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Premise: The ecological implications of hyperaccumulation have been investigated at the organismal level, but are poorly understood at the plant community level. Questions addressed here were: Does the presence of selenium (Se) hyperaccumulators affect Se distribution and concentration in their native soil, and do hyperaccumulators affect overall vegetation properties and species composition? Methods: Plant survey and soil Se mapping were performed at three seleniferous sites in Colorado. In season one, plots with and without hyperaccumulators were compared for (1) bare ground, canopy cover, and species richness; (2) relative species abundance; (3) soil Se distribution and concentration. In season two, a smaller‐scale design was implemented, focusing on areas 3 m in diameter around hyperaccumulators versus nonhyperaccumulators in 44 paired plots on one site. Results: Plots with hyperaccumulators generally showed more bare ground, less canopy cover, higher species richness, and 2–3‐fold higher soil Se levels. These patterns were not consistently significant across all sites; the effects of hyperaccumulators may have been diluted by their low abundance and the relatively large area of survey. In the smaller‐scale study, highly significant results were obtained, showing more bare ground, less canopy cover, and higher species richness in plots with hyperaccumulators; soil Se concentration was also higher in plots with hyperaccumulators. Conclusions: Hyperaccumulators may significantly affect local soil Se concentration and vegetation over at least a 3 m diameter area, or 4× their canopy. These differences may result from the combined positive and negative allelopathic effects observed earlier at the organismal level. [ABSTRACT FROM AUTHOR]

Populations of pronghorn (Antilocapra americana) are subjected to multiple forms of density-dependent and density-independent regulation. Little is known about the combined effects of these variables across multiple populations throughout the landscape. The objectives of this study were to examine long-term trends in density and recruitment in pronghorn and to assess how different forms of regulation influence these trends. We used multiple density-dependent and density-independent explanatory variables in a model selection process to explain variation in pronghorn density and July fawn : doe ratios from 1955 to 1993 in 4 pronghorn management units in Nebraska. We also investigated levels of density-dependent feedback in each management unit. Examination of long-term population trends suggested that pronghorn populations in Nebraska exhibited an Allee effect (inverse density dependence), in which population growth decreases as density decreases. We suggest that variation in rangeland condition and presence of adequate forage could explain the presence of the Allee effect. Both density-dependent and density-independent variables affected pronghorn populations, with density of cattle, spring precipitation, abundance of winter wheat, and hunting harvest most important for explaining fluctuations in pronghorn densities. Snow depth and density of cattle best explained yearly July fawn : doe ratios. The importance of each factor was variable across the different management units. Management objectives aimed at improving access to and abundance of food resources during times when rangeland condition is poor could prevent drastic declines in pronghorn populations. [ABSTRACT FROM AUTHOR]

In Defenders of Wildlife v. Chertoff, the D.C. District Court upheld the constitutionality of an extraordinarily broad waiver provision in the REAL I.D. Act of 2005. That provision, section 102, allows the Secretary of Homeland Security to waive all laws he deems necessary to ensure expeditious construction of border fencing along the United States-Mexico border. While Defenders of Wildlife confirms the legality of waiver provisions like section 102, it also raises the interesting question of what drives legislative decision- making in the face of uncertainty. Behavioral science research shows that in the post-9/1 1 world, our ability to objectively perceive risk is altered by our knowledge of terrorist attacks and by our exposure to media coverage of the terrorist threat the United States faces. This diminished ability to objectively perceive risk can negatively affect the deliberative process when Congress must legislate around uncertain risks, like the risk of environmental harm and the risk of future terrorist attacks. I consider several options that might minimize the effect of this phenomenon on the crafting of legislation, including the creation of a standing risk assessment council, the inclusion of traditional waiver provision elements that limit the effects of potentially irrational legislative behavior, and drafting legislation that requires waiver-invoking officials to accurately characterize the risks to be considered. [ABSTRACT FROM AUTHOR]