Climate is a major catalyst of change in the composition, structure and function of the Ecosphere. Empirical studies of species response to climate consistently reveal that the anomalous warming occurring over roughly the past half-century is having a discernible impact on contemporary biodiversity. Climate change has also been implicated in several species extinctions, a phenomenon projected to be exacerbated in the future. These studies and events indicate that the implications of climate change for biodiversity conservation are considerable. Biodiversity conservation is one of the major modern rationales behind formal protected natural areas establishment, planning and management. However, most protected natural areas have been designed to protect in perpetuity specific natural features, species and communities in-situ, and don't take into account shifts in ecosystem composition, structure and function that are being induced by climatic change. The ecological manifestations of climate change will be such that the established species management objectives of some protected natural areas will no longer be viable. Consequently, protected natural areas agencies will need to be adaptive in order to be able to respond to climate change-induced impacts and improve their ability to deliver their various protected natural area- and biodiversity-related mandates, such as the perpetual protection of representative elements of natural heritage. The principal goal of this dissertation was to begin the process of climate change adaptation (mainstreaming) within the Canadian protected natural areas community, thereby facilitating the ability of jurisdictions, agencies and organizations to adapt to climate change-related impacts and implement adaptation decisions. To realize this goal, four objectives were formulated: i) to synthesize the state of knowledge on climate change, biodiversity and protected natural areas policy, planning and management; ii) to establish the state of climate change adaptation with respect to Canadian protected natural areas agencies; iii) to assess the current position, priorities, and challenges of, and barriers to, Canadian protected natural areas agencies with respect to climate change adaptation; and iv) to develop a climate change adaptation portfolio and evaluate the suitability of the portfolio for implementation by a Canadian protected natural areas agency, Ontario Parks. The research revealed that while mainstreaming climate change into protected natural areas policy, planning and management will be essential for the persistence of biodiversity and the continued viability of current planning and management practices under a changing climate, there is a clear disconnect between the perceived salience of climate change and a lack of available resources (e.g., financial resources and staffing) and scientific capacity required to respond to the issue. Moreover, the limited protected natural areas climate change literature to-date provides little guidance to the planners and managers of already established protected natural areas. Accordingly, there is an indicated need to assist Canadian protected natural areas agencies in the identification and evaluation of adaptation options as a strategic starting point in working towards mainstreaming climate change into relevant program areas. In response to this indicated need, a policy Delphi survey method was used to facilitate the identification and evaluation of adaptation options tailored specifically to Ontario Parks. A panel of protected natural areas experts identified 165 adaptation options within Ontario Parks' six major program areas [(i) Policy, System Planning & Legislation; (ii) Management Direction; (iii) Operations & Development; (iv) Research, Monitoring & Reporting; (v) Corporate Culture & Function; and (vi) Education, Interpretation & Outreach) in the first iteration of the policy Delphi. Adaptation options were subsequently evaluated individually for their perceived level of desirability, feasibility and implementation time-frame by the panel via a second iteration of the policy Delphi. In so doing, the research evaluated the relative merit (or practicality) of alternative adaptation options in these program areas in order to help identify priority (or 'first-order') adaptations for consideration in an official climate change adaptation strategy by Ontario Parks. The research provides a solid conceptual and methodological framework with important practical 'lessons learned' that will help Canadian protected natural areas jurisdictions understand, address and begin mainstreaming climate change into policy, planning and management decision-making. Collectively, the research includes the first practical discussion of adaptation to climate change within the institutional framework of any Canadian protected natural areas jurisdiction, representing a significant contribution to the protected natural areas planning literature at the science-policy interface.