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Abstract. The ecological literature suggests that biodiversity reduces the variance of ecosystem services. Thus, conservative biodiversity management has an insurance value to risk-averse users of ecosystem services. We analyze a conceptual ecological-economic model in which such management measures generate a private benefit and, via ecosystem processes at higher hierarchical levels, a positive externality on other ecosystem users. We find that ecosystem management and environmental policy depend on the extent of uncertainty and risk-aversion as follows: (i) Individual effort to improve ecosystem quality unambiguously increases. The free-rider problem may decrease or increase, depending on the characteristics of the ecosystem and its management; in particular, (ii) the size of the externality may decrease or increase, depending on how individual and aggregate management effort influence biodiversity; and (iii) the welfare loss due to free-riding may decrease or increase, depending on how biodiversity influences ecosystem service provision.
Wood-pastures have been present in Europe for thousands of years. This form of grazed landscape, combining herbaceous vegetation with trees and shrubs, has often co-evolved with its human users into complex social-ecological systems (SES). Wood-pastures are associated with high cultural and biodiversity values and are an example of the sustainable use of resources. However, due to their often relatively labour-intensive management and low productivity, large areas of wood-pastures have been lost over the last century. The loss of these areas means not only the loss of biodiversity on both local and landscape scales, but also the loss of traditional farming and cultural heritage in some regions. Across the European Union, wood-pastures are facing different problems and are embedded in different social systems and ecological environments. Yet they are all affected by global change and common European policies. To understand the challenges for wood-pastures in a changing world, a holistic approach combining different disciplines is needed. This dissertation therefore is analyzing wood-pastures across Europe as a Social-ecological System, combining ecology and social science with the aim to identify the barriers and drivers for wood-pastures persistence into the future.
In the face of uncertainty, ecosystems can provide natural insurance to risk averse users of ecosystem services. We employ a conceptual ecological-economic model to analyze the allocation of (endogenous) risk and ecosystem quality by risk averse ecosystem managers who have access to financial insurance, and study the implications for individually and socially optimal ecosystem management, and policy design. We show that while an improved access to financial insurance leads to lower ecosystem quality, the effect on the free-rider problem and on welfare is determined by ecosystem properties. We derive conditions on ecosystem functioning under which, if financial insurance becomes more accessible, (i) the extent of optimal regulation increases or decreases; and (ii) welfare, in the absence of environmental regulation, increases or decreases.
In an increasingly urbanized world, consequences for humans, animals, plants are often unknown. Fundamental changes in landscapes due to landscape fragmentation, intensified agriculture or biodiversity loss dramatically impact ecosystems and their functions. Humans increasingly shifted their lifestyle from outdoor activities towards indoors, which are facilitated and depend on mostly digital technologies that are discussed to increase the risk of nature alienation. On the other hand, these readily available digital technologies offer chances to connect with people worldwide. This connectivity offers manifold opportunities to share data and to recruit people looking for new entertaining and interesting experiences as cooperation partners for the scientific community in so-called citizen science approaches. In citizen science, non-scientists are integrated in the data gathering of scientists. Being part of scholarly research, the citizen scientists receive up-to-date information on the research topic, which fosters the learning of the scientific background and thereby ideally supports the general scientific literacy that might be little developed due to a lack of interaction with nature. Especially for children in an urban societal background, there are concerns of alienation from nature due a significant shift away from nature-based activity and recreation, when compared to past generations. However, even though direct contact with nature is nowadays often infrequent, a solid knowledge about nature is essential to understand the consequences of biodiversity loss, the limitation of natural resources and the need for a sustainable development. Theoretically, citizen science cooperation offers a unique opportunity to integrate the public in the scientific gain of knowledge, further explaining the nature of science and fostering an increased awareness for biodiversity conservation and sustainable development. Inspired by these challenges, I investigated in my dissertation seed predation, an important ecosystem function that has hardly been part of citizen science project. As seed predation has only rarely been investigated along urban-rural gradients and to integrate the question if the background (urban vs. rural) of primary school children affects their environmental knowledge, I selected study sites in and around Lüneburg and Hamburg, in Northern Germany. In my ecological experiments, I found that slugs are important seed predators that independently of urbanization predated about 30% of all seeds in the anthropogenically used landscapes investigated. Also, I could for the first time integrate primary school children in a citizen science approach into this research and show that even seven year old children can record data as reliable as a scientist. Finally, I investigated the native species knowledge from the children taking part as citizen scientists in my research, considering possible differences due to their urban or rural background. Contrary to my expectation, the urban or rural background had no significant effect on the species knowledge. However, my work provides a good foundation to transfer the approach of introducing a basic foundation of a taxonomical species concept in primary school to foster further understanding on biodiversity and ecosystem functions. In summary, my dissertation combined different disciplinary approaches showing synergies between the single disciplines to support strategies for a successful sustainable development in the spirit of an education for sustainability. I could highlight the great potential of inter- and transdisciplinary approaches combining natural research with scientific literacy in a citizen science project on a local scale, which may serve as a model for implementing citizen science projects in schools elsewhere. I highly recommend this successful approach for similar cooperation on larger scales to counter challenges of pressing societal problems. Even though each cooperation will has its own unique challenges, the synergetic advantages will likely outweigh the disadvantages. In this context, there should be more emphasis on the education for sustainable development, not only in schools but other educational institutions like universities, to face the global urbanization with its manifold challenges and opportunities.
The dissertation deals with the impact of nitrogen deposition on the functioning of heathland ecosystems. Special interests were the displacement of heather (Calluna vulgaris) by the purple moor-grass (Molinia caerulea) as well as the fate of nitrogen loads in dry heathland ecosystems. The results of the studies undertaken in the field and in the greenhouse are presented as five individual journal articles. The nature of nutrient limitation was studied by means of fertilisation experiments with nitrogen (N) and phosphorus for heather and purple moor-grass (Articles I and II). The impact of nitrogen deposition on the outcome of competition between these two species was analysed during a competition experiment in the greenhouse (Article III). The aim of a 15N tracer experiment was to determine the fate of nitrogen deposition as well as allocation patterns (Article IV). In addition, the response of purple moor-grass to the combined effects of nitrogen deposition and summer droughts was investigated in a second greenhouse experiment (Article V). The fertilisation experiments showed that the growth of heather as well as of purple moor-grass is predominantly limited by N (Articles I and II). However, the results of the competition experiment demonstrated that only purple moor-grass has the ability to benefit from additional N loads, which in turn gives the grass the opportunity to displace heather (Article III). Drought treatment resulted in strikingly reduced biomass production of purple moor-grass in N-fertilised pots, mainly as a result of dying aboveground biomass during dry periods (Article V). This striking susceptibility of purple moor-grass to the combination of nitrogen deposition and drought must be taken into account, when predicting future developments of dry heathlands. The results of the 15N tracer experiment showed that the investigated heath is still in an early stage of N saturation, as indicated by a high immobilisation capacity and negligible leaching losses of 15N (Article IV). The findings of the dissertation contribute to a better understanding of the processes underlying the encroachment of purple moor-grass in dry heathlands and can enhance heathland management. The results can also be used to to evaluate the current and future status of this ecosystem particularly with regard to the various stages of N saturation as well as in the determination of “Critical Loads”.
Agro-biodiversity can provide natural insurance to risk averse farmers. We employ a conceptual ecological-economic model to analyze the choice of agrobiodiversity by risk averse farmers who have access to financial insurance. We study the implications for individually and socially optimal agro-ecosystem management and policy design when on-farm agro-biodiversity, through ecosystem processes at higher hierarchical levels, generates a positive externality on other farmers. We show that for the individual farmer natural insurance from agro-biodiversty and financial insurance are substitutes. While an improved access to financial insurance leads to lower agro-biodiversity, the e_ects on the market failure problem (due to the external benefits of on-farm agro-biodiversity) and on welfare are determined by properties of the agro-ecosystem and agro-biodiversity’s external benefits. We derive a specific condition on agro-ecosystem functioning under which, if financial insurance becomes more accessible, welfare in the absence of regulation increases or decreases.