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The environmental problems originating from transport are considerable, persistent and increasing. In personal travel there is a continuing switch away from public transport towards the private car. Also the proportion of freight moving by road is increasing in volume and distance. These trends reveal that the transport of both people and goods is less sustainable than it was. Altering existing transport behaviour to reduce demand, simultaneously shaping suppressed demand, and achieving both whilst maintaining politically acceptable levels of access and mobility are serious challenges. This thesis explores a part of the complex landscape of transport decision making where theses tensions are enacted, focussing on three key group of organisations within the road transport sector of the north east of England. The thesis assess the salience of ‘the environment’ within the minds of organisational transport decision makers in the North East. Their views on the environment and its importance within their decisions will affect the success of policy initiatives. Examining transport choices within this context reveals the depth of ‘environmental’ understanding present within the operational landscape of transport. It is argued that theoretical and conceptual approaches to the process of transport policy development have matured, whilst the implementation of transport policy resulting from this process remains somewhat patchy with traditional approaches to transport provision remaining dominant. The argument is covered in terms of transport paradigms. Though sustainability policies remain, recent integrated transport initiatives are undermined from the centre by a return to the market paradigm and to ‘predict and provide’. Within this research clear evidence has emerged of reinterpretations of ‘the environment’ taking place, Theses discoveries illustrate the ability of governance and organisational actors to assimilate emerging policy requirements into existing or preferred programmes and transport behaviours, in support of the aims of recent transport policies the ability to identify economic and environmental ‘win-win’ opportunities was found to be important. Decisive leadership was found to deliver effective transport policies.

Inverse problems governed by partial differential equations (PDEs) is a means to learn, from data, unknown or uncertain aspects of PDE-based mathematical models. PDE-based models often are constructed from scientific principles and are pervasive in science and engineering. The improvement of such a model can be accomplished by determining a ``best'' set of model parameters, or by reducing the uncertainty of the parameters that characterize the model. Ultimately, the goal is to improve the predictive capacity of such models and quantitatively understand the limitations of model-based predictions.In this dissertation, we describe algorithmic approaches for the Newton-based solution of large-scale computational inverse problems governed by PDEs. We present and motivate hierarchical matrix approximations of the Hessian, a key-component of Newton's method, as a means to exploit localized sensitivities of underlying elliptic PDE operators and which perform well for inverse problems with highly-informative data. To circumvent the computational challenges associated with generating hierarchical matrix approximations of matrix-free operators, such as the Hessian, we describe a local point spread function methodology, whose computational cost is independent of the problem discretization. It is numerically demonstrated that hierarchical matrix approximations of the Hessian can be effective for large-scale ice sheet inverse problems with highly informative data and thin ice sheets. Lastly, we present a scalable means to solve PDE- and bound-constrained optimization problems by an interior-point filter line-search strategy that leverages performant algebraic multigrid linear solvers. Bound constraints arise naturally in many inverse problems as a means to enforce sign-definiteness as dictated by e.g., physical principles. The inclusion of bound constraints does add particular computational challenges such as non-smooth complementarity conditions as part of the conditions for optimality. The Newton linear system solve strategy described in Chapter 4 is accelerated due to the inclusion of bound-constraints, wherein the performance of many other strategies is negatively impacted by such bound-constraints. A theoretical analysis is provided which demonstrates the algorithmic scaling of the approach. In addition, we demonstrate algorithmic and parallel scaling of the described approach by applying the framework to an example elliptic PDE- and bound-constrained problem.

Considerable uncertainty remains regarding what the impacts of sustained or changing ultraviolet radiation (UV) stress may be for aquatic ecosystems. This dissertation represents the first attempt to explore the role of UV in a biological invasion context. Chapter 1 serves as a broad introduction to the role of UV in lakes. It emphasizes the complex interactive and indirect effects of UV on aquatic ecosystems and in particular the implications of UV for disease dynamics, contaminant toxicity, carbon cycling, and biodiversity in lakes. The remaining chapters elaborate on the topic of UV and biodiversity by developing the idea that UV can regulate warmwater fish invasion in transparent lakes. Chapter 2 provides the foundation for this idea. The results from an in situ incubation experiment that manipulated incident UVR exposure of larval bluegill (Lepomis macrochirus), and an assessment of UVR exposure levels in nearshore habitats using DNA dosimeters are reported. The results demonstrate that UVRmediates habitat invasibility in a large sub-alpine lake (Lake Tahoe CA/NV USA). In chapter 3 an invasion-window model is developed which predicts that largemouth bass (Micropterussalmoides) establishment in Lake Tahoe is controlled by the ability of these non-native fish to cope with UV and temperature stress along a UV-temperature stress gradient. In situ incubation experiments in contrasting high and low-UV nearshore habitat corroborated model predictions. In situ incubation experiments with native Lahtonan redside minnows (Richardsonius egregius)showed that the native species overlaps broadly with the range of ambient environmental conditions in the Tahoe littoral zone. The final chapter suggests a novel approach for managing warmwater fish invasion in lakes. A UV Attainment Threshold, which is a target value for watertransparency based on 1) incident solar UV exposure levels during peak spawning season, and 2)experimentally derived UV exposure levels lethal to larval warmwater fish, was developed.Taken together these chapters provide novel insights that could improve our ability to predict and manage aquatic species invasion, especially in transparent lakes.