Impact of tsunami on the forest and biodiversity richness in Nicobar Islands (Andaman and Nicobar Islands), India

Occurrences of extreme events are likely to cause major decline in global biodiversity. In one such event, on December 26, 2004 tsunami caused extensive damage and irreparable losses to the ecology and biodiversity of low-lying areas of the countries located around the Indian Ocean region. Archipelago of Andaman and Nicobar Islands, one of the richest centre of endemism and biodiversity in the Indo-Malayan region, suffered great loss of forests and coastal biodiversity owing to its closeness to the epicenter of tsunami, i.e. just off the coast of Indonesia. There is little insight into the resilience and rate of recovery pattern of tropical coastal habitats consequent to catastrophic impacts of tsunami. It’s important to study the impacts of tsunami on the forest and biodiversity in order to suggest mitigation, restoration measures and long-term conservation planning. Here we have assessed the immediate after-effects of December 26, 2004 tsunami on the forests and areas prioritized for biodiversity conservation analyzing pre and post tsunami satellite imageries. The effect of topographic patterns of Island’s coastal areas and their distance from the epicenter of tsunami with respect to changes in the forests and different levels of biologically rich areas modeled for prioritization for different groups of Islands in Nicobar has been studied. Great Nicobar accounted for higher proportion of total forest area damaged and submerged in Nicobar, followed by Central Nicobar and Car Nicobar. Mangroves, littoral forest, beach forest and low land swamps and Syzygium swamps were most affected. Study brings out spatially explicit scenario of damaged, submerged and lost forest areas and corresponding area statistics, vital for understanding and mitigating medium and long term effects of tsunami an extreme event.     

How effective were mangroves as a defence against the recent tsunami?

Whether or not mangroves function as buffers against tsunamis is the subject of in-depth research, the importance of which has been neglected or underestimated before the recent killer tsunami struck. Our preliminary post-tsunami surveys of Sri Lankan mangrove sites with different degrees of degradation indicate that human activity exacerbated the damage inflicted on the coastal zone by the tsunami.     

Inland forest as a trapping function against tsunami-borne large broken or washed out trees

Landscape and Ecological Engineering - After the 2011 Great East Japan tsunami, field observations have shown the possibility of an inland forest trapping tsunami-borne large driftwood (TLD). This...     

Vegetation bioshields for tsunami mitigation: review of effectiveness, limitations, construction, and sustainable management

Coastal vegetation has been widely recognized as a natural method to reduce the energy of tsunami waves. However, a vegetation barrier cannot completely stop a tsunami, and its effectiveness depends on the magnitude of the tsunami as well as the structure of the vegetation. For coastal rehabilitation, optimal planning of natural coastal systems, and their maintenance, we need to quantitatively elucidate the capacity of vegetation to reduce the energy of tsunami waves. The limitations of coastal forests in relation to the magnitude of a tsunami and the maintenance of forests as natural disaster buffer zones have to be understood correctly for effective coastal vegetation planning. Demerits of coastal forests have also been revealed: for example, an open gap in a forest (i.e., a road, river, difference in elevation, etc.) can channel and amplify a strong current by forcing it into the gap. Floating debris from broken trees also can damage surrounding buildings and hurt people. However, many studies have revealed that these demerits can be overcome with proper planning and management of mangroves and coastal forests, and that coastal vegetation has a significant potential to mitigate damage in constructed areas and save human lives by acting as buffer zones during extreme natural events. However, mangrove forests have been damaged by anthropogenic activities (i.e., tourism, shrimp farming, and industrial development), making coastal areas increasingly vulnerable to tsunamis and other natural disasters. The effectiveness of vegetation also changes with the age and structure of the forest. This highlights the fact that proper planning and management of vegetation are required to maintain the tsunami buffering function of coastal forests. Although many government and nongovernmental organizations have implemented coastal vegetation projects, many of them have been unsuccessful due to a lack of proper maintenance. A pilot project in Matara City, Sri Lanka, revealed that participation and support from local authorities and communities is essential to make the planting projects successful. An integrated coastal vegetation management system that includes utilization of the materials produced by the forest and a community participation and awareness program are proposed to achieve a sustainable and long-lasting vegetation bioshield.     

Field study on planted forest structures and their role in protecting communities against tsunamis: experiences along the coast of the Biobío Region,Chile

A field study using satellite images was carried out to analyze the effect of coastal vegetation in mitigating the impact of a catastrophic tsunami on coastal villages in the Biobío Region, Chile, in February 2010. Two types of stand, Pinus radiata D. Don forests and Cupressus macrocarpa Hartw. shelterbelts, appear to have protected coastal areas behind them from the direct impact of the tsunami. The impacts of the horizontal and vertical structures of these coastal forests on the drag forces were analyzed by observing the characteristics of Pinus radiata forests and Cupressus macrocarpa shelterbelts. The stands absorbed the impact of the tsunami without incurring broken stems or uprooted trees due to their diverse horizontal structure, as they contained short trees with various diameters. However, small areas of the stands were damaged by salinity after the tsunami. For this tsunami, which was less than 3 m high, the horizontal and vertical structures of the P. radiata and C. macrocarpa stands provided effective protection for coastal villages since they reduced the velocity and height of the tsunami. A shelterbelt consisting of three rows of C. macrocarpa in front of the tsunami and a P. radiata forest with a density of 11 trees/100 m² and a width of >50 m immediately behind the shelterbelt are suggested as a means of protecting communities along the coastline of the Biobío Region against tsunamis.     

Prevalence and species richness of trematode parasites only partially recovers after the 2011 Tohoku,Japan, earthquake tsunami

Trematode parasites have complex life cycles and use a variety of host species across different trophic levels. Thus, they can be used as indicators of disturbance and recovery of coastal ecosystems. Estuaries on the Pacific coast of northeastern Japan were heavily affected by the 2011 Tohoku earthquake tsunami. To evaluate the effect of the tsunami on the trematode community, we examined trematodes in the mud snail, Batillaria attramentaria, at five study sites (three sites severely exposed to the tsunami and two sites sheltered from the tsunami) in Sendai Bay for 2 years prior to and 8 years after the tsunami. While the trematode prevalence decreased at all study sites, the species richness decreased only at the sites exposed to the tsunami. Although parasitism increased over the study period post-tsunami, the community had not fully recovered 8 years after the event. Trematode community structure has changed every year since the tsunami and has not stabilised. This could be explained by the alteration of first and second intermediate host communities. Our study suggests that it will take more time for the recovery of the trematode community and the associated coastal ecosystem in the Tohoku region.     

Microbial diversity in coastal sediments during pre- and post-tsunami periods in the south east coast of India

Sediment samples were collected from 12 beaches affected by the 2004 Asian Tsunami in the south-east coast of India between Vanagiri and Nagoor. The objective of the present study is to delineate the microbial diversity in pre- and post-tsunami disaster coastal sediments. The collected marine sediments indicate that the overall microbial diversity is higher in the pre-tsunami sediments. The increase in pathogenic bacteria and fungal species after the tsunami is obscured due to inundation and backwashing of seawater along the coast. The reduction of other microbial diversity after the tsunami is attributed that the coastal and shelf sediments play an important role in the demineralization of organic matter, which supports the growth of microbes. The continuous exchange of ocean water and backwashing of coastal sediments by the tsunami wave probably reduced the pathogenic bacterial diversity in the sediments.     

Coastal vegetation structures and their functions in tsunami protection: experience of the recent Indian Ocean tsunami

This study explored the effects of coastal vegetation on tsunami damage based on field observations carried out after the Indian Ocean tsunami on 26 December 2004. Study locations covered about 250 km (19 locations) on the southern coast of Sri Lanka and about 200 km (29 locations) on the Andaman coast of Thailand. The representative vegetation was classified into six types according to their habitat and the stand structures of the trees. The impact of vegetation structure on drag forces was analyzed using the observed characteristics of the tree species. The drag coefficient, including the vertical stand structures of trees, C _d-all, and the vegetation thickness (cumulative trunk diameter of vegetation in the tsunami direction) per unit area, dN _u (d: reference diameter of trees, N _u : number of trees per unit area), varied greatly with the species classification. Based on the field survey and data analysis, Rhizophora apiculata and Rhizophora mucronata (hereafter R. apiculata-type), kinds of mangroves, and Pandanus odoratissimus, a representative tree that grows in beach sand, were found to be especially effective in providing protection from tsunami damage due to their complex aerial root structure. Two layers of vegetation in the vertical direction with P. odoratissimus and Casuarina equisetifolia and a horizontal vegetation structure of small and large diameter trees were also important for increasing drag and trapping floating objects, broken branches, houses, and people. The vertical structure also provided an effective soft landing for people washed up by the tsunami or for escaping when the tsunami waves hit, although its dN _u is not large compared with R. apiculata-type and P. odoratissimus. In addition, the creeks inside mangroves and the gaps inside C. equisetifolia vegetation are assumed to be effective for retarding tsunami waves. This information should be considered in future coastal landscape planning, rehabilitation, and coastal resource management.     

Tsunami and tropical island ecosystems: a meta-analysis of studies in Andaman and Nicobar Islands

Tropical islands are special and sensitive ecosystems which are subjected to various disturbances imposed by human activities and natural disasters. A detailed study about the changing landscape scenarios of these fragile island systems induced by various driving factors could be used for setting up measurements in support of conservation and sustainable development projects. The current research is a meta-analysis of the studies carried out in Andaman and Nicobar islands which analyzed the impact of tsunami of 2004 using geospatial tools. Based on the analysis, it was observed that the Nicobar islands were more affected compared to the Andaman islands. The majority of the researchers used pre- and post-tsunami satellite imagery and adopted visual interpretation method to delineate the changed classes. The study infers uplift of land in Andaman (exposing) and subsidence in Nicobar islands (inundation) with severe damage to the coastal elements like mangroves, coral reefs, plantations and in few cases interior forest. The analysis showed there were no records of the damage for some small islands. Finally, it is concluded that utility of microwave satellite data for change analysis will prove better in regions like Andaman and Nicobar where it is difficult to get cloud free optical data because of the high monsoon periods in these islands. It is also suggested that future work utilizing suitable temporal satellite imagery should focus on the extent of recovery of vegetation and other coastal elements which suffer the impact of disaster.     

Coastal vegetation planting projects for tsunami disaster mitigation: effectiveness evaluation of new establishments

Coastal vegetation acts as a natural barrier against extreme natural and anthropogenic activities, protecting infrastructure and human lives. Establishment of hard infrastructure for tsunami protection is not feasible in developing countries due to its cost-intensive nature. Coastal vegetation can therefore be a feasible alternative for tsunami and general coastal protection in developing countries. This study investigates the effectiveness of current coastal vegetation projects and reports a pilot-scale vegetation project, which provides insights into the management and sustainability of such projects. Thirty-seven establishments of coastal vegetation for tsunami protection were identified for the study from Hambantota to Colombo along the southern coast in Sri Lanka. Evaluation was carried out to assess whether the coastal vegetation establishments fulfilled the planning objectives, such as vegetation alignment to tsunami direction, tree density and tree species, and whether monoculture or mixed species are grown. The study also assessed continuous maintenance and awareness about coastal vegetation, community participation and long-term institutional support from government, nongovernment groups, academic institutions, and other institutions within an integrated framework. Approximately 50% of the sites were found to be effective in terms of fulfilling the above requirements and had reasonable protection against future tsunami-type events. Continuous maintenance is ensured only for 35% of sites with community participation. The survey also revealed the importance of adopting scientific and nonscientific methods of vegetation establishment and selecting appropriate species and structure of vegetation strips for tsunami protection. It is expected that this will lead to the development of coastal vegetation guidelines for local authorities.     

Managed retreat of settlements and infrastructures: ecological restoration as an opportunity to overcome maladaptive coastal development in France

The effects of climate change on coastal risk factors are increasing due to both rising sea levels and increasingly intense coastal floodings. However, these changes are only just beginning to be incorporated into planning strategies for coastal economies and land use in France. Recent coastal storms marked the turning point, and public authorities have now started to revise coastal management legislation, stating that the managed retreat of settlements and infrastructure is the preferred strategy to adapt to climate change. To date, this managed retreat has almost exclusively been discussed in relation to the current political, social, and economic obstacles that make it difficult to relocate equipment and houses inland. Here, we add to this discussion by depicting how the careful ecological restoration of dunes and salt marshes on land made available by managed retreat could overcome some of these obstacles. First, we describe three possible strategies to adapt to sea‐level rise as well as the maladaptation of the current strategy. Then, we focus on the limitations and advantages of ecological restoration in terms of managed retreat and vice versa. Finally, we depict how a new kind of land lease, introduced in draft legislation, can help tackle the multitemporal and multispatial issues that currently hinder managed retreat.     

Coral recruitment and recovery after the 2004 Tsunami around the Phi Phi Islands (Krabi Province) and Phuket, Andaman Sea, Thailand

The 2004 tsunami left a discontinuous pattern of destruction in the reefs along Andaman Sea coast of Thailand. Here, a comparative assessment of coral recruitment was carried out to assess differences in recovery between damaged and undamaged sites in near-shore fringing reefs 1 and 3 years after the tsunami. Settlement plates showed high frequencies of coral spat after 4 months (<17 spat tile⁻¹) in both, damaged and undamaged locations. Field surveys carried out 3 years after the tsunami on natural substrate confirmed that tsunami damage did not suppress recruitment in damaged sites relative to no impacted controls. New and stable settlement space along with unabated larval supply supported post-tsunami recruit densities up to 7.2 m⁻² year⁻¹. Mean recruit densities were found at the level of post-storm situations with rapid recovery success, suggesting that the duration of disturbance, degree of sorting and, hence, stability of coral rubble is a key determinant of recruitment success. Low regeneration success of some species e.g. branching acroporids and rebounding tourism industry at sites like Patong and partly around the Phi Phi Islands (dense carpets of filamentous algae) led to the assumption of selectivity and eventually to an alternation of the coral community even though live coral cover might be recovered soon.     

东南亚沿海与内陆植被对洪水事件响应的稳定性差异

为探讨东南亚沿海与内陆地区植被对洪水事件的响应差异,基于东南亚2000-2018年MODIS卫星遥感数据和洪水数据,通过比较东南亚洪水发生区域,共确定自2000年来影响最大、破坏程度相近的2个沿海洪水事件、2个内陆洪水事件以及1个沿海内陆洪水事件。以Google Earth Engine为数据处理平台,利用Sen+Mann-Kendall趋势法分析了2000-2018年研究区NDVI变化,发现5个研究区19年间NDVI均呈现出上升趋势,平均增速为0.013/10a,沿海与内陆植被在时空演变格局上无明显差异;基于灾害植被破坏指数的分析发现,内陆与沿海植被在洪水影响下的植被破坏指数分别为0.29与-0.25,植被破坏面积分别占比为14.29%与18.11%,内陆植被破坏程度小于沿海地区。同时,排除人类干扰强烈的耕地与人造地表,沿海研究区植被生态系统对洪水事件的抵抗力指数为88.15,明显强于内陆地区的28.89。草地表现出最强的抵抗力,其次为林地;而在植被恢复力方面,表现出相反的趋势。人类活动影响降低了内陆地区洪水灾害对植被的破坏。研究东南亚沿海与内陆植被对单次洪水事件的差异响应,排除内陆与沿海地区洪水事件累计影响,能够为东南亚沿海与内陆植被抵抗洪水灾害提出有针对性的建议。     

Lichenological evidence for the recognition of inland rain forests in western North America

Aim The coastal temperate rain forests of north‐western North America are internationally renowned as the archetypal expression of the temperate rain forest biome. Less well documented is the existence of somewhat similar forests 500–700 km inland on the windward slopes of the Columbia and Rocky Mountains. Here we attempt to show that these inland ‘wetbelt’ forests warrant rain forest status. Location North‐western North America. Methods We use tree‐dwelling macrolichens to assess the degree of environmental congruence between the coastal temperate rain forests and their inland counterparts. Results We report three key findings: (1) 40% of oceanic, epiphytic macrolichens found in Pacific coastal rain forests occur also in inland regions; (2) epiphytic species richness decreases with decreasing latitude, such that roughly 70% of disjunct oceanic species are restricted to regions north of 51° N; and (3) the southward decline in lichen diversity is correlated with a parallel decrease in summer precipitation, but not with mean annual precipitation. Main conclusions These observations are consistent with the recognition of an inland rain forest formation between 50 and 54° N. Inland rain forests represent a small, biologically significant ecosystem whose continued fragmentation and conversion to tree plantations warrant close scrutiny.     

Spatio-temporal distribution of Aedes mosquitoes in Car Nicobar Island: Implication in the transmission of arboviruses

Arboviral infections, viz. dengue and chikungunya are prevalent in the Andaman & Nicobar Islands. During post-tsunami developmental activities, large plastic tanks were provided to the native, Nicobarese tribal households of Car Nicobar Island, to store water for domestic use. These tanks form an ideal breeding source for mosquitoes, especially the vectors of dengue/chikungunya viruses, and few cases of IgM ELISA positives for these infections were identified from this island. In view of this scenario, a survey was carried out to determine the prevalence of these mosquito vectors. Ten randomly selected clusters (neighborhoods with 50 houses each) were surveyed. Each household was inspected for the water holding receptacles. This was the first attempt to determine the prevalence and distribution of the vectors of dengue/chikungunya virus in this Island, against the backdrop of various post tsunami rehabilitation and developmental activities. The stegomyia indices with respect to houses and containers were high during the winter and post-monsoon periods (House Index and Container Index were 69.40 and 46.41 in winter, while 54.40 and 39.49 in post-monsoon). Large plastic tanks (500–1000 l capacity) recorded the highest Breteau Index during all the four seasons. This habitat was observed to support four mosquito species, of which 52% constituted Aedes albopictus. The pupae/person index ranged from 0 to 0.2946. A community-based control approach with multiple stakeholders is envisaged to prevent the vector breeding. This approach would be feasible and effective, with active participation of the tribal chieftain along with village headmen.     

Detecting mammals in heterogeneous landscapes: implications for biodiversity monitoring and management

With terrestrial mammals facing worldwide declines there is an increasing need to effectively monitor populations so that appropriate conservation actions can be taken. There are many techniques available to survey terrestrial mammals and in recent years there have been a number of studies comparing the effectiveness of different methods. Most of these studies have not considered complementarity (the degree to which techniques detect unique species) and effectiveness across ecological gradients. In this study we examined three widely used techniques, camera trapping, live trapping and hair detection, for their complementarity across a vegetation and disturbance gradient. Overall, camera trapping detected more species than any other single technique, but live trapping complemented the cameras by consistently detecting unique species. Additionally, technique effectiveness differed between vegetation types; cameras alone were most effective in dry forest systems while cameras combined with live traps were most effective in wetter forest systems. These results suggest that care needs to be taken when sampling across heterogeneous landscapes because relying on one technique alone could result in certain taxa being systematically overlooked, leading to potentially erroneous conclusions.     

Causes of reduced clutch size in a tidal marsh endemic

We tested three hypotheses of clutch size variation in two subspecies of the swamp sparrow (Melospiza georgiana georgiana and M. g. nigrescens). Swamp sparrows follow the pattern of other estuarine endemics, where clutch size is smaller among tidal salt marsh populations (M. g. nigrescens) than their closest inland relatives (M. g. georgiana). Our results support predation risk and temperature, but not adult survival, as explanations of this pattern in swamp sparrows. Coastal nests were twice as likely to fail as inland nests, and parental activity around the nest site was positively related to clutch size at both sites. When brood size was controlled for, coastal adults visited nests less often and females vocalized less frequently during visits than inland birds, which may decrease nest detectability to predators. Coastal parents waited longer than inland birds to feed offspring in the presence of a model nest predator, but there was no difference in their response to models of predators of adults, as would be expected if coastal birds possessed increased longevity. Additionally, coastal females laid more eggs than inland females over a single season, following a within-season bet-hedging strategy rather than reducing within-season investment. Coastal territories experienced ambient air temperatures above the physiological zero of egg development more often, and higher temperatures during laying correlated with smaller clutches and increased egg inviability among coastal birds. Similar effects were not seen among inland nests, where laying temperatures were generally below physiological zero. Both subspecies showed an increase in hatching asynchrony and a decrease in apparent incubation length under high temperatures. Coastal individuals, however, showed less hatching asynchrony overall despite higher temperatures. Both air temperatures during laying and predation risk could potentially explain reduced clutch size in not only coastal plain swamp sparrows, but also other tidal marsh endemics.     

Environmental and genetic determinants of reproduction in the house sparrow: a transplant experiment

A transplant experiment was carried out to examine whether genetic differentiation can explain geographical variation in the reproductive strategies of house sparrows Passer domesticus. Individuals from an inland and a coastal population in Central Norway were released on a small island, near the coastal area. No directional selection was found on any of the morphological characters from the release to the onset of breeding, but the proportion of the inland males that remained to start breeding on the island was smaller than that of the coastal males. The new environment influenced the time of egg laying which was, relative to the source populations, more delayed among the introduced inland females than among the coastal females. In 1992, chicks raised by inland females grew faster and were fed more frequently than chicks raised by coastal females. No difference was found between birds of inland and coastal origins in their breeding success and their relative number of surviving recruits. Transplanted parents from the inland fed their offspring more frequently than transplanted parents from the coastal area. This experiment shows that the plasticity of reproductive traits in combination with stochastic factors in the environment may lead to an establishment of introduced genes in small populations.     

基于1980—2018年土地利用变化的福建省生境质量时空演变

分析土地利用变化引起生境质量的时空演变特征可以为区域生态文明建设提供科学依据。本研究以生态文明先行示范区福建省为例,以1980—2018年土地利用变化数据为基础,利用InVEST模型对福建省生境质量进行评估,通过地理探测器分析影响因素,结合土地利用变化规律分析福建省生境质量时空演化特征。结果表明: 研究期间,福建省主要土地利用变化类型是耕地转为林地和建设用地,林地转为耕地、草地和建设用地,草地转为林地,分别占总土地利用变化面积的8.4%、14.5%、7.6%、17.1%、6.4%和31.7%。1980—2018年,福建省总体生境质量处于较高级别(0.6～0.8),局部区域呈现生境退化和生境质量降低的趋势。影响福建省生境质量空间分异的第一主导因素是土地利用类型的变化,社会经济因素对沿海县市生境质量的影响显著高于对全域及内陆县市生境质量的影响。沿海地区建设用地快速侵占周边的林草地,使得生境加速退化,且这个过程具有不可逆性;内陆地区中心城区的生境退化会经历相似的过程,只是在速度和规模上可能低于沿海地区。从长远来看,可通过控制城市规模、发展城市生态绿化及构建生态安全格局,以减缓生境退化的速度。     

Tawny owl prey remains indicate differences in the dynamics of coastal and inland vole populations in southern Finland

Some studies suggest that mild winters decrease overwinter survival of small mammals or coincide with decreased cyclicity in vole numbers, whereas other studies suggest non-significant or positive relationships between mild winter conditions and vole population dynamics. We expect for the number of voles to be higher in the rich and low-lying habitats of the coastal areas than in the less fertile areas inland. We assume that this geographical difference in vole abundances is diminished by mild winters especially in low-lying habitats. We examine these relationships by generalized linear mixed models using prey remains of breeding tawny owls Strix aluco as a proxy for the abundance of voles. The higher number of small voles in the coastal area than in the inland area suggest that vole populations were denser in the coastal area. Vole populations of both areas were affected by winter weather conditions particularly in March, but these relationships differed between areas. The mild ends of winter with frequent fluctuations of the ambient temperature around the freezing point (“frost seesaw”) constrained significantly the coastal vole populations, while deep snow cover, in general after hard winters, was followed by significantly lowered number of voles only in the inland populations. Our results suggest that coastal vole populations are more vulnerable to mild winters than inland ones. We also show that tawny owl prey remains can be used in a meaningful way to study vole population dynamics.