1,720,986 research outputs found
Population modeling in conservation planning of the Lower Keys marsh rabbit
Get PDFRapid development and urbanization of the Lower Florida Keys in the last 30
years has fragmented the habitat of the Lower Keys marsh rabbit (Sylvilagus palustris
hefneri) and threatened it with extinction. Current threats exist at multiple
spatiotemporal scales and include threats due to development, invasive species, and
global climate change. On Boca Chica Key, the Lower Keys marsh rabbit (LKMR)
exists as a metapopulation on Naval Air Station-Key West (NASKW). I conducted a
population viability analysis to determine the metapopulation's risk of extinction under
multiple management scenarios by developing a spatially-explicit, stage-structured,
stochastic matrix model using the programs RAMAS Metapop and ArcGIS. These
management scenarios include clearance of airfield vegetation, habitat conversion, and
control of feral cats as an invasive species. Model results provided the Navy with
relative risk estimates under these different scenarios. Airfield clearance with habitat
conversion increased extinction risk, but when coupled with feral cat control, risk was
decreased.
Because of the potential of sea-level rise due to human-induced global climate
change, and its projected impact on the biodiversity of the Florida Keys, I estimated the impacts of rising sea levels on LKMR across its geographic distribution under scenarios
of no, low (0.3m), medium (0.6m), and high (0.9m) sea-level rise. I also investigated
impacts due to 2 treatments (allowing vegetation to migrate upslope and not allowing
migration), and 2 land-use planning decisions (protection and abandonment of humandominated
areas). Not surprisingly, under both treatments and both land-use planning
decisions, I found a general trend of decreasing total potential LKMR habitat with
increasing sea-level rise. Not allowing migration and protecting human-dominated areas
both tended to decrease potential LKMR habitat as compared with allowing migration
and abandoning human-dominated areas. In conclusion, conservation strategies at
multiple scales need to be implemented in order to reduce threats to LKMR, such as
development, invasive species, and global climate change
Analysis of benefits of sargassum on Galveston Island and indications for beach management policy
Get PDFSargassum fluitans and natans, types of brown algae, wash up on Galveston Island, Texas annually from May to August. Sargassum smells bad, hurts tourism and impairs sea turtle hatchings. Coastal managers are confronted with the difficult choice of cleaning Sargassum off the beach or leaving it alone. The current beach management practice is to rake the algae with tractors and deposit it at the base of the dunes. The environmental impacts of raking and ecological benefits of Sargassum are unknown. The Galveston Island Park Board of Trustees (GIPBT) used to rake all beaches under their management before Hurricane Alicia in 1983. Then, citizens started to complain that raking was causing erosion. Now, there are people who argue for both raking and leaving the beach alone. Environmental policies require complex decisions that take into consideration social, economical, ecological, and cultural values. The GIPBT initiated the Sargassum Policy Committee to gain knowledge of different stakeholder values and scientific research to develop beach management. The first study analyzed elevation changes over a year period on raked and unraked beaches on both the West and East end of Galveston Island. The Analysis ofVariance results indicated that there is not a difference in elevation changes between the raked and unraked beaches over a year.The second study analyzed the effects of Sargassum on the dune plant Panicum amarum. Plants were asexually grown in a greenhouse in sand without (control) and with Sargassum. The effects of small versus large amounts, top versus mixed with sand and washed versus unwashed Sargassum were tested. The results indicated that the addition of Sargassum increased plant growth. The treatments with large amounts of Sargassum and unwashed treatments showed significant growth changes at the 95% confidence level. The last component analyzed the collaborative potential of the Sargassum Policy Committee through observations of meetings and surveys of the members. Daniel and Walker���s Progressive Triangle was used to assess the relationship, procedural and substance dimensions of collaborative learning. Then, suggestions were made for increasing collaboration. The combination of scientific research and stakeholder values has resulted in the creation of sound beach management
Salt Marsh Hydrology and Restoration
Get PDFHydrologic changes have affected coastal ecosystem sustainability along the Texas coast and throughout the Gulf of Mexico. Human utilization of coastal ecosystems has led to the alteration of tidal hydrology. These ecosystems are highly dynamic and are greatly affected by tidal fluctuations and restriction to hydrologic flow.
The main objective of this study was to understand the hydrologic effects of tides, hydrologic alterations, and subsequent restoration on salt marshes along the Texas coast. The selected study site was Magnolia Beach marsh in Matagorda Bay, approximately 10.5 kilometers southeast of Port Lavaca, Texas. The study also had three more specific objectives.
The first objective was to determine the cause of marsh loss observed since 1958. This was accomplished by a GIS analysis that identified over 62 hectares of marsh loss and a hydrologic analysis that identified a pair of tidal barriers. These barriers reduced the volume of water that could be exchanged between the salt marsh and Matagorda Bay. This intermittent connectivity resulted in the internal waters of the marsh becoming hypersaline.
The second objective was to measure the hydrologic response to tidal reconnection with the removal of the two barriers. This was accomplished through the creation of a STELLA computer model, a numerical inlet hydrology model, and a meta-analysis to predict barrier removal success. An analysis of water level and water velocity before and after the barrier removal was used to quantify the success of the hydrologic reconnection.
The final objective was to create a tide prediction model to better estimate wind driven tides. The current NOAA model has been effective to give astronomical tide movements, but is not capable of predicting wind driven tides. The Enhanced Tide Model resulted in a 13.34% average increase in tidal prediction accuracy across all NOAA tidal gauges in the Gulf of Mexico and the East coast of Florida. This tool could be used by the public, the shipping industry, and restoration planners to better understand tide dynamics in the Gulf of Mexico and abroad
Coastal Dunes and Dune Vegetation: Interdisciplinary Research on Storm Protection, Erosion, and Ecosystem Restoration
Get PDFCoastal dunes offer many communities around the world a means to naturally mitigate
the damage caused by coastal storms. This dissertation will address some of the
knowledge gaps concerning the cost effectiveness of dunes in terms of storm damage
mitigation, the role of dune vegetation in erosion resistance during storm surges, and
the best techniques for restoring dune vegetation. To determine dune storm damage
mitigation value, Hurricane Ike FEMA insurance claims for over one thousand homes
in Galveston County, Texas, were analyzed (multivariate regression) with respect to
the size of the dunes protecting those homes. The dunes in this area provided over 8
million dollars in protection across the study area during Hurricane Ike. Dunes were
generally cost-effective (>$50 of damage mitigation per cubic meter of dune sediment)
and were a viable hazard mitigation strategy. With regards to dune vegetation's role
in erosion resistance, the effects of different plant features and species on swash hydrodynamics, sediment properties, and erosion was evaluated utilizing multivariate
regression and a simulated storm surge/wave attack within a wave flume. Aboveground
plant surface area was significantly related to decreased swash flow velocity,
turbulent kinetic energy, and wave reflection while fine root biomass density was
significantly related to increased sediment shear strength. These results indicated
that both above- and below-ground features of plants play a role in reducing dune
erosion during storm surges. Lastly, a variety of dune restoration techniques and the
broader ramifications of planting vegetation on dune biogeomorphology were evaluated
to identify effective dune restoration practices for the Texas Coast. Sargassum
baling, useful for transporting the nuisance seaweed from beaches, was minimally
impactful on plant growth while using rooted plants and native mycorrhizal fungal
inoculations generally increased the accumulation of plant biomass. Dune vegetation
planting also initially promoted accretion but lowered plant diversity compared to
a naturally colonized dune. The research detailed in this dissertation contributes
to the growing body of knowledge concerning engineering with nature and provides
additional support for the integration of coastal dune restoration into sustainable
coastal hazard mitigation strategies
Landscape Scale Impacts of Sea Level Rise and Elevation Changes Along the Matagorda Fault in Matagorda, Texas
Get PDFMovement of growth faults, a type of normal fault which is formed during sedimentation and is characterized by having greater vertical thickness on the downthrown fault side, on barrier islands contributes to wetland losses. The opening objective of this study was to quantify land cover change within a Matagorda, Texas wetland that results from sea level rise and elevation change over time due to coastal faulting. The closing objective of this study was to simulate land cover conversion as a function of relative sea level rise (RSLR) within the wetland and to compare and contrast the impact of specific rates of both fault-induced elevation change and predicted International Panel on Climate Change (IPCC) sea level rise projections.
To accomplish these objectives a time series of aerial images was classified using automated unsupervised classification and hand digitization. After classification, total wetland losses on both the upthrown and downthrown sides of the fault were evaluated as a function of spatial distance from the fault plane. This classified product was draped over a digital elevation model (DEM) layer to evaluate elevations of land cover classes and model potential future outcomes based on RSLR.
Classification results show that while wetland loss occurred on both sides of the fault, losses were far more extensive on the downthrown side. It was concluded that this vertical fault movement impacts wetland losses, especially on the downthrown side. Modeling results show that rapid water level rise can force wetland land cover class conversion regardless of whether this relative rise is caused by vertical fault displacement or eustatic sea level rise, resulting in the destruction of vital wetland areas. Current recorded conditions of sea level rise along the Texas Gulf Coast leave a grim outlook for regions similar to this study area
Oil Spill Detection and Mapping Along the Gulf of Mexico Coastline Based on Imaging Spectrometer Data
Get PDFThe Deepwater Horizon oil spill in the Gulf of Mexico between April and July 2010 demonstrated the importance of synoptic oil-spill monitoring in coastal environments via remote-sensing methods. This study focuses on terrestrial oil-spill detection based on hyperspectral images acquired along the coastline of the Gulf of Mexico. A number of AVIRIS (Airborne Visible/Infrared Imaging Spectrometer) imaging spectrometer images were investigated in this research collected over Bay Jimmy and Wilkinson Bay within Barataria Bay, Louisiana, USA during September 2010.
Various remote-sensing image processing techniques were employed to detect/identify oiled vegetation. Image-derived endmembers were extracted from the atmospherically- and geometrically-corrected hyperspectral AVIRIS data via Minimum Noise Fraction transform, Pixel Purity Index generation, and n-dimensional visualization. Extracted endmembers are then used as input to endmember-mapping algorithms Spectral Information Divergence (SID) and Mixture Tuned Matched Filtering (MTMF) to yield fractional-abundance images and crisp classification images. Field based observations of the degree of oil accumulation along the coastline were also employed, as well as in situ measurements from the literature.
Multiple Endmember Spectral Mixture Analysis (MESMA) was employed for oiled-vegetation detection and mapping in order to enable the number and types of endmembers to vary on a per-pixel basis, in contrast to simple Spectral Mixture Analysis (SMA). MESMA thus better allows accounting for spectral variability of oil (e.g., due to varying oil thicknesses, states of degradation, and the presence of different oil types, etc.) and other materials, including soils and salt marsh vegetation of varying types, which may or may not be affected by the oil spill. The classification results demonstrated that MESMA provides advantageous capabilities for mapping several oiled-vegetation classes along the Gulf of Mexico coastline, relative to the conventional approaches tested
Residential cattle egret colonies in Texas: geography, reproductive success and management
Get PDFA phenomenon of large, upland breeding colonies of cattle egrets in residential
areas of Central Texas has been observed since the early 1960s. These large
concentrations of breeding birds can be a nuisance to nearby residents and their
management has been difficult. To help understand why cattle egrets choose upland,
residential breeding sites, and predict where these might occur, the geographic extent of
the phenomenon was bounded within Texas, a habitat suitability model constructed, and
reproductive success compared by breeding habitat type to evaluate if residential nesting
confers an adaptive advantage..
Records of upland cattle egret colonies were found only in Central Texas, not
other parts of the state. The habitat suitability model was constructed using total edge of
three land use classes: water, forest, and developed classes. The model classified 78.6 %
of upland colonies in very high or high suitability classes and 7.1% of colonies in low or
very low suitability classes. This distribution was significantly different than expected
considering the overall ratio of suitability scores in the entire raster model (p = 0.036).
Nineteen active colonies were found in or bordering the Post Oak Savannah and
Blackland Prairie ecoregions. Colonies were in residential, urban, island, and flooded tree and shrub habitat. Nests were found in 12 different tree and shrub species.
Residential colonies had more breeding pairs, greater nest survival, and were less
productive than non-residential colonies on average, but these differences were not
statistically significant. Colonies where nest substrate was removed were not reused and
no breeding was initiated nearby the next year. Propane cannons discouraged reuse of
colony after prolonged application.
Herons and egrets likely use residential sites when wetland habitats are limited.
Their overall breeding distribution reflects state wide rainfall and wetland availability
patterns with upland nesting in Central Texas, wetland nesting in eastern and coastal
regions, and little large scale nesting in western Texas. Egrets and herons may use edges
of development as breeding sites to limit predation by ground predators when flooded
tree and shrub or island habitats are absent, but this hypothesis needs more testing
Ecosystem-based solutions to dune and beach erosion
Get PDFSandy beach and dune ecosystems make up two-thirds of the world's ice-free coastline and constitute an important part of the global land-sea interface; however, rising sea levels, changing disturbance regimes, and expanding coastal development is expediting their disappearance. Today, coastal managers lean towards the implementation of natural ecosystems for coastal protection because these methods are less expensive, more sustainable, and more resilient compared to engineered structures.
We present investigative results on the protective abilities of Sargassum spp - a widely-distributed pelagic macroalgae, commonly found as beach wrack and heretofore referred to as ���sargassum���. We tested increasing volumes of sargassum in a flume and found that it reduced erosion-causing processes in the offshore and swash zone. Moreover, sargassum directly reduced erosion when placed atop an embryonic dune and exposed to waves. As such, our study provides information for beach managers on the physical benefits of sargassum to beach-dune ecosystems.
We also document the effects of wind and run-up on dune vegetation. We tested common dune plants in a wind tunnel and wave flume and measured the effects with a custom-built force sensor. We found that wind caused relatively constant forces over time whereas run-up produced more varied forces. Additionally, plants were affected differently by wind and run-up depending on their morphology. These results have important implications for the persistence of coastal vegetation under a changing disturbance regime and give insight to a possible evolutionary trajectory of dune plants based on their cross-shore location.
Finally, we demonstrate a complex role for vegetation in the process of storm-induced dune erosion. We performed a near prototype-scale laboratory experiment on a vegetated dune and a bare dune and found that the cumulative erosion rate and total erosional volume of the vegetated dune was greater than that of the bare dune. Additionally, our results showed that vegetation induced scarp formation more quickly and caused a deeper scarp. Vegetation initiated the formation of relatively steep microslopes, which then fed back with wave scouring processes to induce still steeper slopes, cascading into more erosion over time
Environmental Processes, Social Perspectives and Economic Valuations of the Coast
Get PDFCoastal ecosystems provide important resources for social, economic and environmental capital to global and local communities. Socially, coastal ecosystems provide a place for people to recreate and get in touch with nature. Economically, tourism, fisheries, and businesses are dependent upon coastal resources. Environmentally, coasts provide habitat for diverse species of flora and fauna, and protection for watersheds and anthropogenic structures.
This research investigates three studies in order to provide information on social, economic and environmental issues in Matagorda, Texas. The first study uses LIDAR (Light Image Detection-and-Ranging) scanning, a remote sensing methodology that uses laser pulses to collect X, Y, and Z coordinates, to evaluate coastal changes after Hurricane Ike. Results suggest that landscape loss occurs immediately after the hurricane, but recovers and fluctuates throughout the year. Also, different areas of the dunes show unique changes during different times of the year.
The second study uses questionnaire surveys to collect demographic, social perspectives and opinions and economic information about coastal users on Matagorda Peninsula. The questionnaire investigates the most important characteristics to beach users, opinions and perceptions about beach safety, activities, maintenance and presence of seaweed, information about their trip, cost of their trip and demographics. The results provide broader knowledge about the beach users in Matagorda and indicate that while direct costs of using the beach are minimal, the indirect and intrinsic costs are much higher which result in a greater overall use value.
The third study investigates the use of the sargassum, a natural marine subsidy, as a fertilizer for dune plants. Beach raking provides a cleaner, more aesthetically pleasing experience for beach users but alters the natural design of the ecosystem by subsequently moving sand, nutrients, subsidies for habitat and fauna from the fore-beach to the dunes. Results show that sargassum does have potential as a natural fertilizer as it did not negatively affect any of the species. The results could be used to alter management practices in order to capitalize on this natural resource while still providing a clean sandy beach for recreationalists.
These three studies together provide ecological information about coastal functions and processes that can help in creating broad holistic science based management strategies
Postfledging Survival and Movements of Willow and Dusky Flycatchers in the Central Sierra Nevada
Get PDFUnderstanding factors limiting population growth is critical for species exhibiting declining populations. Reproductive success has an important effect on population dynamics; however, our ability to accurately estimate productivity is limited. Studies on avian breeding biology have focused on nest survival; however, surviving to fledging does not ensure survival to the end of the breeding season. Furthermore, our understanding of habitat selection by birds based on the nesting cycle may not adequately represent the breeding habitat requirements because habitat use often changes after the young leave the nest. My goal was to examine the postfledging dependence period of two flycatcher species in the central Sierra Nevada: the California state endangered willow flycatcher (Empidonax traillii) and the dusky flycatcher (E. oberholseri). My focus was to estimate fledgling survival and examine factors that influence survival, evaluate postfledging movements and habitat use, and estimate post-breeding home range sizes of postfledging flycatchers. I monitored nests of both flycatcher species, individually color banded nestlings, and observed family groups daily once the young fledged. Flycatcher fledgling survival ranged from 46 percent to 76 percent and varied by year and species. Survival was lowest during the first week of the postfledging dependence period for both species. Fledgling flycatchers moved on average ~45m per day during the dependence period. I detected family groups in the natal meadows from 13 to 33 days. I detected willow flycatchers in riparian shrub vegetation 94 percent of the time, with the remaining detections being along the upland forest edge. Dusky flycatchers were more likely to use upland forest vegetation after leaving the nest, as I detected them in riparian shrub vegetation 70 percent of the time. For both years combined, mean 95 percwnt home range sizes were 1.80 �� 1.44 ha for willow flycatchers and 1.82 �� 1.70 ha for dusky flycatchers. Mean 50 percent core areas were 0.33 �� 0.27 ha for willow flycatchers and 0.38 �� 0.44 ha for dusky flycatchers. My results suggest that using fledgling survival throughout the dependence period to assess reproductive output is more accurate than using nesting data alone. Furthermore, postfledging family groups used a larger area of habitat than what is typically estimated from territory mapping singing males. Future research should continue to stress the importance of gaining knowledge about the postfledging period, especially for species with declining populations
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