Managing direct and indirect threats to marine ecosystems to balance multiple objectives

Tulloch, Vivitskaia (2017). Managing direct and indirect threats to marine ecosystems to balance multiple objectives PhD Thesis, School of Biological Sciences, The University of Queensland. doi:10.14264/uql.2017.992

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Author Tulloch, Vivitskaia
Thesis Title Managing direct and indirect threats to marine ecosystems to balance multiple objectives
School, Centre or Institute School of Biological Sciences
Institution The University of Queensland
DOI 10.14264/uql.2017.992
Publication date 2017-10-20
Thesis type PhD Thesis
Supervisor Hugh P. Possingham
Éva E. Plagányi
Christopher J. Brown
Carissa J. Klein
Anthony Richardson
Language eng
Subjects 050101 Ecological Impacts of Climate Change
010202 Biological Mathematics
050202 Conservation and Biodiversity
Formatted abstract
Human activities affecting the environment are intensifying. In marine ecosystems, direct stressors of overfishing and habitat destruction have led to biodiversity declines, prompting calls for conservation action and more sustainable resource management. Managing stressors becomes more challenging when stressors interact, or are indirect, whereby the source of the threatening activity is displaced from impacts, such as the localised effects of global warming, or runoff from land-use change degrading coral reefs. Effective management requires improved understanding of ecosystem responses to multiple stressors and consideration of interactions between stressors and species.

Opposing objectives and outcomes of marine conservation (i.e. reducing stressors) versus resource management (often increasing stressors) compromise effective decision-making. Approaches are needed that include ecological and socio-economic information to promote long-term sustainability of extractive uses, protect functioning ecosystems, and conserve biodiversity. The choice of tool used to inform ecosystem management is typically constrained by management goals and available resources - spatial planning is typically used for conservation, whereas resource management relies more on population modelling.

The goal of this thesis is to harness spatial and population modelling techniques to combine resource management with biodiversity conservation and link direct and indirect stressors to marine biodiversity persistence. Chapter 1 provides the context for the thesis, where I explore these themes and outline differences in decision-making for conservation versus extraction. In Chapter 2, I explore how agencies have managed stressors to date, and show that a decision-theoretic approach known as “structured decision-making” (SDM) is a more logical and effective way of managing stressors than traditional approaches that map threats. SDM requires clear objectives, canvassing of alternative management options, and linking outcomes for biodiversity to the effectiveness of each management option. SDM ensures that conservation actions occur where they are the most cost-efficient or effective. I apply recommendations from Chapter 2 in two case studies for managing multiple stressors to marine ecosystems: 1) spatial planning for oil palm agriculture and coral reef fisheries in Papua New Guinea (Chapters 3 and 4), and 2) managing whale species affected by harvesting, climate change and krill population dynamics in the Southern Hemisphere (Chapters 5 and 6).

In Chapter 3 I combine ecosystem models and threat maps with spatial conservation planning to predict responses of coral and seagrass ecosystems to changing land uses. My novel framework identifies high priority areas for marine reserves whilst accounting for indirect impacts of land use change such as oil palm development and uncertainty in future stressor intensities. I demonstrate how we can reduce adverse impacts of oil palm expansion and make more effective whole-of system decisions for coastal systems under multiple stressors.

Balancing the needs of local communities for agriculture and development against conserving marine ecosystems and fisheries is crucial for managing coastal systems. In Chapter 4 I develop a theoretical approach for integrated land-sea planning that trades off livelihood and ecosystem benefits from land-use change. My results support recommendations from Chapter 2 that clearly identifying and targeting resource management and conservation objectives helps identify land-use actions that minimise impacts on connected marine ecosystems whilst benefitting oil-palm developers and local landholders.

In Chapters 5 and 6 I focus on recommendations from Chapter 2 that understanding species’ responses to changes in their environment and stressors is crucial for effective ecosystem management. Migratory baleen whales may be particularly susceptible to climate-induced changes in marine environments due to close synchrony between life histories, water temperature and productivity. In Chapter 5 I develop a multi-species ecosystem model linking ocean productivity, prey availability and historical whaling to baleen whales. I demonstrate spatial and temporal differences in the depletion and recovery of whale species across the Southern Hemisphere, with slow recovery identified particularly for blue, fin, and southern right whales.

In Chapter 6 I expand this model to include two-way interactions between whales and krill and explicitly link changes in temperature, chlorophyll and sea-ice to evaluate how changing climate and associated krill biomass affects whale numbers. I find latitudinal differences in the impacts of changed environmental conditions on both krill and whales. The most severe disturbances occur at lower latitudes (40-60°S) in the Southern Ocean where temperature is predicted to increase past the tolerable threshold for krill survival. This work suggests future whale recovery may slow due to interactions among their prey species and climate, with rapid declines in humpback whale numbers predicted in the Atlantic/Indian oceanic regions.

By accounting for past, current, and future exposure to stressors this thesis resolves issues surrounding effective management of threatened species and ecosystems. Two case studies develop a “tool-box” of decision-making strategies that can be adapted for different multi-objective problems depending on whether the focus is on conservation planning (Chapters 3 and 4) or resource management (Chapters 5 and 6). These applications show that it is possible to resolve complex threat management problems by incorporating interactions between systems and species and navigating effective trade-offs between conservation and resource use in marine ecosystems.
Keyword Conservation planning
Threat management
Ecosystem modelling
Multispecies models
Integrated land-sea planning
Climate change

Document type: Thesis
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Created: Tue, 10 Oct 2017, 12:04:06 EST by Vivitskaia Tulloch on behalf of Learning and Research Services (UQ Library)