Past Forward: Using History to Inform Multi-Benefit Ecosystem Management in Human-Dominated Landscapes

Human-dominated ecosystems are increasingly recognized as a crucial component of biodiversity conservation and ecosystem management, with the potential to support biodiversity, deliver ecosystem services, connect people with nature, and contribute to regional connectivity and management goals. However, understanding what ecosystem conservation, restoration, and management goals and targets are appropriate in such landscapes remains a challenge. We often have an extremely limited understanding of the character and consequences of ecosystem change in human-dominated landscapes as a result of the rapid and extensive transformations of the past centuries, a blind spot that can hamper our ability to manage these landscapes in a way that is place-based, pragmatic, and grounded in local landscape potential./nThis dissertation aims to advance the practice of ecosystem management in human-dominated landscapes by exploring how historical ecology, which provides a long-term historical perspective on system patterns, dynamics, and trajectories, can inform a variety of management goals in human-dominated landscapes. I explore three dimensions of the applicability of a historical perspective to multi-benefit landscape management: ecosystem conservation and restoration, managing for ecosystem services such as carbon storage, and managing for ecological resilience./nIn Chapter 2, I present the first quantitative and systematic review of the global historical ecology literature across ecosystems and identify the specific recommendations for ecosystem management that have emerged from the global body of historical ecology research over the past two decades. I found clear patterns in the types of recommendations generated by the historical ecology literature, including an emphasis on the role of both habitat remnants and human-dominated landscapes in management, the role of people in landscape stewardship, and the value of a landscape-scale perspective. About one-quarter of studies contained at least one surprising recommendation that revised or challenged status quo management for the study system or site in question, affirming the ability of historical ecology to provide new insights that can adjust how we manage species and ecosystems. I found that fewer than 12% of papers contained recommendations that explicitly addressed ongoing or projected climate change, suggesting opportunities to integrate findings from historical ecology with other perspectives to create forward-looking management strategies./nIn Chapter 3, I use historical datasets to reconstruct landscape-scale changes in an ecosystem service, carbon storage, in Santa Clara Valley over the past ca. 200 years from pre-settlement conditions through urban development. This is the first such examination of temporal changes in carbon storage in an urban area extending before 1900. I found that total tree carbon storage in the study area was ~784,000 to 2.2 million Mg ca. 1800, compared to ~895,000 Mg C today, suggestive of considerable losses of up to 60% of former carbon storage. My results suggest that in Mediterranean-climate ecosystems with heterogeneous tree cover, gains in aboveground carbon storage in formerly treeless areas can be offset by losses in high-biomass former woodland areas, challenging the hypothesis that aboveground carbon storage is likely to increase with urbanization in arid and semiarid environments due to irrigation and tree planting./nFinally, in Chapter 4 I explore the role of history in informing resilience-based ecosystem management in highly modified landscapes. I synthesize and simplify the published literature on mechanisms of ecological resilience into seven dimensions of landscape-scale ecological resilience, along with a set of key considerations for evaluating the current state of a landscape and identifying potential management strategies that could contribute to resilience. I then demonstrate application of the approach through case studies in the agricultural Sacramento-San Joaquin Delta and urban Santa Clara Valley, each of which drew on detailed regional-scale assessments of ecological history and change as a first step to analyze landscape context. This work advances the practice of resilience-based management by providing a structured approach and shared vocabulary for identifying potential opportunities and actions likely to increase landscape resilience in highly modified systems, and ultimately better equip landscapes to sustain biodiversity and function into the future. Taken as a whole, this research underscores the continued value of history as a cornerstone of multi-benefit ecosystem management, even in human-dominated landscapes and in the context of transformations in land use and climate.

Advisor: Larsen, Laurel