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

Assemblages of breeding birds as indicators of grassland condition

We developed a measure of biological integrity for grasslands (GI) based on the most influential habitat types in the Prairie Pothole Region of North Dakota. GI is based on proportions of habitat types and the relationships of these habitat types to breeding birds. Habitat types were identified by digital aerial photography, verified on the ground, and quantified using GIS. We then developed an index to GI based on the presence or abundance of breeding bird species. Species abundance data were obtained from 3 min roadside point counts at 889 points in 44, 4050 ha study plots over a 2-year period. Using a modified North American Breeding Bird Survey protocol, species were recorded in each of four quadrants at each point. Fifty species selected for analysis included all grassland species that occurred in at least 15 quadrants and all other bird species that occurred in at least 1% of quadrants. We constructed preliminary models using data from each of the 2 years, then tested their predictive ability by cross-validation with data from the other year. These cross-validation tests indicated that the index consistently predicted grassland integrity. The final four models (presence and abundance models at 200 and 400 m scales) included only those species that were statistically significant (P ≤ 0.05) in all preliminary models. Finally, we interpreted the components of the indices by examining associations between individual species and habitat types. Logistic regression identified 386 statistically significant relationships between species and habitat types at 200 and 400 m scales. This method, though labor-intensive, successfully uses the presence of grassland-dependent species and absence of species associated with woody vegetation or cropland to provide an index to grassland integrity. Once regional associations of species with habitat types have been identified, such indices can be applied relatively inexpensively to monitor grassland integrity over large geographic areas. Indices like the ones presented here could be applied widely using bird abundance data that are currently being collected across the United States and southern Canada through the North American Breeding Bird Survey