Differences among model simulations of climate change on the scale of resource regions

The climate simulations from atmospheric general circulation models (GCMs) are often used to analyze the potential effects of climate change on environmental resources. It has been demonstrated that there are differences among the simulations from various GCMs, on spatial scales ranging from global to regional. This paper quantifies the differences in temperature and precipitation simulated by three major GCMs for four specific regions: an agricultural region (the North American winter wheat belt), a hydrologic region (the Great Basin), a demographic region (the high-density population corridor of the northeast United States), and a political region (the state of Texas). Both the current (control) climate and the climatic response to a doubling of atmospheric carbon dioxide (CO₂) are consideredIn each region, even when the data are averaged on a seasonal basis, marked differences occurred in the areal average climate simulated by the different GCMs for both the control climate and the doubled-CO₂ climate. Thus, climate impact studies based on the simulations of more than one GCM could easily yield a range of possible results     

Synthesizing habitat connectivity analyses of a globally important human-dominated tiger-conservation landscape

As ecological data and associated analyses become more widely available, synthesizing results for effective communication with stakeholders is essential. In the case of wildlife corridors, managers in human-dominated landscapes need to identify both the locations of corridors and multiple stakeholders for effective oversight. We synthesized five independent studies of tiger (Panthera tigris) connectivity in central India, a global priority landscape for tiger conservation, to quantify agreement on landscape permeability for tiger movement and potential movement pathways. We used the latter analysis to identify connectivity areas on which studies agreed and stakeholders associated with these areas to determine relevant participants in corridor management. Three or more of the five studies’ resistance layers agreed in 63% of the study area. Areas in which all studies agree on resistance were of primarily low (66%, e.g., forest) and high (24%, e.g., urban) resistance. Agreement was lower in intermediate resistance areas (e.g., agriculture). Despite these differences, the studies largely agreed on areas with high levels of potential movement: >40% of high average (top 20%) current-flow pixels were also in the top 20% of current-flow agreement pixels (measured by low variation), indicating consensus connectivity areas (CCAs) as conservation priorities. Roughly 70% of the CCAs fell within village administrative boundaries, and 100% overlapped forest department management boundaries, suggesting that people live and use forests within these priority areas. Over 16% of total CCAs’ area was within 1 km of linear infrastructure (437 road, 170 railway, 179 transmission line, and 339 canal crossings; 105 mines within 1 km of CCAs). In 2019, 78% of forest land diversions for infrastructure and mining in Madhya Pradesh (which comprises most of the study region) took place in districts with CCAs. Acute competition for land in this landscape with globally important wildlife corridors calls for an effective comanagement strategy involving local communities, forest departments, and infrastructure planners.     

Coupling PCSWMM and WASP to Evaluate Green Stormwater Infrastructure Impacts to Storm Sediment Loads in an Urban Watershed

We coupled rainfall–runoff and instream water quality models to evaluate total suspended solids (TSS) in Wissahickon Creek, a mid‐sized urban stream near Philadelphia, Pennsylvania. Using stormwater runoff and instream field data, we calibrated the model at a subdaily scale and focused on storm responses. We demonstrate that treating event mean concentrations as a calibration parameter rather than a fixed input can substantially improve model performance. Urban stormwater TSS concentrations vary widely in time and space and are difficult to represent simply. Suspended and deposited sediment pose independent stressors to stream biota and model results suggest that both currently impair stream health in Wissahickon Creek. Retrofitting existing detention basins to prioritize infiltration reduced instream TSS loads by 20%, suggesting that infiltration mitigates sediment more effectively than detention. Infiltrating stormwater from 30% of the watershed reduced instream TSS loads by 47% and cut the frequency of TSS exceeding 100 mg/L by half. Settled loads and the frequency of high TSS values were reduced by a smaller fraction than suspended loads and duration at high TSS values. A widely distributed network of infiltration‐focused projects is an effective stormwater management strategy to mitigate sediment stress. Coupling rainfall–runoff and water quality models is an important way to integrate watershed‐wide impacts and evaluate how management directly affects urban stream health.     

Effects of geothermal effluents on aquatic ecosystems

The use of geothermal energy for electrical generation and a variety of other purposes requires the handling and disposal of large volumes of geothermal fluids. These fluids contain constituents such as dissolved ammonia, hydrogen sulfide gas, and trace elements. Facilities in the United States are not expected to routinely discharge large volumes of toxic geothermal fluids. However, chronic effects on aquatic ecosystems are possible at concentrations where acute toxicity would be neither expected nor observed. Also, some trace elements may accumulate to hazardous levels in ecosystems, even when released at nontoxic concentrations.     

Negative effects of vertebrate herbivores on invertebrates in a coastal dune community

Although competition has been a major focus in ecology for the past century, most empirical and theoretical studies in this area have emphasized interactions between closely related species. However, there is growing evidence that negative interactions among distantly related taxa also occur and may be far more important than previously thought. In this study, we took advantage of an 11-year-old replicated vertebrate-exclosure experiment in a coastal dune community in northern California, USA, to examine the effects of the two most common vertebrate herbivores (jackrabbits and black-tailed deer) on the abundance of the three most visible invertebrate herbivores (two snail, a moth, and a grasshopper species). Our results indicate that four of the six possible pairwise interactions were significantly negative for the invertebrates. Jackrabbits reduced the abundances of snails by 44-75%, tiger moth caterpillars by 36%, and grasshoppers by 62%. Deer reduced the abundances of snails by 32%, increased the abundances of caterpillars by 31%, and had no measurable effect on grasshopper abundance. Our data also revealed that jackrabbits significantly decreased the volume of forbs and common shrubs and the flowering by grasses in our study plots. We were unable to detect an effect of deer on these measures of vegetation. These results suggest that by changing vegetation, jackrabbits may reduce invertebrate populations that are limited by food, protective structures, or microclimate provided by plants. Of these three mechanisms, only shade was strongly supported as limiting snail numbers in smaller-scale manipulations. In most systems, as in this one, the number of pairs of distantly related herbivores far exceeds the number of pairs of congeners. Since interactions among distantly related herbivores may be common in many cases, these interactions are likely to be important and should receive far more attention from ecologists.