The extensive development of surface and subsurface drainage systems to facilitate agricultural production throughout North America has significantly altered the hydrology of landscapes compared to historical conditions. Drainage has transformed nutrient and hydrologic dynamics, structure, function, quantity, and configuration of stream and wetland ecosystems. In many agricultural regions, more than 80% of some catchment basins may be drained by surface ditches and subsurface drain pipes (tiles). Natural channels have been straightened and deepened for surface drainage ditches with significant effects on channel morphology, instream habitats for aquatic organisms, floodplain and riparian connectivity, sediment dynamics, and nutrient cycling. The connection of formerly isolated wetland basins to extensive networks of surface drainage and the construction of main channel ditches through millions of acres of formerly low-lying marsh or wet prairie, where no defined channel may have previously existed, have r...

Effects of Agricultural Drainage on Aquatic Ecosystems: A Review

Road mortality is suspected to have contributed to widespread population declines in turtles in the United States, a country with exceptionally high turtle diversity. We examined the issue through a modeling study that integrated road maps and traffic-volume data with simulated movements of (1) small-bodied pond turtles, (2) large-bodied pond turtles, and (3) terrestrial and semiterrestrial ("land") turtles. Our model predicted that road networks typical of the northeastern, southeastern, and central regions have the potential to limit land-turtle populations and, to a lesser extent, populations of large-bodied pond turtles. Nowhere are populations of small-bodied pond turtles likely threatened regionally by road mortality. We conclude that the demographic traits of some turtles, in combination with their mobility, may jeopardize population persistence within road networks typical of the eastern and central United States.

Estimating the effects of road mortality on turtle populations

Geographically isolated wetlands (GIWs), those surrounded by uplands, exchange materials, energy, and organisms with other elements in hydrological and habitat networks, contributing to landscape functions, such as flow generation, nutrient and sediment retention, and biodiversity support. GIWs constitute most of the wetlands in many North American landscapes, provide a disproportionately large fraction of wetland edges where many functions are enhanced, and form complexes with other water bodies to create spatial and temporal heterogeneity in the timing, flow paths, and magnitude of network connectivity. These attributes signal a critical role for GIWs in sustaining a portfolio of landscape functions, but legal protections remain weak despite preferential loss from many landscapes. GIWs lack persistent surface water connections, but this condition does not imply the absence of hydrological, biogeochemical, and biological exchanges with nearby and downstream waters. Although hydrological and biogeochemical connectivity is often episodic or slow (e.g., via groundwater), hydrologic continuity and limited evaporative solute enrichment suggest both flow generation and solute and sediment retention. Similarly, whereas biological connectivity usually requires overland dispersal, numerous organisms, including many rare or threatened species, use both GIWs and downstream waters at different times or life stages, suggesting that GIWs are critical elements of landscape habitat mosaics. Indeed, weaker hydrologic connectivity with downstream waters and constrained biological connectivity with other landscape elements are precisely what enhances some GIW functions and enables others. Based on analysis of wetland geography and synthesis of wetland functions, we argue that sustaining landscape functions requires conserving the entire continuum of wetland connectivity, including GIWs.

/pdf/do-geographically-isolated-wetlands-influence-landscape-1d677pqe1c.pdf

Do geographically isolated wetlands influence landscape functions

Roads built through or near wetlands cause significant mortality of reptiles and amphibians and create barriers to migration and dispersal. I investigated the number of times turtles and other herpetofauna attempted to cross a 4-lane highway at Lake Jackson, Florida, USA, during a period of severe drought (Feb–Apr 2000). Levels of road mortality were so high that I designed and installed a temporary drift fence system to work with an existing drainage culvert and for the next 2.5 years I evaluated its effectiveness at reducing road mortality and facilitating migration. I monitored roads and fences several times per day for 44 months, during both drought and non-drought conditions. A total of 10,229 reptiles and amphibians of 44 species were found either road killed or alive behind drift fences: 8,842 turtles, 838 frogs, 363 snakes, 152 lizards, 32 alligators, and 2 salamanders. Drift fences combined with intensive monitoring greatly reduced turtle road kills and facilitated the use of an under-highway culvert. Along a 0.7-km section of the highway, turtle mortality before installation of the fence (11.9/km/day) was significantly greater than post-fence mortality (0.09/km/day) and only 84 of 8,475 turtles climbed or penetrated the drift fences. Pre-fence data provided strong evidence that turtles cannot successfully cross all 4 lanes of U.S. Highway 27, as 95% of 343 turtles were killed as they first entered the highway adjacent to the shoulder and the remaining 5% were killed in the first two traffic lanes. According to a probability model, the likelihood of a turtle successfully crossing U.S. Highway 27 decreased from 32% in 1977 to only 2% in 2001 due to a 162% increase in traffic volume. Therefore, at least 98% of turtles diverted by the fences probably would have been killed if fences were not in place. The results of this study represent the highest attempted road-crossing rate ever published for turtles (1,263/km/year). Because of demographic and life history constraints, turtle populations may incur irreversible declines in areas where road mortality is high, especially when mass migrations are triggered by periods of drought.

/pdf/mitigation-measures-to-reduce-highway-mortality-of-turtles-3kjgv11zia.pdf

Mitigation measures to reduce highway mortality of turtles and other herpetofauna at a north florida lake

The effect of sex-specific terrestrial movements and roads on the sex ratio of freshwater turtles

We investigated the habitat use and movements of two turtle species to assess the importance of conserving multiple wetlands and the upland matrix in which they occur. Spotted turtles ( Clemmys guttata) and Blanding's turtles (  Emydoidea blandingii) are considered threatened and endangered, respectively, in Maine where they are near the northeastern periphery of their geographic range. We used resightings of marked individuals (69 spotted, 16 Blanding's) and radiotelemetry (13 spotted, 9 Blanding's, radiotagged for one or two seasons) to investigate the movements and habitat use of both species. Individuals of both species used multiple wetlands throughout the year, including permanent and seasonal pools, forested swamps, and wet meadows. Pools occupied by spotted and Blanding's turtles were small (<0.4 ha), and they were less isolated from other wetlands than pools that did not contain turtles. Both species used uplands extensively for nesting, dormancy, and traveling between wetlands. Turtles traveled 70–570 m (spotted) and 100–1620 m ( Blanding's) to nest, and nests were located 1–120 m (spotted) and 70–410 m ( Blanding's) from the nearest wetland. Spotted and Blanding's turtles entered relatively dormant stages for 15–89 and 3–21 consecutive days, respectively, and upland dormancy sites were 12–80 m (spotted) and 30–110 m ( Blanding's) from the nearest wetland. Total distance traveled overland throughout a season was 0–1680 m and 0–6760 m for radiotagged spotted and Blanding's turtles, respectively. Most spotted turtles followed a seasonal pattern of habitat use: pools for spring activity, upland forest for relative dormancy during part of the summer, and wet meadows or forested swamps for overwintering. A seasonal pattern in the habitat use of Blanding's turtles was not as evident. Our study suggests that protecting small wetlands, maintaining generous terrestrial buffers around individual wetlands, and conserving wetlands in groups are important components of a landscape approach to species conservation.




Resumen: Investigamos el uso de habitat y los movimientos de dos especies de tortugas para evaluar la importancia de conservar multiples humedales y la matriz terrestre en la que ocurren. Tortugas manchadas (Clemmys guttata) y tortugas de Blanding (  Emydoidea blandingii) estan consideradas como amenazadas y en peligro, respectivamente, en Maine donde se encuentran cerca de la periferia noreste de su rango geografico. Utilizamos reavistamientos de individuos marcados (69 manchadas, 16 de Blanding ) y radiotelemetria (13 manchadas, 9 de Blanding, radiomarcadas por 1-2 temporadas) para investigar los movimientos y uso de habitat de ambas especies. Los individuos de ambas especies utilizaron multiples humedales a lo largo del ano incluyendo charcas permanentes y temporales, cienagas boscosas y praderas inundadas. Las charcas ocupadas por tortugas manchadas y de Blanding fueron pequenas (<4 ha), y estaban menos aisladas de los demas humedales que no contenian tortugas. Ambas especies usaron terrenos elevados extensivamente para anidar, para los periodos de aletargamiento, para moverse entre humedales. Las tortugas viajaron entre 50 y 570 m (manchadas) y entre 100 y 1620 m (de Blanding ) para anidar, y los nidos se localizaron entre 1 y 120 m (manchadas) y entre 70 y 410 m (de Blanding ) del humedal mas cercano. Las tortugas manchadas y de Blanding entraron en etapas relativo de letargo por 15-89 y 3-21 dias consecutivos, respectivamente, y los sitios de letargo estaban entre 12 y 80 m (manchadas) y 30 y 110 m (de Blanding  ) del humedal mas cercano. La distancia total recorrida en tierra en una temporada vario entre 0 y 1680 m y entre 0 y 6760 m para las tortugas manchadas y de Blanding radiomarcadas respectivamente. La mayoria de las tortugas manchadas tuvieron un patron estacional de uso del habitat: charcas para la actividad de primavera, bosque elevado cuando la etapa en letargo la etapa de lefargo relativo durante parte del verano y praderas inundadas o cienagas boscosas durante el invierno. En los movimientos de la tortuga de Blanding no fue evidente un patron estacional de uso de habitat. Nuestro estudio sugiere que la proteccion de humedales pequenos, la presencia de amortiguadores terrestres alrededor de los humedales y la conservacion de humedales en grupos son componentes importantes de una aproximacion de paisaje a la conservacion de especies.

Landscape Ecology Approaches to Wetland Species Conservation: a Case Study of Two Turtle Species in Southern Maine

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Landscape Ecology Approaches to Wetland Species Conservation: a Case Study of Two Turtle Species in Southern Maine