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Field studies are necessary for understanding natural processes in spite of the human‐induced disturbances they cause. While researchers acknowledge these effects, no studies have empirically tested the direct (e.g., harvesting plants) and indirect (i.e., trampling) effects of researcher activities on biological structure and edaphic conditions. We leveraged field studies in Alabama and California to monitor the recovery of tidal marshes following research activities. Researcher effects on animals, plants, and sediment conditions remained prevalent almost one year after the disturbance ended. For instance, trampled plots had 14%–97% lower plant cover than undisturbed plots after >10 months of recovery. Researcher effects also impacted plant composition, leading to increased subordinate species abundance. We encourage field researchers to adopt strategies that reduce their scientific footprints, including reducing field visits, limiting field team size, and considering ways to limit potential environmental impacts during study design. [ABSTRACT FROM AUTHOR]

Although the promotion of biodiversity has been recognized as an important conservation goal, salt marsh restoration typically focuses on reestablishing dominant foundation species. Salt marsh restoration projects that add or remove sediment to optimize marsh elevation often result in a bare landscape following construction. Restoration managers must decide whether to plant and, if so, which species. This decision can be difficult because few studies have examined the ecological functions of individual species, especially those that are less abundant. Within a major salt marsh restoration project in Elkhorn Slough, California, where 17,000 plants of five high marsh species were planted, we investigated how rarer species and the naturally recruiting dominant (Salicornia pacifica) differ in ecosystem function. We evaluated 31 different metrics related to blue carbon, plant productivity, environmental effects, and community interactions. No single species had the greatest ecological function across this suite of metrics, and measured effects were mainly independent, with only 16 of 435 pairwise comparisons revealing a strong correlation. We found significant differences among species for 18 metrics, revealing key contrasts in ecosystem function, with significant effects of marsh elevation and interaction between effects of species and elevation on some of these functions. S. pacifica scored highest for metrics such as recruitment and canopy height but other species outperformed Salicornia in other metrics. Frankenia salina had the greatest ecological function in the highest number of metrics, including cover and belowground biomass carbon content, but other species had higher rates of photosynthesis and harbored fewer individuals of invasive arthropods. We recommend planting a suite of less common species at restoration sites to provide more diverse functions across the landscape. F. salina in particular is recommended for its tolerance of hypersalinity and low moisture conditions. Our demonstration of the value of complementing restoration of the dominant foundation species with restoration of less common species is applicable to restoration of other ecosystems beyond salt marshes. The approach we implemented, evaluating a large suite of functions for multiple species across a restored landscape, can serve as a model for investigations of the importance of biodiversity for enhancing multifunctionality in other restored ecosystems. [ABSTRACT FROM AUTHOR]

Terminal channels were historically a common feature of tidal delta ecosystems but have become increasingly rare as landscapes have been modified. Tidal hydrodynamics are a defining feature in tidal terminal channel ecosystems from which native aquatic communities have evolved. However, few studies have explored the relationship between fish community structure and hydrodynamics in these tidal terminal channel ecosystems. We sampled fish communities throughout a network of terminal channels within the northeasternmost region of the San Francisco Estuary to determine the relationship between fish community structure and hydrodynamics within these environments. We collected two years (2017 and 2018) of fish community samples using gill nets and analyzed data using multivariate community analyses and count models. We found metrics of fish diversity and counts of native fishes to be greatest upstream (farthest from tidal influence) of the tidal excursion within terminal channels. Counts of non‐native fishes were less affected by this hydrodynamic feature of terminal channels and more tightly correlated to local habitat conditions (e.g., water temperature, depth). Our results suggest that channel hydrodynamics plays a role in structuring fish communities within terminal channels, particularly native fishes. These results indicate that hydrodynamics in tidal delta ecosystems may be able to be altered in ways that benefit native fishes without the cost of water pumping. [ABSTRACT FROM AUTHOR]

Abstract Habitat specialists are declining at alarming rates worldwide, driving biodiversity loss of the earth's next mass extinction. Specialist organisms maintain smaller functional niches than their generalist counterparts, and tradeoffs exist between these contrasting life history strategies, creating conservation challenges for specialist taxa. There is little work, however, explicitly quantifying “specialization”; such information is necessary for the development of focused conservation strategies in light of the rapidly changing landscapes of the modern world. In this study, we tested whether habitat specialism explains the persistence of breeding bird populations in tidal marshes of the northeastern United States. We used the North American Breeding Bird Survey (BBS) together with contemporary marsh bird surveys to develop a Marsh Specialization Index (MSI) for 106 bird species that regularly use tidal marshes during the breeding season. We produced four metrics of species persistence (occupancy, abundance, total biomass supported, and 14‐yr population trends) and compared them to MSI values in one of the first community‐scale demonstrations of specialist loss in disturbed landscapes. Our results confirm that tidal marsh specialism has short‐term benefits but long‐term consequences for bird persistence in coastal marsh systems, results that are generalizable across many changing landscapes. We then use this robust support of niche theory to recommend MSI as a tool for quantitatively identifying species of conservation concern in disturbed and rapidly changing landscapes such as tidal marsh.

Habitat specialists are declining at alarming rates worldwide, driving biodiversity loss of the earth's next mass extinction. Specialist organisms maintain smaller functional niches than their generalist counterparts, and tradeoffs exist between these contrasting life history strategies, creating conservation challenges for specialist taxa. There is little work, however, explicitly quantifying "specialization"; such information is necessary for the development of focused conservation strategies in light of the rapidly changing landscapes of the modern world. In this study, we tested whether habitat specialism explains the persistence of breeding bird populations in tidal marshes of the northeastern United States. We used the North American Breeding Bird Survey (BBS) together with contemporary marsh bird surveys to develop a Marsh Specialization Index (MSI) for 106 bird species that regularly use tidal marshes during the breeding season. We produced four metrics of species persistence (occupancy, abundance, total biomass supported, and 14-yr population trends) and compared them to MSI values in one of the first community-scale demonstrations of specialist loss in disturbed landscapes. Our results confirm that tidal marsh specialism has short-term benefits but long-term consequences for bird persistence in coastal marsh systems, results that are generalizable across many changing landscapes. We then use this robust support of niche theory to recommend MSI as a tool for quantitatively identifying species of conservation concern in disturbed and rapidly changing landscapes such as tidal marsh. [ABSTRACT FROM AUTHOR]

Reducing uncertainty in data inputs at relevant spatial scales can improve tidal marsh forecasting models, and their usefulness in coastal climate change adaptation decisions. The Marsh Equilibrium Model (MEM), a one-dimensional mechanistic elevation model, incorporates feedbacks of organic and inorganic inputs to project elevations under sea-level rise scenarios. We tested the feasibility of deriving two key MEM inputs—average annual suspended sediment concentration (SSC) and aboveground peak biomass—from remote sensing data in order to apply MEM across a broader geographic region. We analyzed the precision and representativeness (spatial distribution) of these remote sensing inputs to improve understanding of our study region, a brackish tidal marsh in San Francisco Bay, and to test the applicable spatial extent for coastal modeling. We compared biomass and SSC models derived from Landsat 8, DigitalGlobe WorldView-2, and hyperspectral airborne imagery. Landsat 8-derived inputs were evaluated in a MEM sensitivity analysis. Biomass models were comparable although peak biomass from Landsat 8 best matched field-measured values. The Portable Remote Imaging Spectrometer SSC model was most accurate, although a Landsat 8 time series provided annual average SSC estimates. Landsat 8-measured peak biomass values were randomly distributed, and annual average SSC (30 mg/L) was well represented in the main channels (IQR: 29-32 mg/L), illustrating the suitability of these inputs across the model domain. Trend response surface analysis identified significant diversion between field and remote sensing-based model runs at 60 yr due to model sensitivity at the marsh edge (80-140 cm NAVD88), although at 100 yr, elevation forecasts differed less than 10 cm across 97% of the marsh surface (150-200 cm NAVD88). Results demonstrate the utility of Landsat 8 for landscape-scale tidal marsh elevation projections due to its comparable performance with the other sensors, temporal frequency, and cost. Integration of remote sensing data with MEM should advance regional projections of marsh vegetation change by better parameterizing MEM inputs spatially. Improving information for coastal modeling will support planning for ecosystem services, including habitat, carbon storage, and flood protection. [ABSTRACT FROM AUTHOR]