Multi-hazards coastal vulnerability assessment of Goa, India, using geospatial techniques

The state of Goa in West India has a 105km long coastline with beaches and cultural heritage sites of significant importance to tourism. The increasing incidence of tropical cyclones in the Arabian Sea in recent decades and the devastating impacts of the December 2004 tsunami in India stressed the importance of assessing the vulnerability of coastal areas to flooding and inundation, notably in view of climate change induced sea-level rising (SLR). This study aims to develop a Coastal Vulnerability Index (CVI) for the state of Goa and to use this index to examine the vulnerability of the different administrative units of the state, known as talukas. This is accomplished by using seven physical and geologic risk variables characterising the vulnerability of the coast, including historical shoreline change, rate of relative sea-level change, coastal regional elevation, coastal slope, mean tidal range, significant wave height, and geomorphology using conventional and remotely sensed data, in addition to two socio-economic parameters: population and tourist density data. Using a composite CVI based on those relative risk variables, each of the seven coastal talukas was categorised according to its vulnerability. The resulting vulnerability map depicts the talukas that are the most and least vulnerable to erosion, flooding and inundation of coastal lands, and that the inclusion of socio-economic parameters influences the overall assessment of vulnerability. This study provides information aimed at increasing awareness amongst decision-makers to deal with disaster mitigation and coastal zone management, and is a first step towards prioritising areas for climate change adaptation in view of the projected SLR and increased storminess

Understanding historical coastal spit evolution : a case study from Spurn, East Yorkshire, UK

Globally sandy coastlines are threatened by erosion driven by climatic changes and increased storminess. Understanding how they have responded to past storms is key to help manage future coastal changes. Coastal spits around the world are particularly dynamic and therefore potentially vulnerable coastal features. Therefore, how they have evolved over the last few centuries is of great importance. To illustrate this, this study focuses on the historical evolution of a spit at Spurn on the east coast of the UK, which currently provides critical protection to settlements within the Humber estuary. Through the combination of digitized historical mapping and luminescence dating, this study shows that Spurn has been a consistent coastal feature over at least the past 440 years. No significant westward migration was observed for the last 200 years. Results show a long‐term extension of the spit and a decrease in its overall area, particularly in the last 50 years. Breaches of the neck cause temporary sediment pathway changes enabling westward extension of the head. Use of digitized historical maps in GIS combined with OSL dating has allowed a more complete understanding of long‐term spit evolution and sediment transport modes at Spurn. In doing so it helps inform future possible changes linked to pressures, such as increases in storm events and sea‐level rise

Whole-chromosome hitchhiking driven by a male-killing endosymbiont.

Neo-sex chromosomes are found in many taxa, but the forces driving their emergence and spread are poorly understood. The female-specific neo-W chromosome of the African monarch (or queen) butterfly Danaus chrysippus presents an intriguing case study because it is restricted to a single 'contact zone' population, involves a putative colour patterning supergene, and co-occurs with infection by the male-killing endosymbiont Spiroplasma. We investigated the origin and evolution of this system using whole genome sequencing. We first identify the 'BC supergene', a broad region of suppressed recombination across nearly half a chromosome, which links two colour patterning loci. Association analysis suggests that the genes yellow and arrow in this region control the forewing colour pattern differences between D. chrysippus subspecies. We then show that the same chromosome has recently formed a neo-W that has spread through the contact zone within approximately 2,200 years. We also assembled the genome of the male-killing Spiroplasma, and find that it shows perfect genealogical congruence with the neo-W, suggesting that the neo-W has hitchhiked to high frequency as the male-killer has spread through the population. The complete absence of female crossing-over in the Lepidoptera causes whole-chromosome hitchhiking of a single neo-W haplotype, carrying a single allele of the BC supergene and dragging multiple non-synonymous mutations to high frequency. This has created a population of infected females that all carry the same recessive colour patterning allele, making the phenotypes of each successive generation highly dependent on uninfected male immigrants. Our findings show how hitchhiking can occur between the physically unlinked genomes of host and endosymbiont, with dramatic consequences