Dissertations / Theses on the topic 'Responses to climate change'

The high northern latitudes have warmed faster than anywhere else in the globe during the past few decades. Boreal ecosystems are responding to this rapid climatic change in complex ways and some times contrary to expectations, with large implications for the global climate system. This thesis investigates how boreal vegetation has responded to recent climate change, particularly to the lengthening of the growing season and changes in drought severity with warming. The links between the timing of the growing season and the seasonal cycle of atmospheric CO2 are evaluated in detail to infer large-scale ecosystem responses to changing seasonality and extended period of plant growth. The influence of warming on summer drought severity is estimated at a regional scale for the first time using improved data. The results show that ecosystem responses to warming and lengthening of the growing season in autumn are opposite to those in spring. Earlier springs are associated with earlier onset of photosynthetic uptake of atmospheric CO2 by northern vegetation, whereas a delayed autumn, rather than being associated with prolonged photosynthetic uptake, is associated with earlier ecosystem carbon release to the atmosphere. Moreover, the photosynthetic growing season has closely tracked the pace of warming and extension of the potential growing season in spring, but not in autumn. Rapid warming since the late 1980s has increased evapotranspiration demand and consequently summer and autumn drought severity, offsetting the effect of increasing cold-season precipitation. This is consistent with ongoing amplification of the hydrological cycle and with model projections of summer drying at northern latitudes in response to anthropogenic warming. However, changes in snow dynamics (accumulation and melting) appear to be more important than increased evaporative demand in controlling changes in summer soil moisture availability and vegetation photosynthesis across extensive regions of the boreal zone, where vegetation growth is often assumed to be dominantly temperature-limited. Snow-mediated moisture controls of vegetation growth are particularly significant in northwestern North America. In this region, a non-linear growth response of white spruce growth to recent warming at high elevations was observed. Taken together, these results indicate that net observed responses of northern ecosystems to warming involve significant seasonal contrasts, can be non-linear and are mediated by moisture availability in about a third of the boreal zone.

This research addresses the need for processes at the local government level that can effectively move communities towards taking meaningful action on climate change. It evaluates the long-term impact of one such process – the Local Climate Change Visioning Project (LCCV): a community engagement and decision support process in two case study communities: Delta and North Vancouver. The LCCV process uses landscape visualization tools integrated with participatory modeling and future scenario development to illustrate to local government staff, stakeholders, and the broader public what their community could look like under various future scenarios of climate change adaptation and mitigation. Through a document analysis and 12 semi-structured interviews with stakeholders who participated in the LCCV, this research project attempts to discover if the process can facilitate the adoption of climate change mitigation and adaptation responses at the municipal level. While the LCCV was not able to shift the development path of the local communities, the LCCV did help to facilitate action on climate change.

Recent (post-1950s) climate change impacts on society and ecosystems have been recognised globally. However these global impacts are not uniform at regional or local scales. Despite research progress on such scales there are still gaps in the knowledge as to 'what' is happening and 'where'? The goal of this study addresses some of these gaps by analysing climate variability and vegetation response at the furthest south westerly peninsula of the United Kingdom. This research is focused on West Cornwall (South West England) - an area dominated by a strong maritime influence. The first part of this PhD research analysed archive and contemporary instrumental data in order to detect any trends in climate variability. The weather data was retrieved from the Met Office archive for Camborne 1957-2010 and Culdrose 1985-2011 stations; Trengwainton Garden (1940-2010), and from the Royal Cornwall Polytechnic Society, for Falmouth (1880-1952) and Helston (1843-1888). The data showed positive trends in mean annual and maximum temperature with the largest trend magnitude in the 20th and 21st century. Seasonal temperature change varies locally with the highest increase in autumn spring and summer. Precipitation trends were only positive for the 19th century for Helston. Correlation between precipitation data and North Atlantic Oscillation (NAO index) was negative, however the opposite result was detected when the NAO index was correlated with temperatures. Surprisingly, return period analysis showed a decrease in the frequency and intensity of extreme precipitation events post 1975 for Camborne and Trengwainton Garden stations. The second part of this study analysed changes in vegetation distribution in West Cornwall using historical and contemporary vegetation records. Historical vegetation records were used from the Flora of Cornwall collection of herbarium records and contemporary vegetation records which were available online, containing mainly the 'New Atlas of British and Irish flora'. Data sets were geo-referenced using ArcGIS in order to analyse changes in species geographical distribution pre and post-1900. Analysis showed that historical vegetation records can be used to assess any changes in geographic distributions of vegetation. Analysis for the area of West Cornwall showed a loss of range for 18 species, for 6 species this loss was larger than 50% of the area, and there was no change in overall range area for 10 species. Ellenberg values and environmental indicator values showed that they can be used as an indicator of environmental change, showing a decrease in species with lower January temperatures. Analysis also showed an increase in moderate wetter species, where species with extreme low and high precipitation environmental indicator values showed a greater loss. Furthermore species with a higher requirement for light showed a loss as well as species with lower nitrogen values. To analyse the loss of species at the local scale, West Cornwall was divided into three areas (North Border Cells, Central West Cornwall Cells and South Border Cells). The highest loss of 11 species was detected for South Border Cells, where the loss for Central West Cornwall Cells was 6 and for North Border Cells 8 species. It was found that 17 species were experiencing loss on different local sites. For 9 of these 17 species, change at the local scale was different to the national scale change at the individual species level, group level and habitat level. Furthermore, the whole area of West Cornwall lost two species post-1900, with a different loss locally. This showed that species could be protected locally in appropriate microclimate refugia, which will be of benefit for the preservation of regional identity ecosystem services and overall genetic pool of the species.

Climate change is a pressing issue today. Drastic policy change and individual behaviour change are required to mitigate and adapt to the changes. For this to be Implemented successfully the public must be engaged. There is a shortfall in qualitative research into public engagement with climate change where engagement Is defined in terms of cognitive, affective and behavioural responses. A case study was undertaken in Bristol, UK. Focus groups were used to examine public engagement with climate change.

Many species are responding to anthropogenic climate change by shifting their ranges to higher latitudes. Understanding the factors that drive species’ responses will help ecologists and conservationists develop strategies to avoid negative climate change impacts. I investigated shifts at the northern (cool) range margins of 1573 southerly-distributed species from 21 animal groups in Great Britain, over the past four decades. My findings confirm continued polewards range shifts (18 km decade-1 over 1986-2010). I then concentrated on 347 British species from 14 invertebrate taxa, discovering considerable variation in the distances moved within each taxonomic group (but not between groups). I used land cover data and distribution records to determine each species’ habitat specialism, and to quantify habitat availability. Habitat availability explained up to half of the range shift variation. I conclude that interactions between species’ attributes and the environment are important determinants of range shifts. Abundance data are used to study species’ responses to environmental changes but, unlike distribution records, are not available for many taxa. Data from 33 British butterflies revealed a strong correlation between mean year-to-year changes in total number of distribution records and mean year-to-year change in abundance, suggesting that distribution data can be used to identify species’ population variability, and ecologists can investigate the influence of climate change on species’ populations without abundance data. I conclude that rates of range shifting are highly variable among species, suggesting that understanding species-specific range shifts is necessary to assess species’ responses to climate change. The availability of habitat at the range margin strongly influence rates of range shifting which suggests the need for habitat management aimed at facilitating species’ dispersal and population establishment. Citizen science data have potential to assist ecologists in examining species’ responses to climate change and in identifying, predicting and mitigating climate change impacts in the future.

UK-listed companies have multiple mandatory climate reporting requirements that aim to not only engage them in climate change, but also get them to take action beyond reporting. The thesis looks at the two latest mandatory requirements—‘Mandatory Carbon Reporting’, and ‘Adaptation Reporting Power’—and discusses what they mean for business performance and management of climate change. To understand the rationales, practices, and impacts of climate reporting on organisational cultures and behaviours an extensive desktop review analysed websites and Annual reports of 176 companies listed either on the FTSE 100 or as one of the UK’s critical infrastructure providers. This was supplemented by an intensive phase of 36 interviews with individuals representing 19 companies in one of four case-study sectors (e.g., Energy utility, Extractive, Financial service, Water); and an additional 24 third party conversations with Government officials, Regulators, Consultants, and Independent body organisations. It emerged that 93% of companies sampled regard climate change as meriting at least some engagement, with four levels of reporting identified, and a difference in the number of companies engaged in carbon reporting (93%) and adaptation reporting (28%). Rationales for climate reporting mirror those for wider social and environmental reporting. Companies report because of potential win-win outcomes, they are legitimacy seeking, and/or want to ensure auditability. However, reporting per se does not necessarily lead to corporate action on climate change. Instead there are economic, reputational, and regulatory factors, and sectoral characteristics (e.g., environmental sensitivity, energy intensity) that affect reporting’s impact. This research has implications for the aims, designs and purposes of imposing reporting requirements to help business and society tackle climate change and the challenges presents. It contributes to a growing debate on the social implications of corporate reporting by highlighting the need to better understand what motivates businesses to not only disclose information, but also take action beyond reporting.

Climate change and variability are predicted to threaten agricultural production in Southern Africa. For example, Zambia's agriculture remains vulnerable to climate change and variability due to the small-scale farmers' dependence on rain-fed agriculture. Some studies in Zambia have shown the quantitative negative impacts of climate variability on agriculture; however, there is limited knowledge on how farmers perceive the impacts and adapt their agricultural systems. To fill in the knowledge gap mentioned above, the aim of the present study was to evaluate farmers' observations of climate variability impacts and their responses. The study then evaluates the integration of farmers' climate variability observations and adaptation strategies into local district plans. Such integration is deemed critical to ensure agricultural strategies promoted by extension officers are locally relevant and are adopted by the farmers. The study is based on semi-structured interviews and literature review. Thirty-one (31) farmers from Mwembeshi, Chilanga District, Zambia, participated in the study. The findings of the survey indicate that farmers in Mwembeshi are aware of their vulnerability to climate variability impacts. As a result of the observed impacts, they have developed several adaptation strategies. Through this study, extension agents were also interviewed in order find out what adaptation strategies are promoted to the farmers. The findings of the research indicate agricultural extension agents follow national agricultural adaptation strategies (top-down approach). As a result, local agricultural development plans would not specifically integrate/respond to climate variations impacts observed by the farmers. In order to engage local farmer impacts of the climate variability and their adaptation strategies into the local plans, the research suggests a more flexible (or bottom-up) approach to local development planning. Such an approach would allow the integration of local farmer observations of climate variability and their adaptation strategies into district plans. The study also found that extension agents have limited knowledge of climate variability and change, which negatively affects knowledge transfer to farmers on the subject. Therefore, training the extension officers in the subject would most likely increase farmers' knowledge on climate variability and adaptation decision.

Climate change is the most pressing environmental threat faced by humans, yet responses – individually, collectively, and politically – have frequently lacked urgency. Why a threat of such magnitude should meet with inaction is a topic of growing conjecture among social science researchers. Social psychologists in particular have increasingly focused on the possible psychological mechanisms underlying denial and scepticism of anthropogenic climate change. I argue that all responses to climate change can be considered rational and adaptive, because these responses (be they opinions, emotions, or behaviour) afford the individual functional value.In this thesis, I examine what underlies the discordance between climate change threat and response by applying a functional analysis to responses associated with climate change. This analysis is theoretically guided by a motivated social cognition approach. I use the term to refer to theories and perspectives that assume that people’s values, attitudes, and beliefs have motivational underpinnings, and satisfy certain psychological and social needs. These motivations affect reasoning and belief and attitude formation by biasing how information is processed. The approach incorporates accounts such as motivated reasoning, interpersonal and social identity theories, social and system-level legitimacy theories, moral disengagement, and Terror Management Theory. Drawing upon these accounts, I construct a framework detailing the various goals and needs that responses to climate change might function to fulfil.Five main functional areas are identified: the reduction of internal psychological discomfort, self-image and self-esteem maintenance, the maximisation of positive affect, social-system justification, and effort reduction. To test aspects of the framework, I conducted two online national surveys: one in July-August 2010 (N = 5036), the other in July-August 2011 (N = 5030). A total of 1355 respondents completed both surveys. Respondents were asked about their beliefs, opinions, attitudes, and behaviours relevant to climate change, as well as individual difference measures, their levels of support for climate change policy, their emotional responses, and personal and image associations with climate change. In addition, four workshops (total N = 52) were undertaken in December 2010 and March 2011. These workshops were designed to elicit implicit associations and attendant emotions associated with climate change imagery drawn from the national surveys.Analyses of national survey data revealed several key findings: * The scientific consensus that climate change is happening, and is mostly caused by human activity, is not reflected in the opinions of the broader community; * While opinions about the causes of climate change are important in understanding pro-environmental behaviour, considerable variation in behaviour exists within opinion-types; * Negative high-arousal emotions are linked to climate change acceptance and pro-environmental behaviour; * Levels of moral engagement are central to action on climate change, and mediate the link between opinions and behaviour; * Those sceptical of climate change still consider big-polluting countries and multi-national corporations as partly responsible for both causing and responding to it; * Estimates about what the Australian community thinks about climate change differ markedly from actual opinions, and nearly everybody overestimates the levels of ‘climate change denial’ in the Australian community; * Underlying ideological values associated with system justification explain relationships with climate change responses above and beyond political preferences.Analyses of both the survey and workshop data revealed that politicians dominate who we associate with climate change, while scientists and people close to us are less commonly associated with climate change. Images commonly associated with climate change were broad and remote, although national-level impacts of climate change were salient for many people.Together, the results support the idea that responses function to fulfil different needs and goals for individuals, such as a need for social support, the negation of guilt and existential anxiety, maintaining a coherent self-identity, feeling morally adequate, and seeing prevailing social and economic systems as just. I conclude the thesis by modelling the psychological processes involved in fulfilling these needs and goals, and the expressions through which they might be observed with respect to responses to climate change. In particular, the model articulates how the implicit associations of individuals are shaped by societal, group, and intra-individual forces, and by the biased searching of sets of rules and beliefs. A series of recommendations for climate communicators is provided, including framing climate change in such a way as to appeal to competing needs and goals concurrently, alongside an overview of future research directions, and an explanation of why I probably won’t ride my bicycle to work tomorrow.

Anthropogenic climate change poses a serious threat to biodiversity. Accurate predictions of the ecological consequences of future abiotic change will require a broad perspective that takes into account multiple climate variables, species-specific responses, and intra- and interspecific dynamics. I addressed these issues in the context of a marine rocky intertidal community to determine how abiotic and biotic factors can mediate the effects of climate change. I began with two studies on the organismal-level effects of multiple abiotic variables. In the first study, I found that acute exposure to low salinity reduced the survival of littorine snails facing thermal stress, but that ocean acidification (OA) had no such effect. In a second study, I showed that sustained exposure to increased temperature and OA had positive and additive effects on the growth and feeding of the purple ochre sea star. These findings demonstrate that studies of multiple climate variables will be important not only to identify additive and non-additive effects, but also to determine which climate variables will be detrimental for a given species. Next, I measured how species-specific responses to climate change can alter species interactions. By quantifying the effects of body size on the feeding behaviours of sea stars preying on mussels, I demonstrated that climate-driven changes in body size can have profound impacts on the strength of this interaction. Finally, I investigated how population-level responses to multiple abiotic variables can be affected by the presence of an interacting species. I built a predator-prey model that simulates the ecologically important interaction between the purple ochre sea star and its preferred prey, mussels. Using empirical estimates of sea star and mussel responses to increased temperature and OA, I simulated their interaction under various climate scenarios. I found that predation exacerbated the effects of climate change on mussel populations, and that climate change increased the strength of the sea star-mussel interaction. My work demonstrates that the effects of climate change will likely be mediated by a combination of biotic and abiotic factors, and that these factors should be considered when making predictions about the ecological consequences of climate change.

Le changement climatique actuel entraine l'extinction de populations ainsi que des changements dans leur aire de répartition et leur composition. La dispersion impacte ces deux dernières réponses puisqu'elle permet de coloniser de nouveaux habitats et influence la composition des populations au travers du flux de gènes. En fonction de son adaptativité, la dispersion peut promouvoir ou réduire l'adaptation locale et modifier l'importance relative de la plasticité phénotypique et de l'adaptation génétique dans le changement de composition phénotypique des populations. Cependant, la fragmentation du paysage entrave la dispersion, affectant les deux réponses des populations au réchauffement et modifiant l'influence relative des différents processus impliqués dans ces réponses. Le but de cette thèse était de comprendre comment les réponses des populations au changement climatique pouvaient être affectées par la fragmentation du paysage et la dispersion. En suivant des populations de lézards distribuées dans un système expérimental permettant de manipuler simultanément les conditions climatiques et la connectivité entre habitats, nous avons démontré que la connectivité réduisait les effets du réchauffement sur la dynamique et la composition des populations. Nous avons observé que les décisions de dispersion étaient influencées par des facteurs intrinsèques et extrinsèques permettant de réduire l'influence d'un climat plus chaud sur la dynamique des populations, mais en réduisant également la densité des populations en climat plus froid. Etonnamment, nous avons aussi trouvé que la dispersion pouvait modifier la force et la direction des pressions de sélections agissant sur les phénotypes. Les actions conjointes de la dispersion et de la sélection contrebalançaient ainsi la réponse plastique des individus. En les intégrant dans un modèle, des décisions de dispersion adaptative similaires avaient une forte influence sur la persistance prédite des espèces face au réchauffement. En effet, nous avons démontré que la dispersion adaptative favorisait le changement d'aire de répartition des populations et réduisait leur risque d'extinction, en comparaison à un modèle avec dispersion aléatoire (indépendante de facteurs intrinsèques et extrinsèques). Plutôt que de considérer la dispersion comme un processus neutre, nos résultats soulignent l'importance de la considérer comme un mécanisme complexe, façonné par de multiples facteurs et capable de déterminer les réponses des espèces au changement climatique. Nos résultats suggèrent que la fragmentation pourrait fortement augmenter l'influence du changement climatique sur les populations et précipiter leur extinction. Nous appelons donc à une meilleure intégration de la dispersion et de la structure du paysage dans les études sur les réponses des populations au changement climatique
Contemporary climate change is leading to population extinction, range shift and composition changes. Dispersal shapes these two last responses by allowing colonization of new habitats and by affecting population composition through gene flow. Depending on its adaptiveness, dispersal can promote or hinder local adaptation and modify the relative influence of phenotypic plasticity and evolutionary adaptation in population phenotypic change. However, landscape fragmentation hampers dispersal, affecting both population responses to climate change, and modifying the relative influence of the different processes involved in these responses. The aim of this PhD was to understand how population responses to climate change could be influenced by landscape fragmentation and by dispersal. By monitoring lizards inhabiting experimental populations where both climatic conditions and connectivity among them were manipulated, we demonstrated that connectivity among populations buffered climate change effects on population dynamics and phenotypic composition. We found that dispersal decisions depended on multiple intrinsic and extrinsic factors allowing to reduce the influence of warmer climate on population dynamics, but decreasing population density in cooler climate. Surprisingly, we also found that dispersal could modify the strength and direction of climate-dependent selection pressures on phenotypes. As a consequence, selection and dispersal acted in synergy to counteract the plastic response of the individuals. When integrated into a model, similar adaptive dispersal behavior strongly altered predictions of species persistence under climate change. We indeed found that adaptive dispersal promoted species range shift and reduced extinction probability compared to a model where dispersal was random (i.e.independent of intrinsic and extrinsic factors). Rather than considering dispersal as a neutral process, our results highlighted the importance to consider it as a complex mechanism shaped by multiple factors and able to drive population responses to climate change. Our results further suggest that fragmentation could strongly increase the influence of climate change on populations and may therefore precipitate their extinction. We thus call for a better integration of dispersal and landscape structure when studying population responses to climate change

Understanding and predicting ecological responses to climate change is crucial if we are to manage for the detrimental consequences that might ensue in its wake. This thesis looks to develop some new ideas and tools for ecological prediction under climate change, focusing on species traits rather than species themselves as units of prediction. Chapter One begins by reviewing the basis for a trait-based approach to prediction, presenting evidence from natural and experimental systems that responses to climate change cluster by traits. Chapter Two undertakes a proof-of-concept modelling study, using a well-known dataset of contemporary phenological changes under warming to test for trait-based links in the strength and direction of species responses. Chapter Three addresses the critical issue of transferability. One of the strongest justifications for the use of a trait-based approach is that inferences may extend more generally beyond the focal species and system. To test this, it develops trait-based models for long-term datasets of first-arrival dates for migratory birds in two neighbouring US states and assesses cross-applicability between them. Having investigated the functionality and transferability of the trait-based approach, I then explore the bounds of its utility. Chapter Four uses a detailed record of community-wide changes in species abundance under ten years of experimental climate change to assess whether changes in abundance cluster by traits. It also re-evaluates the prevailing hypothesis guiding researchers' interpretations of ecological changes in this system. Chapter Five designs and implements an experiment building on the results of Chapter Four. This experiment tests the role of climatic effects on nitrogen-fixation in driving system dynamics via controlled removal of this trait from experimental communities. Overall, this thesis sheds new light on the role of traits in ecological responses to climate change, highlighting opportunities and limitations for using traits to organise our thinking over prediction and adaptation.

La fenologia és la clau per a controlar els processos fisicoquímics i biològics, especialment l’albedo, la rugositat superficial, conductància de les fulles, fluxos de carboni, aigua i energia. Per tant, l’estimació de la fenologia és cada vegada més important per a comprendre els efectes del canvi climàtic en els ecosistemes i les interaccions biosfera-atmosfera. La teledetecció és una eina útil per a caracteritzar la fenologia, encara que no existeix un consens sobre el tipus de sensor satel·litari i metodologia òptims per a extreure mètriques fenològiques. Els objectius principals de la meva investigació van ser (i) millorar l’estimació de la fenologia vegetal a partir de dades satel·litàries, (ii) validar les estimacions fenològiques amb observacions terrestres i teledetecció propera a la superfície, i (iii) comprendre les relacions entre les variables climàtiques i la fenologia en un context de canvi climàtic, així com avaluar les respostes de la vegetació en esdeveniments extrems. Aquests objectius s’exploren en els següents tres capítols de la tesi. En el capítol 2, vaig investigar la sensibilitat de la fenologia a (I) la variable de vegetació: índex de vegetació NDVI, índex d’àrea foliar (LAI), fracció de radiació fotosintèticament activa absorbida (FAPAR) i fracció de coberta vegetal (FCOVER); (II) el mètode suavitzat per a derivar trajectòries estacionals; i (III) el mètode d’estimació fenològica: llindars, funció logística, mitjana mòbil i primera derivada. El mètode basat en llindars aplicat a la sèrie temporal Copernicus Global Land LAI V2 suavitzada va donar resultats òptims al validar-los amb observacions terrestres, amb errors quadràtics mitjans de ~10 d i ~25 d per a l’inici d’estació fenològica i la senescència respectivament. En el tercer capítol vaig utilitzar mesures fenològiques continues de PhenoCam i FLUXNET a alta resolució temporal (30 minuts). Això permet una comparació més robusta i precisa amb la fenologia estimada a partir de satèl·lit, evitant problemes relacionats amb les diferències en la definició de mètriques fenològiques. Vaig validar la fenologia estimada a partir de sèries de temps de LAI amb PhenoCam i FluxNet en 80 boscos caducifolis. Els resultats van mostrar una forta correlació (R2 > 0,7) entre la fenologia obtinguda mitjançant teledetecció i les observacions terrestres per a l’inici d’estació i R2 > 0,5 per al final d’estació. El mètode basat en llindars va funcionar millor amb un error quadràtic mitjà de ~9 d amb PhenoCam i ~7 d amb FLUXNET per a l’inici de l’estació, i ~12 d i ~10 d, respectivament, per a la senescència. En el quart capítol vaig investigar els patrons espai – temporals de la resposta fenològica a les anomalies climàtiques en l’hemisferi nord utilitzant la fenologia estimada en el Capítol 2 i validat en el Capítol 2 i Capítol 3, i conjunts de dades climàtiques de múltiples fonts per a 2000-2018 a resolucions de 0,1º. També vaig avaluar l’impacte de les onades de calor extremes i les sequeres en la fenologia. Les anàlisi de correlació parcial de les mètriques fenològiques estimades amb satèl·lit i les variables climàtiques van indicar que els canvis en la temperatura pre estacional van tenir major influència sobre les anomalies fenològiques que la precipitació: com més alta és la temperatura, més aviat es l’inici estacional en la majoria de boscos caducifolis (coeficient de correlació mitjà de -0,31). Tant la temperatura com la precipitació van contribuir a l’avanç i retard del final d’estació. Un retard en la senescència es va correlacionar significativament amb un índex de precipitació – evapotranspiració estandarditzat (SPEI) positiu (~ 30% dels boscos). El final i inici d’estació va canviar > 20 d en resposta de l’onada de calor en la major part d’Europa en 2003 i als Estats Units d’Amèrica l’any 2012.
La fenología es clave para controlar los procesos fisicoquímicos y biológicos, especialmente el albedo, la rugosidad superficial, conductancia de las hojas, flujos de carbono, agua y energía. Por lo tanto, la estimación de la fenología es cada vez más importante para comprender los efectos del cambio climático en los ecosistemas y las interacciones biosfera-atmósfera. La teledetección es una herramienta útil para caracterizar la fenología, aunque no existe consenso sobre el tipo de sensor satelital y metodología óptimos para extraer métricas fenológicas. Los objetivos principales de mi investigación fueron (i) mejorar la estimación de la fenología vegetal a partir de datos satelitales, (ii) validar las estimaciones fenológicas con observaciones terrestres y teledetección cercana a la superficie, y (iii) comprender las relaciones entre las variables climáticas y la fenología en un contexto de cambio climático, así como evaluar las respuestas de la vegetación a eventos extremos. Estos objetivos se exploran en los siguientes tres capítulos de la tesis. En el capítulo 2, investigué la sensibilidad de la fenología a (I) la variable de vegetación: índice de vegetación NDVI, índice de área foliar (LAI), fracción de radiación fotosintéticamente activa absorbida (FAPAR) y fracción de cubierta vegetal (FCOVER); (II) el método de suavizado para derivar trayectorias estacionales; y (III) el método de estimación fenológica: umbrales, función logística, media móvil y primera derivada. El método basado en umbrales aplicado a la serie temporal Copernicus Global Land LAI V2 suavizada dio resultados óptimos al validarlos con observaciones terrestres, con errores cuadráticos medios de ~10 d y ~25 d para el inicio de estación fenológica y la senescencia respectivamente. En el tercer capítulo, utilicé medidas fenológicas continuas de PhenoCam y FLUXNET a alta resolución temporal (30 minutos). Esto permite una comparación más robusta y precisa con la fenología estimada a partir de satélite, evitando problemas relacionados con las diferencias en la definición de métricas fenológicas. Validé la fenología estimada a partir de series de tiempo de LAI con PhenoCam y FluxNet en 80 bosques caducifolios. Los resultados mostraron una fuerte correlación (R2 > 0,7) entre la fenología obtenida mediante teledetección y las observaciones terrestres para el inicio de estación y R2 > 0,5 para el final de estación. El método basado en umbrales funcionó mejor con un error cuadrático medio de ~9 d con PhenoCam y ~7 d con FLUXNET para el inicio de estación, y ~12 d y ~10 d, respectivamente, para la senescencia. En el cuarto capítulo, investigué los patrones espacio-temporales de la respuesta fenológica a las anomalías climáticas en el hemisferio norte utilizando la fenología estimada en el Capítulo 2 y validado en el Capítulo 2 y Capítulo 3, y conjuntos de datos climáticos de múltiples fuentes para 2000-2018 a resoluciones de 0.1°. También evalué el impacto de las olas de calor extremas y las sequías en la fenología. Los análisis de correlación parcial de las métricas fenológicas estimadas con satélite y las variables climáticas, indicaron que los cambios en la temperatura pre estacional tuvieron mayor influencia sobre las anomalías fenológicas que la precipitación: cuanto mayor es la temperatura, más temprano es el comienzo estacional en la mayoría de los bosques caducifolios (coeficiente de correlación medio de -0,31). Tanto la temperatura como la precipitación contribuyeron al avance y retraso del final de estación. Un atraso en la senescencia se correlacionó significativamente con un índice de precipitación-evapotranspiración estandarizado (SPEI) positivo (~ 30% de los bosques). El final e inicio de estación cambió >20 d en respuesta a la ola de calor en la mayor parte de Europa en 2003 y en los Estados Unidos de América en 2012.
Phenology is key to control physicochemical and biological processes, especially albedo, surface roughness, canopy conductance and fluxes of carbon, water and energy. High-quality retrieval of land surface phenology (LSP) is thus increasingly important for understanding the effects of climate change on ecosystem function and biosphere–atmosphere interactions. Remote sensing is a useful tool for characterizing LSP although no consensus exists on the optimal satellite dataset and the method to extract phenology metrics. I aimed to (i) improve the retrieval of Land Surface Phenology from satellite data, (ii) validate LSP with ground observations and near surface remote sensing, and (iii) understand the relationships between climate variables and phenology in a climate change context, as well as to assess the responses of vegetation to extreme events. These three main research objectives are explored in the three chapters of the thesis. In chapter 2, I investigated the sensitivity of phenology to (I) the input vegetation variable: normalized difference vegetation index (NDVI), leaf area index (LAI), fraction of absorbed photosynthetically active radiation (FAPAR), and fraction of vegetation cover (FCOVER); (II) the smoothing and gap filling method for deriving seasonal trajectories; and (III) the phenological extraction method: threshold, logistic-function, moving-average and first derivative based approaches. The threshold-based method applied to the smoothed and gap-filled Copernicus Global Land LAI V2 time series agreed the best with the ground phenology, with root mean square errors of ~10 d and ~25 d for the timing of the start of the season (SoS) and the end of the season (EoS), respectively. In the third chapter, I took advantage of PhenoCam and FLUXNET capability of continuous monitoring of vegetation seasonal growth at very high temporal resolution (every 30 minutes). This allows a more robust and accurate comparison with LSP derived from satellite time series avoiding problems related to the differences in the definition of phenology metrics. I validated LSP estimated from LAI time series with near-surface PhenoCam and eddy covariance FLUXNET data over 80 sites of deciduous broadleaf forest. Results showed a strong correlation (R2 > 0.7) between the satellite LSP and ground-based observations from both PhenoCam and FLUXNET for the timing of the start (SoS) and R2 > 0.5 for the end of season (EoS). The threshold-based method performed the best with a root mean square error of ~9 d with PhenoCam and ~7 d with FLUXNET for the timing of SoS, and ~12 d and ~10 d, respectively, for the timing of EoS. In the fourth chapter, I investigated the spatio-temporal patterns of the response of deciduous forests to climatic anomalies in the Northern Hemisphere using LSP derived in Chapter 1 and validated in Chapter 1 and Chapter 2, and multi-source climatic data sets for 2000–2018 at resolutions of 0.1°. I also assessed the impact of extreme heatwaves and droughts on deciduous forest phenology. Analyses of partial correlations of phenological metrics with the timing of the start of the season (SoS), end of the season (EoS), and climatic variables indicated that changes in preseason temperature played a stronger role than precipitation in the interannual variability of SoS anomalies: the higher the temperature, the earlier the SoS in most deciduous forests in the Northern Hemisphere (mean correlation coefficient of -0.31). Both temperature and precipitation contributed to the advance and delay of EoS. A later EoS was significantly correlated with a positive standardized precipitation-evapotranspiration index (SPEI) at the regional scale (~30% of deciduous forests). The timings of EoS and SoS shifted by >20 d in response to heat waves throughout most of Europe in 2003 and in the United States of America in 2012.
Universitat Autònoma de Barcelona. Programa de Doctorat en Ecologia Terrestre

This thesis offers a discursive and cultural analysis of the responses of three urban local authorities in the UK to the threat of climate change, in terms of mitigating its causes rather than responding to its effects. The research is qualitative in nature and focuses on data collected through semi-structured interviews conducted at each site and in related organisations. After an examination of theoretical positions on climate change and local government, with a cultural analysis of the dominant discourses in these areas, the local authority responses to climate change are analysed at three levels. The first level of analysis concludes that there are minor differences in the responses of different authorities, explainable by contingent circumstances, e.g. differences in infrastructure and institutional specialisations at each site. The second draws out commonalities in the responses of all three authorities, employing the analytical concepts of following rituals, utilising rhetoric, and producing results, and utilising aspects of New Institutionalist organisational theory, temporal sociology, discursive analysis, rhetoric and Cultural Theory (Thompson et aI, 1990). The third level of analysis identifies culturally distinct approaches to climate change, reflective of the 'ways of life' of Cultural Theory, across the authorities, through attention to the discourses employed by respondents. The thesis concludes that authorities' responses to climate change are constrained by the dominance of a 'hierarchist' culture within authorities, and of an 'individualist' culture in broader society, leading to the suppression of conceptualisations of, and responses to, climate change which are arise from the other active 'way of life'; egalitarianism. It argues that egalitarianism offers insights and responses appropriate to 'commons' problems, and that to ensure an effective response to climate change within local authorities, there must be a promotion of egalitarian social relations and cultural biases within them.

Species are responding to climate change by shifting their distributions polewards and/or uphill. However, the rates at which distributions are changing vary greatly among species. An understanding of how species’ distributions are changing, and what drives the rate of distribution change, is necessary in order to identify which conservation strategies have the potential to facilitate range shifts and to prevent population and species losses. I studied the responses of southerly-distributed butterflies in Britain to four decades of climate change. I found that not only did the rates of species’ distribution area, northern range margin and abundance changes vary amongst species, but that rates of change also varied within species over time. Some of the variation in distribution change was explained by species’ abundance trends; species required stable or increasing abundances in order to expand their distribution areas. Once species were expanding their range, however, the rate of expansion was affected by the amount of suitable habitat available in the landscape. The application of a simulation model, SPEED, to project species’ distribution change supported these conclusions; all species modelled were capable of distribution expansion given sufficiently high population growth rate. Moreover, increased habitat availability allowed greater rates of distribution expansion. The observed trend towards more negative abundance changes in recent years suggests that habitat quality has deteriorated. Results from this thesis showing that stable or increasing abundance trends are a prerequisite for distribution expansion imply that conservation strategies should focus on improving species’ abundance trends through increasing habitat quality. Results also support the notion that conservation efforts aiming to protect and restore as much natural habitat as possible, in order to facilitate species’ distribution expansion under climate change, are likely to be effective.

Forests are valuable ecosystems to society but are greatly threatened by changing factors from habitat conversion to climate change. South Africa's only extent of indigenous forest is predicted to disappear within the next 30 years. Many challenges are currently faced when trying to detect and interpret directional changes in forests which results in an urgent need to understand any effects that these change factors have on forest ecosystems. We investigate evidence for change in the old growth Lilyvlei Nature Reserve by monitoring growth and dynamics at various levels by examining a 20 year record of tree growth and stand dynamics. Through the inclusion of biodiversity measures and ecologically important plant traits, changes in forest dynamics and growth are investigated. Results show no total change in biomass across the 20 year period, although an intensification of extreme climatic events and dynamics indices were recorded for the second period. Significant correlations were found between community diversity measures and forest growth. Trait variables showed insignificant correlations with forest growth and dynamics. These results suggest that the Knysna forest is controlled by climatic variables and that increased diversity within communities result in increased growth. It is believed that changes in the forest may be masked by compositional shifts of just a few dominant species. These results become important, particularly in the light of changing climatic, atmospheric and environmental changes that threaten global ecosystems in the time to come. However, considering the brief 20 year period observed in a forest where the average individual has a life span of over a century, the importance of long term monitoring becomes an important component in the understanding of forest ecosystems.

Humans are generally having a strong, widespread, and negative impact on nature. Given the many ways we are impacting nature and the many ways nature is responding, it is useful to study responses in an integrative context. My thesis is focused largely (two out of the three data chapters) on butterfly species’ range shifts consistent with modern climate change in Canada. I employed a macroecological approach to my research, drawing on methods and findings from evolutionary biology, phylogenetics, conservation biology, and natural history. I answered three main research questions. First, is there a trade-off between population growth rate (rmax) and carrying capacity (K) at the mutation scale (Chapter 2)? I found rmax and K to not trade off, but in fact to positively co-vary at the mutation scale. This suggests trade-offs between these traits only emerge after selection removes mutants with low resource acquisition rates (i.e., unhealthy genotypes), revealing trade-offs between remaining genotypes with varied resource allocation strategies. Second, did butterfly species shift their northern range boundaries northward over the 1900s, consistent with climate warming (Chapter 3)? Leading a team of collaborators, we found that most butterfly species’ northern range boundaries did indeed shift northward over the 1900s. But range shift rates were slower than those documented in the literature for more recent time periods, likely reflecting the weaker warming experienced in the time period of my study. Third, were species’ rates of range shift related to their phylogeny (Chapter 3) or traits (Chapter 4)? I found no compelling relationships between rates of range shift and phylogeny or traits. If certain traits make some species more successful at northern boundary range expansion than others, their effect was not strong enough to emerge from the background noise inherent in the broad scale data set I used.

Tall fescue is a widely used forage grass in the eastern USA and can form a symbiosis with a fungal endophyte, which can be beneficial for the plant but can cause livestock health issues. Little is known regarding the symbiotic response to predicted climate change. To address this knowledge gap, I analyzed tall fescue variety trial data collected throughout the U.S., exploring relationships between climate variables and yield for two different fescue cultivars that were either endophyte-free or infected. This study showed no endophyte or cultivar effect on fescue yield, but identified temperature, precipitation and location as significant predictors of yield, suggesting that local conditions were more important than endophyte presence or fescue genotype for this dataset. Using a field experiment located in central Kentucky, I quantified the ecophysiological responses of four tall fescue genotypes to endophyte presence, elevated temperature and increased growing season precipitation. In this study, tall fescue genotype was as important as endophyte presence in determining ecophysiological responses to climate change treatments. My thesis illustrates that tall fescue response to climate change will depend on host genetics, the presence and genetics of the fungal endophyte symbiont, and the specific changes to the environment experienced at a site.

This study discusses the extent to which hunter-gatherer mobility strategies are changed by abrupt climate change events by monitoring changes in lithic assemblage compositions through the Pleistocene/Holocene Transition, from ca. 14,000 cal BP to 10,000 cal BP in northwest Europe, with a focus on the Younger Dryas Stadial event, which occurred around 12,900 cal BP to 11,700 cal BP. A set of predicted archaeological indicators were formed from existing theoretical models, based largely on Binford’s logistical and residential mobility model, with the expectation that a more residential mobility strategy would be used by hunter-gatherer-populations during warmer climatic phases (i.e. the Allerød and Preboreal) and a more logistical mobility strategy would be used during cold climatic phases (i.e. the Younger Dryas). The lithic assemblages from sites across northwest Europe were then compared with these expectations in order to determine if a shift from a more residential strategy to a more logistical strategy can be seen from the lithic record. Additionally, a further comparative dataset was collected from south Europe in order to determine if there were differences in the response to the Younger Dryas at lower latitudes where the impact of this event is assumed to be less severe. The results found that in northwest Europe there is evidence to suggest there was indeed a shift from a more residential strategy during the warm Allerød interstadial to a more logistical strategy during the Younger Dryas Stadial, and the adoption of a more residential strategy with the return of warmer conditions during the Preboreal. However, it appears that the Preboreal Interstadial shows significant differences between the Allerød Interstadial, with the Preboreal sharing more characteristics in common with the Younger Dryas. This has been interpreted as a response to the unstable climatic conditions reported from the environmental evidence in this region during the Preboreal, which may have limited the ability of hunter-gatherer populations to return to similar levels of residential mobility seen during the Allerød. The south Europe dataset provides evidence that the lesser impact of the Younger Dryas at lower latitudes brought about a more muted response by hunter-gatherer populations to this event when compared with the northwest. However, there appears to be a reversal of that seen in the northwest, with more logistically mobile populations during the Allerød and especially the Preboreal, and more residentially mobile populations during the Younger Dryas. This is despite the environmental evidence showing a very similar environmental response to the northwest, with a distinct opening of the landscape during the Younger Dryas. The apparent difference in mobility strategies appear to be more related to the available faunal species within a region and their behaviour within their environment rather than directly to the climate. In the south, species such as red deer and ibex are the main source of faunal subsistence throughout the Pleistocene/Holocene Transition, unchanged by shifts in temperature and environment, but the way in which hunter-gatherers would hunt such species would be expected to change in more wooded environments compared with more open environments. If we compare this with the northwest, there is evidence of a distinct change from hunted prey, such as red deer, during the Allerød and Preboreal, to reindeer and horse during the Younger Dryas (although faunal preservation is poor in this region). With this shift to a more mobile prey species, along with a harsher, more open environment it may be more suitable to practise a more logistical strategy. Additionally, the instability of the Preboreal may have also changed the environment on a smaller scale, which would have required the hunting of warmer climate prey in shifting local environments, much like that of the Younger Dryas in south Europe. This might explain the differences seen between the Allerød and the Preboreal. Overall, there appears to be strong evidence supporting the theory that colder, harsher climates promote a more logistically mobile response from hunter-gatherer populations as seen in the northwest of Europe, and that there was a more muted, different response to the Younger Dryas in the lower latitudes of south Europe. However, it is the opinion here that changes in human mobility are not controlled directly be climatic conditions, rather controlled by the available major prey species and their behaviour in changing environments.

This thesis explores how planning policy and practice is responding to the challenge of climate change, particularly in contexts where neoliberal rationales and practices frame decision making. It documents patterns of devolving government responsibilities and experiences of market based mechanisms before reporting on institutional and professional responses to these conditions. The research centred on a qualitative case study and involved thematic content analysis of policy documents and informant interviews. The contribution of the research and thesis is to establish the outlook for climate change adaptation under neoliberal conditions, and to introduce strategies for planners operating within these conditions.

This D.Phil. thesis is an international comparative study looking at the development and implementation stages of policies tasked to reduce emissions from transport. The substance of policy is all too often the primary focus of research, leaving the settings in which these policies are developed and implemented relatively underexplored. Examining the relationships and interplay that exists between departments responsible for climate change and transport at the sub-national (state) level and those with their local and national counterparts, this research tries to unpick the organisational intricacies that may act as barriers to delivery. State governments have become a promising source of action to reduce emissions from other sectors for which they have legislative responsibility; however, the private road transport sector remains a challenge. This research examines the barriers preventing such progress and whether the lack of collaboration between departments and across levels of government are responsible in part for these challenges. Taking a specific policy intervention designed to reduce transport-related emissions from four case study governments (Bavaria, California, Scotland and South Australia) this research is about organisational structures of government and policy processes. The main hypothesis of the research is that conventional environmental/climate change- and transport-policymaking practices are incompatible – and that this incompatibility is hampered by organisational structures of government. Together these factors render implementation of policies to reduce the climate impact of transport difficult. The hypothesis is guided by four research themes – scale, scope, leadership and process. Each of these themes has a distinct yet important part to play in understanding and comparing the case study contexts, in terms of the cross-departmental and cross-level interactions occurring within each of the sub-national governments. Each of the subject case study governments have been chosen since they are self-determined ‘leaders’ on climate change. This research serves to highlight some of the governance issues that need to be overcome or removed for such positive political intent to be realised. It posits that without successfully linking frameworks and interested stakeholders in the process, tangible emissions reductions will be difficult to achieve. The main objective of the research is to investigate the frameworks, interplay and dynamics at the sub-national level of government across departments and between levels of government. The relationship and collaboration with industry is also examined as a supplementary consideration. The second objective is to look at how and whether climate change policy can be more closely integrated with transport policy and the barriers to this integration. This investigation is underpinned by cross-disciplinary governance theory, as well as notions from socio-political governance and applies the concept of institutional interplay in this context between levels of government. It develops the concept of sub-national governance which argues that relationships between levels are distinct and non-hierarchical in terms of policy development and implementation.

This study explores the portrayal of the climate-conflict nexus in global and national communications on climate change response. It utilizes a qualitative inductive approach and the IPCC AR5 (2014) was chosen to represent global communication documents, while two Afghan communications, the Initial as well as Second National Communication, on climate change and response were used to represent the national level. Through a content analysis, several themes were discerned through which the climate-conflict nexus is portrayed. It can be concluded that there are several differences between the global versus Afghan communication documents, as well as between the Initial National Communication (2012) and the Second National Communication (2017). The Second National Communication overall attempts to mirror the communication used by the IPCC by using the same themes but in a more indirect way. The analysis finds that the climate-conflict nexus is often portrayed through indirect communication and that this leads to a lack of conflict-sensitivity in the Afghan national documents, concluding by making suggestions on how to improve conflict-sensitivity in these documents.

Tropical precipitation is linked through the moist static energy (MSE) budget to the global distribution of sea surface temperatures (SSTs), and large deviations from the present-day SST distribution have been inferred for past climates and projected for global warming. We use idealized SST perturbation experiments in multiple atmospheric general circulation models (AGCMs) to examine the hydrologic and energetic responses in the zonal mean and in the African Sahel to SST perturbations. We also use observational data to assess the prospects for emergent constraints on future rainfall in the Sahel.

The tropical zonal mean anomalous MSE fluxes in the NOAA Geophysical Fluid Dynamics Laboratory (GFDL) AM2.1 AGCM due to SST anomalies caused by either historical greenhouse gas or aerosol forcing primarily occur through the time-mean, zonal mean (Hadley) circulation. Away from the Intertropical Convergence Zone (ITCZ), this largely stems from altered efficiency of the Hadley circulation energy transport, i.e. the gross moist stability (GMS). A thermodynamic scaling-based estimate that relates GMS change to the local climatological moisture and temperature change relative to the ITCZ captures most of the qualitative GMS responses. It also yields a heuristic explanation for the well known correlation between low-latitude MSE fluxes and the ITCZ latitude.

Severe Sahelian drying with uniform SST warming in AM2.1 is eliminated when the default convective parameterization is replaced with an alternate. The drying is commensurate with MSE convergence due to suppressed ascent balanced by MSE divergence due to increased dry advection from the Sahara. These qualitative energetic responses to uniform warming are shared by five other GFDL models and ten CMIP5 models, although they do not translate into quantitative predictors of the Sahel rainfall response. Climatological values and interannual variability in observations and reanalyses suggest that drying in AM2.1 is exacerbated by an overly top-heavy ascent profile and positive feedbacks through cloud radiative properties. Simulations with patterned SST anomalies suggest a major role for mean SST variations in discrepancies among models and potentially in observed decadal variations of Sahelian precipitation.

How do firms adapt to the intensity of adverse conditions stemming from the natural environment (ecological adversity intensity)? In this dissertation, I develop several lines of inquiry in exploring this question. First, I seek to contribute to generally diverging perspectives on organizational adaptation, which view firms as either inherently constrained or capable of continuous adaptation to fit their environment. To do this, I examine the conditions under which firms are more likely to adapt to different levels of ecological adversity intensity. My findings from a 13-year longitudinal analysis of western U.S. ski resorts’ adaptation to temperature conditions indicate that firms facing moderate ecological adversity intensity appear more likely to engage in higher adaptation levels while those experiencing low and high ecological adversity intensity show a tendency for lower adaptation levels. That is, both diverging perspectives may predict part of firms’ adaptive responses to ecological adversity intensity. My findings also suggest firms may encounter limits to adaptation when facing increasing ecological adversity intensity. I also undertake a post hoc exploration of firm and institutional environment level factors that may moderate the relationship between ecological adversity intensity and firm adaptation. Second, I use an interdisciplinary approach that draws from resilience theory in socioecology to suggest that the existing conceptualization of organizational resilience could be expanded to include transformative change, which may allow firms to mitigate the operational impacts of reaching adaptation limits. Third, I also consider the resilience implications of the interdependency between firms and the broader ecosystems in which they operate. I conclude with potential avenues for future research in this area.

Kyoto University (京都大学)
0048
新制・課程博士
博士(地球環境学)
甲第14885号
地環博第62号
新制||地環||12(附属図書館)
27307
UT51-2009-K681
京都大学大学院地球環境学舎地球環境学専攻
(主査)教授 松岡 譲, 教授 藤井 滋穂, 准教授 倉田 学児
学位規則第4条第1項該当

Urbanization and global warming are two of the most pressing issues facing humanity over the next 50 years. Why do some local governments enact more climate change mitigation policies than others? What makes some cities leaders in urban sustainability, while others lag far behind? Over the past decade, global climate change negotiations have repeatedly failed to produce binding commitments and robust responses by national governments. These failures have led academics and practitioners to put increasing emphasis on the potential for sub-national governments, including cities, to undertake commitments that might substitute for national action on climate change. Applying concepts from the comparative public policy literature to the study of urban politics, this dissertation puts forward and tests a new theory to explain variation in Canadian cities’ climate change policy. I find that political economy factors reduce the likelihood that cities will adopt climate change policy that will significantly reduce greenhouse gas emissions, but the presence of independent municipal environment departments makes the adoption of such policy more likely. This dissertation employs a systematic and explicit process tracing methodology. It examines the decision-making of four Canadian cities (Brampton, Toronto, Winnipeg and Vancouver) across four policy areas (landfill gas management, fleet services, cycling infrastructure and building standards). The analysis is based on data gathered from primary and secondary sources and expert interviews with over 70 local politicians, bureaucrats, journalists, and NGO and business representatives. This dissertation argues that cities cannot solve the climate change challenge on their own, but knowledge of the dynamics of climate change mitigation policy adoption at the local level may permit scholars and practitioners to increase the effectiveness of municipal governments’ climate change policy choices.
Arts, Faculty of
Political Science, Department of
Graduate

Climate change is a global crisis facing forest management. There are risks to many ecological goods and services from forests due to changes in productivity, mortality, pathogen, and wildfire dynamics. Likewise, there are opportunities such as increases in productivity or targeted funding for climate adaptation and emission reductions. To manage those risks and opportunities, we need the fundamental knowledge of forest carbon (C) cycles. Overall, my dissertation aims to improve our understanding of forest carbon dynamics and how they may respond to natural disturbances, climate change and management activities. This purpose falls within the context of the need to adapt to and mitigate climate change for the ongoing provision of ecological goods and services from forest ecosystems such as timber and biodiversity. The thesis starts with a critical analysis of six papers I have previously published. That chapter includes a synthesis of findings, critique of methods used, and identifies some areas for future research. Each subsequent chapter represents a contributing article. The overall findings of this dissertation are (i) that although forests are often GHG sinks moderate or high intensity natural disturbances can reverse that flux. (ii) That climate change effects on productivity may increase or decrease the natural sinks or even create emission sources in forests that may otherwise have been sinks. (iii) That management strategies to increase species diversity and resilience may be effective at reducing risks of emissions, but they must be assessed for individual ecosystems and may be insufficient to fully offset disturbance or climate change effects.

In this study the behaviour of multivariate plankton communities and their relationships with climate is explored. Existing statistical methodology is adapted to analyse both the plankton communities and sea surface temperature. In the first part of this study a large scale exploratory analysis is applied using principal component analysis. Dominant temporal trends and spatial patterns for a number of indicator species and the joint responses of functional groups of species are found.The community analysis focuses on on the zooplankton and the phytoplankton, the latter respresented by diatoms. This research is novel because the full multivariate structure of the plankton data has not been studied across communities before. The common trends are regressed against different climate signals to determine dominant drivers and cluster analysis identifies regions based on species. In the second part ‘regime shifts’ described by changes in ecoregions are explored. Whilst changes in spatial patterns over time have been studied over indicator species, this study describes the shift across communities, providing an overview of how the ‘regime shift’ is differently expressed for the two species groups. To explore changes in biogeographical patterns, the data is then divided in to a pre-1985 and post-1985 regimes. The results show a northwards movement of zooplankton species and increased spatial structure across the diatom group, following the bathymetry. In the final part the model is used to predict vulnerability of different indicator species and the community as a whole to changes in climate drivers across space, which is used to find climate change ‘hotspots’. Vulnerability is defined as a significant change in abundance in response to a relatively small change in the climate signal. Vulnerability is also explored at different scales. These results highlight the spatial inhomogeneity of species responses and are of great interest to environmental policy makers.

The Arctic areas are warming more rapidly than other parts of the world. Increasing temperatures are predicted to result in shrubification, higher productivity, declining species diversity and new species invasions to the tundra. Changes in species diversity and plant community composition are likely to alter ecosystem functions with potential consequences for human population also at lower latitudes. Thus, in order to better predict the effects of the rapid arctic warming, we need knowledge on how plant communities respond to a warmer climate. Here, I investigate the effects of climate warming on tundra plant communities and focus on the role of mammalian herbivores in mediating these responses. I examined the role of herbivores by incorporating herbivore manipulations to short- and long-term warming experiments as well as along altitudinal gradients. I measured how individual plants and plant communities respond to warming with and without herbivores. Results of my PhD Thesis illustrate several ways how herbivores modify the responses of plants to warming. I found that herbivores (reindeer, hare, voles, lemmings) may prevent lowland forbs from invading open tundra.  Herbivores might also protect small tundra forbs from being outcompeted by taller and denser vegetation under climate warming. Thus, different herbivore pressures may lead to differing plant abundances and distribution shifts in different areas. Furthermore, my results show that high herbivore pressure can reverse the effects of long-term climate warming very rapidly, even in one year. This finding suggests that well-planned targeted reindeer grazing episodes could potentially be used as a conservation tool to keep selected tundra habitats open. Sudden cessation of grazing may initiate rapid changes in plant community, especially if it coincides with warm temperatures. Taken together, I show that herbivores counteract the effects of climate warming by slowing down or preventing vegetation changes in tundra. Therefore, it is important to consider mammalian herbivores when predicting tundra plant community responses to changing climate.

Peatlands are an important component of the global carbon (C) cycle. Peak C accumulation rates (CAR) are associated with higher net primary productivity (NPP) and warmer climates. However, warmer conditions could force peatlands close to the moisture limit of development to cross a critical threshold where decay processes exceed NPP gain. The sensitivity of the peatland C stores in regions proximal to such bioclimatic boundaries must be characterised to assess their likely contribution to the global C cycle under projected future climate warming. This thesis investigates the relationship between climate and CAR over the last 2000 years using four peatlands located towards the southern limit of peat growth in eastern North America. Chronologies were developed using tephra and radiocarbon measurements to determine loss-on-ignition inferred carbon accumulation histories. The Alaskan White River Ash eastern lobe (AD 847 ± 1) was detected at all study sites and four previously unidentified cryptotephras of Russian, Japanese, Mexican and Pacific Northwestern origin were detected in Nova Scotia. Investigations into the relationship between CAR and climate reveal that multi-decadal to centennial CAR fluctuations are related to changes in the summer moisture balance, whilst temperature changes become increasingly important over multi-centennial timescales. The most prominent decrease in CAR over the last 2000 years coincided with drier conditions associated with the Medieval Climate Anomaly (MCA). This suggests that the southern moisture limit of peat growth moved northwards during the MCA, suppressing C sequestration in southern sites. Therefore, whilst projected future climate warming may increase peat CAR in more northern regions, peatlands proximal to the southern moisture limit of peat growth may experience a reduction in their C sequestration rates and act as a positive feedback to climate warming.

Alpine plants are assumed to be in particular danger as the climate changes rapidly worldwide. Specialist alpine species in Norrbotten County, northern Sweden have been surveyed over the last 20 years, providing insight to population dynamics and how the plants might respond to the changing climate. The main current threat to the species is habitat destruction as the climate changes. Variation in the number of plants among populations and years, and correlations with environmental variables were examined. Some species had increased while others had decreased over the years. No uniform relationship for all species and populations were discovered, but some of the species exhibited relationships between population size changes and temperature and precipitation. However, if the future climate in Norrbotten County changes according to the predictions, the habitats of the specialist alpine plants may be severely altered, leaving the species with no alternative places to establish and grow.

This research uses a mixed methods approach to analyze recent climate and land use changes, and farmers\' perceptions of climate change and its impacts on traditional agriculture in the village of Keur Samba Guéye (KSG). This work looks at the influence of social beliefs in adoption of new strategies by small farmers in this region, a topic that has received little or no study to date. Traditional agriculture in KSG is not very productive at present because of the impoverishment of the area and traditional agricultures strong dependency on natural climatic conditions. In this research, I identified recent climatic trends, documented changes in land use/land cover (LULC) from 1989 to 2011, and assessed farmers\' perceptions of climate change and their responses to such changes. To document climate trends and LULC, I analyzed climate data of twelve meteorological stations located across the country and created a classification of satellite images of KSG for two time periods. To examine farmers\' perceptions and agricultural practices, I conducted surveys of the farmers of KSG and in surrounding villages. Most farmers reported negative impacts of climate change on their agriculture activities, and interest in adopting new agricultural strategies despite long-standing tradition. Increasing temperatures and irregularity of rainfall may have negatively impacted crop yields, but more climate data are needed to clarify this phenomenon. LULC has been influenced by both climate change and human pressure; agricultural land has declined, while bare soils have increased. Several recommendations are provided that may help farmers to cope with changing climate.
Master of Science

Estuaries are one of the most important aspects of coastal systems globally. They are often hubs for human civilisation due to the socioeconomic advantages they offer. As they are highly vulnerable to natural forces, including tides, waves, surges and river discharges, it is essential to study the relationship between estuarine morphologies and these natural variables, which is crucial in order to assess estuarine evolution. The Deben Estuary (UK) has been selected as the case study in this study as its morphology has been significantly changed over time. It can be expected that the estuary will undergo significant morphodynamic changes under future climate change. The objective of this study is to investigate the morphodynamic responses of the estuary to the climate change in order to better understand the relationship between morphological change and climate change. A regional scale depth-averaged hydrodynamic and morphodynamic model Delft 3D was set up to the Deben Estuary, which incorporates wave propagation. The model was validated against measurements of water levels and waves before using it to simulate detailed scenarios. Then, the future climate projection data was used as the boundary conditions for the model scenarios. First, the calm weather conditions were considered since the model was run in long-term time scale. Then the episodic events were accounted for to investigate the impact of waves in future storms on the estuarine morphodynamics. The results show that future climate change will enforce different responses of morphodynamics at the estuary. Responses vary depending on whether natural forces are episodic or long term, and also according to different climate change scenarios, such as different emission scenarios. The comparison between the responses under the present and future conditions indicates that the estuary may undergo different evolution to what is historically observed.

Soil organic matter (SOM) decomposition and formation is an important climate feedback, with the potential to amplify or offset climate forcing. To understand the fate of soil carbon (C) stores and fluxes (i.e., soil respiration) under future climate it is necessary to investigate responses across spatial and temporal scales, from the ecosystem to the molecular level, from diurnal to decadal trends. Moreover, it is important to question the assumptions and paradigms that underlie apparently paradoxical evidence to reveal the true nature of soil-climate feedbacks. My dissertation includes research into the response of soil respiration in Pacific Northwest prairies to warming and wetting along a natural regional climate gradient (Chapter II), and then delves deeper into the mechanisms underlying SOM decomposition and formation, examining the temperature sensitivity of SOM decomposition of prairie soils that were experimentally warmed for ~2 yr, and a forest soil in which litter-inputs were manipulation for 20 yr (Chapter III), and finally testing soil C cycling dynamics, including mineral-associated C pools, decomposition dynamics, and the molecular nature of SOM itself, under litter-manipulation in order to understand the controls on SOM formation and mineralization (Chapter IV). This dissertation includes previously published and unpublished coauthored material; see the individual chapters for a list of co-authors, and description of contributions.

Human activity is causing climates to change more rapidly than at any time in the last 10,000 years. If populations of organisms are unable to effectively respond to changing environments, they will be at risk of extinction. In plants, two of the most important mechanisms of response to environmental change are phenotypic plasticity, where the same genotype expresses different phenotypes in different environments, and adaptation, which requires changes in allele frequency in populations as exposed individuals show variable survival and reproduction. Although most researchers accept the importance of both of these mechanisms, they are most commonly considered in isolation in models of response and persistence to climate change. Here, I use the model species Arabidopsis thaliana to investigate the interaction of plasticity and selection in fitness and phenology response to simulated climate warming, the effect of artificial selection on variation for plastic response and cross-generational effects of environmentally induced variation in flowering time. I also study the effects of varying rates of environmental fluctuation on evolvability on populations of self-replicating computer programs using the artificial life platform Avida. I find that a small increase in ambient temperature, in line with predictions for the next few decades, is able to elicit significant plastic responses and that these responses have the potential to alter population genetic structure and affect future evolution. I also find that selection on flowering time can reduce variation for plastic response and that non-genetic effects on flowering time can significantly alter germination in the next generation. Lastly, I find that rapidly changing environments in the long term can select for more evolvable populations and genotypes. These results highlight the importance of considering plasticity and evolution together if we are going to make accurate predictions of climate change response.

As a result of human activities, the level of CO₂ in the Earth’s atmosphere has increased by nearly 40% since the industrial revolution. The rate of green house gas emission is accelerating, with current trends exceeding those predicted by “worst case” global climate change scenarios. The chemistry of the ocean is fundamentally changing as a result of increasing atmospheric CO₂, which dissolves in seawater, making it more acidic, a process referred to as ocean acidification (OA). A rapidly expanding body of science is now being generated to understand the impact of this global environmental change. To date, most studies evaluating OA effects have centered on simplified laboratory analyses that expose single populations to short-term treatments in order to quantify responses of individuals. These designs offer a limited assessment of the degree to which phenotypic plasticity and local adaptation might influence the response of populations to OA.

To address these questions, I carried out studies on members of Phylum Bryozoa, a species-rich clade of calcified colonial marine invertebrates distributed throughout the global ocean. Bryozoans were selected as a model system for this work because the clade exhibits a broad array of growth and calcification strategies, and because of the relative paucity of data regarding their expected response to future acidification. In addition, bryozoans can be subdivided into genetically identical replicate clones, which can then be assigned to separate treatments, allowing variation across treatments to be uniquely partitioned into the variance components of statistical models. In order to culture bryozoans for comparative experiments, I designed and constructed a new flow-through OA system at the Bodega Marine Laboratory, capable of finely manipulating both the temperature and carbonate chemistry of seawater, allowing for controlled laboratory experiments of long duration.

In Chapter 1, I performed a comparative 9-month laboratory experiment examining the effects of ocean acidification on the native Californian bryozoan Celleporella cornuta. C. cornuta was sampled from two regions of coastline that experience different oceanographic conditions associated with variation in the intensity of coastal upwelling. Under different CO₂ treatments, the biology of this bryozoan was observed to be remarkably plastic. Colonies raised under high CO₂ grew more quickly, invested less in reproduction, and produced skeletons that were lighter compared to genetically identical clones raised under current atmospheric values. Bryozoans held in high CO₂ conditions reduced their investment in skeletal carbonate, changed the Mg/Ca ratio of skeletal walls and increased the expression of organic coverings that may serve a protective function. Differences between populations in growth, reproductive investment, and the frequency of organic covering production were consistent with adaptive responses to persistent variation in local oceanographic conditions.

In Chapter 2, I tested whether skeletal mineralogy can vary plastically in some invertebrates using the cosmopolitan bryozoan Membranipora tuberculata as a model. In a 6-month laboratory experiment, I cultured genetic clones of M. tuberculata under a factorial design with varying food availability, temperature, and dissolved CO₂ concentrations. Elevated food availability increased growth in colonies while cold temperatures and high CO₂ induced degeneration of colony zooids. However, colonies were able to maintain equivalent growth efficiencies under cold, high CO₂ conditions, suggesting a compensatory tradeoff whereby colonies increase the degeneration of older zooids under adverse conditions, redirecting this energy to the maintenance of growth. Elevated food and cold temperatures also decreased Mg concentrations in skeletal material, and this skeletal material dissolved less readily under high CO₂ conditions. This suggests that these factors interact synergistically to affect dissolution potential in this and other species.

Finally, in Chapter 3, I explore stable isotope values for δ ¹⁸O and δ¹³C in the calcium carbonate structures of the bryozoan Membranipora tuberculata. I tested whether this species accurately records both temperature and pH variability during periods of coastal upwelling by analyzing δ¹⁸O and δ ¹³C in colonies grown in the field and in controlled laboratory cultures. Field-grown colonies were out planted next to a Durafet^® pH sensor, which provided a high-resolution record of the temperature and pH conditions these colonies experienced. δ¹³C was found to negatively co-vary with pH in both laboratory and field growth, and calculated field temperatures derived from laboratory δ¹⁸O temperature calibrations aligned with the records from the pH sensor. δ¹⁸ O_c values were more depleted under low pH in laboratory trials, which stands in contrast to patterns observed in other taxa. This may indicate that Membranipora utilizes bicarbonate ion (HCO ₃^-) in its calcification pathway, and could help explain why many bryozoan species appear to exhibit enhanced growth under high CO ₂ conditions. (Abstract shortened by ProQuest.)

Attempts to quantify the effects of ocean acidification and warming (OAW) on scleractinian corals provide a growing body of response measurements. However, placing empirical results into an ecological context is challenging, owing to variations that reflect both natural heterogeneity and scientific bias. This study addresses the heterogeneity of climate change induced changes in coral recruitment and calcification. To discern scientific bias and identify drivers of the remaining heterogeneity, 100 publications were analyzed using a combination of weighted mixed effects meta-regression and factorial effect size meta‑analysis. A linear model was applied to quantify the variation caused by differing stress levels across studies. The least squares predictions were then used to standardize individual study outcomes and effect size meta-analysis was performed on original and standardized outcomes separately. On average, increased temperature significantly reduces larval survival, while ocean acidification impedes settlement and calcification. Coral resistance to OAW is likely governed by biological traits (genera and life cycle stage), environmental factors (abiotic variability) and experimental design (feeding regime, stressor magnitude, and exposure duration). Linear models suggest that calcification rates are driven by carbonate and bicarbonate concentrations, which act additively with warming. Standardizing outcomes to linear model predictions proved useful in discerning strong sources of scientific bias. The approach used in this study can improve modelling projections and inform policy and management on changes in coral community structure associated with the expected future intensification of OAW.

Climate change mitigation constitutes a social dilemma, a conflict between personal and collective outcomes. Behaviours that result in personal benefits (e.g. travelling quickly, conveniently and cheaply by plane) also result in a collective cost in the form of climate change. Behavioural theories and evidence suggest this social dilemma structure significantly influences behaviour. This thesis aims to understand how the social dilemma structure of climate change mitigation affects people’s personal actions to address climate change. The first empirical study explores whether people perceive decisions with emission consequences as social dilemmas. Findings show that making salient the effected collective or the pro-social nature of the decision increases awareness of the social dilemma structure. A second set of empirical studies, using quantitative and qualitative methods, further demonstrate that there are two sets of considerations to the climate change mitigation dilemma: 1) non-cooperative considerations (e.g. a focus on immediate personal benefits or a temptation to free-ride) which are linked to a decrease in actions on climate change, and 2) cooperative considerations (e.g. a focus on outcomes for others or fairness considerations) which are linked to an increase in actions on climate change. Results also show that people apply cognitive strategies to counteract the discouraging effect of non-cooperative considerations. A third set of empirical studies tested whether communication massages based on cooperative considerations can increase personal actions to address climate change. Findings suggest that especially framing a message based on the collective outcome can increase actions, but careful consideration of the audience and the situation is required. Overall, this thesis makes the important contribution of demonstrating that the social dilemma structure of climate change mitigation does not necessarily discourage actions to address climate change, but also offers an encouraging perspective through a focus on the collective outcome.