Connectivity and stock composition of loggerhead turtles foraging on the North African continental shelf (Central Mediterranean): implications for conservation and management

The loggerhead turtle, Caretta caretta, is a highly migratory species with a complex life cycle that involves a series of ontogenetic habitat shifts and migrations. Understanding the links amongst nesting populations and foraging habitats is essential for the effective management of the species. Here we used mixed stock analysis to examine the natal origin of loggerhead turtles foraging on the North African continental shelf off Tunisia, one of the most important Mediterranean neritic habitats. An 815-bp fragment of the mitochondrial DNA control region was sequenced from 107 individuals sampled from 2007 to 2009. No temporal variation in haplotype frequencies was detected. Juveniles (n = 87) and adults (n = 23) exhibited weak but significant genetic differentiation that resulted in different stock compositions. Libya was the main source population but the proportion of turtles from this rookery was higher in adults (median = 80%) than in juveniles (median = 35%). Western Greece was the second most important contributing population. Juvenile stock composition derived from mixed stock analysis and the estimates produced by numerical simulation of hatchling dispersion in the Mediterranean Sea were significantly correlated, supporting the recent theory that loggerheads imprint on possible future neritic habitats during the initial phase of their life. This association was not significant for adults, suggesting that other factors contribute to shaping their distribution. Overall, our results show that human activities on the South Tunisian continental shelf pose an immediate threat to the survival of the Libyan rookery

Introduction

The heterogeneous nature of the Mediterranean environment, combined with a wide diversity of socio-economic and cultural identities, make this region particularly amenable to integrated research on climate change impacts, vulnerabilities, and adaptive response. Eleven case-study locations have been strategically selected to represent three generic Mediterranean environments (urban, rural and coastal). While each case study location comprises a unique and complex set of climate-related issues, the range and scope of the case studies allows identification of common lessons and messages for the wider Mediterranean region. The aim is to perform an integrated assessment of climate impacts, vulnerability and adaptation at a regional to local scale. A risk-based \u2018bottom up\u2019 approach (based on regional stakeholder dialogue) is combined with a \u2018top down\u2019 case-study indicator assessment focused on a common conceptual and methodological framework

Climate Impact Assessments

This chapter highlights key climate impacts, hazards and vulnerabilities and associated indicators that have been used to assess current (recent) climate impacts at each of the case-study sites. The aim is to illustrate some of the wide range of information available from individual case studies and highlight common themes that are evident across multiple case-study locations. This is used to demonstrate linkages and sensitivities between the speci fi c climate impacts of relevance for each case-study type (urban, rural and coastal) and the key climate hazards and biogeophysical and social vulnerabilities representing the underlying drivers and site conditions. For some impacts, there are clear, direct links with climate events, such as heat stress and fl ooding, while for others, such as energy supply and demand, the causal relationships are more indirect, via a cascade of climate, social and economic in fl uences. Water availability and extreme temperatures are common drivers of current climate impacts across all case studies, including, for example, freshwater supply and heat stress for urban populations; irrigation capacity and growing season length for agricultural regions; and saltwater intrusion of aquifers and tourist visitor numbers at coastal locations. At some individual case-study locations, speci fi c impacts, hazards and/ or vulnerabilities are observed, such as peri-urban fires in Greater Athens, infrastructure vulnerability to coastal fl ooding in Alexandria, groundwater levels in Tel Hadya and vector-borne diseases in the Gulf of Oran. Throughout this chapter, evidence of current climate impacts, hazards and vulnerabilities from each of the case studies is detailed and assessed relative to other case studies. This provides a foundation for considering the wider perspective of the Mediterranean region as a whole, and for providing a context from which to assess consequences of future climate projections and consider suitable adaptation options

Integration of the Climate Impact Assessments with Future Projections ,in (A.Navarra and L.Tubiana eds), Regional Assessment of Climate Change in the Mediterran

Climate projections are essential in order to extend the case-study impacts and vulnerability assessments to encompass future climate change. Thus climatemodel based indicators for the future (to 2050 and for the A1B emissions scenario) are presented for the climate and atmosphere theme (including indices of temperature and precipitation extreme events), together with biogeophysical and socioeconomic indicators encompassing the other case-study themes. For the latter, the speci fi c examples presented here include peri-urban fi res, air pollution, human health risks, energy demand, alien marine species and tourism (attractiveness and socio-economic consequences). The primary source of information about future climate is the set of global and regional model simulations performed as part of CIRCE. These have the main novel characteristic of incorporating a realistic representation of the Mediterranean Sea including coupling between sea and atmosphere. These projections are inevitably subject to uncertainties relating to unpredictability, model structural uncertainty and value uncertainty. These uncertainties are addressed by taking a multi-model approach, but problems remain, for example, due to a systematic cold bias in the CIRCE models. In the context of the case-study integrated assessments, there are also uncertainties \u2018downstream\u2019 of climate modeling and the construction of climate change projections \u2013 largely relating to the modeling of impacts. In addition, there are uncertainties associated with all socio-economic projections used in the case studies \u2013 such as population projections. Thus there are uncertainties inherent to all stages of the integrated assessments and it is important to consider all these aspects in the context of adaptation decision making