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Tropical forests contain more than half of the world’s biological diversity and play key roles in sustaining human life. In many parts of tropical Latin America, forests continue to be degraded and destroyed despite many efforts to protect them. Determining the extent to which conservation efforts work under different contexts can potentially lead to future improvements of forest cover outcomes at lower financial and social costs. However, rigorous impact evaluations of conservation interventions are still rare. This dissertation reports on estimated impacts of conservation and development interventions on tropical forest cover in Guatemala and Colombia and seeks to explain the quantitative results through qualitative data from surveys and interviews. The primary aim is to provide critical information to improve the efficacy of conservation policies. In Guatemala, the conservation intervention in question is a land tenure clarification project. In Colombia, I compare two conservation interventions (land acquisitions and payments for ecosystem services) for cost-effectiveness. I collected and consolidated spatial data on land acquisitions to create a novel dataset of these interventions. I use quasi-experimental methods with novel remote sensing data to estimate impact on forest cover. Field interviews and surveys inform the quasi-experimental analysis and explain results. This research therefore works across scales and uses multiple methods to tackle questions of project or program effectiveness. In the Colombian Andes, public land acquisitions (PLA) as investments in watershed services covered an area substantial enough to be considered within the broader PA network. However, PLA mostly occurred in lower cost (and relatedly, less-threatened) ecosystems, with some exceptions, such as the high Andean Páramo hills and mountains and Medium dense dry forest on hills and mountains. The percent of area distributions covered by PLA for a subset of species showed mostly marginal increases in protection coverage, with some exceptions, including Hapalopsittaca fuertesi, and endangered parrot, and Spizaetus isidori, an endangered eagle. Half of the area of mapped land acquisitions overlapped with legally protected areas. PLA as investments in watershed services are not guided by ecosystem endangeredness, but rather are moderated by important social and economic factors, including governmental income, land costs, and land tenure informality. In the southeastern subregion of Antioquia, where there is rich empirical data for both PLA and PES (payments for environmental services), we found that there are large differences in the level of implementation of PLA and PES, as well as the geographical characteristics of where they are implemented, with PES covering more area in places with more land tenure informality, lower incomes, and ecosystem threat. Despite PES being more broadly implemented, the impacts of PLA on percent increases in forest cover were consistently higher than those of PES. The overall relative area impacts were dependent on the choice of land cover dataset, but if we believe our ensemble model dataset that we considered most reliable, PLA had a higher area impact than PES. We did not find compelling evidence that either intervention was more cost-effective than the other. We identified unintended consequences of each intervention that should be considered when managers are making decisions about how to implement either of these interventions, including unequal distributions of benefits, perceived undue burden on the participants in either intervention, especially for those who were within PAs. The degree of forest cover gain (or of avoided loss) could be improved through more efficient targeting of PES and PLA. Subgroup analyses suggest that effects on forest cover are higher outside of protected areas PAs, in lower elevation areas, and (for PES) in areas with higher deforestation pressure. In Guatemala’s PAs, we were only able to conduct counterfactual impact evaluations with one type of PA. These were PAs where multiple activities were permitted (with internal zoning), moderate previous levels of deforestation, low drug trade organization (DTO) control, and low to medium land tenure security prior to treatment. We find some effects of the demarcation and cadaster treatments within these PAs – specifically that they prevented approximately 200 ha of forest post-treatment. The other PA types, including those with already-secure land tenure prior to treatment as well as strict protection and nearly no deforestation prior to treatment, strict PAs under DTO control, and buffer zones do not show positive forest outcome post-treatment through non-robust impact estimation methods, but interviews and the literature suggest that there is little reason to expect positive impacts in these areas. We do not have interviews or other data to explain patterns in strict PAs with low deforestation pressure prior to treatment and low levels of insecure land tenure. Common themes amongst intervention studies in this dissertation suggest that developing the right indicators for implementation progress, the efficient targeting of interventions, inter-institutional cooperation and data management could improve conservation outcomes.

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<p> The search for clean, fresh water is of the utmost importance, especially considering the highly industrialized age in which we live and the rising demand caused by increasing population. Many once-clean groundwater reservoirs have been tainted due to the inadequate storage and handling procedures for hazardous materials. One such site operated as a wood-preservation facility between 1937 and 1999 located in western Louisiana in the town of DeRidder. The contaminants that leached into the soils and groundwater supply at this site included creosote, a coal-tar distillate that is an amalgamate of several toxic constituents. The contamination was first detected in 1981, and within the year monitoring wells were installed to evaluate the extent of the pollution. For this study, 61 monitoring wells, 16 of which consistently record hazardous compounds within the subsurface, were analyzed in order to evaluate the temporal and spatial changes of contamination. The data were further correlated with rising and falling groundwater levels, precipitation data, and lithology in order to better understand the trends of the constituents and how they are affected by their environment. Additionally, an indication as to the efficiency of the current remediation practices put in place is examined by evaluating the diminishing contamination values over time compared to previous studies in the area. Hazardous levels within the soil are at their peak near the contamination sources, and spread outward while following the direction of local groundwater flow. This study shows that the total contamination quantities are slowly declining due to the current remediation practices, however, the total area covered by contamination fluctuates over time, and is currently in a state of expansion towards the southwest. A correlation between rainfall events and contamination spikes was noted in a previous study of the area, however, no such correlation was observed in the more recent data.</p>

<p>The principle of competitive exclusion holds that the strongest competitor for a single resource can exclude other species. Yet in many systems, more similar species appear to stably coexist than the small number of limiting resources. Understanding how and when similar species can stably coexist has taken on new urgency in managing biological invasions and their ecological impacts. Recent theoretical advances emphasize the importance of predators in determining coexistence. The effects of predators, however, can be mediated by behavioral changes induced in their prey as well as by their lethality. In this dissertation, I ask how considering multiple trophic levels changes our understanding of how a grass invasion (Pennisetum ciliare) affects species diversity and dynamics in southeastern Arizona. In considering interactions with plant consumers, and with the predators of those consumers, this research reveals more general ecological processes that determine species diversity across biological communities. I first present evidence from a grass removal experiment in the field that shows increased emergence and short-term survival of native perennial plants without grass. This is consistent with Pennisetum ciliare causing the observed concurrent decline in native plant abundance following invasion. I then present results from greenhouse and field studies consistent with that suppression of native plants being driven primarily through resource competition rather than increased rodent granivory. Granivorous rodents do not solely function as consumers, however, because they cache their harvested seeds in shallow scatter-hoards, from which seeds can germinate. Rodents thus act also as seed dispersers in a context-dependent mutualism. They primary granivores in areas invaded by Pennisetum ciliare are pocket mice (genus Chaetodipus), which have a well-studied tendency to concentrate their activity under plant cover to avoid predation by owls. Because the dense canopy of the grass may provide safer refuge, I hypothesized the pocket mice may be directly dispersing native seeds closer to the base of the invasive grass. Such a behavior could increase the competitive effect of the grass on native plant species, further driving the impacts of the invasion. By offering experimental seeds dusted in fluorescent powder and tracking where the seeds were cached, I show that rodents do preferentially cache experimental seeds under the grass. This dispersal interaction may be more general to plant interactions with seed-caching rodents across semi-arid regions that are experiencing plant invasions. Finally, I ask how the predator avoidance behavior exhibited by these rodents affects their ability to coexist with one another. Not only could their diversity affect that of the plant community, but the effects of plant invasions can cascade through other trophic levels. Theoretical understanding of how similar predator avoidance strategy alters coexistence had not yet been developed, however. Instead of a field study, therefore, I modified a general consumer-resource model with three trophic levels to ask whether avoidance behavior by the middle trophic level alters the ability of those species to coexist. I found that more effective avoidance behavior, or greater safety for less cost, increased the importance of resource partitioning in determining overall niche overlap. Lowering niche overlap between two species promotes their coexistence in the sense that their average fitness can be more different and still permit coexistence. These results provide novel understanding of behavioral modifications to population dynamics in multi-trophic coexistence theory applicable to this invasion and more broadly.

<p> This study of the vegetation of the 100,000-acre Connecticut Tract in western New York examines the presettlement characteristics of the forest, including the tree species composition, tree density, and wetland extent. Presettlement vegetation studies add to what is known about the forests of this region before European settlement in the early 1800s brought widespread changes to these forests. The ecological data in original private land surveys from 1811 were transcribed and then analyzed using ArcGIS and IDRISI GIS software. The surveys contained both witness tree data and line descriptions, which were analyzed for species composition and community type and were compared with Forest Inventory and Analysis (FIA) data about the contemporary forest in the study area. The community type results together with surveyor notes were used to extrapolate wetland coverage, which was compared with the 2006 National Wetlands Inventory Database.</p><p> This study fills in missing historical data between the two largest land purchases in western New York and examines forest composition at a finer-grained scale than surveys of those land purchases. Comparing past and present vegetation clarifies past causes of temporal and spatial variability and provides a reference point for land managers who need to understand the effects of land-use history for ongoing restoration efforts.</p>