Long-term Environmental Changes Research Articles

Cross-checking OSL ages from different grain sizes to improve chronological reliability in deltaic environments: an example from the Yangtze River Delta

The Yangtze River Delta has experienced intricate sedimentary and environmental changes throughout the Holocene, driven by the interplay of fluvial and marine forcings. This study presents quartz optically stimulated luminescence (OSL) ages and luminescence sensitivity data from a Holocene sediment core MQ, analyzed across four grain-size fractions, ranging from silt to sand. The results reveal substantial variability in OSL ages and sensitivity among grain sizes, with the medium-grain (45–63 μm) fraction yielding the most consistent and reliable results. In contrast, finer and coarser grains tend to overestimate ages due to incomplete bleaching, with the accurate dating of coarser grains requiring more aliquots or single-grain measurements. The variability in luminescence sensitivity reflects changes in sediment provenance and depositional conditions between estuarine and deltaic environments. OSL ages indicate that the sedimentary evolution of the Yangtze River Delta progressed through distinct phases: rapid accumulation during the early Holocene (10–7 ka) driven by rising sea level and valley infilling; reduced sedimentation during the middle Holocene (7–3 ka) related to a dry climate in the catchment; and accelerated deposition in the late Holocene (3 ka–present) associated with enhanced fluvial input linked to intensified human activities. This study highlights the importance of selecting suitable appropriate grain sizes and carefully comparing different fractions in OSL analysis to reconstruct deltaic chronologies accurately. The finding that the medium-grain fraction yields more reliable OSL ages than finer and coarser fractions should be tested in similar settings elsewhere. The results provide valuable insights for future research on complex depositional environments and contribute to a better understanding of long-term environmental changes.

Innovative use of depth data to estimate energy intake and expenditure in Adélie penguins.

Energy governs species' life histories and pace of living, requiring individuals to make trade-offs. However, measuring energetic parameters in the wild is challenging, often resulting in data collected from heterogeneous sources. This complicates comprehensive analysis and hampers transferability within and across case studies. We present a novel framework, combining information obtained from eco-physiology and biologging techniques, to estimate both energy expenditure and intake in 48 Adélie penguins (Pygoscelis adeliae) during the chick-rearing stage. We employed the machine learning algorithm random forest (RF) to predict accelerometry-derived metrics for feeding behaviour using depth data (our proxy for energy acquisition). We also built a time-activity model calibrated with doubly labelled water data to estimate energy expenditure. Using depth-derived time spent diving and amount of vertical movement in the sub-surface phase, we accurately predicted energy expenditure. Movement metrics derived from the RF algorithm deployed on depth data were able to accurately detect the same feeding behaviour predicted from accelerometry. The RF predicted accelerometry-estimated time spent feeding more accurately compared with historical proxies such as number of undulations or dive bottom duration. The proposed framework is accurate, reliable and simple to implement on data from biologging technology widely used on marine species. It enables coupling energy intake and expenditure, which is crucial to further assess individual trade-offs. Our work allows us to revisit historical data, to study how long-term environmental changes affect animal energetics.

Ant utilization of tree trunks in relation to environmental factors in a temperate forest

Forests exhibit complex three-dimensional structures, wherein abiotic factors vary both vertically and horizontally. The interaction between organisms and these factors drives the remarkable biodiversity within forests. Tree trunks serve as vital conduits for organisms moving vertically within the forest, facilitating biodiversity maintenance. Organisms moving vertically through tree trunks in forests face varying abiotic conditions, which may enhance their resilience to long-term environmental changes. Despite numerous studies comparing canopy and ground communities, the distribution of organisms across multiple strata remains poorly understood. Here, we explore the correlation between the horizontal distribution of ants in a forest and environmental factors (topography, tree size, tree species), with a specific focus on their presence on tree trunks. Visual observations were conducted to document ant species richness on tree trunks, supplemented by pitfall traps to quantify soil arthropod biomass, serving as an indicator of protein availability. The results revealed that ant species richness on tree trunks varied based on topography and tree species, showing a positive correlation with tree size. However, no significant relationship emerged between soil arthropod biomass and ant richness on tree trunks. Furthermore, no discernible trend suggesting that certain species were less likely to co-occur was observed; instead, a tendency for some species to co-occur was found. These findings highlight the horizontal heterogeneity in the distribution of ants with respect to topography, tree species, and tree size within the forest.

Building the foundation for polar bear science: Fifty years of research on polar bears in Western Hudson Bay

In 1966, Environment and Climate Change Canada (ECCC) (then Canadian Wildlife Service) initiated a research program on polar bears belonging to the Western Hudson Bay subpopulation (WH). This paper provides an overview of that program, highlighting the long-term research on WH polar bears with a focus on ECCC-led work. The WH research program, which has now extended across five decades with data on over 4600 individual bears, has evolved from a study of the basic ecology of polar bears into foundational work on the life history, demography, genetics, movement, behaviour, and ecology of an apex predator in a rapidly changing Arctic. Research on polar bears in Canada supports commitments under the Agreement on the Conservation of Polar Bears (1973), the Convention on Biological Diversity (1992), and Canada’s Species at Risk Act (2002). Among Canada’s 13 polar bear subpopulations, only WH has sufficient long-term monitoring of individuals to assess demographic, behavioural, and life history consequences of climate change and other anthropogenic stressors. Future research should continue to ask key questions on how long-term environmental changes impact the ecology of polar bears. Integrating community priorities into the research program is necessary for it to continue to be successful in the future.

Evaluating climatic factors affecting cassava production in North Sumatera, Indonesia

Abstract Cassava is one of the crucial food crops in Indonesia. However, cassava production in several production centers in Indonesia tended to decrease annually. As one of the cassava production centers in Indonesia, data from 2010-2022 shows that North Sumatera once had experienced significant production growth, but the production started to decline again. Climate and weather changes are suspected to be one of the reasons for the difficulty in maintaining this production growth. This study aimed to analyze the impact of climate change, represented by temperature, air humidity, and rainfall, on cassava production in North Sumatera using the Ordinary Least Square estimation method to estimate a Multiple Linear Regression model. Climate change, represented by temperature and air humidity variables, had a positive but insignificant effect. In contrast, the rainfall variable negatively and significantly impacted cassava production. It indicated that the declining trend of cassava production in North Sumatera corresponded with the increasing average rainfall during the cultivation period. Average rainfall noticeably impacted the decline in output, while average temperature and air humidity had a minimal impact. The importance of increasing cassava production to ensure food security must acknowledge sustainability concepts to avoid long-term environmental and climate changes.

Long-term AI prediction of ammonium levels in rivers using transformer and ensemble models

This study provides a cutting-edge machine learning approach to forecast ammonium (NH4+) levels in River Lee London. Ammonium concentrations were predicted over several time intervals using a complete dataset that includes temperature, turbidity, chlorophyll, dissolved oxygen, conductivity, and pH. Our technique captures the intricate connections between environmental conditions and ammonium concentrations using developed algorithms, including Temporal Fusion Transformer (TFT), Random Forest (RF) and Extreme Gradient Boosting (XGBoost) levels versus the important factors, considerably improving prediction accuracy. The novel aspect of this study is the utilisation of the TFT model for multi-horizon forecasting, which offers high accuracy and interpretability in hydrological predictions by combining convolutional components with an attention mechanism. The study also demonstrates the effectiveness of the TFT model in capturing short-term fluctuations while retaining accuracy over long time periods, which is a major difficulty in environmental modelling. The models used, have exceptional forecasting skills, predicting 150, 200, 365, 730, and 1095 days based on daily average and 12, 24 and 30 months based on monthly average. This dual-scale model combines flexibility and resilience, making it an effective tool for forecasting both short- and long-term environmental changes. The RF model excelled in long-term forecasts, sustaining high R-squared (R²) (0.97) values and low root mean square error (RMSE) (0.18), and the second best one was the XGBoost with optimiser with R2 of (0.92) and RMSE of (0.25) with forecasting 1095 days. The results also found that whilst the TFT captured the fluctuations in the short-term, it struggled with the longer-term predictions due to data granularity. The XGBoost model did remarkably well in monthly forecasts up to 12 months, maintaining low RSME. The findings also highlight the necessity of proactive water management techniques to reduce the risk of potential ecological effects, including hypoxia and oxygen depletion. The findings support resource managers in addressing prospective ammonium toxicity concerns such as oxygen depletion and ecological stress.

Editorial preface to special issue: Response of marine and terrestrial environments to Triassic–Paleogene hyperthermals

The Mesozoic–Paleogene hyperthermals represent critical intervals of rapid global warming associated with abrupt carbon cycle perturbations. These events can provide valuable deep-time insights into how climate might respond to the current rise in temperatures driven by anthropogenic greenhouse gas emissions. This special issue comprises 17 publications that cover a broad spectrum of the research on hyperthermals, and these can be grouped into four main themes: (1) carbon-cycle perturbations, (2) environmental changes and biogeochemical extremes, (3) biotic responses to warming, and (4) long-term climatic and environmental changes in greenhouse climates. By integrating sedimentological, geochemical, and paleontological methods, the studies in this issue explore carbon sources and release mechanisms, provide insights into the initiation, development, and termination of hyperthermal events, and elucidate their longer-term impacts. The studies provide new insights into the interactions between short-term extreme events and long-term climate trends, offering valuable perspectives on the future trajectory of Earth's climate in response to ongoing anthropogenic warming.

Continental-scale nutrient and contaminant delivery by Pacific salmon.

The movement of large amounts of nutrients by migrating animals has ecological benefits for recipient food webs1,2 that may be offset by co-transported contaminants3,4. Salmon spawning migrations are archetypal of this process, carrying marine-derived materials to inland ecosystems where they stimulate local productivity but also enhance contaminant exposure5-7. Pacific salmon abundance and biomass are higher now than in the last century, reflecting substantial shifts in community structure8 that probably altered nutrient versus contaminant delivery. Here we combined nutrient and contaminant concentrations with 40 years of annual Pacific salmon returns to quantify how changes in community structure influenced marine to freshwater inputs to western North America. Salmon transported tonnes of nutrients and kilograms of contaminants to freshwaters annually. Higher salmon returns (1976-2015) increased salmon-derived nutrient and contaminant inputs by 30% and 20%, respectively. These increases were dominated by pink salmon, which are short-lived, feed lower in marine food webs than other salmon species, and had the highest nutrient-to-contaminant ratios. As a result, the delivery of nutrients increased at a greater rate than the delivery of contaminants, and salmon inputs became more ecologically beneficial over time. Even still, contaminant loadings may represent exposure concerns for some salmon predators. The Pacific salmon example demonstrates how long-term environmental changes interact with nutrient and contaminant movement across large spatial scales and provides a model for exploring similar patterns with other migratory species9.

The Social Movement of the Wayang Sampah Association in Raising Community Environmental Awareness

This research explores the role of the Wayang Sampah Association in raising environmental awareness and influencing public behavior through traditional Javanese puppetry and gamelan performances. Using a qualitative descriptive method, the study delves into how cultural education drives environmental stewardship. Data was collected from June to August 2024 through direct observation, interviews, and photo documentation, focusing on participants in the association's workshops and performances. The inductive analysis revealed that the Wayang Sampah Association effectively integrates cultural traditions with environmental advocacy, resulting in heightened public awareness and more sustainable waste management practices within the community. The study underscores the significance of culturally resonant approaches in promoting long-term environmental change, illustrating how traditional arts can foster a deeper understanding of environmental issues and inspire actionable change. These findings contribute to the broader discourse on the effectiveness of New Social Movements in tackling contemporary environmental challenges, emphasizing the potential of cultural integration in achieving sustainable outcomes.

Estimation of seismometer clock time offsets using Kalman Filter towards accurate seismic velocity change

SUMMARY Monitoring seismic velocity changes obtained from ambient noise correlations is widely used to understand changes in rock properties in response to earthquakes, volcanic activities and environmental changes. Since continuous seismic data have been accumulated, this method can estimate long-term changes in seismic velocity, such as crustal recovery after a major earthquake and temporal variations in seismic velocity related to long-term environmental change. Changes in seismic velocity can be estimated with a high temporal resolution by measuring the phase differences of ambient noise correlations based on a seismic interferometry method. Still, these phase differences are influenced not only by seismic wave velocity changes but also by errors in clock timing in seismometers. The clock drift occurs due to out-of-synchronization with the GPS clock and the drift of the internal clock. Therefore, to accurately monitor temporal changes in crustal structure by measuring the phase differences of noise correlations, it is crucial to evaluate the contribution of errors in clock timing to the phase differences. Recently, a method using an extended Kalman filter based on a state-space model was developed for reliable detection of temporal changes in the waveforms of ambient noise correlations, with the state-space model offering the advantage of flexible modelling of time-series data. In this study, we incorporated the time-shifts caused by clock time errors of the seismometer into the state-space model of the temporal changes in ambient noise correlations. We estimated seismic velocity changes, amplitude changes of noise correlations and clock time errors from 2010 April to 2021 September at seismic stations around the Shinmoe-dake volcano in Japan, which experienced eruptions in 2011 and 2018, respectively. Several stations exhibited clear clock time offsets, and the occurrence of clock time-shifts coincided with the dates when the data logger was turned off for seismic station maintenance or replacement of the seismometer. The proposed method provides stable estimations with respect to the signal-to-noise ratio of the waveform, and this stable estimation facilitates accurate timing of seismic recordings, enabling precise analysis of seismic phase arrival times.

Modern distribution of Cladocera in lakes of northern China and western Mongolia and its environmental implications

Cladocerans are widely distributed in aquatic ecosystems and are sensitive to environmental changes; hence, they are commonly used to trace ecological changes in aquatic environments. However, the distribution of cladocerans in northern China is poorly known. We investigated the occurrence of cladocerans in 136 water bodies (including lakes and reservoirs), with varying hydro-chemical and climatic gradients, in northern China and western Mongolia. We identified 38 cladoceran taxa in the surface sediments of 88 different water bodies, while the remaining lakes, mainly saline, had no cladocerans. The spatial distribution characteristics of cladoceran species and the environmental factors determining their community composition were investigated using canonical correspondence analysis. The results demonstrate that water depth, trophic status, and water salinity were the top three variables influencing the composition of cladoceran taxa. Transfer functions between the surface sediment cladocerans and lake level and nutrient (NH4) levels in 62 lakes (26 lakes lacked environmental data) were established via multivariate statistical analyses. Using the subfossil cladocerans of Jili Lake, lake level and nutrient values were reconstructed for the past 100 years. The results agree overall with the observational data, and they reveal that the changes in the cladoceran community reflected mainly lake level fluctuations before 1988 CE, and mainly nutrient changes thereafter. Our research clarifies, for the first time, the environmental significance of modern Cladocera in the lakes of northern China and western Mongolia, and it provides a foundation for the future reconstruction of long-term changes in the ecological environment of lakes.

Rock glaciers across the United States predominantly accelerate coincident with rise in air temperatures

Despite their extensive global presence and the importance of variations in their speed as an essential climate variable, only about a dozen global time series document long-term changes in the velocity of rock glaciers – large tongue-shaped flows of frozen mountain debris. By analysing historical aerial photographs, we reconstruct here 16 new time series, a type of data that has not previously existed for the North American continent. We observe substantial accelerations, as much as 2–3 fold, in the surface displacement rates of rock glaciers across the mountains of the western contiguous United States over the past six to seven decades, most consistent with strongly increasing air temperatures in that region. Variations between individual time series suggest that different local and internal conditions of the frozen debris bodies modulate this overall climate response. Our observations indicate fundamental long-term environmental changes associated with frozen ground in the study region.

Weather, climate, and entry into migration of northern fur seal pups

In the migration of young animals, environmental cues can play an outsized role in dispersal, ontogeny, and potentially survival. Identifying and quantifying such cues promotes an understanding of individual species’ migratory evolution and response to long-term environmental change. This study examines weather as a proximate factor for initiating first migration in a wide-ranging subpolar marine predator, the northern fur seal (laaqudax̂, in Unangam Tunuu; Callorhinus ursinus (Linnaeus 1758)). Observations of satellite-telemetered pups on three islands in the eastern Bering Sea, Alaska (US) are used to quantify how inclement weather (high winds, snow, and low temperatures) increases departure rate. Historical weather is then used to reconstruct departure, from the mid-20th century onward. Contemporary surveys provide a test for reconstructed estimates and highlight behavioral processes near the entry to migration. Reconstructions provide novel climate context for large-scale population declines in the eastern Bering Sea since the 1950s; within their limitations, there is a lack of evidence for trends in departure or significant influence on demography. Results here build upon and support historical knowledge regarding the role of weather, while also highlighting potential areas of future study – such as maternal behavior – in influencing the entry into first migration in this species.

Increasing environmental variability inhibits evolutionary rescue in a long-lived vertebrate

Evolutionary rescue, whereby adaptive evolutionary change rescues populations from extinction, is theorized to enable imperiled animal populations to persist under increasing anthropogenic change. Despite a large body of evidence in theoretical and laboratory settings, the potential for evolutionary rescue to be a viable adaptation process for free-ranging animals remains unknown. Here, we leverage a 38-year dataset following the fates of 53,959 Magellanic penguins (Spheniscus magellanicus) to investigate whether a free-ranging vertebrate species can morphologically adapt to long-term environmental change sufficiently to promote population persistence. Despite strong selective pressures, we found that penguins did not adapt morphologically to long-term environmental changes, leading to projected population extirpation. Fluctuating selection benefited larger penguins in some environmental contexts, and smaller penguins in others, ultimately mitigating their ability to adapt under increasing environmental variability. Under future climate projections, we found that the species cannot be rescued by adaptation, suggesting similar constraints for other long-lived species. Such results reveal how fluctuating selection driven by environmental variability can inhibit adaptation under long-term environmental change. Our eco-evolutionary approach helps explain the lack of adaptation and evolutionary rescue in response to environmental change observed in many animal species.

Holocene ecosystem and temperature development inferred from invertebrate remains in Zminje Jezero (Dinaric Alps, Montenegro)

AbstractLake Zminje Jezero (1535 m a.s.l.) in Montenegro was studied for chironomid and other aquatic invertebrate remains in a sediment sequence dating back to 12,000 calibrated 14C years before present (cal yr BP), providing, to our knowledge, the first lake-sediment record studied for chironomids and other associated chitinous aquatic invertebrate remains in the Dinaric Alps. Changes in chironomid and other invertebrate remains along the record make it possible to constrain changes of relevant environmental variables for aquatic invertebrates in the lake including temperature, oxygen availability, trophic status and water depth. The results suggest moderate changes in trophic conditions with chironomid assemblages indicating meso- to eutrophic conditions during the analysed interval. Invertebrate assemblages were typical for lakes with relatively high oxygen availability with a minor trend during the middle to late Holocene to conditions observed in lakes that are more hypoxic. A change in temperature is suggested in the earlier part of the record when the share of chironomid taxa adapted to warmer conditions increased, at the Younger Dryas to Holocene transition, whereas later no particularly pronounced shifts in temperature-sensitive taxa were observed. July air temperatures were estimated based on chironomid assemblages using a transfer function based on calibration data consisting of 117 lakes sampled in the Swiss Alps and northern Switzerland. The results suggest that temperatures rapidly increased by 5 °C at the onset of the Holocene (11,500 cal yr BP) leading to a relatively warm early to mid-Holocene and thereafter slightly decreased during the late Holocene. Reconstructed temperatures are discussed together with a previously published pollen record for our study site and are broadly consistent with other chironomid-based temperature reconstructions from Central, Eastern and Southern Europe. From ca. 3000 cal yr BP sedimentation rates increased and from ca. 500 cal yr BP onwards pollen data suggest that the vegetation and lake catchment were affected by human activities, possibly influencing chironomid and other invertebrate assemblages in the lake and thereby also reconstructed temperatures. Overall, our results show that combining analyses of chironomid and other invertebrate assemblages can provide valuable insights into long-term environmental changes and can provide temperature reconstructions for small mountain lakes in the Balkans, such as Zminje Jezero.

Long-term patterns and trends in water column biogeochemistry in a changing environment

Water column nutrient concentrations and autotrophy in oligotrophic ecosystems are sensitive to eutrophication and other long-term environmental changes and disturbances. Disturbance can be defined as an event or process that changes the structure and response of an ecosystem to other environmental drivers. The role disturbance plays in regulating ecosystem functions is challenging because the effect of the disturbance can vary in magnitude, duration, and extent spatially and temporally. We measured changes in total nitrogen (TN), dissolved inorganic nutrient (DIN), total phosphorus (TP), soluble reactive phosphorus (SRP), total organic carbon (TOC), and chlorophyll-a (Chl-a) concentrations throughout the Everglades, Florida Bay, and the Florida Keys. This region has been subjected to a variety of natural and anthropogenic disturbances including tropical storms, fires, eutrophication, and rapid increases in water levels from sea-level rise and freshwater restoration. We hypothesized that the rate of change in water quality would be greatest in the coastal ecotone where disturbance frequencies and marine P concentrations are highest, and in freshwater marshes closest to hydrologic changes from restoration. We applied trend analyses on multi-decadal data (1996–2019) collected from 461 locations distributed from inland freshwater Everglades (ridge and slough) to outer marine reefs along the Florida Keys, USA. Total Organic Carbon decreased throughout the study area and was the only parameter with a systematic trend throughout the study area. All other parameters had spatially heterogeneous patterns in long-term trends. Results indicate more variability across a large spatial and temporal extent associated with changes in biogeochemical indicators and water quality conditions. Chemical and biological changes in oligotrophic ecosystems are important indicators of environmental change, and our regional ridge-to-reef assessment revealed ecosystem-specific responses to both long-term environmental changes and disturbance legacies.

Exploring how community context informs variations in local perceptions of forest disturbance and land management in Colorado over time

Place-based socio-economic and biophysical context has been viewed as an essential driver in shaping perceptions of forest risks and land management. Growing evidence of the importance of diverse community context in forested landscapes sets the stage to further consider how people's understandings of their local environment influence natural resource management preferences. However, research to date largely lacks considerations of how community context informs social responses to long-term environmental change over time. Using the mountain pine beetle (MPB) outbreak in Colorado, we analyze and compare longitudinal interview and survey data collected from nine north-central Colorado communities to understand the relationships between community context and changing perceptions of forest disturbance and engagement with land management. Both qualitative and quantitative findings show that community context framed and continues to inform variations in local perceptions of the MPB outbreak and forest management. Interviews with key informants provided rich narratives on different context-based trajectories in local residents' perceptional responses, while survey data allowed for general patterns of evolving community variations (e.g., stable or clearer community clustering, reduced community differences) to be uncovered. We explore methodological implications for community indication and future directions for understanding differing community responses to slow-moving environmental change. Incorporating knowledge of changing local contexts and variations can also help practitioners advance toward more dynamic and effective management strategies.

Transcriptomic analysis reveals PC4's participation in thermotolerance of scallop Argopecten irradians irradians by regulating myocardial bioelectric activity

Rising ocean temperatures due to global warming pose a significant threat to the bay scallop aquaculture industry. Understanding the mechanisms of thermotolerance in bay scallops is crucial for developing thermotolerant breeds. Our prior research identified Arg0230340.1, part of the positive cofactor 4 (PC4) family, as a key gene associated with the thermotolerance index Arrhenius break temperature (ABT) in bay scallops. Further validation through RNA interference (RNAi) reinforced PC4's role in thermotolerance, offering a solid basis for investigating thermal response mechanisms in these scallops. In this study, we performed a comparative transcriptomic analysis on the temperature-sensitive hearts of bay scallops after siRNA-mediated RNAi targeting Arg0230340.1, to delve into the detailed molecular mechanism of PC4's participation in thermotolerance regulation. The analysis revealed that silencing Arg0230340.1 significantly reduced the expression of mitochondrial tRNA and rRNA, potentially affecting mitochondrial function and the heart's blood supply capacity. Conversely, the up-regulation of genes involved in energy metabolism, RNA polymerase II (RNAPII)-mediated basal transcription, and aminoacyl-tRNA synthesis pathways points to an intrinsic protective response, providing energy and substrates for damage repair and maintenance of essential functions under stress. GO and KEGG enrichment analyses indicated that the up-regulated genes were primarily associated with energy metabolism and spliceosome pathways, likely contributing to myocardial remodeling post-Arg0230340.1 knockdown. Down-regulated genes were enriched in ion channel pathways, particularly those for Na+, K+, and Ca2+ channels, whose dysfunction could disrupt normal myocardial bioelectric activity. The impaired cardiac performance resulting from RNAi targeting Arg0230340.1 reduced the cardiac workload in scallop hearts, thus affecting myocardial oxygen consumption and thermotolerance. We propose a hypothetical mechanism where PC4 down-regulation impairs cardiac bioelectric activity, leading to decreased thermotolerance in bay scallops, providing theoretical guidance for breeding thermotolerant scallop varieties and developing strategies for sustainable aquaculture in the face of long-term environmental changes.

Machine Learning Vegetation Filtering of Coastal Cliff and Bluff Point Clouds

Coastal cliffs erode in response to short- and long-term environmental changes, but predicting these changes continues to be a challenge. In addition to a chronic lack of data on the cliff face, vegetation presence and growth can bias our erosion measurements and limit our ability to detect geomorphic erosion by obscuring the cliff face. This paper builds on past research segmenting vegetation in three-band red, green, blue (RGB) imagery and presents two approaches to segmenting and filtering vegetation from the bare cliff face in dense point clouds constructed from RGB images and structure-from-motion (SfM) software. Vegetation indices were computed from previously published research and their utility in segmenting vegetation from bare cliff face was compared against machine learning (ML) models for point cloud segmentation. Results demonstrate that, while existing vegetation indices and ML models are both capable of segmenting vegetation and bare cliff face sediments, ML models can be more efficient and robust across different growing seasons. ML model accuracy quickly reached an asymptote with only two layers and RGB images only (i.e., no vegetation indices), suggesting that these more parsimonious models may be more robust to a range of environmental conditions than existing vegetation indices which vary substantially from one growing season to another with changes in vegetation phenology.

Long-term variations in terrestrial carbon cycles and atmospheric CO2 levels: Exploring impacts on global ecosystem and climate in the aftermath of end-Cretaceous mass extinction

The short-term climate and environmental consequences (<∼1.0–10 Kyr) immediately following the end-Cretaceous extinction have been attributed to transient effects originating from Deccan volcanism and the Chicxulub impact. These two events have received significant attention for their role in precipitating extreme climate conditions. In contrast, the long-term (> ∼100 Kyr) climate and environmental changes of the post-extinction have been extensively studied in the marine systems, yet their ramifications within terrestrial ecosystems are less well-characterized and require further elucidation. This study presents a carbon isotope analysis of pedogenic carbonates from matured calcisols in the Nanxiong Basin, South China, to reconstruct carbon cycles and atmospheric CO2 concentrations (pCO2) spanning from 76.0 Ma to 62.0 Ma, aiming to decipher the long-term terrestrial environmental and climatic conditions. Results show that δ13C values range from −12.4‰ to −5.0‰ (mean − 9.0‰) and pCO2 varies between ∼250 ppmV and ∼ 2200 ppmV (mean 920 ppmV). When combined with δ13C data from Songliao Basin, NE China, the carbon cycle variation exhibits a 13C collapse and smooth towards subsequent rebound, indicating a process of ∼600 Kyr deterioration, ∼600 Kyr stabilization and ∼ 400 Kyr recovery in the terrestrial ecosystem. The fluctuation of estimated pCO2 aligns with the change pattern of sea surface temperatures, attesting to the strong perturbation of climate and environment at the same pace as the carbon cycle variations. It is proposed that ecosystems and environments in both terrestrial and surface ocean experienced a more unstable, difficult and erratic recovery process and were much more sensitive to climatic changes than in deep ocean for ∼1.5 million years in the aftermath of the end-Cretaceous mass extinction. In addition, the divergence of proxy variations from expected effects implies the Deccan eruption and Chicxulub impact could not have played a long-term role in governing the climatic and environmental perturbations following the Cretaceous-Paleogene Boundary.