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This report presents the results of a multi-disciplinary research project on the way the Indian coast is transforming and what consequences this has for the original fisher population. It takes Cuddalore District in Tamil Nadu as microcosm and discusses issues such as the industrialization of the coast, the changes affecting fisheries, land-use change, pollution and erosion. The final chapters consider the ways in which fisher wellbeing is impacted and how the fisher population – individually and collectively – responds. The authors argue that coastal transformation in India is many-sided and profound, and that the fishing population is bearing the brunt of modernization.

International audience; Nagapattinam coast remained highly vulnerable to the vagaries of natural disasters for a long time. Keeping in view the demands of the society, this research work has been undertaken to assess the vulnerability of the Nagapattinam coastline, which extends from Porto Novo in the north to Adhiramapattinam in the south. CVI was computed and a comparison was made between classical and sigmoidal CVI. Static inundation analysis was done for the sea level rises by 1m, 2m, 3m, 4m and 5m, and the towns and villages expected to be severely affected were mapped. Aquifer Vulnerability Index was calculated using GALDIT model to study the vulnerability of Nagapattinam coastal aquifers to saline water intrusion. Finally, a multi-hazard zonation map was prepared to demarcate areas that are affected by all the identified hazards. Suitable management strategies are proposed to mitigate the risks.

International audience; Climate change is affecting the agricultural sector since it is dependent on climatic conditions and water resource availability. The impacts tend to be greater in semi-arid and hard rock areas with few water resources. Vast area of the Tamil Nadu comes under Semi-arid and hard rock area. Due to prevailing semi-arid climate in these areas, both surface and ground water resources are very much limited due to several years of low and inconsistent rainfall. The agricultural activity in these areas have particularly became vulnerable to present day climate variability. In order to address these problems, the vulnerability profile is constructed by combining indices of “adaptive capacity” with “sensitivity indices”. The adaptive capacity was measured by biophysical indicators, socioeconomic parameters and technological factors. To measure sensitivity to future climate change IPCC-AR4 GCM climate model output obtained under IPCC SRES-A2 GHG emission scenario projected for the period 2040-2060 were used by downscaling for south India. Finally, the vulnerability of living population to future climate change was assessed for the entire semi - arid and hard rock area of Tamil Nadu state. The results show that six district are highly vulnerable to future climate change.

International audience; Southeastern part of the Chihuahua Desert has always been drought-prone as southerly migrated ITCZ and enhanced ENSO since the early Holocene reduced the moisture supply. This arid region was inhabited by nomadic hunters since 10,500 years BP and agricultural activities started around 1500 years BP. The climate models predict temperature increase of 1-2°C and precipitation reduction of 10-20% in this region over the next couple of decades. The impacts of water scarcity might reduce the crop yield by half by the end of this century, exacerbating the immigration from Mexico to the USA. Additionally, the over-exploitation of groundwater in last decades for irrigation has drastically reduced the water table causing burning of subsurface peat layers and subsidence. We investigated groundwater from three sedimentary basins (El Potosi, Sandia and Cieneguilla), used extensively for agricultural activities, in order to identify the recharge regions and determine their suitability for irrigation and drinking purposes, following the guidelines of WHO as well as using Na% and sodium adsorption ratio and permeability index. These groundwater (pH:7.2-8.2; TDS: 168-1660 mg/L) are of Ca-HCO3 and Ca-SO4 types, due to interaction of recharging water with limestone-gypsum bearing catchment lithologies. Distributions of stable isotopes with respect to the local meteoric water line identify the recharge regions at Mountains of different elevations located to the east (i.e. Sierra Madre Oriental). This recharge, however, does not reach aquifers in central part of these basins due to over-extraction in basin margins. Groundwater from El Potosi is the most suitable for irrigation and drinking. Samples from the Sandia and Cieneguilla are characterized by high to very-high salinity hazard and some of them are also doubtful-unsuitable for irrigation based on the Wilcox diagram. Some samples from El Potosi and Sandia, however, contain nitrate and fluoride more than permissible limits of human consumption.

International audience; Increasing nitrate levels in groundwater have been a source of concern in the recent decades all over the world. The challenges due to the high level of nitrate in water have also receiving more attentions due to the impact of nitrate over health related issues. This study provides the information on the occurrence of nitrate contamination in groundwater in corporation of Tiruchirappalli, Tamilnadu. Moreover, it also gives the insights about the sources and negative effects of nitrate contamination. A total number of 24 groundwater samples have been collected from bore well at depth from 15 to 45 meter in a distributed pattern. An assessment of the level of nitrate contamination in the groundwater samples was determined using UV Spectrophotometer. The nitrate concentration ranges between 1.4 to 104 mg/l. A risk assessment over human health due to nitrate contamination was done using Hazard Quotient (HQ). The spatial analysis of groundwater trace elements was performed by Atomic Absorption Spectroscopy (AAS) combined with geostatistical modeling. The results indicate that, the consumers residing in eastern part of the study area are more exposed to current nitrate concentration. It is identified that improper sewage system and use of nitrate enriched fertilizers are the main source of nitrate in the study area. Hence, it is anticipated that outcomes of this study will provide insights for decision makers taking adaptive measures for groundwater Nitrate and trace element monitoring in Tiruchirappalli district.

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International audience; Each mangrove region has a specific history which needs to be understood as it is a central component for adapting current conservation plans to changing coastal conditions induced by increasing natural or human pressures. As these latter impact the functioning, physiognomy and extent of mangroves, it is urgent to design and implement monitoring programs able to monitor changes in zonations of mangrove species (ZMS). Recent studies highlighted the combined potential of very high spatial resolution (VHSR) satellite images and robust field data to map such mangrove areas dominated by a few species.Here we examined the Pichavaram mangroves, southeast coast of India. The 1100-ha mangrove wetland area was, in 1987, declared to be a Forest Reserve by the Forest Department, Government of Tamil Nadu. Disturbances generated by the 2004-tsunami, decreasing freshwater, and increasing pollutants inflow, combine to modify the geochemistry of the whole region with a potential influence on the zonation of mangrove species. Afforestation programmes have been carried out since the 1980s using the fishbone canal-bank technique.We inventoried species and measured trunk diameters (DBH), tree heights within forest plots representative of a large range of planted and natural ZMS. Based on this ground expertise, we performed a spectral and textural analysis of five VHSR multispectral images acquired between 2003 and 2018 to generate ZMS maps on a scale of 1:2000. Our results indicate that mangrove cover is increasing while species richness decreases in favour of salt-tolerant species. Our analysis also highlights a shrunk in average tree crown size, suggesting alterations in species succession and plant growth capability. We thank the Tamil Nadu Forest Department for allowing us to undertake this study.

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International audience; Flood risk assessment in low-lying coastal areas requires efficient spatial observations of land elevation for theimplementation of protection, evacuation and safeguard plans of people and assets. Here we evaluated the potentialof Digital Surface Model (DSM) derived from satellite observations to map flood prone areas with the objective ofearly warning on flood risk in the Cuddalore and Pondicherry region, southeast coast of India. Coastal zonemanagement of this 100 km long coast is particularly challenging. Indeed, the whole region experiences at leasttwo cyclonic storms accompanied with storm surge, heavy rains, flooding and beach erosion every year; the havocswreaked by the 2004 tsunami, flash floods of 2005 and 2015, and the Thane cyclone in 2011 are still closememories. We analyzed Sentinel-1 Synthetic Aperture Radar (SAR) and ALOS World 3D DSM satellite data, andGoogle Earth images. All these data are freely available and we compared them to the population census dataacquired in 2011. Using Sentinel-1 SAR images, we discriminated flooded from non-flooded areas before comparingmaps of low-lying areas derived from ALOS DSM data. The results suggest a good agreement between real floodedareas and low-lying areas. However, the micro-topography reflecting channels and drainage systems could not becaptured with important issue for delineating areas with high risks of flooding. We explained that spatial resolutionof about 2 m in X, Y and 10 cm in Z directions are necessary for identifying areas with high risk of flooding asdemonstrated in many countries of the world. It is time to rethink national Indian spatial policy about high-resolutionimages in order to prepare safety plans of the property and the lives of populations of Tamil Nadu coasts.

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International audience; Growing pressures on mangroves throughout the world, highlight the need for studies of vegetation across spatio-temporal scales even in relict patches for ecosystem conservation. Mangroves experience human pressure due to coastal development and are also subjected to environmental stress such as cyclones, tsunami, floods, and sea-level rise, often taking decades to recover from these stresses. We estimated changes in mangrove vegetation in the Ariankuppam estuary on the southeastern coast of peninsular India after two phenomenal perturbations, the 2004 tsunami and 2011 cyclone Thane. We compared land cover maps of mangroves from 2005, 2010, and 2011 with 2004 mangrove vegetation maps to detect change in areal extent of mangrove zones. We inventoried all stems ≥ 10 cm gbh in 34 quadrats (5 m x 5 m) prior to the 2011 cyclone, immediately following the cyclone, and eighteen months later to document damages and recovery. The site harbours 2988 trees ha-1 for stems ≥ 10 cm gbh. We found four distinct mangrove zones in 2005 (15.54 ha), and five distinct mangrove zones in 2010 (41.73 ha) and 2011 (40.65 ha). The tsunami and subsequent activities such as dragging the boats swept ashore and dredging resulted in 48 % loss of mangroves. The increase in mangrove area observed during 2010 and 2011 was due to the recovery potential of Avicennia and restoration programs. Cyclonic impact and recovery status inventories revealed that among the different zones, the monodominant Avicennia zone experienced severe damage and the mixed Avicennia zone showed slow recovery. The full impacts on the ecosystem from extreme stochastic events; however, can only be determined with long-term monitoring.

International audience; Changes in ostracode species assemblage suggest presenceof oligohaline and mesohaline waters in the Santiaguillo basin ofsubtropical Mexico over the last ca.27 cal kyr BP. Paleoecologicalreconstruction is based on the distribution of Limnocythere bradburyiForester, Eucandona cf. patzcuaro Tressler, Cypridopsis viduaBrady and Limnocythere ceriotuberosa Delorme. Source of organicproductivity is inferred from C/N ratios. The basin hosted shallowand oligohaline water during the late glacial (ca.27–19 cal kyr BP)and lacustrine phytoplankton contributed to the organic productivity.However, the water body of Last Glacial Maximum (LGM) wasrelatively warmer (>13°C) and more diluted compared to the pre-LGM. Increased salinity and reduced lacustrine productivity atca.19 cal kyr BP marked a shift in the paleoecological conditions.Water body was mesohaline during ca.9.5–4 cal kyr BP andperiodic desiccation of the basin possibly caused the absenceof ostracode valves in sediments of the last ca.3.5 cal kyr BP.Comparison with other proxy-records from the region indicates thatthe hydrological variations in different parts of subtropical north andnorthwestern Mexico were not synchronous during the late Pleistoceneand Holocene.

International audience; This chapter presents the geomorphological features associated with a peat fire occurring in one of the sedimentary basins of northeastern Mexico along with the chemical composition and radiocarbon chronology of one peat horizon. The peat fire has caused the formation of a semicircular sinkhole, vertical ground fissure, and subsidence in the basin. Chemical and chronological characteristics estimated the amount of carbon storage, identified the source of biomass, and presented a conceptual model of different depositional environments up to the initiation of a peat fire. The peat horizon was deposited between 19,100 and 12,200 cal yr BP and comprises different amounts of quartz, gypsum, and rosickýite. The lower part of the peat (19,100–15,600 cal yr BP) has more carbon storage (81–167 mgC/cm3) compared to the upper part (15,600–12,200 cal yr BP; 18–59 mgC/cm3). Chemical and mineralogical compositions and stratigraphy suggest that plants growing in a fresh water marshy environment provided biomass for the lower part. The biomass for the upper part was mainly sourced from lacustrine algae and phytoplankton in a deeper and perennial lake condition. Over the last 12,200 cal yrs, the amount of carbon storage was reduced to 0–23 mgC/cm3 as the basin experienced several intervals of desiccation. The unregulated exploitation of ground water for agricultural activities during AD 1980–2004 has caused a fall in the water table and expansion of the desiccation fissures into the subsurface and has led to the initiation of a peat fire in the basin.

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