The western United States has experienced large-scale degradation due to land use and land cover changes, invasion of annual grasses, and expansion of woody plants into grass and shrublands and the resultant altered fire regimes. These landscape-scale changes have coincided with declining mule deer (Odocoileus hemionus) populations, making habitat loss...
Human alteration of natural landscapes leads to biodiversity loss, often from a combination of area effects and fragmentation effects. Smaller habitat patches support fewer species than large ones and incur additional consequences from isolation. Efforts to preempt biodiversity loss from insular habitat fragments are complicated by individualistic species responses and...
The vast majority of U.S. farm bill spending goes to nutrition assistance, on the one hand, and farm safety net programs, on the other. Although these programs are a major part of federal government expenditures, controversial and governed by a common bill, they have rarely been quantitatively analyzed together. To...
Although only a minority of introduced species become established and have noticeable consequences in their new communities, some can displace native species, alter food webs, and cause local extinctions. Studying these invasive species can provide new insights into basic ecological questions as well as inform management strategies. Pacific lionfish (Pterois...
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Mark A. Hixon
Although only a minority of introduced species become established and
Biological invasions have been identified as one of the prominent drivers of global environmental change. In particular, invasive predators typically have substantial negative effects on populations of native prey, even driving species to extinction in extreme cases. However, beyond direct predatory effects, little is understood regarding the specific mechanisms by...
There is increasing awareness that human activities are altering the ways that natural systems operate and that local shifts in species composition and abundance can lead to abrupt and irreversible global change. Therefore, understanding the processes that buffer biological communities from critical shifts and how our actions affect natural stabilizing...
Whitebark pine (Pinus albicaulis) is an iconic North American high-elevation tree species currently threatened by climate change, mountain pine beetle, and white pine blister rust (WPBR), a lethal disease caused by the non-native fungal pathogen Cronartium ribicola. In collaboration with the USDA Forest Service Dorena Genetic Resource Center, germplasm was...
The publicly subsidized Federal Crop Insurance Program has expanded rapidly in recent decades in the United States. With the reform in the 2014 Farm Bill, the Federal Crop Insurance Program has become the most important component of U.S. farm policies. The primary goal of the program is to provide risk...
Hunger is among the greatest contemporary social problems in the United States. An incredible 48 million people, or 14% of households, experienced food insecurity during 2014. At the same time, public responses to food insecurity, such as the Emergency Food Assistance Program, have increasingly relied on the “emergency food network,”...
The appropriate use of disaggregated economic data not only improves the accuracy and robustness of economic analyses, but also extends the existing economic models to address new aspects of the issue. This dissertation consists of three essays: two essays use disaggregated economic-engineering data to address spatial heterogeneity in economic losses...