- The National Park Service has a dual mission of providing public access to exceptional natural resources, but in a manner such that these resources are left “unimpaired for the enjoyment of future generations.” Human activities in parks undoubtedly affect wildlife, but the degree to which such activities cause impairment is often unclear and difficult to assess. It is the task of park administrators to take actions and impose restrictions to prevent impairment based on park values and the information provided through research and monitoring programs. Finding an appropriate balance between wildlife protection and visitor access is difficult because decision makers must consider numerous interrelated factors, many of which are not known with certainty. In light of these challenges, scientific approaches that allow decision makers to incorporate uncertainty and evaluate trade-offs between human access and resource protection are greatly needed. Glacier Bay National Park (the “Park” hereafter) contends with the challenge of managing visitors in an area containing many species of conservation concern. Therefore, the Park seeks a systematic and data-driven process for evaluating the tradeoffs that current and potential restrictions represent, in terms of protecting sensitive resources versus enabling full access to the public. The goal of my dissertation was to assist administrators and biologists at the Park with the development of an integrated decision tool for the Park through a structured decision making process.
This task entailed first identifying and structuring objectives, then coordinating with subject-matter experts on the development of biological sub-models for informing the future decision tool. Park Service administrators and staff drew on fundamental purposes of the Park to define measurable attributes that characterize the Park’s values and inform management decisions. This process also identified focal species whose conservation status was viewed as a priority and had motivated management actions in the past. Focal species included Steller sea lions (Eumetopias jubatus), harbor seals (Phoca vitulina richardsi), humpback whales (Megaptera novaeangliae), and several species of ground-nesting coastal waterbirds. Much of the work described here involved collaborating with subject-matter experts to develop biological models. These models served three main purposes: (1) characterize the state of focal species by incorporating available research and on-going monitoring; (2) respond interactively to changes in the value of population parameters (e.g., population size, distribution), whose influence decision makers would want to assess; and (3) generate estimates that would serve as valuable inputs in subsequent models of visitor-wildlife encounters.
Biological models provide data-driven descriptions of the state of populations. The structured decision-making process places emphasis on models that are as explicit as possible. To this end, I formulated biological sub-models in a manner that would permit estimation of actual population parameters for focal species rather than raw counts or indices. Survey data were modeled as a function of these key parameters, but also as filtered through an imperfect detection process affected by survey effort and uncontrollable variables, such as weather conditions. The Steller sea lion sub-model estimated abundance, spatial distribution, and the proportion of time spent on land (attendance probability) using counts at terrestrial sites and sightings-at-sea. I used a similar approach to model abundance for a sub-population of harbor seals, but with modifications meant to account for the excessive number of zero counts in the data set. The sub-model describing the condition of ground-nesting coastal waterbirds estimated probabilities of survey sites being occupied, of the species being abundant at the site, and of the nesting status for nine different species across 20 key concentration sites that are surveyed in the Park. Finally, the humpback whale sub-model used sightings of whales from active surveys and observers onboard cruise ships to estimate whale abundance and, for the first time, fine-scale spatial distribution in the Park.
Structuring objectives and developing biological sub-models was a key step in an ongoing process of decision tool development. The Park is now in the position to move forward with combining biological sub-models with information on visitor usage. I describe pathways for accomplishing this task, and assess the capacity of each biological sub-model for generating the measurable attributes that decision makers care about. Although decision tool development is ongoing, the work herein is a valuable contribution to the fields of ecology and resource management for several reasons. At the level of individual studies, population parameter estimates from sub-models contribute to conservation efforts for those species, and the novel modeling techniques described are readily generalizable to other systems. The broader contribution of this body of work, however, is in illustrating the value of adopting a structured decision-making approach to resource management in parks. Specifically, this work shows that the process of connecting fundamental objectives to monitoring information can be used identify information gaps and reveal creative ways of using available information to inform management.