South Africa comprises almost 10% of known plant species and also has the only arid zone "hotspot" defined worldwide, namely the succulent Karoo. Anthropogenic climate change predictions for South Africa suggest rapid climate change in the next 50 years will have adverse effects on its vegetation biomes. This study shows how the aborescent succulent, Aloe pillansii, has a limited distribution due significantly to environmental and climatic variables and therefore it is potentially at risk given anthropogenic climate change predictions. The total South African A. pillansii population investigated is made up of 1202 individuals and is found in the Richtersveld, which is part of the Succulent Karoo. The A. pillansii individuals were sampled in terms of their height and geographical position and then defined into subpopulations by a distance of 2 kms of separation. The sub-populations were then evaluated in terms of their respective environmental and climatic variables acquired from a CCWR database for South Africa using Arc View 3.2. The sub-population size class distributions were also constructed so that population dynamics and recruitment could be investigated. The results show how the A. pillansii sub-populations are limited to a specific environmental and climatic range. The sub-populations group along similar environmental and climatic variables with the healthiest sub-populations found at lower elevation, higher temperatures and higher Potential Evapo-Transpiration. The climatic range of A. pillansii is also evident from the range of its environmental and climatic variables and the associated unhealthy sub-populations that lie on the extremes of this range. Recruitment was found to correlate strongly with the environmental and climatic variables, % winter rainfall and elevation, suggesting it is moisture limited. The evidence found in this study of A. pillansii 's specific environmental and climatic distribution may have negative implications for its future survival and conservation especially with present indications of anthropogenic climate change.

The subantarctic Prince Edward Islands (PEIs, 47◦S-38◦E) are classified as isolated and hostile regions, in which the terrestrial and marine ecosystems are relatively simple and extremely sensitive to perturbations. The island’s location, between the Subantarctic Front (SAF) and the Polar Front (PF), bordering the Antarctic Circumpolar Current (ACC) provides an ideal natural laboratory for studying how organisms, ecological processes and ecosystems respond to a changing climate in the Southern Ocean. Recent studies have proposed that climate changes reported at the islands may correspond in time to a southward shift of the ACC and in particular of the SAF. This southward migration in the geographic position of major ocean fronts is likely to coincide with dramatic changes in the distribution of species and total productivity of this region. However, there are other sources of variability in the hydrodynamic conditions around the PEIs: upstream of the islands, at the South West Indian Ridge (SWIR), a region of high eddy kinetic activity produces mesoscale features that directly irrigate the PEIs and may impact their marine environment. Based on satellite altimetry in that region, the positions of the SAF and PF were found to be highly variable at interannual and monthly time scales. They also revealed a significant long-term southward trend which was highlighted at the Southern Ocean scale. The mesoscale activity also showed an interannual and intra-annual variability and a decrease in eddy kinetic energy over 24 years was observed in the region. At a more local scale, we highlighted that the archipelago’s environment was impacted by the mesoscale features produced at the SWIR. The temperature, the mixed layer and velocities recorded between the islands were clearly affected by the eddies passing in the vicinity of the PEIs. Moreover, a large signal dominating the main current time series appeared to be a tidal signal, another important driver of variability of the circulation in between the two islands. On a second hand, an idealised model configuration was designed for the PEIs region to study the mesoscale eddy properties and the physical mechanisms of their formation at the ridge. The Eddy Available Potential Energy revealed a maximum of energy around 800 m depth, confirming the deep reaching characteristic of the eddy originated in the region and suggested the presence of a local energy source at this depth. This eddies activity was shown to be the result of a combination of barotropic and baroclinic instabilities occurring at the ridge. Finally, we investigated on the potential consequences of a southward shift of the SAF in the region of the islands. Because the model was idealised, it allowed us to simulate an SAF southward shift by shifting the initial and boundary conditions. The main result was the clear decrease of mesoscale activity in the region which could potentially impact the ecosystems of the PEIs.

Climate variability is an important characteristic of regional climate, and a subject to significant control from teleconnections. An extended diagnosis of the capacity of climate models to represent remote controls of regional climate (teleconnections) is vital for assessing model-based predictions of climate variability, understanding uncertainty in climate projections and model development. An important driver of climate variability for Africa is the sea surface temperature (SST) - rainfall teleconnection, such as the El Ni˜no/Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). In this study, an assessment of the teleconnection between tropical SSTs and Eastern African rainfall in global and regional climate models is presented, with particular attention paid to the propagation of large-scale teleconnection signals (as represented by model reanalyses and Coupled Global Climate models (CGCMs)) into the domain of the Regional Climate Models (RCMs). The teleconnection-rainfall relationship with the Eastern Africa region is assessed in two rainfall seasons (June-July-August-September and October-November- December) under present and future periods. Evaluation runs (RCMs driven by reanalysis datasets) and historical simulations (RCMs driven by CGCMs) are assessed to quantify the ability of the models to capture the teleconnection relationship. The future analysis is performed for two Representative Concentration Pathway scenarios (RCP4.5 and RCP8.5) to assess future change in this relationship as a result of global warming. Using ERA-interim reanalysis as perfect boundary conditions, the RCMs adequately simulate the spatial and temporal distribution of rainfall in comparison with observations, although the model performance varies locally and seasonally within the region. Furthermore, the RCMs correctly capture the magnitude and spatial extent regional-scale seasonal rainfall anomalies associated with large-scale oceanic modes (ENSO and IOD). When the lateral boundary conditions are provided by CGCMs, RCMs barely capture the regional teleconnection patterns associated with large-scale modes, and mostly depend on the selection of the driving CGCM. Comparison of the CGCM-driven RCM simulations with the reanalysis-driven RCM simulations revealed that most of the errors in teleconnection found in the RCM simulations are inherited from the host CGCMs. The ERA-Interim driven downscaled results show better agreement with observed spatial teleconnection patterns than the CGCM driven downscaled results. Analysis of the CGCMs and corresponding downscaled results showed that in most cases both the CGCM and the corresponding downscaled simulations had similar teleconnection patterns, but in some cases the RCM results diverge to those of the driving CGCM results. It has been demonstrated that similarities in SST-rainfall teleconnection patterns between the RCM simulations and respective driving CGCM simulations are noted over the equatorial and southern part of the region during OND season, where the rainfall is primarily controlled by large-scale (synoptic-scale) features, with the RCMs maintaining the overall regional patterns from the forcing models. Di↵erences in RCM simulations from corresponding driving simulations are noted mainly over northern part of the domain during JJAS, which is most likely related to mesoscale processes that are not resolved by CGCMs. Looking at the model projections of the future, although the spatial pattern of teleconnections between ENSO/IOD and rainfall still persist, important changes in the strength of the teleconnection have been found. During JJAS, ENSO is an important driver of rainfall variability in the northern parts of the region where dry anomalies are associated with El Ni˜no and wetter anomalies with La Ni˜na. Both regional and global ensemble projections show higher rainfall during La Ni˜na and lower rainfall during El Ni˜no over the northern part of the region compared to the present period. During OND, the teleconnection between ENSO/IOD and rainfall is projected to strengthen (weaken) over Eastern horn of Africa (southern parts of the region) compared to the present period. This implies heavy seasonal rains associated with positive phases of ENSO and IOD will increase in future across the Eastern horn of Africa. The change OND rainfall teleconnections are stronger and also more consistent between the models and scenarios as compared to the change in JJAS teleconnections. These findings have an important implication for the water and agricultural managers and policies in the region to tackle the anticipated droughts and floods associated anthropogenic climate change. Finally, the analysis demonstrated that the largest source of uncertainty in the regional climate model simulations in the context of teleconnective forcing of rainfall over Eastern Africa is the choice of CGCM used to force the RCMs, reinforcing the understanding that the use of a single GCM to downscale climate predictions/projections and using the downscaled product for assessment of climate change projections is insufficient. Simulations from multiple RCMs nested in more than one GCM, as is undertaken in the Coordinated Regional Downscaling Experiment (CORDEX), are needed to characterize the uncertainty and provide estimates of likely ranges of future regional climate changes.

The effects of environmental warming on the reproductive performance of birds are most easily studied in desert habitats where birds already experience air temperatures (Tₐs) close to their upper thermal tolerance. Many desert birds coincide breeding with periods of food availability triggered by rainfall during the summer season. Daily maximum air temperatures (ₘₐₓ) during the Kalahari summer season frequently reach the lower forties (°C) and recent years have been characterised by reduced rainfall and increased Tₐ. Breeding Southern Yellow-billed Hornbills (Tockus leucomelas) could be particularly vulnerable to high Tₐ due to their breeding strategy whereby the females are confined to the nest cavity for most of the nesting period. During this time their male partners are solely responsible for food provisioning, which imposes a considerable energetic demand. In this thesis, I investigated the extent to which Tₐ affects the ability and willingness of breeding males to provision their female partners and offspring. And consequently, the extent to which male investment and the thermal environment affect female body mass (Mb) and chick development rates in Southern Yellowbilled Hornbills in the Kalahari. During three consecutive hornbill breeding seasons (October - March, between 2012 and 2015), I collected life history data during 50 breeding attempts by 32 hornbill pairs. At the study site, Southern Yellow-billed Hornbills readily breed in artificial nest boxes and this allowed me to assess the internal nest climate using temperature and relative humidity loggers which were placed in most of the nests. The male hornbills in the study population were semi-habituated which facilitated behavioural observations. Weather data were recorded at an on-site weather station. Morphometric data from females and chicks were collected on a daily basis at selected nests and perch scales installed at nest entrances recorded Mb data of the provisioning males. From chick hatching to chick fledging, I observed the behaviour of the males during 30-min focal follows and focussed on foraging behaviour, prey allocation decisions (nest versus self), microsite use and thermoregulatory behaviour. Male hornbills spent more than half of their time panting at Tₐs above 34.5 °C. Days on which this threshold temperature was exceeded were therefore described as 'hot days'. The male hornbills experienced trade-offs on hot days between foraging efficiency and panting behaviour, indicating that the additional cost of thermoregulation and high Tₐ affected foraging success (Chapter 2). Males would always provision larger prey items to the nest and consumed the smaller prey items themselves. As Tₐ increased, the males increased their foraging effort, but caught fewer and smaller prey items overall, reducing the total biomass they provisioned to the nest as well as the biomass they consumed. As a result, males were unable to maintain their Mb on days when Tₐ exceeded 37.9 °C (Chapter 3). A similar effect of hot days on Mb maintenance was observed in females and chicks within the nest. Independent of chick age, females departed the nest when their Mb reached a lower limit of 189.3 ± SD 18.1 g. The females would then aid the males in nest provisioning, however the negative effect of increasing ₘₐₓ on provisioning rate was still evident; i.e. females were not able to compensate for reduced male provisioning rates on hot days. High Tₐs during the nesting period resulted in smaller and lighter fledglings and overall reduced the probability of a successful nesting attempt (Chapter 4). A thermal imaging experiment revealed that the large beak of hornbills (both males and females) plays an important role in non-evaporative heat loss. Hornbills were observed to dissipate up to 19.9 % of the total non-evaporative body heat loss via the beak. This water-saving mechanism can be highly advantageous to hornbills living in arid regions where water availability is limited (Chapter 5). Lastly, a comparison of the results of the current study with those of a study on the same hornbill population carried out between 2008 and 2011 revealed that mean ₘₐₓ as well as rainfall during the nesting period had an important impact on overall hornbill reproductive effort and success (Chapter 6). Long-lived species are expected to prioritise future reproductive opportunities over current broods. However, the predicted scenario for the Kalahari is that high Tₐs become more extreme and periods of drought become more frequent. Therefore, I predict an increased risk of breeding failure among Southern Yellow-billed Hornbills in the future which could affect the persistence of this population.

This thesis examines the response mechanisms and adaptation strategies adopted by grapevine farmers to counteract the effects of the 2015-2018 Western Cape drought, which was characterised as particularly rare and severe. The challenges that emerged during the drought within the study area were exacerbated by the increasing competition over water resources between urban and agriculture users, as investment to supply water to urban users are expected to bring more economic and social value than investments in water supply for agriculture. The study responds to the dearth of literature on climate change adaptation strategies by grapevine farmers in South Africa. Using information from 27 open-ended, face to face interviews conducted with grapevine farmers operating in the Berg River catchment area, as well as an analysis of existing economic and weather data, the research sought to understand the effects of the water stress on grapevine production, the main cause of yield loss and the key drivers of farmers’ behaviour shifts. Analysis of industry production performance from 2015 to 2018 and observed rainfall from 2015 to 2017 suggests that water stress remains the key factor influencing grapevine yields. The water stress was also found to have catalysed later ripening of red varieties, higher pH levels in the wine and the introduction of emergency pruning methods to reduce water use, which in turn led to uneven budding budding due to pruning methods, later ripening of red varieties, higher pH levels in the wine. It was also found that the depleting quality of the Berg River water led to reduced yield, as well as heightened financial and psychological stress. The research identifies a portfolio of long-term and short-term adaptation options pursued by farmers in the study area, entailing reduced water consumption and increased water efficiency. The research identified that the drought induced farmers to suspend or reduce plant replacement. However, this behavior cannot be explained simply as responses to climate change, but that this is linked to the low profitability of the local wine grape industry. Most farmers adopted incremental measures rather than transformative strategies, where the major barriers to transformative adaptation included uncertainty regarding climate trends, limited financial capacity for large investments, the belief in grapevine drought resilience and the cultural attachment to viticulture.

Global climatic processes which control the interannual variability of summer rainfall over South Africa are studied. Monthly and seasonal rainfall variations are analysed with respect to fluctuations in sea surface temperature (SST), outgoing longwave radiation (OLR) and tropospheric winds. OLR is used as a proxy for convective intensity and for the identification of areas of sympathy and opposition to convection over South Africa. Wind data (and derived parameters) are employed to explore large- scale tropical dynamical structures. Plausible explanations are offered for the observed associations. A change in sign of the correlation structure from the October/November rainfall regime to the December through March regime is indicative of a shift from downstream advective processes (Atlantic side) to a teleconnection-type of behaviour (Indian Ocean side). Rainfall variations during the late summer months show significant (and negative) links with SST fluctuations within the equatorial/tropical Pacific and Indian Ocean areas and are consistent with results obtained in analyses with respect to OLR fluctuations. December OLR in the Western Equatorial Indian Ocean is associated with a large portion of the variance in late summer rainfall, and points to a possible relation with the evolution of the Indian monsoon. The positive association implies that reduced cloudiness off the eastern coast of equatorial Africa in the spring precedes above normal mid- and late- summer rainfall over South Africa. Vertical mass overturnings are investigated through the velocity potential and derived parameters (the Zonal Circulation and Meridional Circulation Indices). The results suggest that the vertical tropospheric cells are among the important associated components which modulate climate across southern Africa, and that broad scale flows have an impact upon regional circulation cells. Evaluation of the vertical circulations with respect to wet and dry composites reveals that the Walker-type cell which connects a branch over the Indian Ocean gradually forms after November and reaches peak development in February. A slight increase of SST in the Central Equatorial Indian Ocean (CEI) modifies the Walker cell anomaly leading to below normal summer rainfall over South Africa. Additional thermodynamic inputs in the CEI region are conducive to deeper convection, hence elevated outflow signatures are observed in the velocity potential and related fields. It is conjectured that the teleconnections between South Africa, the CEI and the remote Pacific Ocean regulate the depth of moisture influx and convergence over South Africa. Based on the results of this study, it is believed that empirical models could be designed for long-range prediction of summer rainfall anomalies over the central interior of South Africa.

In an attempt to determine why trees and grasses are able to coexist in savannas, Walter (1971) first proposed the root niche separation model for savannas which suggests that trees and grasses have differential access to water due to spatial differences in their rooting profiles. Subsequent studies in various savannas around the world have found that this is often not the case. In the central region of the Kruger National Park February & Higgins (2010) found that trees and grasses root at the same depths within the soil profile. In this study I determine whether the existence of fine roots in the soil profile necessarily indicates root activity. I also aim to determine the effect of increased water and nitrogen availability on root activity of trees and grasses. Pits of 20 x 20 em were dug to a depth of 40 em in plots that were either irrigated with the equivalent of 30 ml of rainfall per month or left without irrigation. This study was performed at the end of the rainfall season. I found that trees and grasses root at the same depths under moist and dry edaphic conditions as well as in plots with increased nitrogen. Tree roots are however, significantly more active than grass roots in non-irrigated plots. Temporal separation in root activity therefore seems to be a factor that allows for the coexistence of trees and grasses in savanna ecosystems.

This thesis investigates the governance of two global challenges in terms of policy learning and collective action. The COVID-19 pandemic and anthropogenic climate change pose critical challenges to human well-being as much as they depend on collective responses to contain them. The comparative analysis of governance structures in climate change and the COVID-19 pandemic shows similarities and differences. A significant difference is the timing and pace of the responses: while international organisations and governments took drastic measures in response to the spread of the coronavirus, global and national responses for climate change have been comparatively slow. However, similarities emerge in the nature of the responses to these two global challenges: individual behavioural change is necessary to manage the challenges, which rarely occur without political guidance and public policy. The thesis combines the concepts of collective action and policy learning in a conceptual framework for the comparative analysis of global governance between the COVID-19 pandemic and climate change. The success of the rapid and large-scale coordinated response to the COVID-19 disease outbreak has indicated that these conceptual notions are required for global governance and that they can be harnessed on a large-scale to address a GPG or commons problem. Therefore, in order to more effectively address the GPG problem of climate change, these conceptual notions of global governance need to be harnessed not only between international organisations and governments but between governments and non-state actors. The shared policy challenges of both crises, therefore, highlight the importance of good policy design and the coordination of actors. The lessons identified can be broadly applied to the global commons problem of climate change and can help policy makers identify where enhanced policy learning and collective action is required. In particular this should be applied to coordinate policy learning and collective action from municipal to global levels and enhance the participation of the global public for long-term climate policy.

Climate change is a threat to food security. A substantial body of research supports this conclusion for climate change threats to plants with agricultural value, as well as wild-harvested food from animals, such as fish. However, much less is known about climate change threats to wild-harvested food plants despite these species meeting important dietary needs for a large number of households in developing countries, especially when crops fail or during other times of hardship. My study was the first to look at climate change risk to a broad group of wild edible plants and focussed on the wild food plants (WFPs) of southern Africa. The aims of my study were to determine where WFPs occur in southern Africa; whether these WFPs will be threatened by climate change; and how climate change risk for WFPs intersects with climate change risk to staple crops. Species distribution models were used to obtain the historical geographic range of 1190 WFP species and to make projections of range change for 2070 under both low (Representative Concentration Pathway (RCP) 2.6) and high (RCP 8.5) greenhouse gas emissions scenarios. I also mapped percentage change between historical and future yields for maize and sorghum to identify regions where both crops and WFPs, or just one of these are at risk from climate change. WFP species richness in southern Africa generally increases from west to east across the region, with the Eastern Cape, Kwazulu-Natal and Mpumalanga provinces of South Africa having the highest WFP species richness. It is projected that for RCP 2.6, 40% of WFP species will experience a decrease in range extent within southern Africa, increasing to 66% of WFP species for RCP 8.5. For RCP 2.6, the loss of suitable climatic conditions is projected to decrease local WFP species richness most in the north-eastern parts of southern Africa, while increases in WFP species richness are projected in the south and east of South Africa. For RCP 8.5, decreases of more than 200 species are projected for multiple regions in north-eastern South Africa, and local WFP species losses of more than 50% are projected for most of Botswana. Despite these decreases, WFPs could still play an important role in food security during times of low agricultural yield as a result of changing climate conditions, especially in low-income, rural communities that are reliant on smallholder farming. For instance, in parts of the Eastern Cape province of South Africa and northern Namibia, WFP species richness is projected to increase while maize and sorghum yield are projected to decrease. People may be more able to rely on WFPs as a nutritional safety net in these regions into the future. This safety net, however, may be lost in large regions of South Africa's North West and Free State provinces, on the north-eastern border between South Africa and Botswana, as well as parts of northern Namibia, where declines in both crop yield and WFP species richness are projected. This research could prove valuable for climate change adaptation planning, especially in more vulnerable rural regions of southern Africa. Furthermore, by integrating traditional knowledge of WFPs into food security risk assessments and response options, it could provide a more inclusive range of food supply options people can use in order to mitigate risk. However, in order to ensure future food security, more research is needed on WFP uses, nutritional value, responses to climate change, and suitability for cultivation. Still, by looking beyond the farm level and conventional crops to the exceptional diversity of WFPs people obtain from their environment, my research has made a first step towards understanding the linkages between WFPs, agriculture, food security, and climate change.

Thesis advisor: Philip E. Strahan / The dissertation consists of two essays on corporate finance, banking, and political economy. The first chapter studies how partisan-driven views about climate change affect institutional investors’ investment in assets that are exposed to climate risk. The second chapter examines how unexpected political chaos can affect politically active companies in a negative way. In “Climate Change, the Partisan Divide, and Exposure to Climate Risk”, I study how partisan-driven beliefs about climate change affect the distribution of climate risk across mortgage lenders. Using wildfires to capture climate exposure, I find that Republican-leaning lenders are more likely to approve mortgage applications in high wildfire risk areas than Democratic-leaning lenders. This difference in approval rates is only evident among second-lien and jumbo mortgage applications, highlighting how securitization affects risk-taking incentives. Lastly, Republican-leaning lenders originate more climate-exposed second-lien and jumbo loans and thus hold more wildfire risk. The findings suggest that dispersion over climate change beliefs affects how institutional investors hold climate risks, potentially affecting financial stability. In “Downsides of Corporate Political Spending: Evidence from Mass Shootings”, I study the negative impacts of corporate political spending on firm outcomes. Using data from 20 years of mass shootings, I find that when mass shootings take place, companies that primarily donate to pro-gun-rights politicians experience negative stock price reactions and worse operating performance. The negative impacts on companies’ bottom line are stronger when incidents are deadlier. The decline in operating performance reverses within a couple of years. The findings are not driven by firms contributing to Republican politicians. Similarly, using Summary of Deposits data from FDIC, I find that banks primarily donating to pro-gun-rights politicians also experience higher deposit outflows around mass shootings. After incidents, firms significantly reduce corporate political donations to pro-gun-rights politicians. Overall, my findings highlight negative impacts on companies resulting from their political spending being disapproved by stakeholders. / Thesis (PhD) — Boston College, 2022. / Submitted to: Boston College. Carroll School of Management. / Discipline: Finance.