Aerial Surveys Research Articles

Distribution and Abundance of California (Zalophus californianus) and Steller (Eumetopias jubatus) Sea Lions in the Inshore Waters of Washington, 2013-2016

Two species of sea lions occur in the in387land waters of Washington State: the California sea lion (Zalophus californianus) and the Steller sea lion (Eumetopias jubatus). Both species breed elsewhere, but they typically move into Puget Sound and adjacent waters of the Salish Sea from autumn through spring. There is a need for information on their current abundance and seasonal use patterns as both species prey heavily on threatened/endangered stocks of salmon and steelhead trout (Oncorhynchus spp.), and empirical abundance estimates of these species are lacking for inland Washington waters. From 2013 to 2016, we conducted 39,399 km of aerial surveys for marine mammals in this area, sighting 255 groups of sea lions. We used a subset of 7,841 km of effort and 165 sea lion sightings made during surveys in good sighting conditions to estimate in-water abundance using line-transect methods. Historical tagging data collected in Pacific Northwest waters were used to evaluate the proportions of time that each species spent on land and conducting dives, and then to develop correction factors to derive total abundance for both sea lion species, providing the first empirical abundance estimates for these waters. We estimated that between 33 and 442 California sea lions were found in Puget Sound/Hood Canal in different seasons, with nearly 3,000 being found in the broader inland Washington waters in the peak season (spring). Steller sea lions occurred in much smaller numbers, with a peak of 219 animals in Puget Sound/Hood Canal/Strait of Juan de Fuca in autumn (and possibly as many as 600 to 700 in the entire study area). While some estimates suffer from low precision, this study demonstrates that substantial numbers of sea lions use waters of the study area throughout much of the year. Our results provide an important step toward a better understanding of these two species in the inland waters of Washington, as well as their potential effects on protected salmonid prey species.

Estimating the change in the rational runoff coefficient through history in Jefferson County, Texas

Jefferson County in Texas has experienced devastating storms in recent years resulting in billions of dollars in damages. The county has gone through temporal milestones in terms of population growth and industrial development. Many studies have shown that urban development increases the risk of flooding by decreasing the soil infiltration capacity. The current study focuses on estimating the extent to which the urban development in the county has led to increased imperviousness using a combination of historical and current spatial data. Rational runoff coefficients of the County were estimated and compared at three different times over a span of 120 years. A land survey map for 1898, an aerial imagery map for 1966 and a land parcel map for 2019 were obtained from various sources. The three maps available, each in different format, were analyzed to determine the land use and land cover type for the respective years. The runoff coefficient increased by 21% from 1898 to 1966 and remained the same from 1966 till 2019. The estimates are in correlation with industrial and population growth patterns of the county. These preliminary spatial analyses are useful in estimating the contributions of recent major flooding from overall development, or if they may be more impacted from other factors such as changes in weather patterns.

Melding wildlife surveys to improve conservation inference.

Integrated models are a popular tool for analyzing species of conservation concern. Species of conservation concern are often monitored by multiple entities that generate several datasets. Individually, these datasets may be insufficient for guiding management due to low spatio-temporal resolution, biased sampling, or large observational uncertainty. Integrated models provide an approach for assimilating multiple datasets in a coherent framework that can compensate for these deficiencies. While conventional integrated models have been used to assimilate count data with surveys of survival, fecundity, and harvest, they can also assimilate ecological surveys that have differing spatio-temporal regions and observational uncertainties. Motivated by independent aerial and ground surveys of lesser prairie-chicken, we developed an integrated modeling approach that assimilates density estimates derived from surveys with distinct sources of observational error into a joint framework that provides shared inference on spatio-temporal trends. We model these data using a Bayesian Markov melding approach and apply several data augmentation strategies for efficient sampling. In a simulation study, we show that our integrated model improved predictive performance relative to models for analyzing the surveys independently. We use the integrated model to facilitate prediction of lesser prairie-chicken density at unsampled regions and perform a sensitivity analysis to quantify the inferential cost associated with reduced surveyeffort.

Regional mapping method of land acquisition for water conservancy and hydropower construction based on UAV aerial survey

In order to improve the regional planning ability of land acquisition for water conservancy and hydropower construction, a technology of land acquisition area mapping for water conservancy and hydropower construction based on UAV aerial survey is proposed. This technology uses UAV aerial survey remote sensing detection technology to realize remote sensing image monitoring of land acquisition planning for water conservancy and hydropower construction, so as to improve the accuracy and efficiency of regional planning. This technology mainly extracts information such as edge contours, key feature points, and texture pixels from remote sensing images for land acquisition mapping in water conservancy and hydropower construction. The line element feature distribution points monitored by drones scatter remote sensing images as the data source, and linear object segmentation detection processing method is used for analysis. Based on the clustering characteristics of geometric attributes such as dams, water body characteristics, fence facilities, and power generation equipment in water conservancy and hydropower construction, a regional clustering analysis model for land acquisition mapping in water conservancy and hydropower construction is established using the diversity clustering method of different terrain and geomorphic feature distribution patterns. By utilizing the regional distribution fusion of concave and convex terrain, detecting and quantitatively estimating the spatial resolution and complexity of land acquisition for water conservancy and hydropower construction, optimizing the mapping of land acquisition areas for water conservancy and hydropower construction, and providing data basis for land acquisition protection management in water conservancy and hydropower construction planning. The experiment shows that this method has good output resolution, land planning ability, and classification performance for different types of land acquisition for water conservancy and hydropower construction, and has broad prospects for promotion and application in practical applications.

STRUCTURE OF THE WINTER FAUNA OF MAMMALS IN THE SEAS OF NORTHEASTERN PALEARCTIC OF RUSSIA

The ecological patterns of structure formation and spatial differentiation of the winter fauna of mammals in the seas of the northeastern Palearctic are analyzed. The method of aviation route surveys in a 1 km wide zone was applied. Aerial surveys in the end of 1987-1988 winter period covered the Bering, Chukchi, East Siberian Seas, and the eastern part of the Laptev Sea. The recorded species of mammals (n = 7) are ecologically associated with open sea areas, sea ice, continental and island coasts, and continental tundra. The winter fauna of mammals in the seas of the northeastern Palearctic accounts for 23% of the total mammalian fauna of the region; pinnipeds and cetaceans predominate in terms of the number of species. The similality of the winter fauna of mammals in the Arctic Ocean and the Northern Pacific is 36%. Most of the mammals were observed on the leads in the contact zones between different types of ice or in iceholes among the ice of autumn formation. Polar bears were most often observed near the Wrangel Island, beluga whales - to the east and northeast of the Navarin Cape, walruses - to the south of the Providence Bay. The average density of the winter population of mammals in the surveyed seas of the Northeastern Palearctic is 6.2 individuals/100 km². Walruses, beluga whales, and ringed seals predominate in the population, totaling 94% of the animal numbers.

Understanding the Spatial Distribution and Behavior of Elderly Residents in Age-Friendly Communities: An Analysis of Outdoor Space Features in Hangzhou, China

In the context of an aging population and the rise of age-friendly communities, the creation of outdoor spaces that cater to the daily needs of elderly residents, promote their physical and mental well-being, and strengthen their sense of community is a pressing matter requiring immediate attention and solutions. This study focuses on boosting the outdoor space of communities that are age-friendly. The research sample consists of four age-friendly communities in the representative city of Hangzhou. Aerial and ground surveys were carried out to examine the spatial distribution and behavioral tendencies of elderly citizens in outdoor community gathering locations. A GoPro MAX panoramic camera and a weather meter were utilized to evaluate the outside space’s landscape components, spatial attributes, and microclimate. Using Pearson correlation and multiple linear regression analyses, we discovered the key parameters impacting the spatial gathering and behaviors of elderly residents in age-friendly communities’ outdoor spaces. When constructing outdoor gathering spaces for the elderly, our findings indicate that weatherproof amenities, a greater variety of pavers, and greenery should be prioritized. Community fitness facilities should be considered throughout the development and refurbishment phases for activity areas. Consideration should also be given to the construction of weatherproof facilities with less walls and increased hard surface areas for chess spaces.

Eastern High Arctic–Baffin Bay beluga whale (Delphinapterus leucas) estuary abundance and use from space

IntroductionThe Eastern High Arctic–Baffin Bay (EHA-BB) beluga whale (Delphinapterus leucas) population spends summer in estuaries around Somerset Island, Nunavut, Canada. A single abundance estimate from 1996 suggests an abundance >21,000 beluga whales; however, more information on abundance and distribution is needed to ensure effective management of this population, especially in estuaries where previous surveys provided minimal coverage. To assess the feasibility of using Very High Resolution (VHR) satellite imagery to obtain estuary abundance estimates for this beluga population, we evaluated a citizen science crowd counting initiative that was designed to monitor remote beluga whale populations and their estuary use.MethodsIn July and August 2020 the WorldView 2 and 3, and GeoEye 1 satellites were tasked to collect VHR imagery (30–41 cm) of estuaries previously known to be used by Eastern High Arctic–Baffin Bay beluga whales. The objectives were to obtain an estuary abundance estimate for this population from satellite imagery, and to evaluate the effectiveness of having imagery annotated using a crowd-source platform. Almost 3,800 km2of ocean imagery was analyzed using Maxar’s Geospatial Human Imagery Verification Effort (GeoHIVE) Crowdsourcing platform. Expert readers then manually compared counts to those performed by crowd-counters to determine variance in observer counts.Results and DiscussionThe estuary abundance estimate from 11 core estuaries was 12,128 (CV 36.76%, 95% confidence interval 6,036–24,368) beluga whales. This represents an estuary abundance estimate only, as the greater Peel Sound and Prince Regent Inlet areas were not photographed. The estuaries with the largest abundance of beluga whales were Creswell Bay, Maxwell Bay, and Prince Whales Island, with over 2,000 crowd-counted whales in each estuary. Although VHR imagery has potential to assist with surveying and monitoring marine mammals, for larger estuaries it was not always possible to photograph the entire area in a single day, and cloud cover was an issue for sections of most images. This work will assist with planning large-scale aerial surveys for monitoring beluga whale populations, identifying high-use areas and important beluga habitat, and highlights the utility of using VHR imagery to enhance our understanding of estuary abundance and distribution of Arctic whales.

Wall-to-wall mapping of carbon loss within the Chornobyl Exclusion Zone after the 2020 catastrophic wildfire

Key messageWe propose a framework to derive the direct loss of aboveground carbon stocks after the 2020 wildfire in forests of the Chornobyl Exclusion Zone using optical and radar Sentinel satellite data. Carbon stocks were adequately predicted using stand-wise inventory data and local combustion factors where new field observations are impossible. Both the standalone Sentinel-1 backscatter delta (before and after fire) indicator and radar-based change model reliably predicted the associated carbon loss.ContextThe Chornobyl Exclusion Zone (CEZ) is a mosaic forest landscape undergoing dynamic natural disturbances. Local forests are mostly planted and have low ecosystem resilience against the negative impact of global climate and land use change. Carbon stock fluxes after wildfires in the area have not yet been quantified. However, the assessment of this and other ecosystem service flows is crucial in contaminated (both radioactively and by unexploded ordnance) landscapes of the CEZ.AimsThe aim of this study was to estimate carbon stock losses resulting from the catastrophic 2020 fires in the CEZ using satellite data, as field visitations or aerial surveys are impossible due to the ongoing war.MethodsThe aboveground carbon stock was predicted in a wall-to-wall manner using random forest modelling based on Sentinel data (both optical and synthetic aperture radar or SAR). We modelled the carbon stock loss using the change in Sentinel-1 backscatter before and after the fire events and local combustion factors.ResultsRandom forest models performed well (root-mean-square error (RMSE) of 22.6 MgC·ha−1 or 37% of the mean) to predict the pre-fire carbon stock. The modelled carbon loss was estimated to be 156.3 Gg C (9.8% of the carbon stock in burned forests or 1.5% at the CEZ level). The standalone SAR backscatter delta showed a higher RMSE than the modelled estimate but better systematic agreement (0.90 vs. 0.73). Scots pine (Pinus sylvestris L.)-dominated stands contributed the most to carbon stock loss, with 74% of forests burned in 2020.ConclusionThe change in SAR backscatter before and after a fire event can be used as a rough proxy indicator of aboveground carbon stock loss for timely carbon map updating. The model using SAR backscatter change and backscatter values prior to wildfire is able to reliably estimate carbon emissions when on-ground monitoring is impossible.

Surface and subsurface oceanographic features drive forage fish distributions and aggregations: Implications for prey availability to top predators in the US Northeast Shelf ecosystem.

Forage fishes are a critical food web link in marine ecosystems, aggregating in a hierarchical patch structure over multiple spatial and temporal scales. Surface-level forage fish aggregations (FFAs) represent a concentrated source of prey available to surface- and shallow-foraging marine predators. Existing survey and analysis methods are often imperfect for studying forage fishes at scales appropriate to foraging predators, making it difficult to quantify predator-prey interactions. In many cases, general distributions of forage fish species are known; however, these may not represent surface-level prey availability to predators. Likewise, we lack an understanding of the oceanographic drivers of spatial patterns of prey aggregation and availability or forage fish community patterns. Specifically, we applied Bayesian joint species distribution models to bottom trawl survey data to assess species- and community-level forage fish distribution patterns across the US Northeast Continental Shelf (NES) ecosystem. Aerial digital surveys gathered data on surface FFAs at two project sites within the NES, which we used in a spatially explicit hierarchical Bayesian model to estimate the abundance and size of surface FFAs. We used these models to examine the oceanographic drivers of forage fish distributions and aggregations. Our results suggest that, in the NES, regions of high community species richness are spatially consistent with regions of high surface FFA abundance. Bathymetric depth drove both patterns, while subsurface features, such as mixed layer depth, primarily influenced aggregation behavior and surface features, such as sea surface temperature, sub-mesoscale eddies, and fronts influenced forage fish diversity. In combination, these models help quantify the availability of forage fishes to marine predators and represent a novel application of spatial models to aerial digital survey data.

Geological-technical study for the design of an underground variant of S.S. 52 “Carnica” in the Passo Mauria area (Carnic Alps)

This study aims to define a preliminary geological model of the Passo Mauria tunnel, designed as an alternative underground route to the current S.S.52 to ensure a safer connection over the top way Belluno (A27 Highway) Tolmezzo (A23 Highway), on which various tourist and economic activities revolve. The survey stage has allowed us to describe and represent the cartographic elements that describe the geology of the study area. The study has mainly focused on the investigation of the presumed entrances of the tunnel, characterized by specific geological and geomorphological conditions. The aerial photogrammetric survey supported the reconstruction of the geometry of discontinuities in the non- accessible areas. Besides, this study has allowed the definition of the possible behaviour of the rock mass subjected to the tunnel excavation and of sections with homogeneous mechanical properties. The drafting of a survey plan supplements the study to determine a geological and geotechnical model, for the subsequent investigation and design phases.

Long-Term Change and Analysis of the Sedimentary Environment of Dadae Beach Using Unmanned Aerial Vehicles

Dadae Beach, located at the Nakdong river estuary, has been continuously evolving over the years, and this is the result of complex interactions between natural and artificial factors. In particular, in the case of Dadae Beach, located at the estuary of the Nakdong river estuary, it is located at the boundary between the river and the ocean, and it is an environment in which various deposition mechanisms operate. It is a very difficult research task to analyze the beach evolution mechanism, and a long-term study using precise measurement methods is required. Therefore, in this study, precision unmanned aerial surveys were conducted three times (2015, 2019, and 2021) for 5 years to identify the sedimentary characteristics of Dadae Beach, and the sedimentary environment was analyzed through the analysis of surface sediment texture characteristics. Seasonal waves and winds caused by the East Asian monsoon climate are the main mechanisms for the sedimentation of Dadae Beach, and finegrained sediments are distributed throughout the beach. In addition, the formation of sandbar, which arose rapidly due to artificial influences such as the construction of estuary banks in the past, is a major factor in the evolution of large-scale beaches. This study is meaningful in identifying the mechanism of beach evolution and presenting quantitative analysis results through comparison of precision aerial survey data over a long period of time.

Connected pixels-based image smoothing filter

Digital image processing heavily relies on the connectivity of pixels, as it is a vital component for accurate object identification and analysis within an image. Grouping together pixels with similar features such as colour and intensity, allows for the formation of meaningful patterns or objects, which is essential for object recognition and segmentation. This approach is particularly valuable in photogrammetric imaging, video surveillance, deep learning as it facilitates the isolation of regions of interest and object tracking. Image smoothing is also a crucial aspect in enhancing visual quality by reducing noise and enhancing details, especially in applications such as aerial mapping, medical imaging, video compression, image resizing and computer vision. The absence of connected pixels and image smoothing would make image processing tasks more challenging and less reliable, making them fundamental to digital image processing and critical to various applications in diverse fields. This paper introduces a novel image smoothing filter called Connected Pixels Based Image Smoothing Filter (CPF), which is based on gray connected pixels. The success of the CPF was compared to that of the Non-Local Means Filter (NLMF) in terms of Structural Similarity Index (SSIM) for the same Mean Squared Error (MSE). The experimental results showed that CPF has a better ability to preserve image details compared to NLMF.

Airborne gamma-ray mapping using fixed-wing vertical take-off and landing (VTOL) uncrewed aerial vehicles.

Low-cost uncrewed aerial vehicles (UAVs) are replacing manned aircraft for airborne radiation mapping applications such as nuclear accident response scenarios or surveying ore deposits and mine sites because of their cost-effectiveness and ability to conduct surveys at lower altitude compared to manned counterparts. Both multi-rotor UAVs and fixed-wing UAVs are well established technologies for aerial radiation mapping applications, however, both also have drawbacks: multi-rotor UAVs are very limited in flight time and range, and fixed-wing UAVs usually require facilities for take-off and landing. A compromise solution is introduced in this work, using a fixed-wing vertical take-off and landing (VTOL) UAV that combines the flexibility of a multi-rotor UAV with the range and flight time of a fixed-wing UAV. The first implementation of a VTOL with radiation mapping capabilities is presented, based on a commercial WingtraOne UAV augmented with CsI scintillator and CZT semiconductor gamma spectrometers. The radiation mapping capabilities of the prototype are demonstrated in a case study, mapping the distribution of radionuclides around the South Terras legacy uranium mine in the south of England, United Kingdom, and the results are compared with previous studies using multi-rotor and manned aircraft to survey the same area.

Satellite image survey of beluga whales in the southern Kara Sea

AbstractThe use of satellite imagery to find, count and monitor whales in remote and hard to access areas has shown some promise, but few satellite studies have, as yet, provided substantial conservation outcomes. Recent studies have shown the ability of very high‐resolution satellites to detect and count previously surveyed populations of belugas and narwhals in Canada. Here we describe the detection of a large aggregation of a poorly surveyed population of belugas in the southern Kara Sea, Russia, in a region where Soviet whaling is known to have had a heavy toll on belugas. We counted over 1,100 surface belugas using very high‐resolution satellite imagery. As only an unknown portion of the belugas can be seen on the surface, accurately converting the surface count to an abundance estimate will need further study, but using the analog of aerial surveys we estimate that this aggregation is between ~1,150–2,870 individuals. Although the species is not currently considered endangered, concern over belugas future population trends is increasing, as the species is reliant on Arctic sea ice, which is rapidly declining due to climate change. This study shows the utility of satellite imagery to discover and monitor new and little‐known cetacean populations.

MEMBANGUN KEMAMPUAN SPASIAL LEWAT PELATIHAN PEMETAAN DENGAN TEKNOLOGI DRONE

Drone technologys are now widely used not only for taking photos, videos, but also for mapping. Therefore, it is necessary to conduct mapping training activities with drone technology so that participants can improve their competence in using drones for mapping. Training purposes are 1) To provide an understanding of spatial knowledge through training with drone technology, 2) To increase competence related to Mapping using drones and 3) To produce high resolution maps. The methods or stages of training activities are 1) Coordination of training implementation with cooperation partners, 2) Preparation of training materials, 3) Opening of registration, 4) Opening of Training Classes, 5) Training of spatial data retrieval using drones, 6) Training of Spatial Data Processing from Drones. The results of the mapping training activity with drone technology were attended by 73 participants, of which 29 participants were declared passed and received certificates. Participants who passed were participants who had followed all the training materials and submitted aerial photography and contour maps assignments. Mapping training activities are carried out in online and offline blended learning. Online activities are carried out when opening classes, delivering material, processing data and closing classes, while offline activities are when the practice of taking aerial photos using drones will be used as data processing material. In addition, the results of the training activities include aerial photo maps and high-resolution contour maps from aerial photographs with drones made by training participants.

Rapid Assessment of Insect Pest Outbreak Using Drones: A Case Study with Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) in Soybean Fields.

Rapid assessment of crop damage is essential for successful management of insect pest outbreaks. In this study, we investigated the use of an unmanned aircraft system (UAS) and image analyses to assess an outbreak of the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), that occurred in soybean fields in South Korea. A rotary-wing UAS was deployed to obtain a series of aerial images over 31 soybean blocks. The images were stitched together to generate composite imagery, followed by image analyses to quantify soybean defoliation. An economic analysis was conducted to compare the cost of the aerial survey with that of a conventional ground survey. The results showed that the aerial survey precisely estimated the defoliation compared to the ground survey, with an estimated defoliation of 78.3% and a range of 22.4-99.8% in the 31 blocks. Moreover, the aerial survey followed by image analyses was found to be more economical than the conventional ground survey when the number of target soybean blocks subject to the survey was more than 15 blocks. Our study clearly demonstrated the effectiveness of using an autonomous UAS and image analysis to conduct a low-cost aerial survey of soybean damage caused by S. exigua outbreaks, which can inform decision-making for S. exigua management.

Deepening research on the construction thought of intelligent substation aerial survey auxiliary system

In the construction and development of modern society, the rational use of intelligent system is the inevitable trend of the development of the world's electric power, and the comprehensive promotion of smart grid is the basic consensus of the world's innovation. Substation intelligentization belongs to a gradual in-depth development process, which will change from traditional substation to integrated automation station, and then to digital substation, and finally become smart substation. Nowadays, Chinese power grid enterprises have already realized the large-scale construction and management of digital substations, and put forward the development goals and basic plans for the construction of smart substations. In 2020, the intelligent development probability of important substations has reached 100%. Therefore, after understanding the construction scheme and development status of smart substation system, this paper mainly discusses the construction ideas and main structure of the new generation of smart substation line measurement auxiliary system, and then defines the future development direction of smart substation auxiliary system, in order to provide effective basis for the construction and operation of power system in the new era.

Waterbird–habitat relationships in South Carolina: implications for protection, restoration, and management of coastal and inland wetlands

South Carolina coastal and inland wetlands are continentally important to resident, migrating, and wintering dabbling ducks (Anatini), diving and sea ducks (Aythini, Mergini, Oxyurini), pelagic waterbirds (Anhingidae, Laridae, Pelicanidae, and Phalcrocoracidae), and wading birds (Ardeidaie, Ciconiidae, Threskiornithidae). Our goal was to model wetland selection of these waterbird guilds in South Carolina during autumn–winter to determine habitat preferences and guide wetland conservation and restoration amid sea‐level rise and other coastal pressures. We conducted aerial surveys and recorded waterbird occurrence and relative abundance in winters 2017–2019. We modeled waterbird–habitat relationships relative to managed and unmanaged coastal and inland wetlands, legally protected conservation lands (e.g. federal, state, and private easements), and habitat diversity. Waterbirds selected a variety of wetlands emphasizing the importance of wetland diversity within habitat complexes. However, only managed tidal impoundments (MTIs) and protected conservation lands were selected across all waterbird guilds. Results suggest these are contemporary keystone habitats for promoting wintering waterbird abundance and diversity in South Carolina and other South Atlantic coastal regions. To compensate for future coastal wetland loss while facilitating the current and future needs of migrating and wintering waterbirds, we recommend: (1) identification and continued management of MTIs resilient to sea‐level rise; (2) strategic planning and partnerships for land acquisition and legal protections inland; and (3) land protection networks between extant coastal and inland sites designated for future construction and emigration of decommissioned MTIs. Stakeholder and partner engagement is paramount to prioritize resource allocation for the restoration, construction, and decommissioning of coastal and inland wetlands.

Dynamically simulating spruce budworm in eastern Canada and its interactions with wildfire

Eastern Spruce Budworm (ESBW) is a major agent of disturbance in Eastern Canada's boreal forests. Outbreaks have historically led to widespread defoliation of its preferred host trees, fir and spruce species, leading to high rates of mortality. This in turn can result in significant economic losses and enhancement of fire potential in the region. Representation of such biotic disturbance has rarely been included in Dynamic Global Vegetation Models (DGVM), which have become essential tools in understanding and predicting forest dynamics in present and future contexts. We present novel representation of host-specific defoliation in a DGVM (LPJ-LMfire), to better represent disturbance regimes in the boreal forest of eastern Canada. Using host foliage density to trigger outbreak, we were able to calibrate and simulate general spatial patterns of defoliation relative to historical aerial sketch map data. Return intervals were thus sensitive to the growth rates of host trees. Modeled return intervals tended to be significantly longer than 30 years, the approximate observed return interval. A factorial experiment was performed on the interactions of ESBW with wildfire, which was found to be slightly enhanced in terms of burned areas after outbreaks due to increased fuel loads. Interactions between ESBW and fire were found to have higher interaction strength in the drier Western region of the boreal forest. Our study demonstrates that biotic disturbance and its interaction with wildfire can be effectively simulated in a DGVM. We show that bottom-up climatic controls are sufficient to drive simulated spatiotemporal patterns of ESBW that can be calibrated to generally match historical observations.

Patterns of overlapping habitat use of juvenile white shark and human recreational water users along southern California beaches.

Juvenile white sharks (JWS) of the Northeastern Pacific population are present in nearshore southern California waters and form mixed size class (~1.5-3 m) aggregations for weeks to months, often within 500 m of shore. These nearshore beach habitats are heavily used for human recreation (e.g., surfing, swimming, body boarding, wading, and standup paddleboarding) and the amount of spatio-temporal overlap between JWS and humans is currently unknown. Increases in human population and the Northeastern Pacific population of white sharks have raised concern over human beach safety. To determine spatio-temporal JWS-human overlap at various spatial scales (e.g., across the entire southern California coastline, across different distances from shore, and within specific beach locations), 26 beach locations across southern California were surveyed monthly resulting in 1644 aerial drone surveys between January 2019 to March 2021. Thirteen environmental variables were assessed to predict when spatio-temporal overlap between JWS and water users was highest. Coast-wide distribution of JWS was clumped, limiting human-shark co-occurrence to specific locations, with 1096 of 1204 JWS observations occurring at Carpinteria and Del Mar Beach locations. Nearshore distribution indicated JWS are often close enough to the wave break to interact with some water users (median = 101 m, range = 2-702 m), although JWS had the most spatial overlap with stand-up paddlers. Daily human-shark co-occurrence was 97% at beaches where JWS aggregations had formed, and human activity showed high spatial overlap at shark aggregation sites. Although there is higher seasonal human-shark spatio-temporal overlap where aggregations form in southern California, the number of unprovoked shark bites across southern California is extremely low. This study provides evidence that high human-shark spatio-temporal overlap does not lead to an increased bite frequency in southern California, and there are a number of possible explanations as to why JWS are not biting water users despite daily encounters.