Dr. Andreas Dietzel

Urban blue and green spaces, like ponds and parks, can mitigate the negative effects of urbanization on biodiversity by providing diverse, connected habitats and enabling resource flows between ecosystems. While studies have evaluated these spaces for terrestrial and aquatic communities individually, few have examined shared factors influencing both communities simultaneously. Consequently, it is unclear how these spaces should be conceived and maintained to support the diversity of both aquatic and terrestrial species, as well as their interactions. Here, we use environmental DNA (eDNA) metabarcoding to identify shared drivers and assess if and how aquatic and terrestrial invertebrate communities are coupled across 54 paired aquatic and terrestrial habitats along an urbanization gradient in the city of Zurich, Switzerland. Contrary to general expectations, we find no significant correlation in aquatic and terrestrial community structure, which we attribute to distinct drivers identified for both communities. Aquatic communities were primarily influenced by local factors related to habitat quality, while terrestrial communities were associated to landscape drivers pertaining to habitat quantity, suggesting that different processes at different spatial scales need to be considered to support both communities. Furthermore, with increasing urbanization, aquatic and terrestrial communities exhibited signs of decoupling driven by the filtering of organisms straddling ecosystem boundaries. We conclude that increasing levels of urbanization weaken resource flow between aquatic and terrestrial environments. By employing eDNA across ecosystem boundaries, our study highlights the critical importance of both the quality and quantity of urban habitats in conserving aquatic and terrestrial communities, as well as their linkages.

Robust, quantitative understanding of the diverse ecological needs of species is needed to inform effective biodiversity conservation, now and in the future, but is lacking for most species. The advent of "big data" in ecology presents unprecedented opportunities to fill this gap and to disentangle the diverse drivers of biodiversity. Variable and model selection in sparse (small sample sizes for most species), high-dimensional (large pool of candidate predictors) problems is, however, non-trivial. Here, we employ cross-validated Bayesian projection predictive variable selection and shrinkage priors to identify, from a list of 70 ecological and biophysical candidate predictor variables, the minimal subset that best predicts the habitat preferences and distributions of 103 species of amphibians, birds, butterflies, dragonflies, and grasshoppers using the city of Zurich, Switzerland, as a case study. We contrast the predictive performance and ecological inference of models fit with the full set of predictors using shrinkage priors (exhaustive models) to models fit with a limited number of predictors obtained by compiling predictors from the full list of predictors using weakly informative priors (selective models). We show that exhaustive models excel in predictive performance, albeit at the cost of greater model complexity compared to selective models. Results from the selective models reveal the importance of access to aquatic habitat for a wide range of taxa, relative to other drivers such as urbanisation, vegetation and environmental hazards. These results are complemented by more nuanced insights from the exhaustive models into the importance of specific types of aquatic habitat (ponds, lakes, streams) and vegetation (herb, shrub, canopy cover) for the distribution of urban biodiversity, as well as the different spatial scales at which drivers are of predictive relevance. Our findings demonstrate the potential of shrinkage-based Bayesian variable selection to leverage big ecological data for species distribution modelling, and contribute to the development of concrete guidelines for urban planning and infrastructure design that account for biodiversity conservation.

Blue-green infrastructure (BGI), combining semi-natural and engineered elements, offers multifaceted benefits like stormwater management, water purification, heat mitigation, and habitat provision. However, current BGI designs prioritize engineering goals, overlooking its ecological potential. Here we advocate for integrating engineering and ecological objectives into BGI design to enhance performance and biodiversity. Through an interdisciplinary literature review, we emphasize the importance of species diversity, abundance, and ecological processes, to improve engineering performance and resilience, and lower management costs. We emphasize the importance of interdisciplinary collaboration to navigate trade-offs between engineering and ecological objectives, ultimately enabling us to engineer both for and with biodiversity.

Eine blau-grüne Infrastruktur aus Fliessgewässern, Pflanzenkläranlagen oder Gründächern kann den Siedlungsraum und vor allem Städte sowohl biodiverser als auch resilienter gegenüber dem Klimawandel machen. Voraussetzung ist die Zusammenarbeit
von Ingenieur- und Naturwissenschaften.

Une infrastructure bleue et verte composée de cours d’eau, de stations d’épuration végétales ou de toits verts peut rendre l’espace urbain, et surtout les villes, à la fois biodiverses et résistantes aux aléas climatiques. La condition préalable est la collaboration entre l’ingénierie et les sciences naturelles.