Urbanization is happening all over the world. Everywhere you look, you can see that cities are expanding and new cities are being built. This is often at the expense of nature. There is not a lot of room for vegetation in cities and more and more existing vegetation and farmlands are being turned into urban land. This creates a problem not only for the plants and animals themselves, but also for us humans, because urban biodiversity plays an important role in the functioning of urban ecosystems. This has a significant impact on the well-being and quality of life for city residents.
In a recent paper from Guilherme et al. (2024), they used a multi-model inference framework to look at the influence of local-scale land cover evolution on urban biodiversity, using species richness of birds as indicators, in the city of Porto, Portugal. With the results gathered in this study, researchers want to inform urban planners, designers and management on how they can improve cities for urban biodiversity, with focus on birds, reptiles and amphibians.
Birds
Regarding birds, the main results of the study are that artificial land cover has a negative effect on the species richness, while vegetation cover has a positive effect. However, the birds can adapt both to older vegetation and recent vegetation. Birds have a high mobility, so they can easily go from one place to another. This makes it easier for them to find areas that are appropriate for them. In the study, they also saw that areas in the city that recently gained vegetation cover had a strong positive effect on bird species richness. Furthermore, they also saw that the age of vegetation cover does not have a big influence on bird species richness, even as the presence of water elements.
For the urban planning and designing it is important for the birds to focus on a balance between opportunistic and exotic species, and specialist and rare species. Right now in Porto the diversity of the birds stems from commensal, opportunistic and/or exotic species, and this will most likely be the same for other cities. To encourage more specialist and rare species you can diversify habitat niches in strategic locations, because current urban green areas have a simplified vegetation composition and structure. It is also recommended to install nest boxes for cavity-nesting birds and to make shrub and herbaceous layers to complement trees.
Reptiles
The main result of the study regarding reptiles is that they benefit from wooded and herbaceous habitats, thus they need local spatial diversity. The fragmentation that happens in urban areas creates limited mobility for reptiles. This can cause separate colonies of reptiles to become isolated. The age of vegetation cover and the trend of vegetation cover evolution do not play a significant role in the species richness of reptiles. Additionally, the presence of water does not have a great effect on the reptile species richness.
While planning and designing urban areas, is it important for reptiles that a diverse matrix of vegetation and habitats are maintained, ensuring the presence of suitable microhabitats. The wooded and herbaceous habitats provide diverse ecological conditions necessary for foraging, predator avoidance, egg-laying, basking and overwintering. To help reptile species overcome fragmentation, there needs to be strengthening of connection between urban green spaces.
Amphibians
The study’s main results for amphibian species is that they tend to avoid newly vegetated zones and that water elements are critical for them. A common problem is that not every aquatic habitat in the city is suitable. Amphibian populations also can become isolated due to the fragmentation and limited mobility in cities. Besides water, tree and shrub cover have also a positive effect on the number of species, herbaceous cover has a negative effect. The number of amphibian species is also higher at older habitat patches, than in newer ones. It is important that, with the urban planning and designing, suitable aquatic habitats for the amphibians are present. Amphibians are able to maintain precarious populations in small habitat patches if the habitat requirements are met, but ideally would there suitable habitats be connected with each other for dispersal.
Future urban planning directions
In general it is important to maintain older and stable habitat patches, because they have a complex vegetation structure and create diverse habitat niches. This enhances the biodiversity, especially for specialist and dispersal-limited species. It is essential to preserve the parks, gardens and undeveloped land to maintain a higher species richness in cities. It is also important to preserve large patches of continuous vegetation, which could act as habitat and corridors for dispersion. For these functions you can also create new green spaces near older vegetation patches. With creating new green spaces and maintaining old green spaces, you should incorporate a combination of woodlands, clearings and multiple vertical layers of vegetation. Additionally, you can also incorporate plant species that are associated with fauna species.
The paper aids efforts to create more ecologically resilient and biodiverse urban environments. When people try to create more biodiversity in a city it is beneficial to know the species diversity at larger scales, the species composition of communities, and to identify priority species for conservation. The species with a restricted distribution, or with greater ecological specificities should be prioritized. The study can be used as valuable resource for decision-makers, urban planners, and conservationists. It will help with efforts to create a more ecologically resilient and biodiverse city.
Read the study
Guilherme, F., Vicente, J. R., Carretero, M. Á., & Farinha-Marques, P. (2024). Mapping multigroup responses to land cover legacy for urban biodiversity conservation. Biological Conservation, 291, 110508. https://doi.org/10.1016/j.biocon.2024.110508
Featured image: Eurasian blackbird (Turdus merula) – © Thomas Jaeger, some rights reserved (CC-BY)
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