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Documenting post-bleaching trajectories of coral reef communities is crucial to understand their resilience to climate change. We investigated reef community changes following the 2015/16 bleaching event at Aldabra Atoll, where direct human impact is minimal. We combined benthic data collected pre- (2014) and post-bleaching (2016–2019) at 12 sites across three locations (lagoon, 2 m depth; seaward west and east, 5 and 15 m depth) with water temperature measurements. While seaward reefs experienced relative hard coral reductions of 51–62%, lagoonal coral loss was lower (− 34%), probably due to three-fold higher daily water temperature variability there. Between 2016 and 2019, hard coral cover did not change on deep reefs which remained dominated by turf algae and Halimeda, but absolute cover on shallow reefs increased annually by 1.3% (east), 2.3% (west) and 3.0% (lagoon), reaching, respectively, 54%, 68% and 93% of the pre-bleaching cover in 2019. Full recovery at the shallow seaward locations may take at least five more years, but remains uncertain for the deeper reefs. The expected increase in frequency and severity of coral bleaching events is likely to make even rapid recovery as observed in Aldabra’s lagoon too slow to prevent long-term reef degradation, even at remote sites.

Atolls are at risk of losing their ability to physically adapt due to rising sea levels and coral reefs’ reduced sediment supply, resulting in faster erosion of reef islands. This research examines Aldabra, a raised atoll and UNESCO World Heritage Site in the Indian Ocean with diverse coastal ecosystems, to track shoreline changes against a regional sea level rise of 2–3 mm yr −1 . Aerial and satellite images in 1960 and 2011 were used to study 85% of the atoll’s shoreline through a Digital Shoreline Analysis System. Over 51 years, 61% of the shoreline remained unchanged, while 24% changed at an average rate of 0.25 ± 0.36 m yr −1 , a low rate compared to global atoll changes. Among the areas that did change, rates of accretion and erosion in absolute values were nearly balanced and affected similar percentages (12%) of the shoreline. However, localized changes were pronounced: for example, part of the lagoon shoreline transformed from a sandy beach to a mangrove habitat, accreting by 214 m over the period. Erosion occurred at crucial turtle nesting sites and the research station. The lagoon shoreline underwent more rapid changes than the erosion-resistant ocean shoreline, particularly in areas exposed to wind and waves. Despite its dynamic shoreline, Aldabra maintained its net shoreline and likely total land area over the past 51 years, akin to other Indo-Pacific atolls—underscoring its adaptive capacity. Our research suggests that current knowledge of geomorphological processes of low reef islands is transferable to the raised Aldabra Atoll, reconfirming similar mechanisms of island-building processes at the island crest. These insights highlight an urgent need to minimize local impacts on sediment availability and transfer that might alter the natural dynamics of the shoreline of reef islands and hence limit adaptation potential. Ongoing shoreline monitoring will remain crucial for informing timely adaptation strategies for the conservation of Aldabra’s unique ecosystem.

Coral recruitment and successive growth are essential for post-disturbance reef recovery. As coral recruit and juvenile abundances vary across locations and under different environmental regimes, their assessment at remote, undisturbed reefs improves our understanding of early life stage dynamics of corals. Here, we first explored changes in coral juvenile abundance across three locations (lagoon, seaward west and east) at remote Aldabra Atoll (Seychelles) between 2015 and 2019, which spanned the 2015/16 global coral bleaching event. Secondly, we measured variation in coral recruit abundance on settlement tiles from two sites (lagoon, seaward reef) during August 2018–August 2019. Juvenile abundance decreased from 14.1 ± 1.2 to 7.4 ± 0.5 colonies m-2 (mean ± SE) during 2015–2016 and increased to 22.4 ± 1.2 colonies m-2 during 2016–2019. Whilst juvenile abundance increased two- to three-fold at the lagoonal and seaward western sites during 2016–2018 (from 7.7–8.3 to 17.3–24.7 colonies m-2), increases at the seaward eastern sites occurred later (2018–2019; from 5.8–6.9 to 16.6–24.1 colonies m-2). The composition of coral recruits on settlement tiles was dominated by Pocilloporidae (64–92% of all recruits), and recruit abundance was 7- to 47-fold higher inside than outside the lagoon. Recruit abundance was highest in October–December 2018 (2164 ± 453 recruits m-2) and lowest in June–August 2019 (240 ± 98 recruits m-2). As Acroporid recruit abundance corresponded to this trend, the results suggest that broadcast spawning occurred during October–December, when water temperature increased from 26 to 29°C. This study provides the first published record on coral recruit abundance in the Seychelles Outer Islands, indicates a rapid (2–3 years) increase of juvenile corals following a bleaching event, and provides crucial baseline data for future research on reef resilience and connectivity within the region.

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.

Resilience-Based Management of coral reefs aims to maintain ecosystem function and maximise resilience. This requires identification of resilience indicators and clear ecological reference thresholds for reef managers to maintain or aim for. In the absence of local thresholds, managers can assess reef condition by comparing locally collected indicator data to broadscale thresholds, which account for spatial and temporal variability. This study assesses reef condition at Aldabra Atoll, a remote MPA in the western Indian Ocean, relative to broadscale thresholds for structural complexity, fish biomass, herbivore biomass, juvenile coral density, and trophic-level fish biomass. Results were synthesized into a resilience index, and sites were classified into ‘management strategies’ using a published reef management framework. Resilience scores were then compared to observe coral cover changes following the 2016 bleaching event, tracking recovery through to 2022. Findings showed that seven of the eight assessed seaward reefs at Aldabra displayed the resilience expected of a remote, well-managed marine reserve. The research station and associated human activity appeared to have minimal negative impacts on reef resilience. We recommend expanding the range of broadscale threshold categories and integrating site-specific factors to improve future assessments and management decisions.

Seabirds are excellent ecosystem indicators and are amongst the most threatened taxa globally. Aldabra Atoll, Seychelles, supports significant breeding colonies of seabirds, especially red-footed boobies Sula sula . The population was surveyed by boat during 1968–1969 and in 2000, over which period the population grew from c. 6,500 to 10,000 breeding pairs. In 2022–2023, we monitored five subcolonies across Aldabra to determine breeding phenology and breeding success. In August 2022 and February 2023, we surveyed the atoll-wide population using the boat-based survey methodology followed in earlier studies. We also carried out unmanned aerial vehicle (UAV) surveys in February 2023 to compare the results with the boat-based counts and to quantify inland colonies undetectable by boat. Boat surveys revealed that Aldabra’s red-footed booby population had grown to 36,720 pairs by 2023, an increase that is intrinsically possible based on our population model but only if the much lower count in 2000 was an underestimate. The UAV and boat counts were closely aligned in our study, and aerial images captured a similar number of nests to boat surveys for shoreline colonies. However, UAV surveys revealed several undocumented inland colonies. An additional 5,574 inland breeding pairs of red-footed boobies were counted from images captured inland during aerial surveys in the 2023 wet season, bringing the atoll-wide population to at least 45,817 pairs. We recommend UAVs for surveys of large, conspicuous seabird species at low-lying mangrove colonies. Our study highlights the global importance of Aldabra as the most significant red-footed booby colony in the Indian Ocean and possibly the world.

The failure to meet global biodiversity targets clearly indicates the need for biodiversity management and conservation efforts to be more effective, and this in turn requires better understanding of the current barriers to success. Islands are known as biodiversity hotspots but nowhere has biodiversity loss been so acute as in island ecosystems. To identify the barriers to effective island ecosystem conservation, we conducted 32 semistructured interviews with conservation and management practitioners from island nations in the Western Indian Ocean region. Practitioners described 33 barriers to meeting their objectives under 12 overarching topics and suggested 14 solutions to these. Most barriers described by interviewees existed at organization level (55%), followed by national (24%) and site/project level (21%). Of the 33 barriers described by practitioners, the most commonly associated cause was limited capacity (23.5%), followed by lack of government coordination and limited resources (both 21.6%), lack of incentives (11.8%), poor leadership (11.7%), and finally interpersonal issues interfering with progress (9.8%). Most solutions centered around bridging capacity gaps. By defining these barriers, we can bring them forward for discussion and allocate resources and efforts to bridging them. Only by doing so can we increase the effectiveness of our management efforts and maximize our chances of achieving global biodiversity targets. To identify the barriers to effective island ecosystem conservation, we conducted 32 semistructured interviews with conservation and management practitioners from island nations in the Western Indian Ocean region. Most barriers described by interviewees existed at organization level (55%), followed by national level (24%), and site/project level (21%). Of the 33 barriers described by practitioners, the most commonly associated cause was limited capacity (23.5%), followed by lack of government coordination and limited resources (21.6%), lack of incentives (11.8%), poor leadership (11.7%), and finally interpersonal issues interfering with progress (9.8%).

Invertebrates have a central role in food webs and ecosystem functioning. By boosting productivity, allochthonous nutrient inputs influence the food webs of recipient communities. Understanding how allochthonous nutrient subsidies affect invertebrates is crucial, particularly in highly productive coastal areas. Here, we examine how mangrove macroinvertebrates are impacted by nutrient‐rich guano delivered by nesting seabird populations at Aldabra Atoll in the Indian Ocean. We compare nitrogen and carbon stable isotope ratios and nitrogen composition of basal resources and macroinvertebrate consumers in mangroves with and without nesting seabirds. Seabird‐derived nutrient enrichment increased the nitrogen content of basal food sources and herbivorous littorinid gastropods and sesarmid crabs. In mangroves with breeding seabirds, mean carapace widths of sesarmid and omnivorous portunid crabs were 6% and 11% larger, respectively. Isotopic niches of littorinid gastropods and sesarmid crabs were larger and had higher overlap at seabird compared to non‐seabird sites. Epiphytic macroalgae and guano comprised >50% of resource contributions to littorinid gastropods and sesarmid crabs at seabird sites. This differed markedly from non‐seabird sites where the main resource contributions were 77% mangrove leaves for littorinid gastropods, 36% sediment organic matter, and 41% mangrove leaves for sesarmid crabs. The increased sizes of mangrove crabs suggest that seabird nutrient enrichment can promote mangrove crab fisheries productivity and benefit the provisioning of mangrove ecosystem services. By shifting resource use of functionally important macroinvertebrates, we discuss how seabirds modify trophic interactions, with potential consequences for mangrove ecosystem processes and resilience.

As 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. A free Plain Language Summary can be found within the Supporting Information of this article.

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. Read the free Plain Language Summary for this article on the Journal blog.