The biodiversity value of urban areas is often overlooked; yet it is here that many humans come into closest contact with nature.

Urban biodiversity provides immediate opportunities to engage people of all ages and backgrounds with plants and animals and the issues of biodiversity loss and climate change. It is also increasingly crucial in climate adaptation, providing resilience to extreme weather including heatwaves and flooding, and improving water security.

Blue-green cities

With ongoing climate change, rainfall in Scotland is set to become more frequent and intense, particularly in winter. We are working to progress the concept of Blue-Green Infrastructure, bringing together community needs, water management and spaces for biodiversity to co-create improved quality of life in urban areas and to transform storm water from a hazard into a resource. Blue-Green Infrastructure works best when integrated with the engineered (grey) infrastructure, providing benefits including flood resilience, improved water quality, enhanced wildlife habitats, amenity value, climate regulation, and further intangible social, cultural and economic benefits.

Urban ponds, in particular, along with their surrounding greenspace, provide multiple benefits. Using our own Edinburgh Garden as a case study, and working with colleagues from Newcastle and Heriot-Watt Universities, we use ecological surveying and hydrodynamic modelling to assess the benefits of urban ponds and raingardens for biodiversity, flood resilience and other ecosystem services. During once-in-a-century-type rainfall events, the presence of the historic RBGE pond – part of a network of blue-green infrastructure in a single river catchment – reduces peak discharge by at least 27%. The pond is also a local biodiversity hotspot supporting a range of native organisms.

The study of Edinburgh's Blackford Pond and surrounding green space has also shown the importance of a wide range of ecosystem services provided by green and blue-green infrastructure. In particular, the site in Blackford has been used as a globally significant ‘Natural laboratory’ and teaching space by the University of Edinburgh and RBGE for many years.

Elsewhere in Edinburgh, our studies of much newer (10-15 year old) pond sites at Granton, Oxgangs and Juniper Green also demonstrated considerable biodiversity value and amenity function alongside alleviation of flood risk by delaying and reducing runoff in the local area. A further study of the Victorian-era Blackford Pond and adjacent green space showed that it provided high levels of biodiversity and contributed to the flood resilience of the surrounding area, despite not having been designed as a drainage feature.

Spaces for nature

Wildflower meadows and green roofs are increasingly popular ways to enhance plant biodiversity and provide habitats for animals including pollinators. We work with Edinburgh University and Edinburgh City Council to promote planting of wildflower meadows throughout the city. Preliminary results of our ongoing research at Silverknowes indicate a dramatic increase in pollinators in new wildflower meadows compared to adjacent rough grassland.

Unlike many European countries, Scotland does not currently have a mandatory policy on creating urban green roofs, and there is a distinct lack of data on Scotland’s green roofs and their benefits to biodiversity, climate change mitigation and adaptation, and human wellbeing. Our inventory revealed a total of 83 green roofs across the city – much higher than previously recorded, with a concentration on commercial properties in the city centre, indicating growing buy-in from local businesses. Our work also assesses the costs and benefits of installing green roofs - even on spaces as small as bus shelters! We are now working to measure and monitor the benefits of green roofs – including those at RBGE’s Edinburgh and Dawyck Gardens – for biodiversity and ecosystem services, and to analyse potential trade-offs between different aspects of blue-green infrastructure (such as green roofs and urban ponds). Our latest report can be read here. 

What could you do to reduce your impact on our green planet, or to make your urban patch greener?