Date of Award

5-2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Wildlife and Fisheries Biology

Advisor

Dr. Kyle Barrett

Committee Member

Dr. Patrick Jodice

Committee Member

Dr. Yoichiro Kanno

Abstract

Global wetland degradation and loss is occurring at a rapid rate, and in the United States over 50% of wetlands in the lower 48 states have been altered since European settlement. In some cases, wetlands that were historically transformed for agriculture are now managed as wetland habitat. We conducted occupancy surveys for black rails (Latterallus jamaicensis) in managed and unmanaged areas of coastal South Carolina. We modeled landscape and local factors potentially influencing occupancy and we assessed whether these habitat associations indicated vulnerability following expected alterations from sea level rise. Black rails occupied 17 of 344 sites surveyed. Landscape factors had the strongest influence on black rail occupancy. Occupancy was significantly associated with impounded marshes, increasing distance to forest, and greater proportion of marsh landscape within a 200 m buffer. We mapped parameters from our top-ranked model to predict the amount of current and future suitable habitat under various sea level rise scenarios at Bear Island Wildlife Management Area, a black rail hotspot. Suitable habitat decreases in tidal marshes but increases in impounded areas. The current use of impoundments by black rails could represent a new management strategy for mitigating the loss of black rail habitat. However, assessing vulnerability is often difficult because predictions made in space or time may not always hold up. Therefore we evaluated how well species-habitat models derived in one locale would transfer to another in an effort to promote effective species-habitat conservation across a region (between states).

Species distribution models have been applied across a wide range of spatial scales to generate information for conservation planning. But the generality of these models has rarely been tested. When transferability of models is evaluated it is typically done using occurrence data. However, we assess model transferability in coastal tidal marshes of the Southeastern United States using point counts of a widespread marsh bird: the clapper rail (Rallus longirostris). We first derived the top species-habitat models at a state-level in both South Carolina and Georgia, and then assessed how well top models from each state predicted abundances across the region (between states). Internally (locally) validated models exhibited reasonable fit and high significance; however, during the independent model validation process (between states) both models performed poorly. We discuss potential reasons model transferability was not successful and address the need for better regional datasets and further studies addressing issues associated with transferability.

Overall, coastal wetlands are some of the world's most productive and ecologically valuable habitats but they remain greatly disturbed. Understanding the influence potential disturbances, such as sea level rise and development, will have on wildlife species is critical toward helping to promote effective conservation of coastal ecosystems.

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Biology Commons

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