How does the choice of trees in favour of high carbon storage benefit faunistic biodiversity in urban areas? A systematic review

Land-use change, climate crisis, and subsequent biodiversity loss are critical challenges that need to be addressed in sustainable urban development. The concept of ecosystem services (ES) is a promising approach to guide this development. Trees are key elements of urban nature that provide a variety of ES, including carbon storage and food and habitat for diverse faunistic groups. It is often suggested that the design of cities in favor of biodiversity also benefits ES and vice versa, but the relationship between tree species, carbon storage, and faunistic biodiversity remains underexplored. Traits of species and characteristics describing a state of an individual have been suggested as ES-indicators. Therefore, we investigated how the choice of tree species and their characteristics in favor of high carbon storage affect faunistic biodiversity and other ES in urban areas.

We conducted a systematic literature review using Web of Science and Bibliometrix, aiming to investigate (i) which tree species have high carbon storage and shared characteristics, (ii) which of the tree species with high carbon storage also support the species diversity of different faunistic groups and which tree characteristics are relevant for both carbon storage and faunistic diversity, and (iii) whether there are synergies or trade-offs between optimizing carbon storage and faunistic biodiversity with other ES.

We identified 68 studies that tested at least one of (i), (ii), or (iii). We found that characteristics of trees (i.e., age and size) and their environment (e.g., location, cover) rather than tree species are most relevant to strengthen synergies between carbon storage and faunistic diversity, with large old trees being key. However, studies were predominantly from the Global North, restricting the generalizability of results. We recommend complementing urban tree registers with information about the value of tree species for faunistic biodiversity, protecting large old trees in urban areas, and emphasizing research beyond the Global North. Our results are relevant for urban planners and designers aiming to create cities that account not only for climate change but also for the needs of urban faunistic biodiversity.