Explore the vast range of titles available.

The ranges and abundances of species that depend on freshwater habitats are declining worldwide. Efforts to counteract those trends are often hampered by a lack of information about species distribution and conservation status and are often strongly biased toward a few well-studied groups. We identified the 3,906 vascular plants, macroinvertebrates, and vertebrates native to California, USA, that depend on fresh water for at least one stage of their life history. We evaluated the conservation status for these taxa using existing government and non-governmental organization assessments (e.g., endangered species act, NatureServe), created a spatial database of locality observations or distribution information from ~400 data sources, and mapped patterns of richness, endemism, and vulnerability. Although nearly half of all taxa with conservation status (n = 1,939) are vulnerable to extinction, only 114 (6%) of those vulnerable taxa have a legal mandate for protection in the form of formal inclusion on a state or federal endangered species list. Endemic taxa are at greater risk than non-endemics, with 90% of the 927 endemic taxa vulnerable to extinction. Records with spatial data were available for a total of 2,276 species (61%). The patterns of species richness differ depending on the taxonomic group analyzed, but are similar across taxonomic level. No particular taxonomic group represents an umbrella for all species, but hotspots of high richness for listed species cover 40% of the hotspots for all other species and 58% of the hotspots for vulnerable freshwater species. By mapping freshwater species hotspots we show locations that represent the top priority for conservation action in the state. This study identifies opportunities to fill gaps in the evaluation of conservation status for freshwater taxa in California, to address the lack of occurrence information for nearly 40% of freshwater taxa and nearly 40% of watersheds in the state, and to implement adequate protections for freshwater taxa where they are currently lacking.

The last 8 years have seen a dramatic increase in the flow of Central American apprehensions by the U.S. Border Patrol. Explanations for this surge in apprehensions have been split between two leading hypotheses. Most academic scholars, immigrant advocates, progressive media outlets, and human rights organizations identify poverty and violence (the Poverty and Violence Hypothesis) in Central America as the primary triggers responsible. In contrast, while most government officials, conservative think tanks, and the agencies that work in the immigration and border enforcement realm admit poverty and violence may underlie some decisions to migrate, they instead blame lax U.S. immigration policies, incorrect perceptions of U.S. immigration policy, and the exploitation of immigration system loopholes (the Policy and Loophole Hypothesis) as the real cause of the surge. Despite the existence of opposing claims, neither side has provided a clear data-based explanation regarding what has caused the sudden surge of unauthorized immigration from Central America. To address these competing claims, this study explored both hypotheses from a macrolevel using an empirically-driven quantitative research design. The study first identified the universe of data as tracked and gathered by large reputable organizations for the seven relevant countries/regions in the study (El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Latin America, and United States). A total of 195 independent variables were selected with 181 of them being specific to each country/region. This data produced a series of 68 independent stepwise regression models that explored the direct and indirect effects of both competing hypotheses. Ultimately, the study found more overall support for the Policy and Loophole Hypothesis, though it did not produce findings that confidently dismiss the Poverty and Violence Hypothesis. However, findings do suggest the often-cited Poverty and Violence Hypothesis has likely been overstated and exaggerated as a cause of the Central American migration surge. Furthermore, while neither hypothesis had enough inferentially robust support to conclusively back its claims, the findings do provide credence to the argument that the often-dismissed Policy and Loophole Hypothesis must be considered along with the Poverty and Violence Hypothesis in any analysis looking at unauthorized immigration from Central America.

Population growth and increasing water‐use pressures threaten California's freshwater ecosystems and have led many native fishes to the brink of extinction. To guide fish conservation efforts, we provide the first systematic prioritization of river catchments and identify those that disproportionately contribute to fish taxonomic diversity. Using high‐resolution range maps of exceptional quality, we also assess the representation of fish taxa within the state's protected areas and examine the concordance of high‐priority catchments with existing reserves and among distinct taxonomic groups. Although most of the state's native fishes are found within protected areas, only a small proportion of their ranges are represented. Few high‐priority catchments occur within protected areas, suggesting that fish conservation will require active management and targeted river restoration outside of reserves. These results provide the foundation for systematic freshwater conservation planning in California and for prioritizing where limited resources are allocated for fish recovery and protection.

Between 2004 and 2012, United States Border Patrol (USBP) apprehensions of Mexican nationals along the US-Mexico border declined to numbers not seen since the early 1970s. Scholars and immigration experts have attempted to explain the current declines by looking at the same three factors that have historically been associated with causing the rise in illegal Mexican migration: immigration policy changes in the United States, demographic changes in Mexico, and economic factors in Mexico and the United States. In addition, scholars and immigration experts have continued to dismiss border enforcement as a possible explanatory variable, despite specific findings in much of their own research suggesting otherwise. I analyze the three historic causes of illegal Mexican migration and argue that they in fact could not have been responsible for the decline in USBP Mexican apprehensions since the mid-2000s. I found that while there have been some changes within these three factors; the changes have not been significant enough to cause a 40-year low in Southwest Border Mexican apprehensions. More importantly, I found that the only other factor that could have reduced illegal Mexican migration has been border enforcement. In fact, it is the only factor that has seen a significant change. The exponential increases in Southwest Border enforcement efforts since the mid-2000s, and the simultaneous decline in Mexican apprehensions along the US-Mexico border, suggests that border enforcement is the principal factor responsible for the historic drop in illegal Mexican migration.