The marine environment is polluted by plastics of all forms and sizes. To reduce this serious pollution, it is important to identify its sources. This work focuses on the me-chanically induced breakdown of plastic into smaller fragments as a source of secondary microplastic, the time scale in which these microplastics are formed as well as the influ-ence of different environmental conditions like matrix conditions, collision potential or UV irradiation on the abrasion and fragmentation behaviour of plastic debris. Since a systematic investigation of parameter influence is not possible in the environ-ment, laboratory experiments were developed to simulate natural conditions such as drift on the beach or wave action in the (low tide) surf and swash zone. For this purpose, selected plastic objects (PET bottles, HDPE caps, PS cups and LDPE bags) were ex-posed to collision and/or friction forces under different conditions. Besides visual in-spection of the destruction procedure, a number of different methods was used to char-acterize the process, e.g., counting of visible fragments (larger than 350 μm), micro-scopic analysis of the surface structure (binocular, SEM) and highly resolved analysis of particle numbers in the size range below 350 μm. In order to extract microplastic parti-cles (<5 mm) from the matrix, extraction methods were developed that were adapted to the given sample properties (matrix volume). Furthermore, based on the particle num-bers, the power law model was applied to analyse the fragmentation process in the con-text of the observed particle size distributions. Plastic samples exhibited various signs of mechanical impairment in form of surface abrasion, cracks, tears, perforation, crumpling and finally fragmentation. The formation of fragments in different sizes (macro-, meso- and microplastics) was observed. The plastic objects were classified according to their degree of destruction to elucidate the effect of the different experimental conditions. Results show that fragmentation and abrasion depend on individual properties of the plastic objects such as thickness or shape and on the potential of weakening the plastic structure by mechanical forces (collisions) or chemical degradation (UV irradiation). Environmental conditions also influence the plastic damage; surface abrasion plays a major role on the beach; fragmentation will most likely happen in the surf- and in the swash zone. However, both processes occur simultaneously and interact with each oth-er. Formation of secondary microplastics was shown to be likely in the marine environ-ment; it must therefore be considered as an important process in the light of microplastic contamination.

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In this thesis, the central interest is to better understand how participatory methods applied during participatory processes in natural resources management can serve as nuclei for social learning. Thereby, the main focus is on learning via interaction in groups. My approach begins with the aim of developing an analytical framework which reflects the main processes that are effective within participatory methods. The framework presents an analytical tool, including proposed methods to monitor and compare the results of participatory approaches with respect to social learning. Building upon this framework, I develop an agent-based model to simulate and explore group dynamics. This model is intended to support a theoretical exploration of whether or not and if so, at what stage, personal views of a problem evolve into a shared understanding of a problem (which can be seen as a key element of social learning), and an assessment of how individual mental models and group properties relate to each other. Results of the model are interpreted to offer suggestions about factors hindering or fostering social learning during the application of participatory methods.

Up to now, politics and societies from all over the world have sought an economy that is built on the idea of continual growth to establish a wealthy future and achieve societal prosperity. At the same time, people have neglected to consider that the resulting environmental pollution is the largest cause of disease and death in the world today. Therefore, it appears sensible to ensure that people’s well-being and nature’s well-being is uncoupled from profit-orientated aims. To break the circle of continual growth and the decreasing well-being of humans and nature, individual sustainability traits that are able to foster a transition to sustainable development need to be explicitly identified. Today’s young people will presumably face an even more severe level of consequences resulting from continual growth, which will reach far into the future, thereby affecting the living environment of future generations even more drastically. Therefore, this dissertation aims to answer the question of how young people possess and profit from their sustainability traits in terms of well-being. This work approaches this question by empirically investigating different interrelations between environmental values, the perception of environments (including the perception of naturalness and the perception of aesthetics), environmental concern and well-being in the context of young people. The empirical section is divided into three parts that investigate the different relationships step by step. These three parts are based on three different quantitative questionnaire surveys of young people in Germany. In the first survey (N = 229; Mage = 13.27 years, SD = 2.37 years), the relation between secondary school students’ human-nature relationship as a sustainability trait and their well-being was investigated. Analyses showed that the sustainability trait of human-nature relationships was significantly related to young people’s age-dependent well-being through nature perception in terms of naturalness and aesthetics as well as through individual nature connection. Young people were shown to profit from nature as resource for their own well-being. A positive human-nature relationship could be described as an important requirement for people to achieve sustainable development. In a second inquiry, university students (N = 237; Mage = 22.12 years, SD = 3.09 years) with a focus on the interrelations of sustainability traits that showed relations to people’s well-being in past research were surveyed. The results describe the interrelations between the specified sustainability traits of environmental values, a newly developed scale that theoretically and empirically validated affective nature connection, cognitive nature connection, and environmental concern. The findings indicate that the chosen sustainability traits mutually contribute to each other’s impact and do not preclude each other. Future research based on the results of the two described studies will likely show that sustainability traits are desirable characteristics and useful attributes that are available all over the world, no matter what a person’s age. As a final step, secondary school students’ environmental concern and well-being were quantitatively surveyed (N = 2173; Mage = 14.56 years, SD = 1.45 years) to analyze how environmental concern as a sustainability trait predicts young people’s well-being. The children’s and adolescents’ sustainability trait of environmental concern was able to predict young people’s well-being, with a clear dependence on age. The obtained outcomes supporting the aim to possess nature as a resource of well-being need to be considered in terms of young people’s age. Youth seem to experience sensitive periods of time in which the youth’s sustainability traits evidently act differently than in other stages of life. Hence it is important to point out that especially young people need age-appropriate treatment in terms of education for sustainable development to successfully foster young people’s sustainability traits. The main goal of this dissertation was to explore and identify in-depth insights into young people’s sustainability traits and their interrelations as well as the connections to young people’s well-being. As such interrelations between sustainability traits and well-being meet the aims of sustainable development as well as political and societal aims for a healthy future life environment for everyone which is expected of continual (economic) growth up to the present time, age-dependent education for sustainable development could address the need for young people to become progressive decision makers who create future-proof solutions for themselves and others, considering the constitution of a worthy life for present and future generations.

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