Our new review about urban grassland restoration has been published in Journal of Environmental Management.

Our latest paper, a global review about urban grassland restoration has been published in Journal of Environmental Management. This is a result of a nice cooperation between our research group and Valentin Klaus (ETH Zürich) and Leonie Fisher (University of Stuttgart).

The paper is open access and can be freely downloaded from the journal website (please click here).

Citation

*Fekete, Réka, *Valkó, Orsolya, Fischer, Leonie, **Deák, Balázs **Klaus, Valentin (2024): Ecological restoration and biodiversity-friendly management of urban grasslands – a global review on the current state of knowledge. Journal of Environmental Management 368: 122220.

 *, **: equal contributions.

Urban grasslands, like parks, meadows, vacant lots and other green spaces, play a crucial role in enhancing biodiversity in cities. However, as urbanization accelerates, these green spaces are increasingly threatened by factors like habitat degradation, pollution, and human activities. Our recent review explores the best strategies for restoring and managing urban grasslands to support biodiversity, focusing on lessons learned from various global studies.

The results of the review in numbers - location of the reviewed studies, and data on city population, site type, studied taxa, and main interventions.

The review found that restoration efforts in urban grasslands can indeed boost biodiversity, but the outcomes vary depending on factors such as the methods used to prepare the soil, the types of species introduced, and the specific conditions of each site. For instance, some sites benefit from introducing native plants, while others may need specific soil treatments or adjustments to local management practices. The success of these efforts also depends on maintaining diverse habitats, reducing mowing frequency, and avoiding the use of chemicals, all of which can create a more favourable environment for a wide range of species.

One key recommendation from our review is to create a network of interconnected green spaces across cities. This could involve enhancing connectivity between parks, vacant lots, and even small patches of green space that act as "stepping stones" for wildlife. Maintaining spontaneous vegetation in unused areas, like vacant lots, can also provide valuable habitats for various invertebrate species, which are essential for the overall ecosystem. Additionally, evaluating soil conditions before starting restoration projects is crucial, as the existing soil's seed bank and nutrient levels can significantly impact the success of the restoration.

The review also highlights the importance of shifting towards low-intensity, biodiversity-friendly management practices in urban grasslands. For example, reducing the frequency of mowing and eliminating the use of fertilizers and chemicals can significantly enhance biodiversity while also reducing maintenance costs. Using native, drought-tolerant species that require little to no irrigation is another cost-effective strategy, particularly as cities face the challenges of climate change.

However, we also identified several knowledge gaps that need to be addressed in future research. For instance, more studies are needed to understand the large-scale effects of urban grassland restoration, such as how these efforts impact entire cities or regions. Additionally, research is lacking in certain parts of the world, particularly in the Global South, and in cities of particulars sizes (especially small cities and mega-cities). Understanding how different local factors interact to influence restoration outcomes is essential for developing more widely applicable guidelines for urban grassland management.

In conclusion, while there is clear evidence that urban grassland restoration can enhance biodiversity, the success of these efforts depends on a variety of factors, including local conditions, management practices, and the specific methods used. By addressing the identified knowledge gaps and continuing to refine our approaches, we can better support biodiversity in urban environments, ultimately contributing to healthier and more resilient cities.

This photo collection shows the large variety of urban grasslands with native plant species in different greenspaces: A) garden meadow (Zürich, Switzerland), B) vacant lot (Detmold, Germany), C) right-off-way infrastructure (Zürich, Switzerland), D) tallgrass meadow in an urban park (Gödöllő, Hungary), E) mini-meadows in containers (Weesen, Switzerland), and F) roadside verge (Zürich, Switzerland)

Abstract

In the face of the global biodiversity decline, ecological restoration measures to actively enhance urban biodiversity and options for biodiversity-friendly greenspace management are high on the agenda of many governments and city administrations. This review aims to summarize and advance the current knowledge on urban grassland restoration by synthesizing research findings on restoration approaches and biodiversity-friendly management measures globally. Indeed, we found restoration approaches to be generally effective in increasing biodiversity; yet, there were variations in the outcomes due to the difference in soil disturbance methods, management regimes, the set of species introduced to a site, and the specific local setting. Based on the reviewed studies, we formulated recommendations for maximizing restoration success of urban grasslands through: i) creating a network of heterogeneous urban greenspaces and enhancing connectivity between them; ii) maintaining the spontaneous vegetation in vacant lots and wasteland sites that can provide habitats for various invertebrate species; iii) evaluating actual soil conditions, soil seed bank, and seed rain before restoration efforts take place since these seed sources could considerably affect the restoration outcomes, iv) preserving nutrient-poor conditions in urban greenspaces instead of introducing nutrient-rich topsoil; v) shifting to less intensive, biodiversity-friendly management in urban greenspaces by reducing mowing frequency and avoiding the use of chemicals; and vi) utilizing native dry grassland species for climate adaptation without irrigation. We further identified knowledge gaps regarding i) city-scale and regional-scale effects of restoration, ii) effects of interventions on multiple taxa and multiple ecosystem services, iii) restoration in small versus mega-cities, and iv) in the global south. These gaps should be addressed in future studies for making general guidelines for urban grassland restoration broadly applicable.