Impacts Of Climate And Land Use Change On Fish Species Distributions In The Central United States

Species distribution models are useful tools that can be used to evaluate tradeoffs of management and conservation strategies under scenarios of environmental change. Modeling efforts for fish species have largely focused on cold-water, commercial, and recreationally-valued species, even though warm-water, non-game species have important roles in ecosystem services and processes. I developed species distribution models for fourteen warm-water fish species native to the Central United States and evaluated environmental drivers and predictive performance. I used an ensemble model approach produced by combining forecasts of five single-model techniques. Response plots and variable importance calculations were used to evaluate the influence of individual variables. The predictive performance of the ensemble models was assessed using area under the curve (AUC) of the receiver-operating characteristic plot. Ensemble model AUC values generally performed better than single-model types, suggesting ensemble models are more reliable and applicable for management purposes than single-models. Most models were influenced by a mix of climate, land use and geophysical variables; however, climate variables were the dominant environmental drivers across models. Next, I projected distribution responses of 14 warm-water fish species to climate and land use scenarios using the ensemble models combined with scenario analyses. I incorporated different time periods, greenhouse gas emissions scenarios, and general circulation models into the scenario analysis. I then tested the effect of climate change scenario and the incorporation of land use on range change. Although it has been hypothesized that warm-water fishes will generally benefit from future climate changes through range expansion, I found wide variability in range change across the species modeled. There was a significant effect of greenhouse gas scenario and year on overall range change for half of the species modeled. The incorporation of future land use projections into scenarios generally led to increased range expansion. I combined all scenarios into consensus projections to visualize range change projections across all scenarios. Some species expanded their range to the north and into higher elevations while other species were projected to lose significant portions of their range. For example, orangethroat darter ( Etheostoma spectabile ) is projected to gain between 30 to 90 percent new range and lose between 0 to 6 percent of its current range while bigmouth shiner (Hybopsis dorsalis ) is projected to gain between 0 to 20 percent new range and lose 75 to 100 percent of its current range. Variability in climate change responses across warm-water species may be a result of ecological traits, such as range size and fecundity. The variability in warm-water species' responses suggests management of these species can be informed through the use of species distribution modeling and scenario analysis.

This report indicates that climate change will significantly affect the availability and trade of fish products, especially for those countries most dependent on the sector, and calls for effective adaptation and mitigation actions encompassing food production.

Global changes, including climate change and intensive fishing, are having significant impacts on the world's oceans. This book advances knowledge of the structure and functioning of marine ecosystems and their major sub-systems, and how they respond to physical forcing.

Freshwaters ecosystems support extraordinary biodiversity relative to their extent and provide important societal benefits. As such, freshwater environments and biota are often heavily impacted by anthropogenic activities. Freshwater fishes in Mediterranean-climate regions are especially impacted because of large human populations in these regions and extensive agricultural production, extensive river modification for flood control and to meet societal demands, and because these systems are heavily invaded by non-native organisms. The distribution and ecology of freshwater fishes in Mediterranean-climate regions are also influenced by the distinct wet and dry periods and the high inter-annual variability in precipitation. Thus, efforts to manage and conserve native fishes in Mediterranean-climate regions require understanding both the effects of human disturbance and the strong seasonality that characterizes these regions. In this dissertation, I examine the relationship between land use and Mediterranean seasonality on freshwater fishes in streams within the greater San Francisco Bay region in California, USA. In my second chapter, I use a multivariate approach to explore variability among fish communities in 25 Bay Area watersheds. I found that a combination of local (water conductivity) and watershed-scale factors (percent forested watershed, watershed area, elevation) were important predictors of fish communities across sites. Furthermore, watershed-scale factors had indirect effects on fish communities through their influence on a local-scale factor, water conductivity. The results of this chapter highlight the importance of considering both the direct and indirect effects of watershed-scale factors on freshwater fish communities. In my third chapter, I continued my analysis of land use and fish communities with a focus on contemporary land change. For this chapter, I performed a resurvey study, surveying the habitat and fish communities in 32 sites in the Alameda Creek Watershed that had been surveyed by Dr. Robert Leidy in the mid-1990s, including sites in the rapidly urbanizing Livermore Valley region. Again using a multivariate approach, I found that the increase in urbanization across an approximately 16-year period was related to change in fish community composition, a decline in native species richness, and a decline in a common native cyprinid - changes that were not observed in another part of the watershed that has experienced little land use change in the last 16 years. The relationship between land use change and fish community change was strongest when considering land use change at a local scale. These results suggest that ongoing land change alters fish communities and that contemporary resurveys are an important tool for examining how freshwater taxa respond to recent and ongoing environmental change. In my final chapter, I assessed how seasonal drought, a characteristic feature of Mediterranean-climate systems, influenced food webs in a small intermittent stream in Marin County, CA that provides rearing habitat for threatened steelhead trout (Oncorhynchus mykiss). I used stable isotopes of carbon and nitrogen to characterize food web structure and the trophic position of a suite of predators in this system, including O. mykiss and several macroinvertebrate predators. I compared food web snapshots across time, as well as between permanent and temporary pools. I found that the intermittent stream food web remained relatively stable across time and did not differ between pool types. However, I also found significant changes in the trophic position, niche width, and mean [delta]13C values for aquatic predators. This study provides an important first look at the trophic ecology of an imperiled fish species in intermittent streams during the summer drought season, and emphasizes that food chain length increases across the drought season, possibly because invertebrate prey are concentrated with declining water levels. In conclusion, my research shows that anthropogenic factors at the watershed scale influence instream conditions and freshwater fish communities, and emphasizes that contemporary changes in land use can have subtle changes on fish community structure, which may be indicative of future declines of extirpations of native fishes. Finally, my research shows that changing conditions across the summer drought season lead to shifts in the trophic ecology of some, but not all, aquatic predators, including threatened steelhead trout. Overall my research contributes to a growing body of research that demonstrates how multi-scale natural and anthropogenic factors influence freshwater fishes in Mediterranean-climate region.

Climate change poses many challenges that affect society and the natural world. With these challenges, however, come opportunities to respond. By taking steps to adapt to and mitigate climate change, the risks to society and the impacts of continued climate change can be lessened. The National Climate Assessment, coordinated by the U.S. Global Change Research Program, is a mandated report intended to inform response decisions. Required to be developed every four years, these reports provide the most comprehensive and up-to-date evaluation of climate change impacts available for the United States, making them a unique and important climate change document. The draft Fourth National Climate Assessment (NCA4) report reviewed here addresses a wide range of topics of high importance to the United States and society more broadly, extending from human health and community well-being, to the built environment, to businesses and economies, to ecosystems and natural resources. This report evaluates the draft NCA4 to determine if it meets the requirements of the federal mandate, whether it provides accurate information grounded in the scientific literature, and whether it effectively communicates climate science, impacts, and responses for general audiences including the public, decision makers, and other stakeholders.

"The bibliography is a guide to recent scientific literature covering effects of agricultural conservation practices on fish and wildlife. The citations listed here provide information on how conservation programs and practices designed to improve fish and wildlife habitat, as well as those intended for other purposes (e.g., water quality improvement), affect various aquatic and terrestrial fauna"--Abstract.

The Working Group II contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) provides a comprehensive assessment of the scientific literature relevant to climate change impacts, adaptation and vulnerability. The report recognizes the interactions of climate, ecosystems and biodiversity, and human societies, and integrates across the natural, ecological, social and economic sciences. It emphasizes how efforts in adaptation and in reducing greenhouse gas emissions can come together in a process called climate resilient development, which enables a liveable future for biodiversity and humankind. The IPCC is the leading body for assessing climate change science. IPCC reports are produced in comprehensive, objective and transparent ways, ensuring they reflect the full range of views in the scientific literature. Novel elements include focused topical assessments, and an atlas presenting observed climate change impacts and future risks from global to regional scales. Available as Open Access on Cambridge Core.