RESUMEN
Controlling invasive species is critical for conservation but can have unintended consequences for native species and divert resources away from other efforts. This dilemma occurs on a grand scale in the North American Great Lakes, where dams and culverts block tributary access to habitat of desirable fish species and are a lynchpin of long-standing efforts to limit ecological damage inflicted by the invasive, parasitic sea lamprey (Petromyzon marinus). Habitat restoration and sea-lamprey control create conflicting goals for managing aging infrastructure. We used optimization to minimize opportunity costs of habitat gains for 37 desirable migratory fishes that arose from restricting sea lamprey access (0-25% increase) when selecting barriers for removal under a limited budget (US$1-105 million). Imposing limits on sea lamprey habitat reduced gains in tributary access for desirable species by 15-50% relative to an unconstrained scenario. Additional investment to offset the effect of limiting sea-lamprey access resulted in high opportunity costs for 30 of 37 species (e.g., an additional US$20-80 million for lake sturgeon [Acipenser fulvescens]) and often required ≥5% increase in sea-lamprey access to identify barrier-removal solutions adhering to the budget and limiting access. Narrowly distributed species exhibited the highest opportunity costs but benefited more at less cost when small increases in sea-lamprey access were allowed. Our results illustrate the value of optimization in limiting opportunity costs when balancing invasion control against restoration benefits for diverse desirable species. Such trade-off analyses are essential to the restoration of connectivity within fragmented rivers without unleashing invaders.
Asunto(s)
Especies Introducidas , Petromyzon , Animales , Conservación de los Recursos Naturales , Peces , LagosRESUMEN
Growing energy demand has increased the need to manage conflicts between energy production and the environment. As an example, shale-gas extraction requires substantial surface infrastructure, which fragments habitats, erodes soils, degrades freshwater systems, and displaces rare species. Strategic planning of shale-gas infrastructure can reduce trade-offs between economic and environmental objectives, but the specific nature of these trade-offs is not known. We estimated the cost of avoiding impacts from land-use change on forests, wetlands, rare species, and streams from shale-energy development within leaseholds. We created software for optimally siting shale-gas surface infrastructure to minimize its environmental impacts at reasonable construction cost. We visually assessed sites before infrastructure optimization to test whether such inspection could be used to predict whether impacts could be avoided at the site. On average, up to 38% of aggregate environmental impacts of infrastructure could be avoided for 20% greater development costs by spatially optimizing infrastructure. However, we found trade-offs between environmental impacts and costs among sites. In visual inspections, we often distinguished between sites that could be developed to avoid impacts at relatively low cost (29%) and those that could not (20%). Reductions in a metric of aggregate environmental impact could be largely attributed to potential displacement of rare species, sedimentation, and forest fragmentation. Planners and regulators can estimate and use heterogeneous trade-offs among development sites to create industry-wide improvements in environmental performance and do so at reasonable costs by, for example, leveraging low-cost avoidance of impacts at some sites to offset others. This could require substantial effort, but the results and software we provide can facilitate the process.
Asunto(s)
Conservación de los Recursos Naturales , Bosques , Gas Natural , Ecosistema , Agua DulceRESUMEN
Hydraulic fracturing and related ground water issues are growing features in public discourse. Few have given much attention to surface impacts from shale gas development, which result from building necessary surface infrastructure. One way to reduce future impacts from gas surface development without radically changing industry practice is by formulating simple, conservation-oriented planning guidelines. We explore how four such guidelines affect the locations of well pads, access roads, and gathering pipelines on state lands in Pennsylvania. Our four guidelines aim to (1) reduce impacts on water, reduce impacts from (2) gathering pipelines and (3) access roads, and (4) reduce impacts on forests. We assessed whether the use of such guidelines accompanies tradeoffs among impacts, and if any guidelines perform better than others at avoiding impacts. We find that impacts are mostly synergistic, such that avoiding one impact will result in avoiding others. However, we found that avoiding forest fragmentation may result in increased impacts on other environmental features. We also found that single simple planning guidelines can be effective in targeted situations, but no one guideline was universally optimal in avoiding all impacts. As such, we suggest that when multiple environmental features are important in an area, more comprehensive planning strategies and tools should be used.