Estimating offsets for avian displacement effects of anthropogenic impacts

Biodiversity offsetting, or compensatory mitigation, is increasingly being used in temperate grassland ecosystems to compensate for unavoidable environmental damage from anthropogenic developments such as transportation infrastructure, urbanization, and energy development. Pursuit of energy independence in the United States will expand domestic energy production. Concurrent with this increased growth is increased disruption to wildlife habitats, including avian displacement from suitable breeding habitat. Recent studies at energy-extraction and energy-generation facilities have provided evidence for behavioral avoidance and thus reduced use of habitat by breeding waterfowl and grassland birds in the vicinity of energy infrastructure. To quantify and compensate for this loss in value of avian breeding habitat, it is necessary to determine a biologically based currency so that the sufficiency of offsets in terms of biological equivalent value can be obtained. We describe a method for quantifying the amount of habitat needed to provide equivalent biological value for avifauna displaced by energy and transportation infrastructure, based on the ability to define five metrics: impact distance, impact area, pre-impact density, percent displacement, and offset density. We calculate percent displacement values for breeding waterfowl and grassland birds and demonstrate the applicability of our avian-impact offset method using examples for wind and oil infrastructure. We also apply our method to an example in which the biological value of the offset habitat is similar to the impacted habitat, based on similarity in habitat type (e.g., native prairie), geographical location, land use, and landscape composition, as well as to an example in which the biological value of the offset habitat is dissimilar to the impacted habitat. We provide a worksheet that informs potential users how to apply our method to their specific developments and a framework for developing decision-support tools aimed at achieving landscape-level conservation goals

Rising from the Sea: Correlations between Sulfated Polysaccharides and Salinity in Plants

High salinity soils inhibit crop production worldwide and represent a serious agricultural problem. To meet our ever-increasing demand for food, it is essential to understand and engineer salt-resistant crops. In this study, we evaluated the occurrence and function of sulfated polysaccharides in plants. Although ubiquitously present in marine algae, the presence of sulfated polysaccharides among the species tested was restricted to halophytes, suggesting a possible correlation with salt stress or resistance. To test this hypothesis, sulfated polysaccharides from plants artificially and naturally exposed to different salinities were analyzed. Our results revealed that the sulfated polysaccharide concentration, as well as the degree to which these compounds were sulfated in halophytic species, were positively correlated with salinity. We found that sulfated polysaccharides produced by Ruppia maritima Loisel disappeared when the plant was cultivated in the absence of salt. However, subjecting the glycophyte Oryza sativa Linnaeus to salt stress did not induce the biosynthesis of sulfated polysaccharides but increased the concentration of the carboxylated polysaccharides; this finding suggests that negatively charged cell wall polysaccharides might play a role in coping with salt stress. These data suggest that the presence of sulfated polysaccharides in plants is an adaptation to high salt environments, which may have been conserved during plant evolution from marine green algae. Our results address a practical biological concept; additionally, we suggest future strategies that may be beneficial when engineering salt-resistant crops

A Historical Perspective: Changes in Grassland Breeding Bird Densities Within Major Habitats in North Dakota Between 1967 and 1992-1993

Population declines of many grassland-nesting birds are now widely recognized. Fundamental to understanding these declines is knowing if they are caused by changes in the availability of suitable habitats or changes in the densities of birds within those habitats. We address that issue with information from systematic surveys of breeding birds throughout North Dakota in 1967, 1992, and 1993. We compared the availability of 8 major habitat types, and the densities of 24 species of grassland birds in each habitat type, for 128 randomly selected quarter-sections (64.7 ha or 160 ac) that were surveyed in each of those years. Between 1967 and 1992-1993, the area of cropland, planted cover, woody vegetation, and other habitats increased in the 128 quarter-sections, whereas the area of grassland, hayland, and wetland habitats declined. Our results are mixed concerning patterns of population change within habitats, which primarily reflect the disparate habitat requirements of individual species. Some species increased in density in 1 habitat between the 2 periods (e.g., horned lark [Eremophila alpestris] in grassland), whereas others declined in that same habitat (e.g., western meadowlark [Sturnella neglecta]). Other species (e.g., lark bunting [Calamospiza melanocorys]) declined in densities in 1 habitat but increased in another. Some species declined (e.g., Baird’s sparrow [Ammodramus bairdii]) or increased (e.g., northern harrier [Circus cyaneus]) in 1 or more habitats but their statewide populations were stable between the 2 periods; whereas other species were relatively stable within habitats but their statewide populations increased (e.g., upland sandpiper [Bartramia longicauda]) or declined (e.g., Le Conte’s sparrow [Ammodramus leconteii]). Nonetheless, our results provide evidence that populations of some species have declined on their breeding grounds in North Dakota. The disparate habitat requirements of grassland birds emphasize the importance of large-scale conservation efforts for grassland birds, especially those efforts that can provide a complex mixture of vegetation or habitat types

Digestive plasticity in Mallard ducks modulates dispersal probabilities of aquatic plants and crustaceans

1. The consequences of plastic responses of the avian digestive tract for the potential of birds to disperse other organisms remain largely uninvestigated. 2. To explore how a seasonal diet switch in Mallard (Anas platyrhynchos L.) influences their potential to disperse plants and invertebrates, we recorded the retention time of markers, following exposure to two diets of contrasting digestibility (trout chow vs seeds). 3. We then recorded the retrieval and germination of Fennel Pondweed (Potamogeton pectinatus L.) seeds and Brine Shrimp (Artemia franciscana Kellogg) cysts ingested by the same birds. 4. Gut passage rates of markers were increasingly longer in birds on the seed-based, high-fibre diet and shorter in birds on the animal-based, low-fibre one. 5. Propagule digestibility, and thus survival to gut passage, differed between diet groups, with more seeds and fewer cysts retrieved from ducks on the animal-based diet. Germination decreased with retention time, but was not affected by diet. 6. Differences in passage rates of markers but not of seeds and cysts suggest no change in dispersal distances of plants and invertebrates between seasons, while differences in digestibility would affect the numbers of propagules dispersed. [KEYWORDS: Artemia franciscana ; diet switch ; endozoochorous dispersal ; Potamogeton pectinatus]