Paying the Extinction Debt in Southern Wisconsin Forest Understories

Abstract: The lack of long‐term baseline data restricts the ability to measure changes in biological diversity directly and to determine its cause. This hampers conservation efforts and limits testing of basic tenets of ecology and conservation biology. We used a historical baseline survey to track shifts in the abundance and distribution of 296 native understory species across 82 sites over 55 years in the fragmented forests of southern Wisconsin. We resurveyed stands first surveyed in the early 1950s to evaluate the influence of patch size and surrounding land cover on shifts in native plant richness and heterogeneity and to evaluate changes in the relative importance of local site conditions versus the surrounding landscape context as drivers of community composition and structure. Larger forests and those with more surrounding forest cover lost fewer species, were more likely to recruit new species, and had lower rates of homogenization than smaller forests in more fragmented landscapes. Nearby urbanization further reduced both alpha and beta understory diversity. Similarly, understory composition depended strongly on local site conditions in the original survey but only weakly reflected the surrounding landscape composition. By 2005, however, the relative importance of these factors had reversed such that the surrounding landscape structure is now a much better predictor of understory composition than are local site conditions. Collectively, these results strongly support the idea that larger intact habitat patches and landscapes better sustain native species diversity and demonstrate that humans play an increasingly important role in driving patterns of native species diversity and community composition.     

Variation in Physiological Stress between Bridge‐ and Cave‐Roosting Brazilian Free‐Tailed Bats

Abstract: Since the late 1980s, Brazilian free‐tailed bats (Tadarida brasiliensis) have increasingly used bridges as roosts in the southern United States. We examined differences in blood cortisol levels, body condition, and parasite load, as measures of physiological stress in bats roosting in bridges and bats roosting in caves. We collected data during three periods, coinciding with female phases of reproduction. For all measures, bats were captured during the nightly emergence from the roost and immediately sampled. Cortisol levels were significantly higher during pregnancy and lactation and in individuals with lower body‐condition scores (length of forearm to mass ratio) and significantly higher in bats roosting in caves than in those roosting in bridges. Thus, we concluded that individuals of this species that roost in bridges are not chronically stressed and seem to be unaffected by human activities present at bridges. This is a rare documented instance where a human‐dominated environment does not appear to be adversely affecting the physiological health of a free‐ranging animal.     

Economic and Social Dimensions of Environmental Behavior: Balancing Conservation and Development in Bhutan

Abstract: One of the primary approaches to environmental conservation emphasizes economic development. This conservation‐and‐development approach often ignores how development affects sociocultural characteristics that may motivate environmental behaviors (actions that actively benefit or limit one's negative impacts on the environment). Evolutionary anthropologists espouse a theoretical perspective that supports the conservation‐and‐development approach. Others believe sociocultural factors are the foundation of environmental behavior and worry that development will erode the values and norms that may shape such behavior. My research assistants and I surveyed 170 individuals from eight villages in two communities in Bhutan to explore whether economic (wealth, market integration) or social (religious behaviors, environmental values, social capital) factors are better indicators of environmental behavior. I used multilevel modeling to analyze use of fuelwood, use of agricultural chemicals, and tree planting, and to determine whether social norms were associated with these behaviors. Although economic factors were more often associated with these behaviors than social factors, local conditions and control variables were the best indicators of behaviors. Furthermore, economic factors were not always associated with positive environmental outcomes. Instead, farmers attempted to make the best economic decisions given their circumstances rather than seeking to conserve resources. Although religion was not a strong predictor of any of the behaviors I examined, I found evidence that the understanding of Buddhist philosophy is growing, which suggests that social factors may play a more prominent role as Bhutan's development progresses. My results highlight the need for conservation planners to be aware of local conditions when planning and implementing policies aimed at motivating environmental behaviors and that economic and social motivations for conservation may not be mutually exclusive.     

Forecasting the Spread of Invasive Rainbow Smelt in the Laurentian Great Lakes Region of North America

Abstract:  Rainbow smelt ( Osmerus mordax ) have invaded many North American lakes, often resulting in the extirpation of native fish populations. Yet, their invasion is incipient and provides the rationale for identifying ecosystems likely to be invaded and where management and prevention efforts should be focused. To predict smelt presence and absence, we constructed a classification-tree model based on habitat data from 354 lakes in the native range for smelt in southern Maine. Maximum lake depth, lake area, and Secchi depth (surrogate measure of lake productivity) were the most important predictors. We then used our model to identify lakes vulnerable to invasion in three regions outside the smelt's native range: northern Maine (52 of 244 lakes in the non-native range), Ontario (4447 of 8110), and Wisconsin (553 of 5164). We further identified a subset of lakes with a strong potential for impact (potential–impact lakes) based on the presence of fish species that are affected by rainbow smelt. Ninety-four percent of vulnerable lakes in the non-native range in Maine are also potential–impact lakes, as are 94% and 58% of Ontario and Wisconsin's vulnerable lakes, respectively. Our modeling approach can be applied to other invaders and regions to identify invasion-prone ecosystems, thus aiding in the management of invasive species and the efficient allocation of invasive species mitigation and prevention resources.     

Recovery Trajectories After In Situ Burning of an Oiled Wetland in Coastal Louisiana,USA

The high degree of physical disturbance associated with conventional response options to oil spills in wetlands is driving the investigation of alternative cleanup methodologies. In March 1995, a spill of gas condensate in a brackish marsh at Rockefeller Wildlife Refuge in southwestern Louisiana was remediated through the use of in situ burning. An assessment of vegetation recovery was initiated in three treatment marshes: (1) oil-impacted and burned, (2) oil impacted and unburned, and (3) a nonoiled unburned reference. We compared percent cover, stem density, and biomass in the treatment marshes to define ecological recovery of the marsh vegetation and soil hydrocarbon content to determine the efficacy of in situ burning as a cleanup technique. Burning led to a rapid decrease in soil hydrocarbon concentrations in the impacted-and-burned marsh to background levels by the end of the first growing season. Although a management fire accidentally burned the oil-impacted-and-unburned and reference marshes in December 1995, stem density, live biomass, and total percent cover values in the oil-impacted-and-burned marsh were equivalent to those in the other treatment marshes after three years. In addition, plant community composition within the oil-impacted-and-burned marsh was similar to the codominant mix of the grasses Distichlis spicata (salt grass) and Spartina patens (wire grass) characteristic of the surrounding marsh after the same time period. Rapid recovery of the oil-impacted-and-unburned marsh was likely due to lower initial hydrocarbon exposure. Water levels inundating the soil surface of this grass-dominated marsh and the timing of the in situ burn early in the growing season were important factors contributing to the rapid recovery of this wetland. The results of this in situ burn evaluation support the conclusion that burning, under the proper conditions, can be relied upon as an effective cleanup response to hydrocarbon spills in herbaceous wetlands.     

Shifting Priorities at the Department of Energy's Bomb Factories: Protecting Human and Ecological Health

More than 50 years of research, development, manufacture, and testing of nuclear weapons at Department of Energy (DOE) sites has left a legacy of on-site contamination that often spreads to surrounding areas. Despite substantial cleanup budgets in the last decade, the DOE's top-to-bottom review team concluded that relatively little actual cleanup has been accomplished, although milestones have been met and work packages completed. Rather than solely use regulatory constraints to direct cleanup, many people have suggested that human and ecological health should guide long-term stewardship goals of DOE-managed sites. The main questions are how ecological and human health considerations should be applied in deciding the extent of cleanup that contaminated sites should receive and how near-term and longer run considerations of costs and benefits should be balanced as cleanup decisions are made. One effort to protect ecological integrity is the designation of the largest sites as National Environmental Research Parks (NERPs). Recently, the Competitive Enterprise Institute (CEI) suggested isolating and conserving DOE sites as a policy priority because of their rich ecological diversity. A more effective long-term stewardship approach for former nuclear weapons complex sites may emerge if the guiding principles are to (1) reduce risks to human and ecological health, (2) protect cultural traditions, and (3) lower short- and long-term cleanup and remediation costs. A “net benefits” perspective that takes both near- and longer-term costs and consequences into account can help illuminate the trade-offs between expensive cleanup in the near term and the need to assure long-term protection of human health, cultural values, and high levels of biodiversity and ecological integrity that currently exist at many DOE sites.