Uninhabited Islands Research Articles

Assessment of transboundary macro-litter on the remote island of Andaman and Nicobar: Unveiling the governing factors and risk assessment

The increasing occurrence of mismanaged plastic litter along India's coastline and the ominous challenges it poses to biodiversity and ecosystem health is a growing environmental concern. To address this issue, we comprehensively investigated the abundance, composition, and probable sources of marine litter on North Cinque Island, a remote uninhabited island in the Andaman and Nicobar archipelago, Bay of Bengal. This island is a designated wildlife sanctuary and serves as an important nesting site for Green, Hawksbill and Leatherback turtles. A total of 6227 litter items were enumerated, with an average concentration of 0.12 items/m2, representing 20 diverse litter types, with plastic dominating the litter composition (86 %). The cleanliness and environmental hazards of the coast due to the litter were assessed using different indices such as the Clean Coast Index (CCI), Plastic Accumulation Index (PAI), Hazardous Item Index (HII), and Clean Environment Index (CEI). CCI indicates the moderately clean-to-clean status of the surveyed sites. PAI points to low to moderate accumulation of plastic litter. HII of all five coasts fell in category II, suggesting a moderate abundance of hazardous items that can inflict injuries to the foraging turtle and their hatchlings. The CEI articulates the moderately clean to very clean status of the sites. Litter brand audit suggests a considerable amount of stranded litter on the coasts was transboundary and originated from six Indian Ocean Rim Countries (IORC), namely Thailand, Myanmar, Malaysia, Indonesia, Sri Lanka, and UAE. Joint solid waste management by the IORC is the need of the hour to avert litter accumulation on the pristine, remote islands.

Current Situation, Problems and Suggestions of Uninhabited Island Management—Taking Dalian City as an Example

Current Situation, Problems and Suggestions of Uninhabited Island Management—Taking Dalian City as an Example

Net evaporation-induced mangrove area loss across low-lying Caribbean islands

Abstract Although mangroves provide many beneficial ecosystem services, such as blue carbon storage and coastal protection, they are currently under threat due to changes in climate conditions, such as prolonged drought exposure. Under drought conditions, evaporation exceeds precipitation and high soil salinities can lead to stunted growth and die-back. To quantify this interplay, we developed a database for low-lying and uninhabited mangrove islands in the Caribbean under various evaporation and precipitation regimes. We extracted physical and biological information from each island using remote sensing techniques and coupled it with a process-based model. We used this database to develop a model that explains both the spatial variability in vegetated area across the Caribbean—as a function of rates of evaporation and precipitation—and porewater salinity concentration and dispersion from island edge towards the interior of mangrove islands. We then used this validated model to predict mangrove area loss associated with increases in evaporation to precipitation rates by 2100 for different Shared Socioeconomic Pathways (SSP). Less wealthy Caribbean regions such as Belize, Puerto Rico, and Venezuela are disproportionally affected, with mangrove area losses ranging from 3%–7% for SSP 2.6 and 13%–21% for SSP 7.0. Furthermore, foregone carbon sequestration in lost biomass under SSP 4.5 and 7.0 scenarios could compromise the ability of low-lying Caribbean mangrove islands to vertically adjust to sea level rise.

Birds influence vegetation coverage and structure on sandy biogeomorphic islands in the Dutch Wadden Sea

Small uninhabited islands form important roosting and breeding habitats for many coastal birds. Previous studies have demonstrated that guano can promote ecosystem productivity and functionality on island ecosystems. Here, we assess the role of external nutrient input by coastal birds on the vegetation structure and coverage on sandy biogeomorphic islands, where island-forming processes depend on vegetation-sedimentation feedbacks. As a first step, we investigated whether breeding birds affect vegetation productivity on sandy back-barrier islands in the Wadden Sea. Using a combination of bird observations and plant stable isotope (δ15N) analyses, we demonstrate that (i) breeding birds transport large quantities of nutrients via their faecal outputs to these islands annually and that (ii) this external nitrogen source influences vegetation development on these sandy, nutrient-limited, islands. Based on these results we discuss how this avian nutrient pump could impact island development and habitat suitability for coastal birds and discuss future directions for research. In general, we conclude that avian subsidies have the potential to affect both the ecological and biogeomorphic functioning of coastal soft-sediment systems. However, the strength and scale of especially these biogeomorphic interactions are not fully understood. For the conservation of both threatened coastal birds and sandy back-barrier islands and the design of appropriate management strategies, we argue that three-way interactions between birds, vegetation and sandy island morphodynamics need to be further elucidated.

Transformation of coastal wetlands in the Sundarban Delta (1999–2020)

Spanning across Bangladesh and India, the Sundarban Delta consists of over a thousand islands, the majority of which are protected. These islands are important for the rich biodiversity and unique species found here. However, these islands are also at the forefront of climate change due to the impact of rising sea levels and extreme weather events. Therefore, we analyzed the long-term transformations in the land use land cover (LULC) between 1999 and 2020. We used a variety of geostatistical methods, including optimized hot spots cold spots and join count statistics, to examine the spatial patterns of changes in LULC across the study area. The results of our analysis revealed substantial changes in the spatial patterns of mangroves and pond aquaculture. The changes revealed a distinct north–south demarcation in spatial patterns, in the form of clustering of mangroves in the uninhabited islands located in the south and pond aquaculture clustered in the northern inhabited islands. The loss of area under mangroves was concentrated in the southern edges of the islands, which were most exposed to erosion in the open ocean. Nevertheless, we observed an increase in the area under mangroves in some of the northern riverine islands (17 km2). In the case of pond aquaculture, it was mostly concentrated in inhabited islands in the north. Most of the expansions were concentrated in the Indian part of the delta (631 km2). It is noteworthy that because of effective conservation measures, there was very limited overlap between mangroves and pond aquaculture, denoting the conversion of agricultural land to pond aquaculture instead of mangroves. Thus, the results of our study revealed the importance of local level conservation policies and anthropogenic activities, such as deforestation and local level disturbance like over-extraction of water and pollution, on the changing patterns of LULC across this unique, fragile ecosystem. Future studies may incorporate a finer resolution time series of LULC changes over time and space to enable more detailed analysis.

Soil bacterial community diversity and life strategy during slope restoration on an uninhabited island: changes under the aggregate spray-seeding technique.

We investigated the effects of the aggregate spray-seeding (ASS) technique on soil bacterial community diversity, life strategies, and seasonal change. Soil from six plots with original vegetation (CK, n=6) was compared to soil from 15 plots with spray-seeding restoration (SR, n=15) using environmental DNA sequencing. The bacterial Shannon and Chao1 indices of SR soils were significantly greater (P<0.05) than those of CK soils. The Chao1 index for the SR soil bacterial community was significantly greater in summer (P<0.05) than in winter. The ratio of the relative abundance of bacterial K-strategists to r-strategists (K/r) and the DNA guanine-cytosine (GC) content in the SR soil were significantly lower (P<0.05) than those in the CK soil. Principal coordinate analysis revealed significant differences between the SR and CK bacterial communities. The GC content was positively correlated with the K/r ratio. Soil conductivity was negatively associated with the K/r ratio and GC content, indicating that ionic nutrients were closely related to bacterial life strategies. The ASS technique improved soil bacterial diversity, altered community composition, and favored bacterial r-strategists.

Restoration via the aggregate spray-seeding technique affected the soil proteobacteria on an Uninhabited Island: Community structure, metabolic function, nutritional type, and life strategy

This study aimed to explore the impact of aggregate spray-seeding (ASS) restoration measures on the soil proteobacterial community. Using environmental DNA sequencing, we analyzed the proteobacterial communities in the soils of 3 natural vegetation (NV) plots, 3 traditional afforestation (TA) plots, and 12 spray-seeding restoration (SR) plots located on Triangle Island in Zhuhai city, China, during both the summer and winter seasons. We estimated the metabolic function, nutritional type, and life strategy of Proteobacteria through the FAPROTAX and rrnDB databases. Our findings demonstrated that Proteobacteria was the predominant phylum (relative abundance = 40.1–48.4%) in the soil bacterial communities across all three treatments. The relative abundance of Alphaproteobacteria ranged from 28.5% to 38.1%, which was significantly greater (2.6–10.3 times, p < 0.05) than that of Betaproteobacteria or Gammaproteobacteria. Most (90%) proteobacterial genera and all rhizobial genera found in the NV and TA soils were also present in the SR soil, but there were distinct differences in the proteobacterial community structures between the SR soil and NV/TA soil. Across all seasons and treatments, the proteobacterial communities were related to functions such as ureolysis, nitrogen fixation, nitrate reduction, and hydrocarbon degradation. The relative abundance of Proteobacteria associated with chitinolysis was greater in the SR soil than in the NV and TA soils. Among the overall proteobacterial community, the chemoheterotrophic, chemoautotrophic, and phototrophic bacteria accounted for 65–77%, 19–31%, and less than 5%, respectively. Alphaproteobacteria tended to be K strategic, while Betaproteobacteria and Gammaproteobacteria tended to be r strategic. The soil pH, organic carbon content, and nitrogen content were significantly correlated with the metabolic function and nutritional type of the soil Proteobacteria according to the Mantel test results. In conclusion, the application of the ASS technique can effectively restore the biodiversity, metabolic function, and nutritional-type structure of the soil proteobacterial community. Additionally, this study highlights that certain metabolic functions of the proteobacterial community in SR soil undergo changes in response to the use of certain restoration materials. These findings suggest that the targeted addition of specific repair materials can modulate soil microorganism functionality and provide a valuable theoretical foundation for ecological restoration engineering practices.

Spatiotemporal variations in marine macro-litter pollution along the shoreline of Koh Mun Nai, an uninhabited island in the Gulf of Thailand

Despite a recent ambitious plan to improve waste management in Thailand, few studies have monitored the impact of these policies on beached marine litter. Here, we assessed weekly the amounts and composition of stranded macro-litter (≥2.5 cm) on five beaches from an uninhabited island in Thailand during one year. A total of 24,407 items (391.86 kg) yielded a mean abundance of 3.18 ± 11.39 items m−2 (52.75 ± 204.68 g m−2), with plastic being the most abundant marine litter (48% of the total number). The overall Clean Coast Index (30.1) classified the beaches as ‘extremely dirty’, with a Plastic Abundance Index of 9.8 (‘very high abundance’ of plastics). When assessing the seasonal rates of accumulation, we found a higher flux pre-monsoon (0.05 items m−2 d−1; 0.66 g m−2 d−1) than post-monsoon (0.01 items m−2 d−1; 0.35 g m−2 d−1). Using modeling of the local hydrodynamic conditions, we explored the potential sources of the pollution, and surprisingly found that the closest river appeared not to be the source. Our results denote that the distribution and typology of marine litter were representatives of household and fishing activities, which in turn highlights the need for better regional litter management measures.

Identification of Dominant Species and Their Distributions on an Uninhabited Island Based on Unmanned Aerial Vehicles (UAVs) and Machine Learning Models

Comprehensive vegetation surveys are crucial for species selection and layout during the restoration of degraded island ecosystems. However, due to the poor accessibility of uninhabited islands, traditional quadrat surveys are time-consuming and labor-intensive, and it is challenging to fully identify the specific species and their spatial distributions. With miniaturized sensors and strong accessibility, high spatial and temporal resolution, Unmanned Aerial Vehicles (UAVs) have been extensively implemented for vegetation surveys. By collecting UAVs multispectral images and conducting field quadrat surveys on Anyu Island, we employ four machine learning models, namely Gradient Boosting Decision Tree (GBDT), Support Vector Machine (SVM), Random Forest (RF) and Multiple Classifier Systems (MCS). We aim to identify the dominant species and analyze their spatial distributions according to spectral characteristics, vegetation index, topographic factors, texture features, and canopy heights. The results indicate that SVM model achieves the highest (88.55%) overall accuracy (OA) (kappa coefficient = 0.87), while MCS model does not significantly improve it as expected. Acacia confusa has the highest OA among 7 dominant species, reaching 97.67%. Besides the spectral characteristics, the inclusion of topographic factors and texture features in the SVM model can significantly improve the OA of dominant species. By contrast, the vegetation index, particularly the canopy height even reduces it. The dominant species exhibit significant zonal distributions with distance from the coastline on the Anyu Island (p &lt; 0.001). Our study provides an effective and universal path to identify and map the dominant species and is helpful to manage and restore the degraded vegetation on uninhabited islands.

Estimating soil organic carbon and total nitrogen across inhabited and uninhabited islands based on dual simulations in the entire- and sub-areas

Soil total organic carbon (TOC) and total nitrogen (TN) mapping methods have been developed for different ecosystems; however, little attention has been paid to archipelagos comprising inhabited and uninhabited islands. In this study, we proposed a method of dual simulations in the entire- and sub-areas to adequately improve the simulation accuracy of soil TOC and TN in the archipelago. A typical archipelago, Miaodao Archipelago, was selected to demonstrate the method. The dual simulations comprehensively considered the common characteristics of the entire-area and the unique conditions of each sub-area in the archipelago. Through the dual simulations, the accuracy can be viewed in three hierarchies: the entire area (the first hierarchy), the inhabited and uninhabited islands (the second hierarchy), and the single island (the third hierarchy). The simulation accuracies for TOC were increased by 12.03%, 12.03%, and 16.94% in the first, second, and third hierarchies, respectively, compared with the baseline, and those for TN were increased by 7.13%, 9.21%, and 14.72%, respectively. The lowest normalized root mean squared errors for TOC and TN were 0.114 and 0.105, respectively, which were similar to those reported in previous studies that achieved high simulation accuracy in other areas. Considerable differences in soil TOC and TN existed across the inhabited (39.95 g/kg TOC and 3.61 g/kg TN) and uninhabited (63.42 g/kg TOC and 7.08 g/kg TN) islands, which were driven by the great differences in natural conditions and human activities across the two sub-areas. The dual simulations contributed to the further improvement of simulation accuracy in soil mapping, providing a practical method for soil TOC and TN estimation in the archipelago, and revealing the spatial differences in soil TOC and TN across the inhabited and uninhabited islands.

Beneficial use of sediments to restore a Chesapeake Bay marsh island

Despite rapidly expanding interest in the use of natural coastal habitats for their ability to protect against erosion and flooding, implementation of coastal natural infrastructure (NI) projects has been limited to date. Uncertainty over how the benefits of NI will change over time as they mature and adapt to changing environmental drivers, and a lack of well-documented demonstrations of NI, are often cited as roadblocks to their widespread acceptance. Here, we begin to fill that knowledge gap by describing implementation and early (3 years post-implementation) monitoring results of an NI project at Swan Island, MD. Swan is an uninhabited marsh island in mid-Chesapeake Bay, United States whose position renders it a natural wave break for the downwind town of Ewell, MD. Prior to project implementation, Swan had experienced significant losses in areal extent due to subsidence and erosion. To reverse this trend, the island was amended with dredged sediments in the winter of 2018–2019. The overarching goal was to preserve the Island’s ability to serve as a wave break and make it more resilient to future sea level rise by increasing the elevation of the vegetated platform, while also increasing the diversity of habitats present. A monitoring program was implemented immediately after sediment placement to document changes in the island footprint and topography over time and to evaluate the extent to which project goals are met. Data from the initial three years of this effort (2019 through 2022) indicate an island that is still actively evolving, and point to the need for rapid establishment of vegetative communities to ensure success of coastal NI.

A first assessment of marine litter on a beach of an uninhabited island in the Mozambique Channel

Marine litter is ubiquitous and associated with both ecological and socio-economic consequences. Beaches are major sinks of marine litter and as such its assessment and monitoring are needed. An opportunistic marine litter survey was performed for 12 consecutive days on the island of Juan de Nova in the central Mozambique Channel in February 2007. Plastic dominated the marine beach litter with daily accumulation of plastic positively related to the tide height (R2 = 0.768, p&lt;0.01). Annual deposits could reach an average of 1 t.km-1, suggesting that regular cleaning of the coastline should be conducted to limit the impact on the local wildlife of this protected area.

Madeira: 300 years of an astronomical site

The history of science in islands is not a well worked out discipline. This article offers the first thorough historical account of astronomical activities at Madeira, from the discovery of the uninhabited island in the fifteenth century (600 years ago), through its establishment as an astronomical observatory (300 years ago) and up to the recent past.

The Guesthouse Phenomenon in the Maldives – Development and Issues

Summary The tourism industry in the Maldives has long been dominated by the “one island, one resort” model, where luxury resorts on uninhabited islands kept tourists isolated from local communities. However, recent legislative changes have opened up new opportunities for community-based tourism (CBT) with the establishment of guesthouses on inhabited islands. This shift aims to increase local participation in the tourism sector and has led to greater interaction between tourists and the island communities. The guesthouse industry has witnessed rapid growth, surpassing the number of resorts, providing more affordable options for visitors, and offering the potential for economic and social benefits for local communities. Despite the benefits, the lack of clear guidelines and varying sizes and facilities of guesthouses has caused confusion among stakeholders and tourists. The increased interaction between conservative local communities and tourists has also led to conflicts. This case study is based on a research project conducted in September 2019 exploring the sustainable development opportunities and challenges of the guesthouse tourism industry in the Maldives. Extensive in person interviews were conducted with tourists staying at three local island islands in the country, as well as guesthouse operators and managers from the same islands. Information © The Authors 2024

Île Dumet (Armorican Massif, France) and its glaucophane eclogites: the little sister of Île de Groix

Abstract. Blueschist-facies rocks are scarce within the Variscan orogen. Two main occurrences are known in the Armorican Massif (NW France), at Île de Groix and Bois-de-Céné. Another glaucophane occurrence was discovered in 1988 but went unnoticed; it is located on Île Dumet, an uninhabited island off the coast of southern Brittany, in the estuary of the river Vilaine. Orthogneiss occurs on the SW half of the island; the original granitoid magma had intruded mica schists on the NE half, where numerous 1 to 10 m long boudins of mafic rocks occur. These lenses are typically retrogressed into plagioclase-bearing amphibolite, but a few contain remnants of glaucophane-bearing eclogite, which also occurs as numerous loose blocks along the NE coast of the island, suggesting that the best-preserved eclogites lie in situ offshore in that direction. The glaucophane eclogites contain garnet, omphacite, quartz, amphibole, clinozoisite/epidote, minor phengite, paragonite, rutile and rare apatite. Prograde metamorphic evolution is indicated by garnet crystals zoned from Mn-rich cores to Mg-richer rims (typically (core→rim): Alm44→58 Prp1→12 Grs33→29 Sps22→1) and amphibole grains with glaucophane nuclei and Ca–Na-amphibole overgrowths that show sharp transitions, supporting evolution through a solvus, as predicted by the thermodynamic modelling. Modelling of the P–T conditions using the P–T pseudosection technique indicates a peak of metamorphism at about 620 ∘C and 16 kbar. The retrograde evolution of the metabasites is evidenced by the late formation of albite, titanite and ferro-actinolite. The surrounding mica schists, composed of quartz, garnet, phengite, paragonite and chlorite, were also largely retrogressed during exhumation. The orthogneiss of the SW part of the island does not show clear evidence of high-pressure metamorphism, since the magmatic feldspars are still preserved, similarly to the orthogneiss of Les Sables Rouges on the island of Groix. Île Dumet and the western part of the Vilaine estuary represent a blueschist-facies equivalent to Île de Groix (Brittany) and Bois-de-Céné (Vendée) on the mainland. All three occurrences occupy the centres of wide synforms whose concentric units are, from rims to core (i.e. from base to top), (a) a high-T migmatitic basement; (b) Cambro-Ordovician metasediments and acid metavolcanites (“porphyroids”); and (c) blueschist-facies mica schists and metabasites, serpentinites, and minor orthogneisses derived from a pre-Variscan oceanic accretionary prism. There are about 10 similar occurrences within the Ibero-Armorican Arc, forming a discontinuous high-pressure belt, but most of them have remained unnoticed due to a high degree of retrogression.

Lost and found: Patterns of marine litter accumulation on the remote Island of Santa Luzia, Cabo Verde

Santa Luzia, an uninhabited island in the archipelago of Cabo Verde, serves as a natural laboratory and important nesting site for loggerhead turtles Carettacaretta. The island constitutes an Integral Natural Reserve and a Marine Protected Area. We assessed marine litter accumulation on sandy beaches of the island and analysed their spatial patterns using two sampling methods: at a fine scale, sand samples from 1 × 1 m squares were collected, identifying debris larger than 1 mm; at a coarse scale, drone surveys were conducted to identify visible marine debris (>25 mm) in aerial images. We sampled six points on three beaches of the island: Achados (three points), Francisca (two points) and Palmo Tostão (one point). Then, we modelled the abundance of marine debris using topographical variables as explanatory factors, derived from digital surface models (DSM). Our findings reveal that the island is a significant repository for marine litter (>84% composed of plastics), with up to 917 plastic items per m2 in the sand samples and a maximum of 38 macro-debris items per m2 in the drone surveys. Plastic fragments dominate, followed by plastic pellets (at the fine-scale approach) and fishing materials (at the coarse-scale approach). We observed that north-facing, higher-elevation beaches accumulate more large marine litter, while slope and elevation affect their spatial distribution within the beach. Achados Beach faces severe marine debris pollution challenges, and the upcoming climate changes could exacerbate this problem.

Characteristics of main plant communities on uninhabited islands in Bohai Sea, China

Characteristics of main plant communities on uninhabited islands in Bohai Sea, China

An extremely rare serovar of Salmonella enterica (Yopougon) discovered in a Western Whip Snake (Hierophis viridiflavus) from Montecristo Island, Italy: case report and review

Reptiles, including snakes, can be asymptomatically infected with multiple pathogen microorganisms, including Salmonella spp., which is considered an important concern for public and animal health. Small and uninhabited isles are quite ecologically different from mainland and represent interesting fields of study, to discover unexpected biological and microbiological aspects of their wild inhabitants. This work reports the presence of the very rare Salmonella enterica serovar Yopougon, isolated in a carcass of a native wild snake (Hierophis viridiflavus) from an Italian uninhabited island of Mediterranean Sea, Montecristo. To our knowledge, S. enterica serovar Yopougon was previously isolated only once 34 years earlier in Ivory Coast, from a human fecal sample. In the present study, we present the genomic characterization of the new isolate, the phylogenetic comparison with the previously isolated S. enterica serovar Yopougon strain of human origin and with other sequences available in public databases. In addition, an extensive review of available data in the literature and from our case history is provided. Our finding represents an example of the ability of some pathogens to travel for very long distances within their hosts and then to infect others, even from different taxa.

Mangrove Ecotourism as an Education and Learning Facility

This study investigates the educational benefits of mangrove tourism on Gili Sulat, an uninhabited island designated as an Aquatic Tourism Park in Lombok, Indonesia. The study is exploratory research. The research sample was determined purposively, they were 10 fifth-semester Biology Education students engaged in practicums on Gili Sulat. Through a questionnaire and interview sessions, the study explores the students' perceptions and experiences regarding the educational aspects of mangrove ecotourism. Perception data was analyzed qualitatively. The findings reveal that the primary motivation for the students' visit was education and learning, emphasizing the unique ecosystem's allure. The students demonstrated a nuanced understanding of the mangrove ecosystem's role in protecting coastal environments and expressed heightened inspiration for environmental protection. Their suggestions for improvement, such as species name boards, and the willingness to revisit Gili Sulat for educational activities underscore the enduring impact of mangrove ecotourism on fostering environmental awareness and responsibility. The study contributes to the discourse on the educational potential of ecotourism, particularly in the context of mangrove ecosystems, advocating for the continued promotion and preservation of such destinations as invaluable educational resources.

Uninhabited Islands in the Bay of Bengal, Penang, Singapore and Botany Bay: What Did Terra Nullius Mean in British Colonial Thinking?

Enlightenment colonial actors never used the term ‘terra nullius’, they used the phrase ‘uninhabited land or island’. In the 1780s, uninhabited did not mean nobody lived there, but rather signified a land without a sovereign. This article contrasts British East India Company deliberations on the habitation of islands in the Eastern Indian Ocean, with the discussions on habitation in Botany Bay prior to 1788. Between 1778 and 1786, there were proposals for British settlements in the Nicobar Islands, Andaman Islands, Junk Ceylon and Penang. The people who lived on these islands were not considered the inhabitants. Instead, the British looked at the relationship between people on the islands and mainland Asian sovereigns to determine who inhabited these islands. A retrospective discourse developed that Penang and Singapore were uninhabited prior to the British arrival. This discourse was part of plans to end legal pluralism in the settlements and assert colonial sovereignty.