Forests are a critical biome but are under threat from unprecedented global change. The need to understand forest dynamics across spatial, temporal and biological scales has never been greater. Critical to this will be understanding how the demographic rates of individuals translate into patterns of species diversity, biomass and carbon turnover at much larger scales. In this thesis, I present a modelling framework focussed on demography. In Chapter 2, I introduce methods for translating forest inventory data into population models that account for the size-dependency of vital rates and persistent differences in individual performance. Outbreaks of forest pest and pathogens are increasing in frequency and severity, with consequences for biodiversity and forest structure. In Chapter 3, I explore the impact of ash dieback on the community dynamics of a British woodland, describing a spatially explicit individual based model that captures the effect of an opening of the canopy on local competitive interactions. Chapter 4 introduces methods to infer the impact of historical deer herbivory on the juvenile survival of forest trees. The approach is generalisable and could be applied to any forest in which patterns of regeneration and community structure have been impacted by periodic disturbance (e.g. forest fires). Finding meaningful ways of incorporating species diversity into global vegetation models is increasingly recognised as a research priority. In Chapter 5, I explore the diversity of demographic rates in a tropical forest community and identify groups of species with similar life history strategies. I discuss the potential of integrating demographic and physiological traits as a way to aggregate species for inclusion in global models. In summary, translating measurements of individuals into population dynamics provides opportunities to both explore small-scale community responses to disturbance events, and to feed into much larger scale vegetation models.

This thesis conducts empirical analysis on the determinants of migration and remittance sending decisions in Kenya and the impact on the expenditure patterns of households using cross-sectional household survey data. The first empirical chapter explores the factors that influence the subsequent migration decisions of Kenyan siblings using binary logit models. The findings reveal that preceding sibling migrants have a strong negative effect on the probability of migration for other siblings. Evidence in support of migration as a joint household level decision is obtained as preceding sibling and non-sibling migrants are found to exhibit similar effects. Conditional on migrating, siblings are shown to utilize existing sibling networks by moving to the same internal or external destination as preceding migrants. Discrete failure time models are also employed so as to account for any neglected heterogeneity at the household level. Controlling for neglected heterogeneity, the overall effect of preceding sibling migrants is found to be statistically insignificant. However, non-sibling migrants are found to decrease the probability of migrating. The second empirical chapter examines the remittance behaviour of multiple compared to sole sibling migrants, and the motivations of Kenyan siblings in sending remittances to their household of origin. No evidence of selection bias in the decision to remit is detected when a Heckman selection model is estimated. Using probit and OLS models, the presence of other siblings is found to decrease the probability of remitting but to have no effect on the amount of remittances sent. The amount of remittances sent by other siblings is also found to have no statistically significant effect on the remittances sent by a sibling using IV regression methods. In the third empirical chapter, the expenditure patterns of Kenyan households are investigated according to whether the household is a migrant or non-migrant household, and whether a migrant household is in receipt of remittances or not using an Almost Ideal Demand System (AIDS) approach. The analysis reveals that remitters who are spouses and siblings of the household have higher bargaining power towards the allocation of remittances to physical investments and durable goods, respectively. The expenditure patterns also show that remittances are not pooled together with general income when allocating the household budget towards durable goods and physical investments. In addition, the findings reveal that the reported uses of remittances by Kenyan households contrast with their actual uses. In the fourth chapter, the uses of remittances for the acquisition of physical investments and durable goods are analysed in more detail using IV and bivariate probit models. Remittances are found to be exogenous for the durable goods category but endogenous for physical investments. The evidence obtained is supportive of remittances being used by households to purchase these categories of commodities.

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Today migrants are increasingly seen as potential ‘philanthropists' or even as the ‘instigators' of development transition in their countries of origin. This thesis explores, via an original multiperspective bottom-up approach, how the discourse of migrants' contribution to development is constructed and put into concrete practice in the case of Moldova. The young republic is one of Europe's lesser-known countries and yet, with its intense recent experience of migration, it presents a fertile territory for in-depth study of the migration–development dynamic, with special reference to the role of migrant associations. More specifically, the heart of the thesis investigates, with a transnational lens, representations and negotiations of migrants' collective development efforts, firstly among migrants, secondly among development actors, and thirdly the aid-relationships between the two. The thesis engages with the literature on the relationship between migrants' transnational development practices and transnational power hierarchies, highlighting the role of international development policy discourses and initiatives from an interdisciplinary perspective. It aims to contribute to the broader theoretical discussion on linkages between transnational collective practices of Eastern European migrants living in EU countries and the development transition in the Eastern European 'neighbourhood'. Using a variety of field methods including multi-sited ethnography, the data collection took place over a period of one year – following the ‘discourse on migrants' contribution to development' in the transnational social field of migrant civil society and in the transnational field of development organisations across seven European countries: Belgium, France, Germany, Italy, Moldova, Switzerland and the UK. The findings reveal significant differences between migrants and mainstream development agencies on the issues of Moldova's transformation process, development practices and on the notion of ‘ideal' development partners. Migrants' collective transnational development practices appear as a dynamic process shaped not only by the current and understudied Moldovan migration features and based on various socio-economic and cultural indicators, but also by the country's Socialist past and its marginalised place within Europe. The results also show unexpected relationship patterns between migrants and state institutions and aid agencies, in which the latter two rely on migrant associations to carry out their newly-created migration–development policies and programmes. And an overall discomfort was found among aid-workers in engaging Moldovan migrants as their partners, expressed in double standards applied to migrants in ‘aidland'.

This thesis investigates the dual transnationalism of ancestral return migrants, that is to say people “returning” to the territory where their ancestors had once migrated from. Dispersed from their homeland in the second half of the 19th century, the Adyge-Abkhaz diaspora has been involved in a variety of transnational practices in relation to their homeland in the Caucasus; and some, with considerable effort, have been settling there especially in the last two decades. The transnational involvement of this diaspora, most of whom live today in Turkey, is motivated by their search for belonging. Many who go back and forth between Turkey and the Caucasus are involved in transnational diaspora associations and take an active role in the formation of a transnational ethno-political-cultural environment for new generations growing up in the diaspora. The majority of those who have “return migrated” to their homeland in the Caucasus, in this study to two republics, Adygeya (an autonomous republic under the Russian Federation) and Abkhazia (a republic with contested independence), develop new transnational links to their diaspora communities in Turkey. This thesis is the product of a multi-sited, multi-method research project that combines theories related to transnationalism, diaspora and return, as well as migrant adaptation. Using life-history interviews, semi-structured interviews and participant observation, fieldwork for the research took place in rural diaspora settlements and urban diaspora organisations in Turkey as well as in the Caucasus, thereby enabling the researcher to study both ends of the migration route. Existing studies on ancestral return migration focus on pull and push factors, which hitherto have focused on sending and receiving countries separately. This thesis argues that their dual transnationalism, both in the diaspora (in Turkey) looking back towards the diasporic homeland, and after return looking back towards the diaspora, turns them into the “diaspora of their diaspora”.

This thesis is based on eighteen months' fieldwork in Tissana: a bustling multi-ethnic fishing town on Sierra Leone's southern coast. It tells the story of the successive waves of young migrants who, for several decades, have been arriving on the coast from rural areas seeking an alternative to the indentured labour conditions of a farming economy still shaped by the legacy of domestic slavery. Set against the backdrop of a rapidly changing post­‐war economy, and in an ecological context in which fish stocks are in treacherous decline, I explore the intersection between people's everyday struggles for economic survival and their taken-for-granted knowledge of the substance of the world within which those fragile livelihoods play out. In a region in which we have come to correlate ‘memory' with the collective scars of slavery and civil war, Tissana's older residents look back with nostalgia and remember the youthful energy, conspicuous consumption and seemingly easy ‘freedom' of their town's early boom years. In some respects, the pattern is familiar from accounts of resource rushes all across Africa: the convergence of large numbers of young strangers in an unfamiliar landscape far from the authority of village elders opened up a space in which a new kind of moral economy emerged. However, within just a few decades of its initial boom, the fluidity of Sierra Leone's fishing economy is already under intense pressure. Fish stocks have suffered a noticeable decline and, as catches become smaller and more erratic, people find themselves drawn once more into networks of dependency and reciprocity that offer their only viable hope of material security. A constant tension animating everyday life in Tissana is how people are able to work, through the strategic deployment of material gifts, to nurture the relationships that they rely upon for their subsistence, whilst simultaneously attempting to protect themselves from becoming entangled in other, less appealing social bonds. At its core, then, this is a work about the materiality of human relationships; of social bonds formed and lived under conditions of such stark economic uncertainty that, very often, ‘love' and ‘livelihoods' are difficult to disaggregate — and even more difficult to trust. Here relationships often have a peculiarly fleshy, ethnographically observable aspect. One can go a long way towards mapping the town's fluctuating networks of friendship, love, debt, and obligation simply by watching the gifts of fish exchanging hands on the wharf. The town also raises a quite particular set of problems for an anthropologist interested in the materiality of social life. I explore how the lived experience of poverty, and the anxiety of stretched livelihoods are entangled with quotidian discussions of blessings, swears, initiation societies, and ‘fetish' medicines: elements of social life that we might intuitively gloss as ‘ritual', but that are, in fact, integral to the everyday economic order. Here, my work builds on a long literature in Sierra Leonean ethnography. Anthropologists working in this region have often revealed how their interlocutors do not draw any sharp distinction between ‘material' and ‘immaterial' elements of the physical environment and the agencies that inhabit it (Ferme 2001; Tonkin 1979; Bellman 1984). My contribution to this literature is to explore how such apparently abstruse questions of im/materiality become relevant in people's lives through economic practice: through the everyday decisions people make, and the work they invest, in fishing, trading, and gift-exchange.

This thesis conducts empirical analysis on the intergenerational transmission of adiposity, using various types of data from various countries; the same intergenerational transmission in China and how it varies with the family socioeconomic factors and age levels; the way in which health impinges on the decision to migrate in China. In the first empirical chapter we find that the intergenerational elasticity of adiposity is relatively constant – at 0.2 per parent, and this elasticity is comparable across time and countries. Quantile estimates suggest that this intergenerational transmission mechanism is more than double for the fattest children as it is for the thinnest children. The second empirical chapter examines the intergenerational transmission of adiposity in China: we use BMI z-score as another measure of adiposity, the longitudinal structure of CHNS data (1993-2009) allows us to control for individual fixed effects or family fixed effects and focus on changes in BMI z-score over the life cycle. We report patterns of the intergenerational relationship of BMI z-score varying by family socio-economic factors and the age of the child, the magnitude of this relationship reaches the peak over the stage between childhood and later adolescence. In the third empirical chapter, which also uses the CHNS data, we examine whether migrants are healthier than those who do not migrate in the places of origin in the context of internal migration in China. Based on the relative wage rates, costs of migration and the assumption of optimization, we set up a theoretical model and estimate the effects of health on the migration probability, we find that people self-evaluating as having “good” or “excellent” health are more likely to migrate, this health effects vary with the type of occupation, we also find evidence on the indirect health effects which operates through the education attainment.

This doctoral thesis commences with a meticulous examination on whether financial, social and institutional determinants associate with the migration performance in Europe and accordingly in Greece. Motivated by the intensity, the magnitude and the financial recession, this thesis presents three empirical chapters on the examination of the determinants that affect the phenomenon of migration. Prior to these three empirical studies a chapter introduces and defines all the variables used as well as the theoretical and methodological framework of the thesis. The first empirical chapter demonstrates a comprehensive sample of 15 European countries from 1990 – 2012, which have been divided into 3 groups (Weak-EMU, Strong-EMU and Non-EMU countries) in order to investigate the behaviour of each group during these periods. It follows a quantitative analysis of the economic and social determinants on migration, in order to comprehend their relationship with the phenomenon. The chapter concludes with the discussion of our results with an analytical review of the selected variables upon migration. Results reveal that Portugal, Ireland, Italy, Greece and Spain are countries that are more exposed to the financial crisis, something that consequently affects negatively the behaviour of each employed economic variable. Additionally, results detect that one significant outcome is that the GDP growth rate, inflation and the imports of goods are related to migration, while on the other hand the 10-year government bond yield is not affiliated to the phenomenon. The second empirical chapter covers the financial, social and institutional determinants that motivate Greek nationals to leave their country and emigrate to wealthier destinations during the recent financial crisis. First, it reviews the theoretical explanations for the efficiency of the factors on migration. It then provides a survey on the relevant empirical studies and subsequently an analysis of the variables, which have a significant impact on labour migration. Based on the theories presented, the study develops a model to explain how financial, social and institutional factors are correlated with the economic downturn and lead to adverse financial and social shocks such as massive migration outflows of Greek nationals. More precisely, the second chapter indicates that Greece has been very exposed to the financial crisis, thus had a strong impact on the decision of Greek natives to emigrate. As conditions deteriorate, Greece was in a severe financial situation due to the financial crisis and was dependent on the monetary policy support, something that emerged the country to experience major and drastic changes on its social cohesion. Further, we can identify, that debt to GDP, exports of goods, ln of imports of goods, long term unemployment and population growth are positively related to emigration from Greece, while on the other hand cash surplus, foreign direct investment and bank capital are negatively associated to the phenomenon. Finally, we employed advanced techniques to model the factors that motivate the existing regular immigrants in Greece to abandon the country and return to their own during the economic crisis period (return-migration). The findings reveal details on the imbalances of the economic, social and political framework of Greece that consequently affected negatively the growth rate of the country and created a fragile economy with high rates of unemployment and inflation. Hence, it compares the economic, social and institutional factors, which are related to the literature of return migration. According to the estimated results, the phenomenon of return migration is neither related in a predetermined way with unemployment rates nor poverty levels, but with tax revenue, corruption and government debt. Consequently, this situation had a strong negative impact in the behaviour of each financial, social and institutional determinant, with immediate result to the migrant families who pursue an improved quality of life back to their home country.

The overwhelming focus on causal linkages between environmental stressors and the migration decision making, disagreement among stakeholders regarding the positioning of migration within CCA discourse, and the lack of empirical evidence surrounding the role of migration as adaptation have been major impediments to mainstreaming migration in adaptation policies. There is a growing consensus among migration scholars regarding the potential contribution of migration to the lives and livelihoods of the migrants and their families left behind. However, the extent to which migration can contribute to climate change adaptation (CCA) in migrant-sending households, origin communities, or origin countries is a complex issue and requires further exploration. This thesis attempts to fill some of this knowledge gap by developing a conceptual approach to understand the effects of migration in the context of adaptation to extreme events such as drought and floods. As such, it is not concerned as to why someone migrates, but purely on its effects. This thesis shifts the focus to consequences of migration outcomes. The discourse on migration and adaptation has witnessed the same contestations of structuralism, neo-classical, and pluralist viewpoints with reference to effects of migration on development of migrant-sending households and origin communities. These lessons are pertinent for migration and adaptation discourse, and I use these lessons to build the conceptual framework of this thesis. It attempts to understand how the choices on remittance usage already made by households affects the CCA to extreme events. This thesis adopts a mixed-methods and comparative approach to validate the conceptual framework, based on case studies from Baoshan County of Yunnan Province in China and Upper Assam in India. A key component of CCA is the reduction of vulnerability of a system to climate change and variability. The vulnerability concept provides a framework to unpack the constituents of vulnerability. A reduction in vulnerability to an extreme event requires a reduction in sensitivity and enhancement of capacity to adapt. This thesis analyses the vulnerability of the remittance-recipient households compared to households that do not have access to remittances. It also characterises sensitivity and adaptive capacity of the remittance-recipient households in context of duration for which a household has received remittances and distance to destination. Results suggest that remittances affect certain sub-dimensions and attributes of vulnerability and these affects vary in different contexts. The mobility patterns and its consequences within a country are shaped by a wide range of policies and institutions. The creation of an enabling condition for adaptation remains a critical function for the governments, thus migration could not be a substitute for public investment in development and adaptation in origin communities. The availability of an enabling environment and reduction in structural constrains would reduce the risks from migration and help remittance-recipient households to leverage remittances for CCA.

This thesis is formed of three separate essays. The essays are empirical in nature and use the Kagera Health and Development Survey from Tanzania. The survey spans a 19-year period offering a unique opportunity to study many long-run dynamic processes of development in rural Africa. In the first essay, a version of which was co-authored with Joachim De Weerdt, we use these data to shed light on how mass internal migration changes the nature of informal risk-sharing. By quantifying how shocks and consumption co-move across linked households, our analysis shows that migrants unilaterally insure their extended family members who remain at home. This finding contradicts risk-sharing models based on reciprocity, but is consistent with assistance driven by social norms. Migrants sacrifice three to five per cent of their consumption growth to provide this insurance, which seems too trivial to have a stifling effect on their growth through migration. The second essay studies the role of exogenous income shocks on long-term migration decisions. The results reveal that temperature shocks cause large fluctuations in household consumption and inhibit long-term migration among men. These findings suggest that liquidity constraints are binding and prevent potential migrants from tapping into the opportunities brought about by internal migration. The final essay focuses on child nutrition and examines whether under-nourished children are able to recover the height losses later in life. The essay questions the methods used in the existing empirical literature and challenges the conventional view that recovery is nearly impossible after five years of age. The empirical part of the essay documents how puberty offers an opportunity window for recovery in the case of children in Kagera.