Doctor of Philosophy in Geography (PhD)
Coral reefs, climate change, and resilience in the central Pacific
I am a climate scientist focused on helping the world prevent and prepare for climate change. I serve as a member Canada’s Net-Zero Advisory Body, which advises the Canadian government on climate change solutions, and was a lead author on the most recent assessment report by the Intergovernmental Panel on Climate Change assessments.
My research program lies primarily at the intersection of climate change science, marine science, and policy. The specific research areas evolve over time in response to advances in climate change knowledge and to real-world events. Prospective students and post-doctoral researchers should check my personal web site for current and planned areas of research, as well as for guidance for applicants.
I am able to admit students via the Institute for Resources, Environment and Sustainability, the Institute for the Oceans and Fisheries, the Department of Geography (science degrees only) or the Atmospheric Sciences program.
I look for highly self-motivated graduate students and post-doctoral fellows with strong analytical and communication skills who are prepared to conduct climate change research. While our research touches on many fields including coral reef ecology, marine conservation and other areas, climate change science and policy is the glue within the research group.
The applicants are chosen based on the strength of their ideas, clarity of expression, technical ability, passion for problem-solving, and contribution to diversity of mr research group and the field. The ideal applicant has a vision of what they hope to accomplish by attending graduate school or doing post-doctoral work; in my mind, a lot of self-reflection is necessary for a successful and positive experience in graduate school or post-doctoral research.
Interested parties are asked to review the current and planned areas of research on my website, and then send the materials I request to my UBC email address, rather than to use this system.
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Dissertations completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest dissertations.
Both local and global stressors threaten coral reefs, putting the food security, cultural continuity, and livelihoods of millions of reef-dependent people at risk. Still, scientists lack an understanding of how climate-driven heat stress interacts with local stressors such as fishing and pollution to influence reef health. Coral reef communities in the Marshall Islands and Kiribati, both low-lying atoll nations in the central Pacific, offer an opportunity to examine these interactions. The Gilbert Islands of Kiribati, which straddle the equator, experience highly variable sea surface temperatures (SSTs) inter-annually due to El Niño / Southern Oscillation, driving coral bleaching events in 2004/2005 and 2009/2010, while the Marshall Islands further north of the equator experience more stable SSTs. Both nations are home to degraded reefs near their capitol atolls, which host over half of each country’s populations. I first analyzed the benthic trajectories of coral reefs in the Gilbert Islands from 2012, 2014, 2016, and 2018, across a gradient of local human disturbance after multiple stressors, including two heat stress events and an outbreak of the corallivorous Crown-of-Thorns (CoTs) starfish, finding that locally degraded reefs were more resistant to heat stress than less trafficked reefs because the former were home to hardier taxa. Next, comparing locally disturbed and undisturbed reefs in Kiribati to those in the Marshalls demonstrated that the interactions between local and global stressors were context-dependent; the taxa that were present dictated the interactions. Then, via a meta-analysis of 1,205 sites in the Indian and Pacific Oceans, I demonstrated that a proxy often used to assess the effects of local human disturbance on reef health, the percent cover of macroalgae, does not correlate with local human disturbance. Instead, different genera of macroalgae exhibited diverse and often opposing responses to various sources of local human disturbance. Finally, I used public archives from an email listserv popular among the coral conservation community to analyze the policy narratives used by participants when discussing local threats to reefs, the actors involved in the local threat, their distal drivers, and the proposed solutions, revealing underlying assumptions about reefs and local people, which could inadvertently undermine conservation.
Climate change represents one of the principal threats to coral reef ecosystems because of an increase in mass coral bleaching and associated coral mortality due to more frequent and severe thermal stress. Even though most research has focused on temperature, coral bleaching results from the interacting effects of temperature and other environmental variables such as solar radiation. Exposure of corals to high light exacerbates the impact of thermal stress on corals, whereas reductions in light can reduce sensitivity to thermal stress. This dissertation aims to integrate the effects of light and temperature to assess how corals have responded to periods of cold and warm water, and under various future climate change scenarios. The synergetic effect of light is evaluated through the development of different models and methods. First, performing a logistic regression model approach on cold-water bleaching observations I find that cold-water bleaching can be best predicted with an accumulated cold-temperature metric (Degree Cooling Weeks), although the effect of light marginally improved prediction accuracy. Second, using mixed-effects models on a global database of warm-water bleaching observations and environmental metrics, I find that coral reefs exposed to severe bleaching-level heat stress show a reduced bleaching response if exposed to high cloudiness. Then, I developed a ‘cloudy refugia’ index which identifies regions where cloudiness is most likely to protect corals from bleaching. The findings suggest that incorporating cloudiness into prediction models can help identify reefs that may be more resilient to climate change. Finally, using mixed-effects models on future climate projections from GFDL-ESM4, I find that though warming ocean water is the primary driver of future coral bleaching conditions, cloudiness might delay the onset of frequent bleaching by four decades in low emission scenarios. However, the protection of clouds in addition to corals' ability to adapt to climate conditions are likely to be outpaced in high-emission scenarios. This research provides an overarching assessment of the influence of thermal stress and light on mass coral bleaching patterns globally. Furthermore, it demonstrates the value of including more driving variables when examining the fate of coral reefs in different future greenhouse gas emissions scenarios.
People seeking to lower their carbon footprints can consult a broad, quantitative literature to help them identify the most impactful lifestyle decisions. Absent from this literature is research into which political actions might be more effective in reducing greenhouse gas emissions. Here I report my findings on obstacles and opportunities for motivated individuals to contribute to climate change mitigation both by changing their lifestyles and by taking political actions. I begin by examining how individuals can model low-carbon mobility in the workplace. Using data collected at the University of British Columbia, I found preliminary evidence that academics could lead by example in reducing air travel without limiting their academic productivity. Next, I surveyed 965 members of the North America public and found that individuals underestimated the emissions associated with air travel and meat consumption, while overestimating the emissions of symbolic actions like eating organic food. Furthermore, participants rarely considered political actions to be the most effective way to reduce emissions. To follow up on the question of how effective political actions are, I used the 2019 Canadian federal election as a case study. In that election, where climate change was a central concern of voters, I found the emissions responsibility associated with voting was higher than the emissions typically associated with lifestyle choices. While I was unable to quantify the emissions associated with other political actions, I attempted to further our understanding of which political actions are more effective through a field experiment. In partnership with a non-profit organization, members of the public sent generic emails to their elected officials, requesting that the officials post a pro-climate message to their social media accounts. I analyzed the elected officials’ social media accounts, and combined with interviews of their staffers, the data suggest that generic campaign emails are only marginally persuasive. I conclude that motivated members of the public may be missing opportunities, in multiple domains, to maximize their impact on the climate.
In order to address the expected impacts of climate change, international development institutions have instigated adaptation projects and policies. These efforts promise to mitigate anticipated harms in vulnerable-to-climate-change social and ecological systems. This dissertation examines the operation and dissemination of adaptation projects and policies in the context of small island states in the Pacific region. It also explores the important role that the pre-eminent development institution, the World Bank, plays in programming adaptation. The research questions explored here are: i) How do finance, policy and science circulate in the name of adaptation? ii) What do the circulation of finance, policy and science achieve for adaptation in Kiribati and Solomon Islands? and iii) Why is the World Bank invested in adaptation, or what does adaptation do for the World Bank and other developmental actors? In answering these questions, I draw from multi-sited primary fieldwork, participant observation, and documentary analysis: at the World Bank in Washington, DC and Sydney, within the public bureaucracies of Australia, Kiribati, and Solomon Islands, and with regional organizations and development partners in the Pacific region. This dissertation posits the emergence of a Pacific Adaptation Complex. The analytical concept of the Pacific Adaptation Concept recognizes the vast institutional arrangements, configurations of expertise, and project technologies that come together to make adaptation happen. Within the Complex, experimental nodes are key, as are multi-directional flows. Yet, I find that, overwhelmingly, flows and investments for adaptation are dogged by persistent stickiness, and a rhetorical attention to mobility and success that is indifferent to practical outcomes. However, the promise of adaptation finance, policy, and science works through failing development institutions and imaginaries, allowing reinvention in an era of development crisis.
The Athabasca River Basin faces challenging tradeoffs between energy production and water security as climate change alters the seasonal freshwater supply and water demand from the oil sands mining industry is projected to increase. Effective water management will depend on a physical understanding of the scale and timing of water supply and demand. This dissertation aims to synthesize the impacts of water withdrawals and climate change on streamflow in the Athabasca oil sands region, in order to develop a scientific basis for the management of water resources. The combination of a land surface process model and a hydrological routing model is used to evaluate the influence of water withdrawals and climate change on streamflow under a variety of different scenarios, and to evaluate the adaptation options. Climate warming is projected to be the primary driver of future streamflow availability, with little influence from direct water withdrawals. Seasonal patterns that show a decline in summer flows and an increase in winter flows are consistent with the response of a snowmelt-dominated basin to warming. Increases in the frequency of low flows that are below a threshold of maximum environmental protection suggest that daily bitumen production could be interrupted by up to 2-3 months a year by mid-century. It is also projected that water storage will be required to supplement river withdrawals to maintain continuous bitumen production under the impacts of future climate warming. Based on the model results, a range of water management options are developed to describe the potential tradeoffs between the scale of bitumen production and industry growth, water storage requirements, and environmental protection for the aquatic ecosystems. This physically-based assessment of future water tradeoffs can inform water policy, water management decisions, and climate change adaptation plans, with applicability to other regions facing trade-offs between industrial development and ecosystem water needs.
Theses completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest theses.
No abstract available.
Coral reefs support a high biodiversity, providing a natural, physical barrier from waves that protects coastal communities from shoreline erosion and inundation. The three-dimensional (3D) structural complexity of living coral communities provides frictional resistance as waves and currents pass over the reef. A shift in coral community assemblages towards small, weedy, stress-tolerant corals due to climate change and local human stressors may alter wave attenuation, threatening low-lying coastal regions facing sea-level rise. In this thesis, I investigated the effect of coral community composition on shoreline protection in Kiribati’s Tarawa and Abaiang Atolls by collecting fore reef and reef flat field data and creating 3D reconstructions of the fore reefs. I found that the 3D structure and contribution of certain coral growth forms to reef complexity varied depending on the complexity metric used. Surface rugosity and standard deviation of elevation were not significantly different between atolls, while the average terrain ruggedness was significantly greater at disturbed sites in South Tarawa dominated by the weedy species Porites rus. I show that the abundance of Porites rus and branching corals were positively related for all three complexity metrics, with the strongest positive association between Porites rus and terrain ruggedness. Lastly, I determined that South Tarawa reef flats, long mined of rocks for human use, have lower benthic roughness and receive higher offshore wave energy relative to North Tarawa. My research suggests that at current mean sea level, the difference in the diversity of coral growth forms on the fore reef across Tarawa and Abaiang have less effect on wave attenuation than other factors like coral cover, steepness of the fore reef, and benthic composition of the reef flat. Additionally, the most significant variation in wave runup will be due to parameters influencing fore reef slope and reef flat composition. As such, steeper fore reef slopes and smooth reef flats of South Tarawa are expected to dissipate less wave energy relative to reefs in North Tarawa and Abaiang. To summarize, my findings offer insights into possible trade-offs between reef resilience to climate change and shoreline protection, including shoreline vulnerabilities to sea-level rise around Kiribati.
Both local and global threats are affecting the health of coral reefs worldwide. In addition to endangering the livelihoods and source of food for millions of people, threats to coral reefs may result in flattening reefs, which reduce habitat complexity and the ability of reefs to protect shorelines from erosion. This could be particularly detrimental to low-lying Pacific atolls like those found in the Republic of the Marshall Islands (RMI). I examined the influence of local human disturbance and heat stress on coral and algal community composition in Majuro and Arno Atolls in the RMI to explore how human disturbance affects coral and algal communities, and how to best characterize those communities. With a population of approximately 30,000 people, Majuro is home to the largest population of all of the RMI's 29 atolls and underwent extensive human modifications after American occupation during World War II. By contrast, Arno is home to fewer than 2,000 people and has remained relatively undisturbed. In June of 2016, I conducted benthic surveys at 25 sites along a gradient of human impacts across the two atolls. At each site at 10m depth, I measured percent cover of coral and algae genera and size-frequency of coral. I also utilized limited historical data to explore how reefs had recovered after a thermal stress event in 2014. In order to estimate human disturbance, I used the mean normalized difference vegetation index (NDVI) of the nearby coastline, which measures vegetation intensity. The coral and macroalgae composition of sites differed by atoll, mean NDVI, and wind and wave exposure, but not by sea surface temperature. The most degraded sites had low macroalgae cover and were dominated by turf algae, sponges, and cyanobacteria. One genus of macroalgae, Halimeda, was associated with sites that had low disturbance, while another, Hypnea, was correlated with higher disturbance. These results suggest that using macroalgae as an indicator of degradation may mask the influence of local human disturbance on reef community composition. Instead, it is important to consider identifying other indicator taxa and to measure coral and macroalgae cover to at least the genus level.
Mass coral bleaching in recent years has become a recurring event and was suspected to have a relationship with El Niño events. Changes in the understanding of what constitutes an El Niño event prompted further research into the relationship with Caribbean sea surface temperatures due to their impact on corals.Multiple statistical tests were employed to profile the relationship between the individual event types and the Caribbean. Ultimately, a bootstrapping technique determined that Central Pacific El Niño events bear a relationship, while Eastern Pacific event types do not.An attempt to hindcast El Niño events in order to comment on the history of impacts upon the Caribbean was unsuccessful due to a lack of sufficient input data, but a model determining potential locations of data is presented.
The rise of ocean temperatures globally has become a grave threat to coral reefs, as it is increasing the severity and frequency of mass coral bleaching events and post-bleaching coral mortality. The continued existence of productive coral reefs will rely on corals’ ability to undergo recovery. In 2010, Tobago’s coral reefs were exposed to severe heat stress leading to mass bleaching of up to 29-60% of colonies at observed sites. This study evaluated the impact of coral bleaching and recovery of coral communities across three major reef systems in Tobago that differ in their exposure to terrestrial runoff. Assessments were done on the 1) density and composition of coral juveniles to characterise the levels of recruitment, 2) sedimentation rates and composition to understand its potential impact on recovery, and 3) species’ size frequency distributions in 2010, 2011 and 2013 to examine temporal changes among population size structure. In 2013, low juvenile densities were observed (5.41 ± 6.31 m-²) at most reef sites, which were dominated by brooding genera while broadcasting genera were rare. Sediment material, measured in May and June (end of Tobago’s dry season) was mostly terrigenous and deposited at rates below coral stress threshold levels at most sites. Out of 27 species populations assessed between all sites, 4 populations mean colony size had significantly changed by the bleaching event, and only changed 5 populations over the two following years. The few populations that were significantly altered (mainly S. siderea and M. faveolata) after the bleaching saw a rise in small sized colonies, mostl likely as a result of colony fragmentation. This study highlights that recovery via sexually produced recruits among broadcasting species was limited. While sedimentation rates were low, it is likely they are significantly higher throughout the rainy season, thus a long-term sedimentation study is highly recommended. Most coral populations resisted significant alteration from heat stress in 2010. However, given that future thermal stress is projected to become more intense, this study shows that mass bleaching disturbance could lead to decline coral population’s mean colony size, which could affect coral recovery as smaller colonies are less fecund.
The El Niño/ Southern Oscillation (ENSO) is known to influence the weather in western North America through teleconnections. Several studies have established a relationship between ENSO and forest fire occurrence. However, a recently discovered variant of ENSO, called Central Pacific El Niño, may cause a different teleconnection and forest fire pattern.Investigating and classifying past El Niño events and their possible influence on weather and forest fire patterns in western North America from 1981-2010 was the objective of this study.The analysis revealed that current El Niño classification methods are suboptimal and that a binary distinction leads to misclassification of events. It, however, confirms that the two types show a different warming pattern as well as different wind and precipitation patterns. These characteristics of the Central Pacific El Niño can cause different extra tropical teleconnections in western North America than the canonical El Niño. Variation of teleconnections within the events and the limited amount of events, however, complicate a clear conclusion. Further, other oscillations such as the Arctic Oscillation play a major role in impacting the climate in western North America. Exploratory analysis of natural forest fires of North America identified hot spots of annual area burned in central Alaska, north-west and central Canada and western United States. Further, singular value decomposition and spatial correlation analysis revealed a different teleconnection response in summer drought patterns over western North America related to the two types of El Niño. The drought pattern is significantly related with forest fire frequency and area burned in certain regions across western North America. A clear connection between the different El Niño types and the forest fire pattern however remains inconclusive.
In this thesis I analyse the effects of the Kiribati Adaptation Project (KAP). The KAP is an early climate change adaptation project and it has been instrumental in the World Bank’s (the implementer of the KAP) expansion into the climate change agenda. I situate the KAP in the long, colonial, history of developmentalism and draw from critical development and policy studies to understand this project. Although climate change adaptation and development are contradictory in many senses, they have similarities: they are practiced by the same institutions, with the same project management techniques, and they are implemented through projects. I ask the following research questions:1. What work does climate change adaptation do as an organising principle for a project?2. How is climate change adaptation as a policy articulated into grounded practices?3. What are the unintended effects of a novel climate change adaptation project in an archetypical vulnerable place?To answer these research questions I draw from six weeks field work in Kiribati, where I met with KAP project managers and consultants, government officials and other interested onlookers. In chapter three, I observe that the KAP was focused on producing technical reports and technical expertise. I analyse why this is the case and what some of the effects of this are. By participating in the KAP, consultants, funders and other i-Matang relatives of the project gain expertise in the novel, and increasingly lucrative, arena of climate change adaptation. In chapter four, I analyse the ways in which i-Kiribati actors assemble and perform their vulnerability to climate change. Performances are an intentional strategy to gain recognition for the plight of the low-lying and fragile atoll nation. Officials and public servants have little choice but to perform their vulnerability; the Government of Kiribati depends on these finances, but this dependence is uncertain. The KAP is a key site, as it exemplifies the asymmetries of climate change adaptation and mitigation. The KAP expects to create local resilience in the face of an exogenous threat, in the place least able to be resilient, and least responsible for causing the threat.
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