently on the market for this purpose are heavy, cumbersome, have a large power requirement, not sensitive in low light conditions, measure absorbance at single wavelengths, require frequent recalibration by trained operators and provide data based on hidden algorithms that limit interpretation of the resulting data. We have developed a new smaller, lighter, and self-calibrating instrument, combining novel miniaturisation of Fourier Transform Spectrometry, and a new scientifically peer-reviewed (and published) approach to assessing DOC concentrations in water. The portable sensor system uses a xenon flash lamp, where the light pulse is collimated and focused into one input of a bifurcated fibre dip probe. At the fibre tip, light is collimated and reflected in the water sample region over a total path length of 5mm. Shorter wavelengths (near the UV) are absorbed due to water containing DOC concentration. Light from the output end of the bifurcated fibre is collimated and coupled to the micro Fourier Transform Spectrometer. Within the interferometer, a broadband beam splitter and two concave mirrors are used to create an optical path difference between the beams. A UV sensitive detector is placed at the focus point of the generated interferogram. The interferogram is recorded and a Fourier Transform is applied to retrieve the spectral data. An absorbance of the DOC is measured and when a ratio is taken between the water sample containing DOC and DI water. Both detector and flash-lamp are triggered by an on-board dual wavefunction generator with a delay of 100us between the pulses. The instrument has its own portable power supply for powering the flash-lamp and pulse generator and has the capability and input for connecting with a solar panel for recharging when required

Advancing reproducible research by publishing R markdown notebooks as interactive sandboxes using the learnr package

Various R packages and best practices have played a pivotal role to promote the Findability, Accessibility, Interoperability, and Reuse (FAIR) principles of open science. For example, (1) well-documented R scripts and notebooks with rich narratives are deposited at a trusted data centre, (2) R Markdown interactive notebooks can be run on-demand as a web service, and (3) R Shiny web apps provide nice user interfaces to explore research outputs. However, notebooks require users to go through the entire analysis, while Shiny apps do not expose the underlying code and require extra work for UI design. We propose using the learnr package to expose certain code chunks in R Markdown so that users can readily experiment with them in guided, editable, isolated, executable, and resettable code sandboxes. Our approach does not replace the existing use of notebooks and Shiny apps, but it adds another level of abstraction between them to promote reproducible science

Inferring past trends in lake water organic carbon concentrations in northern lakes using sediment spectroscopy

Changing lake water total organic carbon (TOC)concentrations are of concern for lake management because of corresponding effects on aquatic ecosystem functioning, drinking water resources and carbon cycling between land and sea. Understanding the importance of human activities on TOC changes requires knowledge of past concentrations; however, water-monitoring data are typically only available for the past few decades, if at all. Here, we present a universal model to infer past lake water TOC concentrations in northern lakes across Europe and North America that uses visible-near-infrared (VNIR) spectroscopy on lake sediments. In the orthogonal partial least squares model, VNIR spectra of surface-sediment samples are calibrated against corresponding surface-water TOC concentrations (0.5–41 mg L-1) from 345 Arctic to northern temperate lakes in Canada, Greenland, Sweden and Finland. Internal model-cross-validation resulted in a R2 of 0.57 and a prediction error of 4.4 mg TOC L-1. First applications to lakes in southern Ontario and Scotland, which are outside of the model’s geographic range, show the model accurately captures monitoring trends, and suggests that TOC dynamics during the 20th century at these sites were primarily driven by changes in atmospheric deposition. Our results demonstrate that the lake-water TOC model has multi-regional applications and is not biased by post-depositional diagenesis, allowing the identification of past TOC variations in northern lakes of Europe and North America over timescales of decades to millennia

Fifty years of reduction in sulphur deposition drives recovery in soil pH and plant communities

1. Sulphur deposition through rainfall has led to species loss and ecosystem degradation globally, and across Europe huge reductions in sulphur emissions since the 1970s were expected to promote the recovery of acidified ecosystems. However, the rate and ecological impact of recovery from acidification in terrestrial ecosystems is still unclear as is the influence of management and climate, as to date there has been no long-term spatially extensive evaluation of these changes. 2. Here, we present data from thousands of sites across Great Britain (pH range 3.3–8.7) surveyed repeatedly from 1978–2019 and assess change in soil pH and plant acidity preference (Ellenberg R) in response to atmospheric deposition of sulphur and nitrogen. We analyse change in grasslands managed for pasture, referred to as high-intensity habitats, and compare to seminatural habitats comprising rough grassland, broadleaved woodland, bog and heathland, referred to as low-intensity habitats. 3. Soil pH increased from 1978 to 2007 but then decreased between 2007 and 2019, resulting in a net increase of ~0.2 pH units in low-intensity habitats but no change in high-intensity habitats. The community average Ellenberg R increased in seminatural habitats by ~0.2 units but remained stable in intensive grasslands. 4. In seminatural habitats, but not intensive grasslands, these changes in plant community composition were associated with the soil pH changes which were in turn linked to decreasing sulphur deposition and differences in rainfall. 5. Nitrogen deposition, which was relatively stable over the survey period, showed no additional effect upon soil acidity once sulphur deposition was accounted for. 6. Synthesis: Our results provide conclusive evidence that reductions in acid emissions are stimulating the gradual recovery of chronically acidified terrestrial ecosystems at a whole-country scale, while also suggesting this recovery is being compromised by changing climate and land management

Trends and patterns in surface water chemistry in Europe and North America between 1990 and 2016, with particular focus on changes in land use as a confounding factor for recovery

The report presents trends in sulphate, nitrate, chloride, base cations, ANC (acid neutralising capacity), pH and DOC at circa 500 ICP Waters sites in Europe and North America for the period 1990-2016. Time series were analysed for trends in annual median values, annual extreme values and change points, that indicate years with sudden changes in trend or level. Also provided is a brief overview of possible implications of land use change for recovery of acidified surface waters

Responses of benthic invertebrates to chemical recovery from acidification

Prosjektleder: Heleen de WitThe report provides an assessment of biological recovery from acidification in freshwater environments in Europe. The report consists of two parts, a regional data analysis based on an international dataset of biological and water chemical records, and a collection of national contributions on monitoring and assessment of biological recovery in different countries. The regional analysis showed that 47% of all included rivers (21 sites, for the period 1994-2018) and 35% percent of all lakes (34 sites, for the period 2000 to 2018) showed significant increases in species richness. Correlations between species diversity and water chemical components (ANC, pH, SO4) were found, supporting that the biological responses were related to chemical recovery. Additionally, the composition of functional traits in rivers underwent significant changes over time. Both parts of the report demonstrate ongoing biological recovery from acidification in European acid-sensitive freshwater environments.Norwegian Ministry of Climate and Environment, United Nations Economic Commission for Europe (UNECE)publishedVersio

Data Descriptor : Long-term chloride concentrations in North American and European freshwater lakes

Anthropogenic sources of chloride in a lake catchment, including road salt, fertilizer, and wastewater, can elevate the chloride concentration in freshwater lakes above background levels. Rising chloride concentrations can impact lake ecology and ecosystem services such as fisheries and the use of lakes as drinking water sources. To analyze the spatial extent and magnitude of increasing chloride concentrations in freshwater lakes, we amassed a database of 529 lakes in Europe and North America that had greater than or equal to ten years of chloride data. For each lake, we calculated climate statistics of mean annual total precipitation and mean monthly air temperatures from gridded global datasets. We also quantified land cover metrics, including road density and impervious surface, in buffer zones of 100 to 1,500m surrounding the perimeter of each lake. This database represents the largest global collection of lake chloride data. We hope that long-term water quality measurements in areas outside Europe and North America can be added to the database as they become available in the future.Peer reviewe