• Energy Research

This is the author accepted manuscript. The final version is available from Inter Research via the DOI in this record.

Climate change plays a key role in the development and survival of oviparous ectotherms such as sea turtles. Higher environmental temperatures are expected to lead to increased production of female hatchlings and potential feminization of many populations, as well as reduced hatching success and hatchling fitness. We investigated how different sand temperatures affect sea turtle embryo mortality, hatchling phenotype, and hatchling predation during their crawl to the sea. The study was conducted in Cabo Verde, the only rookery of the endangered loggerhead turtle (Caretta caretta) in the Eastern Atlantic. During three consecutive seasons (2015–2017), 240 loggerhead clutches were exposed to three different incubation temperature regimes created by different sand colours. The warm treatment (mean = 32.3 °C ± 0.5) killed 33% more embryos than the cold treatment (mean = 29.7 °C ± 0.6). Hatchlings from the warm treatment were mostly females, smaller in size, and had lower performance. Hatchling predation by ghost crabs during seaward transit was higher for hatchlings incubated in the warm treatment. Combining embryo mortality and hatchling predation, the rate of female hatchling arrival at the sea was more than twice as high in the cold treatment (34.4 females per 100 eggs) than in the warm treatment (16.0 females per 100 eggs). This increase in mortality caused by warmer incubation temperatures may cancel any potential benefit of a female-biased sex ratio. Conservation planners should consider behavioural adaptations and the potential dispersal of the nesting areas to colder areas to increase resilience of loggerhead turtles to climate change.

Global warming is affecting habitat quality and availability on our planet and some species are predicted or are by now changing their distribution range. Here we show that loggerhead turtles have already started to expand their nesting range into the Western Mediterranean, which has until recently hosted only sporadic nests. We compiled information on nesting activity from beaches surrounding the Western Mediterranean and collected metadata on loggerhead turtle nests in Spain, France, Italy, and Tunisia between 2010 and 2020 to provide an exhaustive overview on the phenomenon of emerging new nest sites for loggerhead turtles. The number of recorded nests has increased drastically since 2013 from 1 to 3 nests/year to a record number of 84 registered in 2020. While this increase may partly be explained by grown awareness and reporting by citizens, there is no doubt of an upward trend in nesting activity. The nests are unevenly distributed over the study area with most nests occurring on the coasts of the warmer Tyrrhenian Sea. A hotspot analysis identified beaches in SW Italy, SE Sardinia, and NW Tunisia with statistically significant clustering of nests. Within these hotspots, three beaches in SW Italy and one in Tunisia had nests at least four out of the five last years. Nesting phenology corresponds to that of Eastern Mediterranean rookeries, and mean hatching success of naturally incubating, non-manipulated nests was 66 %, although there was variability across the region. Mean incubation durations also varied between countries indicating a diversity in inferred sex ratios, with sufficient female production to foster future colonisation of this region. Unfortunately, these beaches are already under high tourist pressure and subject to intense coastal development, imposing many threats to the females, eggs, and hatchlings. Thus, while this study reveals the unique opportunity to witness and study an ongoing new colonisation process in loggerhead turtles, it also calls for urgent proactive conservation actions to mitigate these threats and allow the turtles to establish new rookeries.

Beaches are constantly being reshaped by storms and tidal action; however, the increased frequency of storms and the sea-level rise due to climate change could cause loss of beaches that are vital breeding habitats for sea turtles. Here we evaluated the effects that erosion/ accretion cycles have on the nesting behavior (nest site selection in relation to the presence of dune scarps) and nesting success (the proportion of nesting activities with oviposition) of leatherback turtles Dermochelys coriacea at Pacuare Nature Reserve, in Caribbean Costa Rica. Dune scarps accounted for over 20% of the beach, creating a barrier which prevented turtles from accessing the upper parts of the beach where nests would be safe from high tides and the storm line. About a quarter of the turtles, 24.1% (n = 20) in 2013 and 18.6% (n = 19) in 2014, did not crawl over scarps when they were present, regardless of their height, and laid their eggs below them. Additionally, during the period 2008 to 2014, the percentage of nests laid in high-risk areas sig - nificantly increased (R = 0.91). The end result of the formation of scarps was that nests were laid in areas at risk of being flooded, threatening the survival of those eggs, and therefore the longterm population survival. Since sea levels have been rising significantly in the Caribbean between 1950 and 2010, and projections show a further increase throughout the 21 century, beach erosion may become an important threat not just for leatherbacks, but for many other endangered coastal species. Peer Reviewed

As climate-related impacts threaten marine biodiversity globally, it is important to adjust conservation efforts to mitigate the effects of climate change. Translating scientific knowledge into practical management, however, is often complicated due to resource, economic and policy constraints, generating a knowledge-action gap. To develop potential solutions for marine turtle conservation, we explored the perceptions of key actors across 18 countries in the Mediterranean. These actors evaluated their perceived relative importance of 19 adaptation and mitigation measures that could safeguard marine turtles from climate change. Of importance, despite differences in expertise, experience and focal country, the perceptions of researchers and management practitioners largely converged with respect to prioritizing adaptation and mitigation measures. Climate change was considered to have the greatest impacts on offspring sex ratios and suitable nesting sites. The most viable adaptation/mitigation measures were considered to be reducing other pressures that act in parallel to climate change. Ecological effectiveness represented a key determinant for implementing proposed measures, followed by practical applicability, financial cost, and societal cost. This convergence in opinions across actors likely reflects long-standing initiatives in the Mediterranean region towards supporting knowledge exchange in marine turtle conservation. Our results provide important guidance on how to prioritize measures that incorporate climate change in decision-making processes related to the current and future management and protection of marine turtles at the ocean-basin scale, and could be used to guide decisions in other regions globally. Importantly, this study demonstrates a successful example of how interactive processes can be used to fill the knowledge-action gap between research and management.

Abstract The impacts of anthropogenic climate change will be most dramatic for species that live in narrow thermal niches, such as reptiles. Given the imminent threat to biodiversity, and that actions to reduce carbon emissions are not yet sufficient, it is important that a sound evidence base of potential mitigation options is available for conservation managers. Successful incubation and production of male sea turtle hatchlings is threatened by increased global temperatures (sex is determined by the temperature at which eggs incubate). Here we test two conservation tools to reduce incubation temperatures: clutch splitting and clutch shading, on a nesting loggerhead turtle Caretta caretta population in the Eastern Atlantic Ocean. During the thermosensitive period of incubation, split and shaded clutches were both 1.00°C cooler than control nests. Clutch splitting (mean: 45 eggs) reduced nest temperatures by reducing metabolic heating during incubation compared to controls (mean: 92 eggs). Modelled primary sex ratios differed between nest treatments, with 1.50% (±6% SE) females produced in shaded nests, 45.00% (±7% SE) females in split nests and 69.00% (±6% SE) females in controls. Neither treatment affected hatchling size, success, mass or vigour. When clutch splitting was repeated 2 years later, hatch success was higher in split clutches compared to controls. Synthesis and applications. Clutch splitting and clutch shading successfully altered the thermal profile of incubating turtle nests. When there is sufficient knowledge to better understand the effects of intervention on fundamental population demographics, they will be useful for reducing incubation temperatures in sea turtle nests, potentially increasing nest survival and male hatchling production. The effect of clutch splitting in reducing nest temperature was lower relative to clutch shading, but requires significantly less funding, materials and specialist skill, key factors for management of turtle rookeries that are often in remote, resource‐limited areas.

The future persistence of biodiversity is likely to be affected by global climate change. We propose a qualitative framework for assessing the resilience of coastal species to climate change, incorporating current and likely future breeding success, the availability of temporal and spatial climate refugia, the effect of future sea-level rise, behavioural plasticity and the level of other specific threats.We test this framework using one of theworld's largest nesting rookeries of loggerhead sea turtles (Caretta caretta) in the island of Boa Vista (Republic of Cape Verde, West Africa). We measured air, sand and nest temperatures across more than 50 km of nesting habitat and four years to model the likely sex ratios produced and predicted what future sex ratios might be under one conservative future climate change scenario (RCP 2.6). We assessed the relative threat of sea-level rise, and other threats including beachfront construction, pollution and human harvest as well as to estimate the level of foraging behaviour plasticity observed for this population. Estimated sex ratio over the study period was 79.15% female and while an increase of 2 °C air temperature would lead to 99.86% female production, incubation temperature is unlikely to be lethal even in the hottest part of the year. Only half the total suitable length of coastline is currently used for nesting and there is a size-linked dichotomy in foraging strategies of loggerhead turtles of both sexes. Under our qualitative framework,we make the surprising observation that this population of conservation concern should have remarkable resilience to climate change due to some unique features of their habitat use and preferences. This may be compromised by high levels of human harvest and planned and on-going coastal development. The framework may be of utility in assessing the threat of climate change to other climate-sensitive, coastal and mobile species such as migratory seabirds, coastal fish and butterflies. This work was carried out with funding from the Ministry of the Environment of the Regional Government of Andalusia, the Regional Government of the Canary Islands and the Fuerteventura Inter-Island Council (Cabildo de Fuerteventura). LAH was supported by a BBSRC post-doctoral award at Bangor University during the study.