Coastal ecosystems lie at the forefront of sea level rise. We posit that before the onset of actual inundation, sea level rise will influence the species composition of coastal hardwood hammocks and buttonwood (Conocarpus erectus L.) forests of the Everglades National Park based on tolerance to drought and salinity. Precipitation is the major water source in coastal hammocks and is stored in the soil vadose zone, but vadose water will diminish with the rising water table as a consequence of sea level rise, thereby subjecting plants to salt water stress. A model is used to demonstrate that the constraining effect of salinity on transpiration limits the distribution of freshwater-dependent communities. Field data collected in hardwood hammocks and coastal buttonwood forests over 11 years show that halophytes have replaced glycophytes. We establish that sea level rise threatens 21 rare coastal species in Everglades National Park and estimate the relative risk to each Climatic Change (2011) 107:81-108 species using basic life history and population traits. We review salinity conditions in the estuarine region over 1999-2009 and associate wide variability in the extent of the annual seawater intrusion to variation in freshwater inflows and precipitation. We also examine species composition in coastal and inland hammocks in connection with distance from the coast, depth to water table, and groundwater salinity. Though this study focuses on coastal forests and rare species of South Florida, it has implications for coastal forests threatened by saltwater intrusion across the globe.

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As part of ongoing efforts to understand, document, and conserve the flora of southeastern North America, we propose two new species, the recognition of a usually synonymized variety, the acceptance of two species of Waltheria as being present in peninsular Florida, taxonomic acceptance of a sometimes deprecated species transferred with a new name into a different genus, and we clarify the distribution and ecology of a species. In Carex (Cyperaceae), we re-analyze infrataxa in Carex intumescens and recommend the recognition of two varieties, a taxonomic schema first proposed in 1893, but usually not followed in the 128 years since. In Euphorbia (Euphorbiaceae), a careful assessment of south Florida material of Euphorbia subg. Chamaesyce sect. Anisophyllum subsect. Hypericifoliae reveals the need for taxonomic changes to best classify endemic representatives of this group, resulting in the naming of a new species, and a new name at species rank in Euphorbia for a taxon first named in Chamaesyce and sometimes subsequently treated at only varietal rank in Euphorbia. Chamaecrista deeringiana (Fabaceae, subfamily Caesalpinioideae) has been repeatedly misinterpreted to include two different and disjunct population systems with differing morphologies and habitats, which are here interpreted as separate species, one newly named and the other Chamaecrista deeringiana returned to its original and narrower interpretation as a south Florida endemic. Waltheria (Malvaceae) has sometimes been interpreted as being represented in Florida by a single taxon, Waltheria indica, but we disentangle the concepts of the widespread W. indica and the West Indian W. bahamensis and clarify that both are present in the southeastern United States. We reconsider the occurrence and habitat of Toxicoscordion nuttallii (Melanthiaceae) in three states in which it has been reported as a rare species, Mississippi, Missouri, and Louisiana, and remove it from the Mississippi flora as a garbled and false report. In Louisiana, its occurrence in calcareous prairie complexes limits its potential occurrence in the state to a specialized and rare habitat, but careful exploration of habitat remnants may result in the discovery of additional populations. Taxonomic studies and re-assessments of this kind are critical in laying the best scientific foundation for regulatory, policy, and land conservation decisions. This paper names or makes the case for the renewed acceptance of six species with range-wide conservation concern: one Critically Imperiled (G1 – Euphorbia ogdenii), one Imperiled (G2 – E. hammeri), and four Vulnerable (G3 – E. garberi, E. porteriana, Chamaecrista deeringiana, C. horizontalis).

We examine salinity, ground water depth, and water uptake of common plant species in coastal upland communities: buttonwood hammocks, hardwood hammocks, and buttonwood prairies of Everglades National Park. We show that the elevation gradient is gentle with a mean gradient of 0.12 m North American Vertical Datum of 1988 from buttonwood prairie to hardwood hammocks, but the species composition and canopy cover among communities are different. Plant communities differ significantly in groundwater salinity. Hardwood hammocks have brackish groundwater [14-27 parts per thousand (PPT)], buttonwood hammocks have brackish to saline groundwater (23-35 PPT), and buttonwood prairies have saline groundwater (30-44 PPT). The depth to water table is greater for plants in hardwood and buttonwood hammocks than in buttonwood prairies, which makes the freshwater recharge capacity of vadose zone larger in hammocks than in buttonwood prairies. The majority of species accessed water from deep soil (5-30 cm) and groundwater in dry season and switched to using shallow soil water (0-5 cm) in wet season. Exception to this pattern is herbaceous Chromolaena frustrata, endemic to buttonwood hammocks of South Florida, which accessed shallow soil water in dry season and deep soil water in wet season. Our study assesses susceptibility of coastal upland species to sea level rise (SLR)-driven changes in water table and salinity; the results of which can be incorporated into planning for adaptation to SLR.

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Recreational motor boating in shallow water can damage submerged natural resources through propeller scarring and these impacts represent one of many factors that affect the health of seagrass ecosystems. Understanding the patterns of seagrass scarring and associations with physical and visitor-use factors can assist in development of management plans that seek to minimise resource damage within marine protected areas. A quantification of seagrass scarring of Florida Bay in Everglades National Park, using aerial imagery, resulted in the detection of a substantial number and length of seagrass scars. Geospatial analyses indicated that scarring was widespread, with the densest areas found in shallow depths, near navigational channels, and around areas most heavily used by boats. Modelling identified areas of high scarring probability, including areas that may experience increased scarring in the future as a result of a reallocation of impacts if management strategies are implemented. New boating-management strategies are warranted to protect seagrass in Florida Bay. An adaptive approach focusing on the most heavily scarred areas, should consider a variety of management options, including education, improved signage, new enforcement efforts and boating restrictions, such as non-motorised zones, or temporary closures. These methods and recommendations are broadly applicable to management of shallow water systems before and after resource impacts have occurred.

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