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Highly Pathogenic Avian Influenza Viruses (HPAIV) Associated with Major Southern Elephant Seal Decline at South Georgia
Get PDFThe emergence of highly pathogenic avian influenza viruses (HPAIV) has caused widespread mortality wildlife globally. In 2023, mass mortalities of southern elephant seals Mirounga leonina were observed in South America, and the virus subsequently reached the sub-Antarctic, affecting multiple species. The remoteness of these islands has limited assessment of its true impact. Here we present evidence of HPAIV’s effect on the number of breeding females at the world’s largest southern elephant seal population at South Georgia. Following the virus’ arrival in 2023, we recorded a 47% (SD = 14.2%) decline in the number of breeding females at the three largest breeding colony beaches in 2024 compared to 2022. The apparent loss of nearly half the breeding female population has serious implications for recruitment and future stability of the population. These findings highlight the urgent need for continued, intensive monitoring to track the long-term effects on this species
Associating local-scale physical habitat assemblages with reach-scale stream hydrogeomorphological types in mountain headwater catchments
Get PDFBuilding an understanding of river ecosystems often involves integrating information from different locations, spatial scales and points in time. Geomorphologists and ecologists have long considered ways to explore river ecosystems at different, hierarchical, spatial scales so that features observed locally can be linked to the character of the larger spatial units within which the features are located. The present research builds on a classification of mountain stream reach types and their associated physical habitat assemblages proposed by Cox et al. for headwater streams across the Republic of Ireland. In this article we augment physical habitat and bed material data collected as part of an integrated investigation of within-catchment variations in water quality, physical habitat and biota in two small, Irish, mountain headwater catchments to explore two main research questions. Do the associations among mountain headwater stream types, physical habitat assemblages and bed material, identified at a national level, persist across short stream reaches within small, Irish, mountain headwater catchments? To what extent do the properties used to assign a stream hydromorphological type to a reach vary spatially along these headwater streams and what are the im-plications of these variations for identifying ‘homogenous’ reaches that can be associated with particular physical habitat assemblages? Our analysis and results from these two small catchments are necessarily exploratory and indicative. Nevertheless, we reveal a number of patterns, associations, and scale-related issues that need to be considered when surveying such streams and which could contribute to a larger, purpose-designed and more comprehensive study
Conditions for instability in the climate–carbon cycle system
Get PDFThe climate and carbon cycle interact in multiple ways. An increase in carbon dioxide in the atmosphere warms the climate through the greenhouse effect, but also leads to uptake of CO2 by the land and ocean sink, a negative feedback. However, the warming associated with a CO2 increase is also expected to suppress carbon uptake, a positive feedback. This study addresses the question: “under what circumstances could the climate–carbon cycle system become unstable?” It uses both a reduced form model of the climate–carbon cycle system as well as the complex land model JULES, combined with linear stability theory, to show that: (i) the key destabilising loop involves the increase in soil respiration with temperature; (ii) the climate–carbon system can become unstable if either the climate sensitivity to CO2 or the sensitivity of soil respiration to temperature is large, and (iii) the climate–carbon system is stabilized by land and ocean carbon sinks that increase with atmospheric CO2, with CO2-fertilization of plant photosynthesis playing a key role. For central estimates of key parameters, the critical equilibrium climate sensitivity (ECS) that would lead to instability at current atmospheric CO2 lies between about 11 K (for large CO2 fertilization) and 6 K (for no CO2 fertilization). Given the apparent stability of the climate–carbon cycle, we can view these parameter combinations as implausible. The latter value is close to the highest ECS values amongst the latest Earth Systems Models. Contrary to a previous study that did not include an interactive ocean carbon cycle sink, we find that the stability of the climate–carbon system increases with atmospheric CO2, such that the glacial CO2 concentration of 190 ppmv would be unstable even for ECS greater than around 4.5 K in the absence of CO2 fertilization of land photosynthesis
Laboratory measurement of sonic (1–20 kHz) P‐wave velocity and attenuation during melting of ice‐bearing sand
Get PDFWe measured the acoustic properties of ice-bearing sand packs in the laboratory using an acoustic pulse tube within the frequency range of 1–20 kHz, similar to sonic well-logs. We analyzed how wave velocity and attenuation (the inverse of quality factor) change with ice saturation and measurement frequency during melting. We found strong frequency-dependent correlations for both acoustic parameters with ice saturation. For any frequency within the studied range, velocity decreases and attenuation increases as the ice melts. For lower ice saturations (Si < ∼0.5), attenuation was particularly sensitive to frequency linked to acoustic wave scattering from patchy ice saturation. We used rock physics models with three-phase approaches to assess our experimental results. The comparison highlights the influence of ice formation distribution (i.e., uniform vs. patchy), permeability, and gas content on both velocity and attenuation. Our results pave the way for monitoring ice saturation from sonic measurements, as ice saturation has contrasting effects on velocity and attenuation, and the effects vary with frequency. Overall, this research contributes to a better understanding of the acoustic response of ice-bearing sediments and provides valuable insights for various applications, including permafrost monitoring and natural gas hydrate dissociation studies
An estimation of Network Rail soil carbon stocks based on data from disused rail lines
Get PDF•The rapid expansion of the rail network in the 19th century created nearly 30,000 km of Technosol corridors across Great Britain (GB). Today, the GB railway estate covers over 51,000 ha and is managed by Network Rail Infrastructure Limited. A base line estimate of the soil organic carbon (SOC) stock is required to support Net Zero objectives. For this study 338 cores from 87 sites were collected from disused railway lines as an accessible proxy to the active network. Technosols are often excluded from soil carbon accounting and there are no estimates of railway soil carbon stocks.
•Our analysis of soil cores revealed a mean (±SD) SOC concentration (SOCc) of 5.0 % (±3.7), corresponding to an average SOC density of 49.7 t ha−1 (±27.8) to a depth of 30 cm. Significant factors affecting SOCc included parent material, bulk density, moisture and soil texture while habitat and climate had less influence. Railway-specific factors such as structure, construction and abandonment dates had minimal impact. Mixed effects linear modelling explained 55 % of the SOCc variation (R2 = 0.55). With no soil data available for the working railways, a reduced-factor general linear model, incorporating underlying bedrock, adjacent soil type and habitat (R2 = 0.19), was used to produce an initial SOC density map for the active rail network This gave an average carbon density for the Network Rail estate of 29.7 t ha−1 and a total soil carbon stock of 1.52 million tonnes (±6430). This is significantly lower than natural soils and many other technosols and suggests that these immature soils have the potential to sequester more carbon, assisted by appropriate land and vegetation management
Unexpected large photosynthetic thermal plasticity of montane Andean trees
Get PDFTropical forests play a significant role in global carbon sequestration. However, our understanding of how tropical tree species adjust to climate warming remains limited to studies on seedlings grown in pots and highly controlled growth conditions. To reduce this knowledge gap, we used a field experiment with 5‐year‐old juvenile trees of 12 naturally co‐occurring dominant tropical Andean montane and lowland species growing in three common gardens established along a natural thermosequence in the tropical Andes. Based on a few previous studies, we hypothesized that montane species would exhibit a weaker photosynthetic thermal acclimation capacity compared to lowland counterparts. Our results showed that montane tree species can thermally acclimate net photosynthesis by shifting their thermal optimum ( T opt ) by 0.6°C per 1°C of warming. This strong shift in T opt was correlated to simultaneous strong shifts in T opt of apparent photosynthetic capacity parameters ( V cmax and J max ), which increased by 0.7°C per 1°C of warming. This strong thermal acclimation resulted in similar rates of net CO 2 assimilation between montane and lowland species across different thermal environments. At last, rates of net photosynthesis at growth temperature explained 30% of the variation in the relative tree growth rates across the two species groups and thermal environments. Our results suggest that the strong physiological acclimation of photosynthesis to warming among montane Andean tree species should be considered when predicting future impacts of warming on Andean plant communities
Eddleston groundwater monitoring
Get PDFThis report describes work undertaken to continue monitoring at two experimental sites on the Eddleston Water, a tributary of the River Tweed. The Eddleston experimental sites were set up as part of the wider Eddleston Water Project, which aims to reduce the impact of flooding in and downstream of the village of Eddleston.
The first experimental site is part of Darnhall Mains Farm, adjacent to the village of Eddleston (Ó Dochartaigh et al. 2019). It is approximately 0.2 km2 (approximately 400 m by 500 m) and covers most of the width of the Eddleston Water floodplain on both sides of the river (Figure 1). The site is farmland predominately comprising mixed livestock farming on improved grassland, but part of the floodplain has been fenced which has allowed trees to be planted and vegetation to recover. The monitoring at this site comprises eight boreholes in which groundwater level is recorded. Previous data are stored with the National Geoscience Data Centre (https://www.bgs.ac.uk/geological-data/national-geoscience-data-centre/, ID 128585). A key objective of the experimental site is to improve understanding of the role of groundwater in floodplain environments and in flooding, and of how groundwater interacts with climate, rivers and soils.
The second experimental site is the Cringletie hillslope observatory (Figure 1; Peskett et al., 2020). The site is approximately 2500 m2 (approximately 50 m by 50 m) and comprises two transects parallel to the slope: one through a narrow forest strip and one on improved grassland used for mixed livestock farming (see Peskett et al., 2020). The installed monitoring equipment comprises soil moisture sensors, rain gauges and piezometers fitted with pressure transducers. The site was set up by Dr Leo Peskett as part of his PhD and was handed over to the BGS in 2020. The aim of the experimental site was to determine whether forest strips planted perpendicular to a hillslope can reduce surface runoff during flood events. Further information about the observatory is available in Peskett et al. (2020).
Since 2022/2023, the monitoring has been unfunded and kept going sporadically by BGS staff. In 2024/2025 BGS received a small portion of funding from the FDRI programme to download all data at the Eddleston sites and reset the loggers; audit broken equipment; and collate, process and quality check the data. This will enable a decision whether Eddleston will be included as part of the wider Tweed FDRI research sub-catchment and monitoring of shallow groundwater levels continue at Eddleston through FDRI
Developing a Southern Ocean Marine Ecosystem Model Ensemble to Assess Climate Risks and Uncertainties
Get PDFClimate change could irreversibly modify Southern Ocean ecosystems. Marine ecosystem model (MEM) ensembles can assist policy making by projecting future changes and allowing the evaluation and assessment of alternative management approaches. However, projected changes in total consumer biomass from the Fisheries and Marine Ecosystem Model Intercomparison Project (FishMIP) global MEM ensemble highlight an uncertain future for the Southern Ocean, indicating the need for a region-specific ensemble. A large source of model uncertainty originates from the Earth system models used to force FishMIP models, particularly future changes to lower trophic level biomass and sea-ice coverage. To build confidence in regional MEMs as ecosystem-based management tools in a changing climate that can better account for uncertainty, we propose the development of a Southern Ocean Marine Ecosystem Model Ensemble (SOMEME) contributing to the FishMIP 2.0 regional model intercomparison initiative. One of the challenges hampering progress of regional MEM ensembles is achieving the balance of global standardised inputs with regional relevance. As a first step, we design a SOMEME simulation protocol, that builds on and extends the existing FishMIP framework, in stages that include: detailed skill assessment of climate forcing variables for Southern Ocean regions, extension of fishing forcing data to include whaling, and new simulations that assess ecological links to sea-ice processes in an ensemble of candidate regional MEMs. These extensions will help advance assessments of urgently needed climate change impacts on Southern Ocean ecosystems
Optimising ensemble streamflow predictions with bias correction and data assimilation techniques
Get PDFThis study evaluates the efficacy of bias correction (BC) and data assimilation (DA) techniques in refining hydrological model predictions. Both approaches are routinely used to enhance hydrological forecasts, yet there have been no studies that have systematically compared their utility. We focus on the application of these techniques to improve operational river flow forecasts in a diverse dataset of 316 catchments in the United Kingdom (UK), using the ensemble streamflow prediction (ESP) method applied to the (Génie Rural à 4 paramètres Journalier) (GR4J) hydrological model. This framework is used in operational seasonal forecasting, providing a suitable test bed for method application. Assessing the impacts of these two approaches on model performance and forecast skill, we find that BC yields substantial and generalised improvements by rectifying errors after simulation. Conversely, DA, adjusting model states at the start of the forecast period, provides more subtle enhancements, with the biggest effects seen at short lead times in catchments impacted by snow accumulation or melting processes in winter and spring and catchments with a high baseflow index (BFI) in summer. The choice between BC and DA involves trade-offs considering conceptual differences, computational demands, and uncertainty handling. Our findings emphasise the need for selective application based on specific scenarios and user requirements. This underscores the potential for developing a selective system (e.g. a decision tree) to refine forecasts effectively and deliver user-friendly hydrological predictions. While further work is required to enable implementation, this research contributes insights into the relative strengths and weaknesses of these forecast enhancement methods. These could find application in other forecasting systems, aiding the refinement of hydrological forecasts and meeting the demand for reliable information by end-users
Ray tracing of very low frequency waves produced by active experiments or lightning events at low Earth orbit
Get PDFWe investigate the propagation in the plasmasphere of Very Low Frequency (VLF) electromagnetic
waves, such as natural lightning-generated whistler waves and waves produced by active experiments. An
active experiment is an artificial controlled disturbance of the low orbit space or the ionosphere. The aim is
often to produce electromagnetic waves for removing high-energy particles (mostly electrons). We study the
wave propagation parameters whether they are geometric, background, or intrinsic parameters, such as the
magnetic field model, the ambient plasma density model of the plasmasphere, and the wave frequency. All
of these parameters cause different behaviors of propagation, which are discussed in this articl
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