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This study develops an integrative and thorough assessment of storm-related coastal risk in Mexico. Through Bayesian networks (BN), we explore an approach that blends an ecological understanding of coastal dynamics and concepts of coastal risk based on hazards, exposure, and vulnerability. We used two approaches. First, we calculate a coastal risk index based on coastal hazards (storms, flooding potential and shoreline change rate), exposure (occurrence and size of human settlements), and vulnerability (extension of natural ecosystems which provide storm protection: mangroves and coastal dunes). Then, we used a Bayesian network approach to perform a causal-driven and spatially explicit probabilistic assessment of storm-induced risks. This study shows that the population living on the coast has grown drastically over the last decades, resulting in more significant exposure of people and assets to risk. We showed the importance of natural ecosystems in reducing coastal risk and that the highest coastal risk was associated with (i) the reduced cover (or absence) of mangroves and coastal dunes, (ii) the conservation status of vegetation, and (iii) higher population density. Overall, the study shows that utilizing a Bayesian network is an effective tool for exploring coastal risk scenarios. [ABSTRACT FROM AUTHOR]

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A palynological analysis of sediments sampled from core HI-178, offshore High Island, Texas, provided a diverse and well-preserved palynoflora. The main objective was to analyze the environmental conditions at time of deposition. A secondary objective was to evaluate whether or not this site might have been occupied by Native Americans by looking for signs of human-driven changes in vegetation. Here we focus on the abundance of hornwort spores recovered from these samples, review their diversity, compare the fossil spores to modern analogues and discuss the paleoenvironmental implications of hornwort abundance. Although no direct evidence of human occupation was found, the pollen and spore assemblage recovered, marked by high abundance and diversity in spores of hornworts belonging to the families Anthocerotaceae and Notothyladaceae, indicate that this site was most likely not submerged at the time of deposition; human occupation was therefore possible. This site represents a coastal low-lying area with ponds or slow-moving waters that provided the humid environment needed for hornworts to reproduce and thrive under warm climatic conditions. [ABSTRACT FROM PUBLISHER]

Transgressive dune fields often comprise a multiplicity of landforms where vegetation processes largely affect landform dynamics, which in turn, also affect vegetation processes. These associations have seldom been studied in detail. This paper examines four separate landform types in a complex coastal transgressive dunefield located in the central Gulf of Mexico, in order to assess the relationships between dunefield habitat, local environmental factors, vegetation associations and landform evolution. Topographic surveys using tape and clinometer were conducted in conjunction with vegetation survey transects at four locations across the Doña Juana dunefield. Vegetation surveys allowed the estimation of relative plant cover of each plant species found along the transects. A large variety of landforms were found at the Doña Juana Dunefield: deflation plains, gegenwalle (counter) ridges, transverse dune trailing ridges, blowouts and parabolic dunes, aklé (fish-scale shaped) dunefields and precipitation ridges, with plant species associations developing on these different landforms equally variable. Flood tolerant species were located in the lower parts (deflation plain and gegenwalle ridges) whereas the older and dryer parts were covered by coastal matorral shrubs. Burial-tolerant species were dominant in the most mobile areas (blowouts and aklé dunefield and margin). The dune trailing ridge, with relatively milder conditions, showed the highest richness, with no dominant species. A dual interaction was found such that colonizing species both create and affect topography, and in turn, topography determines vegetation association and succession patterns. In coastal dunes, the vegetation and abiotic environment (namely the different landforms and the inherent micronevironmental variability) interact tightly and generate a complex and highly dynamic biogeomorphic system where substrate mobility and colonization processes reinforce one another in positive feedback. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]