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Native fishes of desert-aquatic ecosystems have been dramatically impacted by nonnative species. Over time, habitat modification and degradation set the stage for the influx of many nonnative taxa. Traditionally, nonnative-fish control has meant attempting to eliminate every individual from habitats of interest. In larger systems, this has proven impossible, and managers have sought ways for nonnatives and natives to coexist by reducing stressors on natives. This chapter describes the nonnative-fish dilemma, lessons learned, and possible pathways for remediation, with a focus on the Colorado River basin. It is argued that greater habitat complexity and more natural flow regimes help natives and nonnatives coexist and concludes that a multiplicity of tools and techniques, along with improved education and public outreach, remain important for conserving native fishes.

In its early history, the US National Park Service (NPS) had no policy on nonnative species, and even introduced nonnative fishes for sport fishing and plants for landscaping. By the 1920s, scientists within and outside the NPS militated against new introductions and urged the agency to minimize or eradicate existing ones, but not until a 1968 directive was such a policy substantially implemented. Some park efforts to eradicate or decrease mammal populations aroused opposition from hunters or advocates of animal rights. Park Science was first published in 1980 and initially targeted NPS managers; in the 1990s it broadened its audience to include the general public. Articles in Park Science, though more heavily focused on management than those in most academic journals, track most of the explosive recent development of invasion biology, in particular incorporating the recognition that some invasions can affect entire ecosystems rather than just particular native species. The journal has generally downplayed controversies that have recently roiled invasion biology. National parks, islands in a larger landscape and unable to control national policy on nonnative species, are continually invaded by new nonnatives, but the NPS has risen to the challenge of managing them with some striking successes.

This chapter presents some of the ways human activities have changed western fire regimes. The fire suppression policies of federal agencies resulted in a heavy accumulation of fuels in forests. One example is fire-suppression fuel buildups based on the study of ponderosa pine forests. In other ecosystems, suppression policy plays only a minor role in creating fires. The major anthropogenic factors that cause changing fire regimes are: global climate change, unrestrained development in the wildland-urban interface, inappropriate logging and grazing practices, and the introductions of nonnative species.

One of the primary priorities of conservation is to prevent extinctions. Thirty-three fishes and 23 aquatic invertebrates are recorded as recently extinct within the desert and adjacent regions of the United States and Mexico. Additionally, five fishes are listed as extinct in the wild. The process of extinction often begins with habitat degradation or other disturbance that diminishes local populations or causes local extirpations that lead to the entire species or subspecies being more susceptible to loss. Extinction itself was often linked to some catastrophic change in water supply, such as water diversion or spring failure due to over-withdrawal of groundwater. Introductions of nonnative species that may prey on, compete with, or hybridize with native species, were more common in extinction of desert fishes than for aquatic invertebrates. Detailed obituaries are provided for the Amistad gambusia, Nevada pyrg, Julimes tryonia, Tecopa pupfish, poolfishes of the genus Empetrichthys, and the Alvord cutthroat trout. Increasing numbers of endangered and extinct species are a cautionary account about our own future. The question for humans is whether the warning signs will be obeyed or whether society proceeds headlong into a future where our own species may be at risk.

This chapter provides an introduction to various applications of correlative approaches used in ecological niche modeling, along with the theoretical principles on which the applications are based. It demonstrates how the methods can be applied to interesting challenges to yield highly useful results, provided that the researcher understands exactly what is being estimated based on which data. It also gives examples of types of model predictions that can yield useful information. Each of the following chapters describes key questions that the niche models address, for example, where unknown populations are likely to be present, or which areas are most susceptible to nonnative species invasions. Practical considerations for implementing each application are also taken into account, and future directions and challenges are discussed.

Invasive plants, animals, and disease organisms strongly affect both our biological resources and economy. Some scientists believe that invasions are inevitable and feel that it is futile to attempt to stop them. However, most who work with invasives feel strongly that much can and should be done to protect natural areas from the impacts of invasive species. A broader awareness of which species are of concern and the problems they cause is key to containing the current infestations and preventing the import of new harmful species. This chapter examines the status of invasive terrestrial species in Wisconsin: the history of their introduction and spread, their impacts, projections for future change, a summary of what is currently being done at different levels, and recommendations for further actions.