Showing papers by "Robert R. Twilley published in 2018"

BioTIME: A database of biodiversity time series for the Anthropocene

Abstract: Motivation: The BioTIME database contains raw data on species identities and abundances in ecological assemblages through time. These data enable users to calculate temporal trends in biodiversity within and amongst assemblages using a broad range of metrics. BioTIME is being developed as a community-led open-source database of biodiversity time series. Our goal is to accelerate and facilitate quantitative analysis of temporal patterns of biodiversity in the Anthropocene.Main types of variables included: The database contains 8,777,413 species abundance records, from assemblages consistently sampled for a minimum of 2 years, which need not necessarily be consecutive. In addition, the database contains metadata relating to sampling methodology and contextual information about each record.Spatial location and grain: BioTIME is a global database of 547,161 unique sampling locations spanning the marine, freshwater and terrestrial realms. Grain size varies across datasets from 0.0000000158 km(2) (158 cm(2)) to 100 km(2) (1,000,000,000,000 cm(2)).Time period and grainBio: TIME records span from 1874 to 2016. The minimal temporal grain across all datasets in BioTIME is a year.Major taxa and level of measurement: BioTIME includes data from 44,440 species across the plant and animal kingdoms, ranging from plants, plankton and terrestrial invertebrates to small and large vertebrates.

Global controls on carbon storage in mangrove soils

Abstract: Global-scale variation in mangrove ecosystem properties has been explained using a conceptual framework linking geomorphological processes to distinct coastal environmental settings (CES) for nearly 50 years. However, these assumptions have not been empirically tested at the global scale. Here, we show that CES account for global variability in mangrove soil C:N:P stoichiometry and soil organic carbon (SOC) stocks. Using this ecogeomorphology framework, we developed a global model that captures variation in mangrove SOC stocks compatible with distinct CES. We show that mangrove SOC stocks have been underestimated by up to 50% (a difference of roughly 200 Mg ha−1) in carbonate settings and overestimated by up to 86% (around 400 Mg ha−1) in deltaic coastlines. Moreover, we provide information for 57 nations that currently lack SOC data, enabling these and other countries to develop or evaluate their blue carbon inventories. A global model that incorporates information about coastal environmental settings indicates that mangrove soil organic carbon stocks have been significantly underestimated in carbonate settings, and overestimated in deltaic coastlines.

Island Edge Morphodynamics along a Chronosequence in a Prograding Deltaic Floodplain Wetland

Abstract: Bevington, A.E. and Twilley, R.R., 2018. Island edge morphodynamics along a chronosequence in a prograding deltaic floodplain wetland. Much of the previous research on coastal deltaic land building has focused on the planform delta dimensions; whereas this research focuses on shifts in vertical elevation and deltaic island edge cross-sectional morphology in relation to a proposed conceptual model of deltaic island edge morphological development. This study was conducted using data collected from the Wax Lake Delta in the northern Gulf of Mexico. Island edge cross-sectional elevation profiles were extracted from a 2012 LIDAR elevation survey. Four morphometric variables (levee width, interior slope, mean elevation range, and total elevation range) were selected to describe the shape of each of these profiles, and each profile was also assigned to an age class, which was determined based on mapping of historic deltaic island extent from aerial imagery. Multivariate analysis of variance was used to ...

Assessment of the evolution of storm surge in coastal louisiana

Abstract: The Louisiana coastal landscape comprises an intricate system of fragmented wetlands, natural ridges, man-made navigation canals, flood protection and oil and gas infrastructure. Louisiana lost approximately 1,883 square miles (4,877 sq km) of coastal wetlands from 1932 to 2010 including 300 square miles (777 sq km) lost between 2004 and 2008 due to Hurricanes Katrina, Rita, Gustav and Ike (Couvillion et al., 2011). A projected additional 2,250 square miles (5,827 sq km) of coastal wetlands will be lost over the next 50 years if no preventative actions are taken (Coastal Protection and Restoration Authority of Louisiana, 2017). Storm surge models representing historical eras of the Louisiana coastal landscape can be developed to investigate the response of hurricane storm surge (e.g. peak water levels, inundation volume and time) to land loss and vegetative changes. Land:Water (L:W) isopleths (Gagliano et al., 1970; Twilley et al., 2016; Siverd et al., 2018) have been calculated along the Louisiana coast from Sabine Lake to the Pearl River. These isopleths were utilized to develop a simplified coastal landscape (bathymetry, topography, bottom roughness) representing circa2010. Similar methods are employed with the objective of developing storm surge models that represent the coastal landscape for past eras (circa1890, c.1930, c.1970).

The Giving Delta

Abstract: The Giving Delta project provides a vision for reengaging the Mississippi River's seasonal flood pulse to build and maintain coastal wetlands within a management framework that allows for human adaptation to estuarine transgression over time. This project conceptually modeled three layered frameworks: Ecosystem, Community, and Economy. The Giving Delta framework plan lays out a vision for restoring the environment and reintroducing the natural river dynamics into parts of Louisiana's coast. Over the course of various generations, residents and businesses adapted to the negligible risk of riverine flooding introduced by the levee system up and down the Mississippi River. During the first generation, the controlled flood and multi-height spillway structures will be constructed, as well as the settling basins and sediment traps. Uninterrupted deep draft navigation cannot be guaranteed through the Southwest Pass and an alternative deep draft navigation channel entrance into the Mississippi River and the inland waterways of the nation is constructed at Port Sulphur during the second generation.