Soil nutrient content and water level variation drive mangrove forest aboveground biomass in the lagoonal ecosystem of Aldabra Atoll

Lagoonal mangrove ecosystems are vital for carbon capture, protection of coastlines and conservation of biodiversity. Yet, they are decreasing globally at a higher rate than other mangrove ecosystems. In addition to human drivers, local environmental factors influence the functioning of lagoonal mangrove ecosystems, but their importance and combined effects are relatively unknown. Here, we investigate the drivers of mangrove functioning, approximated by mangrove aboveground biomass (AGB), in a protected lagoonal mangrove ecosystem on Aldabra Atoll, Seychelles. Based on a survey of the mangrove forest structure in 54 plots, we estimated that the mean mangrove forest AGB was 82 ± 13 Mg ha−1. The total AGB of the mangrove area (1720 ha) was nearly 140,600 Mg, equivalent to about 66,100 Mg of carbon stored in the standing biomass on Aldabra. To assess the direct and indirect effects of soil nutrient content, water level variation and soil salinity on mangrove AGB, we used a structural equation model. Our structural equation model explained 82 % of the variation in mangrove AGB. The soil nutrient content (concentration of essential macronutrients in the soil column) had the greatest influence on mangrove AGB variation. Additionally, high variation in water level (change in water depth covering a location) increased mangrove AGB by increasing nutrient content levels. Our results highlight the important contribution of Aldabra's lagoonal ecosystem to Seychelles' carbon storage and the role of hydroperiod as a regulator controlling the availability of crucial nutrients needed for the functioning of mangroves within lagoonal systems. We suggest conservation managers worldwide focus on a holistic ecosystem-level perspective for successful mangrove conservation, including the protection and maintenance of nutrient cycling and hydrological processes

Island invasives: scaling up to meet the challenge

Management and eradication techniques for invasive alien birds remain in their infancy compared to invasive mammal control methods, and there are still relatively few examples of successful avian eradications. Since 2011, five separate eradication programmes for invasive birds have been conducted on three islands by the Seychelles Islands Foundation (SIF). Target species were prioritised according to their threat level to the native biodiversity of the UNESCO World Heritage Sites of the Seychelles, Aldabra Atoll and Vallée de Mai, which SIF is responsible for managing and protecting. Red-whiskered bulbuls (Pycnonotus jocosus) and Madagascar fodies (Foudia madagascariensis) occurred on Assumption, the closest island to Aldabra, which, at the time, had no known introduced bird species. The growing population of ring-necked parakeets (Psittacula krameri) on Mahé posed a threat to endemic Seychelles black parrots (Coracopsis barklyi) on Praslin where the Vallée de Mai forms their core breeding habitat. In 2012, red-whiskered bulbuls and Madagascar fodies were detected on Aldabra, so an additional eradication was started. All eradications used a combination of mist-netting and shooting. The intensive part of each eradication lasted three years or less. On Assumption, 5,279 red-whiskered bulbuls and 3,291 Madagascar fodies were culled; on Mahé, 545 parakeets were culled; and on Aldabra 262 Madagascar fodies and one red-whiskered bulbul were culled. Each programme underwent 1–2 years of follow-up monitoring before eradication was confirmed, and four of the five eradications have been successful so far. None of these species had previously been eradicated in large numbers from other islands so the successes substantially advance this field of invasive species management. The challenges and insights of these eradications also provide unique learning opportunities for other invasive avian eradications

Envisioning a resilient future for biodiversity conservation in the wake of the COVID-19 pandemic

NE/T010401/1 UIDB/04647/2020 UIDP/04647/2020As the COVID-19 pandemic continues to affect societies across the world, the ongoing economic and social disruptions are likely to present fundamental challenges for current and future biodiversity conservation. We review the literature for outcomes of past major societal, political, economic and zoonotic perturbations on biodiversity conservation, and demonstrate the complex implications of perturbation events upon conservation efforts. Building on the review findings, we use six in-depth case studies and the emerging literature to identify positive and negative outcomes of the COVID-19 pandemic, known and anticipated, for biodiversity conservation efforts around the world. A number of similarities exist between the current pandemic and past perturbations, with experiences highlighting that the pandemic-induced declines in conservation revenue and capacity, livelihood and trade disruptions are likely to have long-lasting and negative implications for biodiversity and conservation efforts. Yet, the COVID-19 pandemic also brought about a global pause in human movement that is unique in recent history, and may yet foster long-lasting behavioural and societal changes, presenting opportunities to strengthen and advance conservation efforts in the wake of the pandemic. Enhanced collaborations and partnerships at the local level, cross-sectoral engagement, local investment and leadership will all enhance the resilience of conservation efforts in the face of future perturbations. Other actions aimed at enhancing resilience will require fundamental institutional change and extensive government and public engagement and support if they are to be realised. The pandemic has highlighted the inherent vulnerabilities in the social and economic models upon which many conservation efforts are based. In so doing, it presents an opportunity to reconsider the status quo for conservation, and promotes behaviours and actions that are resilient to future perturbation. A free Plain Language Summary can be found within the Supporting Information of this article.publishersversionpublishe

Integration of population genetics with oceanographic models reveals strong connectivity among coral reefs across Seychelles

Many countries with tropical reef systems face hard choices preserving coral reefs in the face of climate change on limited budgets. One approach to maximising regional reef resilience is targeting management efforts and resources at reefs that export large numbers of larvae to other reefs. However, this requires reef connectivity to be quantified. To map coral connectivity in the Seychelles reef system we carried out a population genomic study of the Porites lutea species complex using 241 sequenced colonies from multiple islands. To identify oceanographic drivers of this connectivity and quantify variability, we further used a 2 km resolution regional ocean simulation coupled with a larval dispersal model to predict the flow of coral larvae between reef sites. Patterns of admixture and gene flow are broadly supported by model predictions, but the realised connectivity is greater than that predicted from model simulations. Both methods detected a biogeographic dispersal barrier between the Inner and Outer Islands of Seychelles. However, this barrier is permeable and substantial larval transport is possible across Seychelles, particularly for one of two putative species found in our genomic study. The broad agreement between predicted connectivity and observed genetic patterns supports the use of such larval dispersal simulations in reef system management in Seychelles and the wider region

Rapid loss of flight in the Aldabra white-throated rail

Flight loss has evolved independently in numerous island bird lineages worldwide, and particularly in rails (Rallidae). The Aldabra white-throated rail (Dryolimnas [cuvieri] aldabranus) is the last surviving flightless bird in the western Indian Ocean, and the only living flightless subspecies within Dryolimnas cuvieri, which is otherwise volant across its extant range. Such a difference in flight capacity among populations of a single species is unusual, and could be due to rapid evolution of flight loss, or greater evolutionary divergence than can readily be detected by traditional taxonomic approaches. Here we used genetic and morphological analyses to investigate evolutionary trajectories of living and extinct Dryolimnas cuvieri subspecies. Our data places D. [c.] aldabranus among the most rapid documented avian flight loss cases (within an estimated maximum of 80,000–130,000 years). However, the unusual intraspecific variability in flight capacity within D. cuvieri is best explained by levels of genetic divergence, which exceed those documented between other volant taxa versus flightless close relatives, all of which have full species status. Our results also support consideration of Dryolimnas [cuvieri] aldabranus as sufficiently evolutionary distinct from D. c. cuvieri to warrant management as an evolutionary significant unit. Trait variability among closely related lineages should be considered when assessing conservation status, particularly for traits known to influence vulnerability to extinction (e.g. flightlessness)

Towards sustainable management of Lodoicea maldivica (Gmelin) persoon

The islands of the Seychelles, lying in the Indian Ocean 1 800 km south of Sri Lanka and ca. 1500 km east of Africa, are of exceptional biological interest. ~o of the granitic islands, namely Praslin and Curieuse, are home to the plant producing the biggest seed in the plant kingdom, the Lodoicea maldivica (Gmelin) Persoon (Arecaceae). Not only is the seed harvested for sale to tourists, but the sites where it grows are important visitor destinations. The long life cycle and lack of demographic data are major impediments in the present management of the species. Historical information is scattered and to establish baseline information is one key challenge. The few scientific studies undertaken in the past were limited to one population which was automatically identified to be representative without testing this hypothesis. The collation of historical information demanded an in depth research in two archives in Seychelles. All available Annual Reports of the Department of Agriculture from 1884 to 1971 were reviewed and analysed for information related to Lodoicea. In addition reports of visiting scientists and foresters were also reviewed, as much as all locally available historical unpublished reports. Besides the analysis of historical documents, several interviews with retired forestry personnel were carried out. It can be stated that historical information on the size, structure, productivity and health of Lodoicea populations is scattered and incomplete. The historical information collated can not be used to answer the two main questions: have the size and structure of populations been stable or increasing and did the rate of harvesting allow adequate recruitment or not? Also the success of past efforts in restoring and rehabilitating populations can not be evaluated for the same reasons. As a result clear baseline information could not be established. To evaluate the demography and health of the three main populations (vallee de Mai and Fond Ferdinand on Praslin and one population on Curieuse) two survey methods were applied permanent sample plots and trail transects. The combination of the two methods proved to be an effective sampling compromise. The data collected indicate that there is a considerable difference in the growth and appearance of Lodoicea growing on Praslin and Curieuse. The significance of the difference observed in this study needs further research. In addition the data suggest that the population structure of the Lodoicea population on Curieuse is much more natural than in the other two sites. Since the Lodoicea forests on Curieuse differs in structure and appearance ~om the more intensively studied site, the Vallee de Mai, it is concluded that low stature forests represent a part of the natural variation of Lodoicea forest that has been neglected. It is recommended to extend the existing monitoring scheme and include the Curieuse and Fond Ferdinand forests. Besides the survey work eight data collection protocols were developed. There are several agencies involved in the management of the three main populations. The capacity of the management teams in conservation management differs greatly. These protocols are intended to ensure that the data collected by different surveyors as well as collected in the three different populations are comparable in future. The first legal protection considering the Lodoicea was announced by the government in 1979. The Coco de Mer (Management) Decree, was developed as management tool and the nut was declared as a licensable product. A review of the decree was initiated and the findings and recommendation are presented. In the past all main populations were under the direct management of the state. This has changed and the three organisations involved differ in missions and objectives. Consequently the different management practices are analysed and gaps identified.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Towards sustainable management of Lodoicea maldivica (Gmelin) persoon

The islands of the Seychelles, lying in the Indian Ocean 1 800 km south of Sri Lanka and ca. 1500 km east of Africa, are of exceptional biological interest. ~o of the granitic islands, namely Praslin and Curieuse, are home to the plant producing the biggest seed in the plant kingdom, the Lodoicea maldivica (Gmelin) Persoon (Arecaceae). Not only is the seed harvested for sale to tourists, but the sites where it grows are important visitor destinations. The long life cycle and lack of demographic data are major impediments in the present management of the species. Historical information is scattered and to establish baseline information is one key challenge. The few scientific studies undertaken in the past were limited to one population which was automatically identified to be representative without testing this hypothesis. The collation of historical information demanded an in depth research in two archives in Seychelles. All available Annual Reports of the Department of Agriculture from 1884 to 1971 were reviewed and analysed for information related to Lodoicea. In addition reports of visiting scientists and foresters were also reviewed, as much as all locally available historical unpublished reports. Besides the analysis of historical documents, several interviews with retired forestry personnel were carried out. It can be stated that historical information on the size, structure, productivity and health of Lodoicea populations is scattered and incomplete. The historical information collated can not be used to answer the two main questions: have the size and structure of populations been stable or increasing and did the rate of harvesting allow adequate recruitment or not? Also the success of past efforts in restoring and rehabilitating populations can not be evaluated for the same reasons. As a result clear baseline information could not be established. To evaluate the demography and health of the three main populations (vallee de Mai and Fond Ferdinand on Praslin and one population on Curieuse) two survey methods were applied permanent sample plots and trail transects. The combination of the two methods proved to be an effective sampling compromise. The data collected indicate that there is a considerable difference in the growth and appearance of Lodoicea growing on Praslin and Curieuse. The significance of the difference observed in this study needs further research. In addition the data suggest that the population structure of the Lodoicea population on Curieuse is much more natural than in the other two sites. Since the Lodoicea forests on Curieuse differs in structure and appearance ~om the more intensively studied site, the Vallee de Mai, it is concluded that low stature forests represent a part of the natural variation of Lodoicea forest that has been neglected. It is recommended to extend the existing monitoring scheme and include the Curieuse and Fond Ferdinand forests. Besides the survey work eight data collection protocols were developed. There are several agencies involved in the management of the three main populations. The capacity of the management teams in conservation management differs greatly. These protocols are intended to ensure that the data collected by different surveyors as well as collected in the three different populations are comparable in future. The first legal protection considering the Lodoicea was announced by the government in 1979. The Coco de Mer (Management) Decree, was developed as management tool and the nut was declared as a licensable product. A review of the decree was initiated and the findings and recommendation are presented. In the past all main populations were under the direct management of the state. This has changed and the three organisations involved differ in missions and objectives. Consequently the different management practices are analysed and gaps identified.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Mapping the Lagoon at Aldabra Atoll, Western Indian Ocean

Aldabra Atoll occupies a unique place among the world\u27s atolls due to the wealth of biodiversity it supports, its relatively undisturbed status and its designation as a World Heritage Site. This landmark conservation designation was due largely to the scientific advocacy and campaigning work of David Stoddart, with its strong focus on creating detailed and accurate inventories of the biological and physical attributes of this remote atoll. The lagoon mapping campaign described in the present study continues this tradition, making use of recent developments in geospatial technology to provide a detailed snapshot of the large and shallow lagoon that has hitherto been unavailable to physical and ecological science. Here we provide the first detailed maps of benthic community character and bathymetry in the Aldabra lagoon, the output of two related mapping exercises undertaken in February 2009 as part of a collaborative project between Cambridge Coastal Research Unit and the Seychelles Islands Foundation. The lagoon environment of Aldabra Atoll was mapped using satellite remote sensing techniques in conjunction with detailed in situ ground-referencing conducted over a 3.5 week period with the aim of creating large-scale, high resolution habitat and bathymetry maps. A series of closed loop levelling surveys were undertaken to establish the relative positioning of a network of five benchmarks around the Research Station, providing a common vertical datum against which the bathymetric map could be referenced. Eight habitat groupings were identified in the lagoon, with the two dominant classes mapped being sparse macroalgae and seagrass assemblage on sand and dense macroalgal mat on sand , which covered 35% and 33% of the lagoon area respectively. Variations in lagoon floor elevation range from -0.2 to -30 m. Much of the lagoon is a flat, shallow (\u3c3 \u3em) platform and the deepest areas are associated with the channels, particularly Grande Passe in the northwest. These maps represent a detailed record of the contemporary lagoon character against which future change of the lagoon environment can be monitored

The nutrient economy of Lodoicea maldivica, a monodominant palm producing the world's largest seed.

The iconic Lodoicea maldivica palm appears to invest heavily in reproduction, with females bearing the world's largest seeds and males producing copious pollen. We asked how these palms, which grow in extremely poor soils, obtain sufficient nutrients to support such high levels of reproductive function. Our study site was the Vallée de Mai UNESCO Site on Praslin, Seychelles. We measured the trees' allocations of dry matter, nitrogen (N) and phosphorus (P) to aboveground growth and reproduction, quantified stemflow and throughfall, and measured availabilities of N and P in the soil. We show that the nutrient costs of reproduction are very high in male and female plants, and for P far exceed those of vegetative growth. We describe how the palm leaves form a huge funnel that intercepts particulate material, especially pollen, which is flushed to the base of the trunk when it rains. In this way, Lodoicea improves its nutrient supply and that of its dispersal-limited offspring. Lodoicea shares many functional characteristics with dominant trees of other monodominant forests in the humid tropics. It also exhibits unique features, including its huge seed, effective funnelling mechanism and diverse community of closely associated animals, suggesting a long evolutionary history under relatively stable conditions

An international assessment of the barriers influencing the effectiveness of island ecosystem management

Abstract Island ecosystems are disproportionally impacted by biodiversity loss and as such their effective management is critical to global conservation efforts. Practitioners world‐wide work to manage island sites and species to conserve them, but various day‐to‐day barriers compromise these efforts, reducing management effectiveness and preventing local and potentially even national biodiversity targets from being met. Identifying the most important barriers that currently impede effective island conservation could streamline investment to focus on cost‐efficient interventions that better reflect realities on the ground and the need to address barriers under substantial time and budget constraints. A survey of 360 practitioners working in island ecosystem management across 77 countries was conducted. The three most common barriers perceived by practitioners to prevent them from achieving more effective management are: low staff capacity; difficulties turning data into useful information for management (including lack of capacity and time to analyse data); and lack of a research and management strategy. Practitioners' perceptions of national‐level management effectiveness were mostly associated with their perception of governance issues, the presence/absence of research and management strategies and their experience of collaboration outcomes. Practitioners' experience of staffing and monitoring programme issues was important in shaping their perception of management effectiveness within the organisation(s) they worked with. Despite the indisputable need for transformative change to address the underlying causes of many of these barriers, more immediate and direct investment in strengthening the people and systems that are at the frontline of preventing biodiversity loss on islands is needed to bridge these barriers and achieve more effective management of island ecosystems. Read the free Plain Language Summary for this article on the Journal blog