Linking human impacts to community processes in terrestrial and freshwater ecosystems.

Human impacts such as habitat loss, climate change and biological invasions are radically altering biodiversity, with greater effects projected into the future. Evidence suggests human impacts may differ substantially between terrestrial and freshwater ecosystems, but the reasons for these differences are poorly understood. We propose an integrative approach to explain these differences by linking impacts to four fundamental processes that structure communities: dispersal, speciation, species-level selection and ecological drift. Our goal is to provide process-based insights into why human impacts, and responses to impacts, may differ across ecosystem types using a mechanistic, eco-evolutionary comparative framework. To enable these insights, we review and synthesise (i) how the four processes influence diversity and dynamics in terrestrial versus freshwater communities, specifically whether the relative importance of each process differs among ecosystems, and (ii) the pathways by which human impacts can produce divergent responses across ecosystems, due to differences in the strength of processes among ecosystems we identify. Finally, we highlight research gaps and next steps, and discuss how this approach can provide new insights for conservation. By focusing on the processes that shape diversity in communities, we aim to mechanistically link human impacts to ongoing and future changes in ecosystems.

Life Cycle Assessment and Cost-Benefit Analysis of Technologies in Water Resource Recovery Facilities: The Case of Sludge Pyrolysis.

In Europe, sewage sludge is mostly used in agriculture (49%) or incinerated (25%). Technologies for sludge management that can support the transformation of wastewater treatment plants (WWTPs) to water resource recovery facilities (WRRFs) are emerging. Sludge pyrolysis is one of them. It can generate two main high-value co-products: heat and biochar. Moreover, biochar can be transformed into activated carbon. The economic and environmental impacts of sludge pyrolysis and its comparison to the direct application of sludge in agriculture and incineration are unknown. Therefore, we applied a life cycle assessment (LCA) and a cost-benefit analysis (CBA) of sludge pyrolysis. We quantified environmental externalities in an LCA and then applied the benefit transfer method to monetize these externalities, which were included in an economic CBA. Pyrolysis reduced impacts in five to nine LCA categories and had a positive economic net present value (NPV) compared to using sludge in agriculture. Pyrolysis with biochar production was not better than incineration, showing increased impacts in nine categories and negative NPVs (-19 to -22 €/t sludge). The factor driving differences between the alternatives was the assumed CO2 externality price (164 €/ton CO2-eq) and the removal rate of pharmaceutical micropollutants of the sludge-based activated carbon. High uncertainty in environmental prices is one of the limitations of our study.

Data on the stated adoption decisions of Swiss farmers for variable rate nitrogen fertilization technologies.

We present data on the stated preference for the adoption of variable rate technologies from 418 crop farmers in Switzerland. The online survey was conducted online in spring 2021. It consisted of two parts: 1) a choice experiment and 2) questions about farmers' characteristics, expectations and beliefs, as well as their risk preferences. In the choice experiment, farmers were presented with eight consecutive choice tasks. Each task consisted of three alternatives, two hypothetical scenarios for variable rate technologies adoption and the status quo option. We used a split-sample approach and varied the additional profit margin gained through higher yields, label premiums or subsidies for one subsample (focussing on the willigness to accept) and additional cost (acquisition, maintenance and other costs) for the other subsample (focussing on the willigness to pay). Non-monetary attributes include 1) ownership of the technology; 2) potential to increase nitrogen use efficiency and thus reduce nitrogen losses to the environment; 3) uncertainties about the actual impact of the technology on yields and profits (reliability); 4) support in case of technical difficulties. We also collected data on farmers' experiences, attitudes and goals, as well as their risk preferences. Additionally, the survey data were matched with data from the cantonal farm census, which contains information on farm characteristics.

Do the societal benefits of river restoration outweigh their costs? A cost-benefit analysis.

Switzerland plans to restore 4000 km of rivers by 2090. Despite the immense investment costs, river restoration benefits have not been valued in monetary terms, and a cost-benefit analysis (CBA) does not exist for any river restoration project in Switzerland. We apply stated preference methods to elicit public preferences and willingness to pay for restoring two specific but representative river sites. The benefits of restoration are compared with its costs. Upscaling the results to the national level shows that the government budget allocated for river restoration (CHF 1200/m) is insufficient to cover the costs of local restoration projects. However, the surveyed local populations are willing to pay substantially more for restoring rivers in their area of residence than they are legally obliged to do. The CBA results demonstrate that the benefits outweigh the costs in the two case studies, and hence that restoration efforts are justified from an economic point of view. A sensitivity analysis shows that the main results and conclusions do not change when we change some of the key assumptions underlying the CBA.

Multi-criteria decision analysis for integrated water quality assessment and management support.

In densely populated areas, surface waters are affected by many sources of pollution. Besides classical pollutants like nutrients and organic matter that lead to eutrophication, micropollutants from various point- and non-point sources are getting more attention by water quality managers. For cost-effective management an integrated assessment is needed that takes into account all relevant pollutants and all sources of pollution within a catchment. Due to the difficulty of identifying and quantifying sources of pollution and the need for considering long-term changes in boundary conditions, typically substantial uncertainty exists about the consequences of potential management alternatives to improve surface water quality. We therefore need integrated assessment methods that are able to deal with multiple objectives and account for various sources of uncertainty. This paper aims to contribute to integrated, prospective water management by combining a) multi-criteria decision support methods to structure the decision process and quantify preferences, b) integrated water quality modelling to predict consequences of management alternatives accounting for uncertainty, and c) scenario planning to consider uncertainty from potential future climate and socio-economic developments, to evaluate the future cost-effectiveness of water quality management alternatives at the catchment scale. It aims to demonstrate the usefulness of multi-attribute value functions for water quality assessment to i) propagate uncertainties throughout the entire assessment procedure, ii) facilitate the aggregation of multiple objectives while avoiding discretization errors when using categories for sub-objectives, iii) transparently communicate the results. We show how to use such multi-attribute value functions for model-based decision support in water quality management. We showcase the procedure for the Mönchaltorfer Aa catchment on the Swiss Plateau. We evaluate ten different water quality management alternatives, including current practice, that tackle macro- and micropollutants from a wide spectrum of agricultural and urban sources. We evaluate costs and water quality effects of the alternatives under four different socio-economic scenarios for the horizon 2050 under present and future climate projections and visualize their uncertainty. While the performance of alternatives is catchment specific, the methods can be transferred to other places and other management situations. Results confirm the need for cross-sectoral coordination of different management actions and interdisciplinary collaboration to support the development of prospective strategies to improve water quality.

Cost-benefit analysis of the Swiss national policy on reducing micropollutants in treated wastewater.

Contamination of freshwater with micropollutants (MPs) is a growing concern worldwide. Even at very low concentrations, MPs can have adverse effects on aquatic ecosystems and possibly also on human health. Switzerland is one of the first countries to start implementing a national policy to reduce MPs in the effluents of municipal sewage treatment plants (STPs). This paper estimates the benefits of upgrading STPs based on public's stated preferences. To assess public demand for the reduction of the environmental and health risks of MPs, we conducted a choice experiment in a national online survey. The results indicate that the average willingness to pay per household is CHF 100 (US$ 73) annually for reducing the potential environmental risk of MPs to a low level. These benefits, aggregated over households in the catchment of the STPs to be upgraded, generate a total annual economic value of CHF 155 million (US$ 113 million). This compares with estimated annual costs for upgrading 123 STPs of CHF 133 million (US$ 97 million) or CHF 86 (US$ 63) per household connected to these STPs. Hence, a cost-benefit analysis justifies the investment decision from an economic point of view and supports the implementation of the national policy in the ongoing political discussion.

Respondent uncertainty in contingent valuation of preventing beach erosion: an analysis with a polychotomous choice question.

Respondent uncertainty is often considered as one of the main limitations of stated preference methods, which are nowadays being widely used for valuing environmental goods and services. This article examines the effect of respondent uncertainty on welfare estimates by applying the contingent valuation method. This is done in the context of beach protection against erosion. Respondent certainty levels are elicited using a five-category polychotomous choice question. Two different uncertainty calibration techniques are tested, namely one that treats uncertain responses as missing and another in which uncertain 'yes' responses are recoded as 'no' responses. We found no evidence that the former technique offers any gains over the conventional model assuming certainty. The latter calibration technique systematically reduces welfare estimates. The reduction is statistically significant only when the most certain 'yes' responses are recoded as 'no' responses. The article further identifies determinants of respondent uncertainty. Finally, it explores how real market experience affects respondent uncertainty.