Island Ecosystems Research Articles

Drastic changes in ground-dwelling beetle communities following high-intensity deer culling: insights from an island ecosystem.

The overabundance of large herbivores can have detrimental effects on the local environment due to overgrazing. Culling is a common management practice implemented globally that can effectively control herbivore populations and allow vegetation communities to recover. However, the broader indirect effects of culling large herbivores remain relatively unknown, particularly on insect species such as ground-dwelling beetles that perform key ecosystem processes such as decomposition. Here we undertook a preliminary investigation to determine how culling sika deer on an island in North Japan impacted ground-beetle community dynamics. We conducted pitfall trapping in July and September in 2012 (before culling) and again in 2019 (after culling). We compared beetle abundance and community composition within 4 beetle families (Carabidae, Scarabaeidae, Geotrupidae, and Silphidae), across seasons and culling treatments. We found each family responded differently to deer culling. Scarabaeidae displayed the greatest decline in abundance after culling. Silphidae also had reduced abundance but to a lesser extent compared to Scarabaeidae. Carabidae had both higher and lower abundance after culling, depending on the season. We found beetle community composition differed between culling and season, but seasonal variability was reduced after culling. Overall, the culling of large herbivores resulted in a reduction of ground-dwelling beetle populations, particularly necrophagous species dependent on dung and carrion for survival. Our preliminary research highlights the need for long-term and large-scale experiments to understand the indirect ecological implications of culling programs on ecosystem processes.

Mapping and Monitoring of the Invasive Species Dichrostachys cinerea (Marabú) in Central Cuba Using Landsat Imagery and Machine Learning (1994–2022)

Invasive plants are a serious problem in island ecosystems and are the main cause of the extinction of endemic species. Cuba is located within one of the hotspots of global biodiversity, which, coupled with high endemism and the impacts caused by various disturbances, makes it a region particularly sensitive to potential damage by invasive plants like Dichrostachys cinerea (L.) Wight & Arn. (marabú). However, there is a lack of timely information for monitoring this species, as well as about the land use and land cover (LULC) classes most significantly impacted by this invasion in the last few decades and their spatial distribution. The main objective of this study, carried out in Central Cuba, was to detect and monitor the spread of marabú over a 28-year period. The land covers for the years 1994 and 2022 were classified using Landsat 5 TM and 8 OLI images with three different classification algorithms: maximum likelihood (ML), support vector machine (SVM), and random forest (RF). The results obtained showed that RF outperformed the other classifiers, achieving AUC values of 0.92 for 1994 and 0.97 for 2022. It was confirmed that the area covered by marabú increased by 29,555 ha, from 61,977.59 ha in 1994 to 91,533.47 ha in 2022 (by around 48%), affecting key land covers like woodlands, mangroves, and rainfed croplands. These changes in the area covered by marabú were associated, principally, with changes in land uses and tenure and not with other factors, such as rainfall or relief in the province. The use of other free multispectral imagery, such as Sentinel 2 data, with higher temporal and spatial resolution, could further refine the model’s accuracy.

Original plant diversity and ecosystems of a small, remote oceanic island (Corvo, Azores): Implications for biodiversity conservation

Remote islands harbour many endemic species and unique ecosystems. They are also some of the world's most human-impacted systems. It is essential to understand how island species and ecosystems behaved prior to major anthropogenic disruption as a basis for their conservation. This research aims to reconstruct the original, pre-colonial biodiversity of a remote oceanic island to understand the scale of past extinctions, vegetation changes and biodiversity knowledge gaps.We studied fossil remains from the North Atlantic island of Corvo (Azores), including pollen, charcoal, plant macrofossils, diatoms and geochemistry of wetland sediments from the central crater of the island, Caldeirão. A comprehensive list of current vascular plant species was compiled, along with a translation table comparing fossilized pollen to plant species and a framework for identifying extinctions and misclassifications.Pollen and macrofossils provide evidence for eight local extinctions from the island's flora and show that four species listed as ‘introduced’ are native. Up to 23 % of the pollen taxa represent extinct/misclassified species. Corvo's past environment was dynamic, shifting from glacial-era open vegetation to various Holocene forest communities, then almost completely deforested by fires, erosion and grazing following Portuguese colonisation. Historical human impacts explain high ecological turnover, several unrecorded extinctions and the present-day abundance of vegetation types like Sphagnum blanket mire.We use Corvo as a case study on how fossil inventories can address the Wallacean and Hookerian biodiversity knowledge gaps on remote islands. Accurate baselines allow stakeholders to make informed conservation decisions using limited financial and human resources, particularly on islands where profound anthropogenic disruption occurred before comprehensive ecological research.

Patterns of Wolf Dispersal Respond to Harvest Density across an Island Complex.

Wolves are highly mobile predators and can disperse across a variety of habitats and over long distances. However, less is known about dispersal capabilities across water and among islands. The biogeography of island systems fosters spatially structured local populations, and their degree of connectivity may influence the dynamics and long-term viability of the regional population. We sought to quantify wolf dispersal rate, distance, and dispersal sex bias throughout Prince of Wales Island, a 6670 km2 island in southeast Alaska, and the surrounding islands that constitute the wildlife management unit (9025 km2). We also investigated patterns of dispersal in relation to hunting and trapping intensity and wolf population density. We used DNA data collected during 2012-2021 long-term monitoring efforts and genotyped 811 wolves, 144 of which (18%) were dispersers. Annual dispersal rates were 9-23% and had a weakly positive relationship with wolf density. Wolves dispersed 41.9 km on average (SD = 23.7 km), and males and females did not disperse at different rates. Of the dispersing wolves, 107 died, and the majority (n = 81) died before they were able to settle. The leading manner of death was trapping (97% of mortalities), and wolves tended to disperse from areas with low harvest density to areas where harvest density was relatively higher. Dispersal occurred both to and from small islands and the larger Prince of Wales Island, indicating bidirectional as opposed to asymmetrical movement, and the genetic overlap of wolf groups demonstrates connectivity throughout this naturally patchy system. Island ecosystems have different predator-prey dynamics and recolonization processes than large, intact systems due to their isolation and restricted sizes; thus, a better understanding of the degree of population connectivity including dispersal patterns among islands in the Prince of Wales archipelago could help inform the management and research strategies of these wolves.

Dampak Investasi Asing di Pulau Komodo

Komodo Island, as Indonesia's famous tourism destination, has attracted foreign investment which has the potential to influence the economic, social and environmental sectors. This investment brings benefits in the form of opening jobs, increasing local community income, and developing tourism infrastructure. However, the impact also creates economic disparities between local and foreign workers, as well as social problems related to cultural interactions and local community access to the benefits of tourism. Meanwhile, developing tourist infrastructure also threatens the Komodo dragon habitat and the Komodo Island ecosystem. Therefore, mitigation measures are needed to ensure foreign investment supports sustainable development and preservation of the Komodo Island ecosystem. This research uses a literature review method which involves analysis from various sources such as scientific journals, books, reports and articles related to the impact of foreign investment on Komodo Island. This research aims to analyze the impact of foreign investment on Komodo Island on the economic, social and environmental sectors. The research focus includes discussing the economic impact through opening jobs and increasing income, the social impact related to cultural interactions, and the environmental impact of tourism infrastructure development.

Genomics reveals repeated landlocking of diadromous fish on an isolated island.

Landlocking of diadromous fish in freshwater systems can have significant genomic consequences. For instance, the loss of the migratory life stage can dramatically reduce gene flow across populations, leading to increased genetic structuring and stronger effects of local adaptation. These genomic consequences have been well-studied in some mainland systems, but the evolutionary impacts of landlocking in island ecosystems are largely unknown. In this study, we used a genotyping-by-sequencing (GBS) approach to examine the evolutionary history of landlocking in common smelt (Retropinna retropinna) on Chatham Island, a small isolated oceanic island 800 kilometres east of mainland New Zealand. We examined the relationship between Chatham Island and mainland smelt and used coalescent analyses to test the number and timing of landlocking events on Chatham Island. Our genomic analysis, based on 21,135 SNPs across 169 individuals, revealed that the Chatham Island smelt was genomically distinct from the mainland New Zealand fish, consistent with a single ancestral colonisation event of Chatham Island in the Pleistocene. Significant genetic structure was also evident within the Chatham Island smelt, with a diadromous Chatham Island smelt group, along with three geographically structured landlocked groups. Coalescent demographic analysis supported three independent landlocking events, with this loss of diadromy significantly pre-dating human colonisation. Our results illustrate how landlocking of diadromous fish can occur repeatedly across a narrow spatial scale, and highlight a unique system to study the genomic basis of repeated adaptation.

Conservation applications of niche modeling: Native and naturalized ferns may compete for limited Hawaiian dryland habitat.

Competition from naturalized species and habitat loss are common threats to native biodiversity and may act synergistically to increase competition for decreasing habitat availability. We use Hawaiian dryland ferns as a model for the interactions between land-use change and competition from naturalized species in determining habitat availability. We used fine-resolution climatic variables and carefully curated occurrence data from herbaria and community science repositories to estimate the distributions of Hawaiian dryland ferns. We quantified the degree to which naturalized ferns tend to occupy areas suitable for native species and mapped the remaining available habitat given land-use change. Of all native species, Doryopteris angelica had the lowest percentage of occurrences of naturalized species in its suitable area while D. decora had the highest. However, all Doryopteris spp. had a higher percentage overlap, while Pellaea ternifolia had a lower percentage overlap, than expected by chance. Doryopteris decora and D. decipiens had the lowest proportions (<20%) of suitable area covering native habitat. Areas characterized by shared environmental preferences of native and naturalized ferns may decrease due to human development and fallowed agricultural lands. Our study demonstrates the value of place-based application of a recently developed correlative ecological niche modeling approach for conservation risk assessment in a rapidly changing and urbanized island ecosystem.

Examining the Social Costs of Carbon Emissions and the Ecosystem Service Value in Island Ecosystems: An Analysis of the Zhoushan Archipelago

Assessments of the ecosystem service value (ESV) and the social cost of carbon (SCC) inform national and government management decisions in the areas of human well-being and climate change mitigation and adaptation, respectively. Studying the correlation between the two provides a theoretical basis for low-carbon and high-quality regional development, achieving economic decarbonization, and improving human well-being. In this study, we take Zhoushan Archipelago as a case study, consider the ESV and SCC in Zhoushan Archipelago during the period 2010–2020, analyze their spatial development characteristics, and analyze the correlation between the two in time and space. The findings indicate that, with only a 1.5% change, the overall ESV in the Zhoushan Archipelago fell between 2010 and 2020. Conversely, there was a 1604.01 × 104 t increase in net carbon emissions and a quick 2452% increase in SCC. During the study period, a substantial positive association was found between ESV and SCC in the Zhoushan Archipelago, according to the global spatial correlation analysis of the two variables. It passed the test for p-value. This study presents a new potential way to solve the environmental and economic difficulties caused by climate change by providing a mechanism for quantitatively assessing the environment from the perspective of monetary worth. In order to improve the ecological security pattern and ease the burden of regional carbon emissions, it is vital to make use of regional advantages, maintain forests, and develop blue-carbon resources such as mudflats. It is a good idea to cooperate regionally with nearby metropolitan agglomerations. The study’s findings are crucial for advancing sustainable development planning in the Zhoushan Archipelago, both theoretically and practically.

Analysis of carbon emission drivers and peak carbon forecasts for island economies

Sea islands are an essential support for expanding the blue economic space, and the study of the carbon emissions of Changhai County's island economies and their carbon peaking time is of great significance for achieving the goal of building an ecological low-carbon demonstration island with northern characteristics in Changhai County. In this study, the Logarithmic Mean Divisia Index (LMDI) method was used to explore the three main drivers affecting the carbon emissions of the island economies in Changhai County. The carbon emissions of Changhai County in 2012–2019 were estimated through the system dynamics model. The low-carbon development path and possible carbon peak time of Changhai County in 2020–2035 were predicted. The results show that: ①The urban system is the first positive driver of carbon emissions, followed by the residential system, and finally, the fishery system, the energy structure effect is the main positive driving effect affecting carbon emissions, and the population effect always shows a negative inhibitory impact on carbon emissions. ②The activities on the islands of Changhai County in 2012–2019 cumulatively produced 167.53 × 104 t of carbon emissions, 46.83 × 104 t of carbon sinks, and their net carbon emissions were 120.69 × 104 t. The results of the future scenario projections show that neither non-intervention nor a single policy of only adjusting land use and transport can achieve minor carbon emissions and that the best path for future low-carbon development in Changhai County is to develop all kinds of activities in a low-carbon (L) mode. ④Among the future forecast scenarios, Scenario 5 is an ideal model for the fastest way to achieve carbon peak, which generates 318.39 × 104 t of carbon emissions, and the cumulative emission reduction reaches 26.37 × 104 t.

Exploring the Relationships between Tradeoffs and Synergies among Island Ecosystem Service Bundles: A Study on Zhoushan Archipelago Located on the Southeast Coast of China

Due to the rapid rise of China’s coastal economic zone, the urbanization of the surrounding islands has accelerated. Intensive disturbance caused by human activities and frequent changes in land types have resulted in the continuous erosion of ecological sources and the degradation of ecosystem services on the islands year by year. It is particularly important to explore sustainable development strategies for the islands to achieve a balance between conservation and development, which is particularly important for the islands in the process of urbanization. Taking Zhoushan Archipelago as an example, this paper uses multi-source spatial data and employs InVEST models and USLE to quantify island ecosystem services. Furthermore, using principal component analysis and cluster analysis, the study aims to identify clusters of island ecosystem services and investigate their tradeoffs, synergistic mechanisms, and regional heterogeneity using spatial analysis. In addition to providing island urban planners with effective zoning governance recommendations and assistance in spatial planning to promote coordinated and sustainable development, the findings of this study can assist in the development of appropriate management plans for each ecological functional service cluster on islands.

Comparative Analysis of the Distribution and Composition of Grouper Fish (Family Serranidae) in the Coral Reef Ecosystems of Batanta and Salawati Islands, Raja Ampat

The Coral Reef Ecosystems of Batanta and Salawati Islands, Raja Ampat is a critical habitat for grouper species (Family Serranidae), which play essential roles in coral reef ecosystems. This study assessed the species composition, abundance, and biomass of groupers across 12 sampling sites in the region. Using the Underwater Visual Census (UVC) method, we identified 14 grouper species, with Plectropomus areolatus classified as vulnerable by the IUCN. Our results revealed an average grouper abundance 17.33 ind/350m2 for Batanta and 18.33 ind/350m2 for Salawati. An average biomass the mean biomass 4288.16 gr/350m2 for Batanta and 1881.10 gr/350m2 for Salawati, indicating substantial biomass within the area. Statistical analyses, including the Kruskal-Wallis test and t- tests reveal no significant difference in abundance between the two locations, as indicated by the non-significant p-value (p = 0.87). Correlation analysis demonstrated a very strong positive relationship between grouper abundance and biomass, suggesting that the Anthropogenic activities have not yet significantly impacted the grouper populations in Salawati and Batanta. The study emphasizes the importance of habitat protection and sustainable fisheries management to support grouper populations. Additionally, ongoing monitoring and adaptive management strategies are necessary to ensure the long-term health of grouper populations and the coral reef ecosystems they inhabit.

Standardising field‐based assessment of invasion degree: A case study in two habitats of Reunion Island

Abstract Biological invasions represent one of the major threats to biodiversity conservation, especially in island ecosystems. Field‐based assessments of the invasion degree are required for managing and monitoring invaded habitats but there is no unifying measure available in the literature. Here, we developed a standardised method for quantifying invasion degree based on four metrics: alien and native species cover, alien species richness, the occurrence frequency of alien species and invasion level, and demonstrated its use in two contrasted habitats of Reunion Island. This rapid survey quantified relative abundance and diversity of alien plant species among three vegetation strata (herbaceous, shrub and tree) in a systematic sampling. In lowland tropical forest, it took 40 person days to survey 150 ha (344 plots), and 52 person days in subalpine vegetation to survey 125 ha (304 plots). Our results showed that the herbaceous stratum was the most invaded in terms of invasion level; more than 45% in lowland tropical forest and almost 55% in subalpine vegetation. Based on cluster analysis and kriging, we mapped three different levels of invasion highlighting potential invasion fronts. We found that it was important to differentiate invasion degree per vegetation strata as mean alien cover was significantly different between strata at each site. This method is suitable for the majority of protected areas where fine‐scale assessment is required to characterise the spatial pattern of plant invasions, monitor invasive species and identify invasion foci to control or populations of emerging species to eradicate.

Insectivorous bat activity dataset across different land-use types in the Islands of São Tomé and Príncipe, Central West Africa.

São Tomé and Príncipe oceanic islands, in Central West Africa, are characterised by exceptional levels of endemism. Since human colonisation in the mid-15th century, São Tomé and Príncipe have lost 74% and 67% of their native habitat, respectively. Today, these islands are mainly covered by remaining old-growth forests, secondary regrowth forests, shaded plantations (mostly of cocoa), oil palm plantations (in the case of São Tomé), small-scale agricultural areas and urban areas. Yet, little is known about how species on these islands are coping with land-use changes. Island ecosystems are particularly important for bats, with about 25% of the world's bat species being entirely restricted to island systems. São Tomé and Príncipe Islands comprise six and four native insectivorous bats, respectively. Two species, Chaerephontomensis and Macronycteristhomensis, are island-endemics in São Tomé; Pseudoromiciaprincipis is an island-endemic in Príncipe; and Miniopterusnewtoni is endemic from both São Tomé and Príncipe. Here, we present a dataset comprising a comprehensive compilation of occurrence records derived from acoustic sampling of insectivorous bats across the predominant land-use types of both the São Tomé and Príncipe Islands. In each sampling site, standardised surveys consisted of deploying one Audio Moth device that recorded for 1 minute every 5 minutes over a 48-hour period. We identified a total of 19,437 bat-passes across the 115 sites surveyed in São Tomé Island and 17,837 bat-passes across the 50 sites surveyed in Príncipe Island. Based on a sampling effort of 1,584 hours of recordings manually processed to identify all the contained bat passes, this dataset, publicly available on GBIF, provides comprehensive information on the activity of insectivorous bats across two endemic-rich oceanic islands in the Gulf of Guinea. For each bat pass identified, we report the identified species, geographic coordinates, land-use type, altitude, date and time. This is the first public dataset providing detailed information on species-level habitat use for insectivorous bats on oceanic islands in Africa.

A review of predator exclusion fencing to create mainland islands in Hawai'i.

Invasive species are the primary threat to island ecosystems globally and are responsible for approximately two-thirds of all island species extinctions in the past 400 years. Non-native mammals-primarily rats, cats, mongooses, goats, sheep, and pigs-have had devastating impacts on at-risk species and are major factors in population declines and extinctions in Hawai'i. With the development of fencing technology that can exclude all mammalian predators, the focus for some locations in Hawai'i shifted from predator control to local eradication. This article describes all existing and planned full predator exclusion fences in Hawai'i by documenting the size and design of each fence, the outcomes the predator eradications, maintenance issues at each fence, and the resulting native species responses. Twelve predator exclusion fences were constructed in the Hawaiian Islands from 2011-2023 and six more were planned or under construction; all were for the protection of native seabirds and waterbirds. Fences ranged in length from 304-4,877m and enclosed 1.2-640 ha. One-third of the 18 fences were peninsula-style with open ends; the remaining two-thirds of the fences were complete enclosures. The purpose of twelve of the fences (67%) was to protect existing bird populations, and six (33%) were initiated for mitigation required under the U.S. Endangered Species Act. Of the six mitigation fences, 83% were for the social attraction of seabirds and one fence was for translocation of seabirds; none of the mitigation fences protected existing bird populations. Rats and mice were present in every predator exclusion fence site; mice were eradicated from five of six sites (83%) where they were targeted and rats (three species) were eradicated from eight of 11 sites (72%). Mongoose, cats, pigs, and deer were eradicated from every site where they were targeted. Predator incursions occurred in every fence. Rat and mouse incursions were in many cases chronic or complete reinvasions, but cat and mongoose incursions were occasional and depended on fence type (i.e., enclosed vs. peninsula). The advent of predator exclusion fencing has resulted in great gains for protecting existing seabirds and waterbirds, which demonstrated dramatic increases in reproductive success and colony growth. With threats from invasive species expected to increase in the future, predator exclusion fencing will become an increasingly important tool in protecting island species.

Evergreen forests on the Korean Peninsula faced a new threat: Schizomyia castanopsisae (Jat-bam-na-mu-hok-pa-ri) inducing galls on reproductive organs of Castanopsis sieboldii in the Yokjido Island Natural Monument Forest

Unnoticed and silently, a certain midge has emerged that could pose a threat to the evergreen forests on the Korean Peninsula and the associated island ecosystems. We report the discovery of an unrecorded species on the Korean Peninsula, identified as Schizomyia castanopsisae Elsayed &amp; Tokuda, 2018 (Diptera: Cecidomyiidae). This previously unrecorded gall midge species induces galls on a reproductive organ of Castanopsis sieboldii, specifically the inflorescences, and was found in the natural monument forest on Yokjido Island. A total of 40 larvae were collected from 8 inflorescence galls, each obtained from individual hosts within the forest. Morphological examinations and mitochondrial DNA cytochrome oxidase subunit I (COI) region sequencing were conducted for each specimen, confirming the identification of the gall inducer as S. castanopsisae. The COI sequences from the 40 specimens collected on Yokjido Island were identical, showing a 99.8% match with individuals from Kyushu, Japan. Additionally, a maximum likelihood tree analysis revealed a sister relationship between Yokjido Island and Kyushu individuals. Considering the tropical nature of gall midge species, it suggests recent northward migration from Kyushu to Yokjido Island. This species not only significantly reduces acorn production but also has the potential to negatively impact organisms associated with acorns. Drawing from cases in Japan, this species has the potential to rapidly dominate evergreen broad-leaved forests on numerous islands in the Korean Peninsula. Therefore, urgent additional research on aspects such as natural enemies of this species, its dispersal mechanisms, and other relevant factors is necessary. We also investigated the distribution of trees with inflorescences gall-induced by S. castanopsisae in the Yokjido Island Natural Monument Forest. The occurrence frequency of these galls is estimated to be approximately 10 percent.

Preserving coastal ecosystem through micro-zonation analysis of Karimunjawa, Indonesia.

Small island ecosystems and their inhabitants face a significant threat from global warming, jeopardizing their sustainability. These communities are particularly vulnerable to the impact of climate change, as they heavily rely on natural resources for their livelihoods and are more vulnerable than mainland regions. Therefore, it is essential to take urgent action to address the challenges small island states face and promote their resilience in the face of climate change. To preserve the coastal ecosystems in Karimunjawa Islands, Indonesia, this study proposes an alternative spatial plan through micro-zonation analysis. The study conducted literature reviews and field surveys to collect data and develop recommendations for the current spatial plans through spatial, descriptive statistics, and comparative analysis. The findings show that the sea surface temperatures of Karimunjawa and Kemujan Island have increased by 1-2℃. Stress levels were found for coral reefs at the bleaching warning position for all Karimunjawa Island marine areas, including Kemujan Island. Legon Lele and Tanjung Gelam were found to have suspended sediment traces and indications of heavy metal contamination, making them the research focus. The Karimunjawa micro-zonation boundaries were obtained, especially in the Legon Lele and Tanjung Gelam areas, with an area of 640.63 and 817.45ha, respectively. The proposed micro-zonation for Karimunjawa National Park refers to watershed-sedimentary cells, making it an example of implementing integrated coastal management (ICM) spatial boundaries in Karimunjawa and other nations. By applying this micro-zonation, coastal ecosystem rehabilitation efforts can be carried out precisely.

Food web of lizard species in a land-bridge island from Western Mexico

Island ecosystems provide valuable opportunities to explore some aspects associated with resource partitioning. While some ecological studies have suggested that island populations could keep a narrow dietary niche due to limited food sources, recent studies challenge this long-held belief for insular lizards. Herein, we evaluated the trophic web of the lizard community from María Cleofas Island in the Gulf of California, Western Mexico. We quantified the inter-individual diet variation for each lizard species, compared prey diversity between species, and analyzed any potential variations across different years. Our research revealed a wide variety of arthropods within the stomach contents of the lizards, regardless of their foraging strategy and habitat use. Our results also showed the inclusion of prey items that have not been previously reported in studies focusing on mainland-island populations. For example, we observed Anolis nebulosus predating cockroaches, hemipterans, and isopods. We observed differences in prey groups among lizard species, highlighting the broader niche of Anolis nebulosus, Phyllodactylus cleofasensis, and Aspidoscelis communis, as well as the narrowest trophic niche of Ctenosaura pectinata. Our research on the lizard community of María Cleofas Island has not only demonstrated the wide dietary diversity among species but has also expanded our understanding of trophic relationships in island ecosystems, with important implications for ecological studies.

Landscape structure does not hinder the dispersal of an invasive herbivorous mammal in the New Caledonian biodiversity hotspot

Biological invasions are a major threat to biodiversity and have particularly devastating impacts on island ecosystems. The New Caledonia archipelago is considered a biodiversity hotspot due to its diverse native flora. Javan rusa deer (Rusa timorensis) were introduced to New Caledonia in 1870 and the population consists of several hundred thousand individuals today. They directly threaten rare endemic species and affect the composition and structure of the vegetation. While a rusa deer management plan has identified ten priority areas for deer control operations, removing deer could be offset by the dispersal of animals back into the control areas. Here, we genotyped 628 rusa deer using 16 microsatellite markers to analyse the genetic structure of the animals in New Caledonia. We aimed to assess fine-scale genetic structure, to identify natural barriers to deer movement and to assess functional connectivity by optimising individual-based landscape resistance models. Our results suggested that rusa deer formed a single genetic population on the main New Caledonian island. The isolation-by-distance pattern suggested that female dispersal was limited, whereas males had larger dispersal distances. We assessed functional connectivity using different genetic distance metrics and all models performed poorly (mR2 ≤ 0.0043). Landscape features thus hardly affected deer movement. The characteristics of our results suggested that they were not an artefact of the colonisation history of the species. Achieving an effective reduction of deer population sizes in specific management areas will be difficult because of the deer’s high dispersal capabilities and impossible without very substantial financial investment.

Microplastics in sediment and surface water from an island ecosystem in Bay of Bengal

Microplastics (MPs) have garnered global attention as emerging pollutants in aquatic and terrestrial ecosystems. Despite their significance, studies on MP pollution have overlooked a biodiverse island ecosystem in the northeast Bay of Bengal. Hence, the current study is a pioneering effort to delve into this issue with the island. This research embodies the first comprehensive report exploring the presence of MP pollution in sediment and surface water and their influencing factors along Sandwip island in the northeast Bay of Bengal. The average MP concentration was 305 ± 37.16 (items/kg) in sediment and 106.14 ± 22.57 (items/m3) in surface water. Fragments emerged as the predominant type in sediment (78.77%) and surface water (54.64%) samples. Fourier Transform Infrared Spectroscopy identified three plastic polymers, the most abundant being polyethylene (56%) and polypropylene (41%). Anthropogenic activities, particularly fishing practices, improper waste disposal, and inadequate waste management strategies, were pinpointed as potential sources of MP contamination on the island. MP concentrations in water and sediment correlated positively with pH and organic matter (p < 0.000), indicating important factors influencing MP distribution. The spatial distribution and hotspots of MPs followed significant human routes. By shedding light on the extent of MPs' presence and their potential sources, this study contributes essential insights that can inform effective environmental management strategies for the island's future well-being.

The Grocer, the Hunting Dog, and the Solar Park: “This Web Radiating Out from Every Object”

In this essay I meet an elderly grocer and a caged dog, and visit a solar park. In telling the story of these particular encounters I hope to use the genre of creative non-fiction to offer the reader some glimpse of the complex eco-social web on the Aegean islands of Halki and Symi, where the memory of the sponge industry is a powerful image of wealth and devastation, where the island ecosystems are catastrophically depleted and their non-human beings abused, and where for all this there is yet some hope of renewal.