A new Guide to Promote Biodiversity in Developments

Ingrid Swan, Clúid’s in-house Landscape Designer, introduces the new Landscaping and Biodiversity Guide…

If you have ever walked through a new housing development, you may have noticed the total absence of bird song. The lack of nesting or foraging areas has meant that they have abandoned the area during construction. Often, they only come back as the private gardens start to offer them food and cover. The flora and fauna that access our built environments is determined not only by our behaviour, but also by the design and implementation of landscaping.

Our new Landscaping and Biodiversity Guide hopes to address this absence of flora and fauna from our developments and encourage wildlife to quickly return by providing an attractive habitat, retaining wildlife corridors and preserving soil quality.

The measures outlined in the guide are mindful of the need to have a holistic overview of the opportunities and constraints that shape our built environment. Our built environment and associated landscape are hugely constrained by concerns surrounding liability. As far as possible, risk has to be designed out of our public open spaces. This issue affects all sectors of Irish industry and life, and is unlikely to change.

We acknowledge that the Irish landscape industry cannot cater for all our recommendations contained in this guide. Therefore, some aspirational ‘Gold Standards’ have been included. We hope the industry can provide for these in the future.

The landscape industry, like many sectors, is suffering from a lack of skilled trained staff. Without skilled horticulturalists it is exasperatingly difficult to maintain a landscape without chemicals. For this reason, the guide outlines a requirement for well designed, self-sustaining planting matrices. These solution-based schemes are becoming increasingly popular in Europe and the USA. They focus on understanding how growth habits, patterns and rates can be utilised to create a scheme of minimal maintenance. These types of schemes are typically herbaceous. The herbaceous perennials can be mown down in January before the bulbs emerge to herald spring. This ensures that there is a significant overwintering habitat for invertebrates and pollinators. This is the most effective method to boost beneficial insect populations. Planting is usually 9 to 11 plants per m2. Planting this densely protects the soil from erosion, sequesters carbon and prevents nitrogen and phosphorus leaching from the soil. It also helps to retain moisture in the soil and can be utilised to filter surface water before it enters the piped drainage system. Indeed, this approach to planting is well suited to bio-swales and sustainable drainage systems (SuDS).

The plants are typically 9cm pot size. This means that they are small enough to adapt quickly to their change in environment at planting time. The 9cm pot size ensures that we are minimising the requirement for growing medium, water and fertiliser during their formative months in a nursery. The planting can be tailored to suit the soil conditions on the site. Often, perennial plants adapt more easily than shrubs to being transferred from their pampered nursery location to the harsh reality of housing developments. This ability to adapt and tailoring the plant choice to conditions minimises the need for watering and soil improvement. Indeed, watering should only ever be required during establishment.

The planting can even become a cog in the wheel of topsoil creation. The planting areas can be mulched into the soil when they are cut back in spring. In short; it is more sustainable.

It does, however, require a stale planting bed. The planting scheme does require care in its formative 2 years. Hoeing will be required, and a spring and autumn tidy will be needed to ensure that ruderols are not compromising the planting scheme balance. A skilled horticulturalist will be able to make the call on which native species can be allowed to inveigle their way into the matrix. Some of our native species may be able to exploit the climatic and soil conditions in a development. If they are not too aggressive, there should be a place for them. However, some weeding will always be required. Invasive species will require removal, and not all of our native species are desirable in every situation. For instance, gorse is not an ideal shrub to allow into a housing scheme because it is highly flammable. A roof garden or a podium deck will always need to be protected from some of our deeper rooting natives. This approach to planting relies more on highly skilled planting designers than unsustainable inputs.

The guide also addresses the difficulties in using native tree species. Climate change has resulted in the explosive spread of Phytophora fungi that have limited or removed the availability of some tree species. We must face the horrifying possibility that ignoring climate change impacts on our own native species may result in a dramatic loss of tree canopy cover across the country. This year RHS Wisley relocated valuable Rhododendron plants, approximately 200 years old, to RHS Harlow Carr. They took this risk because they have accepted that they won’t survive another ten years in the south of England. Beech will not be able to survive in the south of England in another 20 years. To continue specifying only native Irish trees is leaving us worryingly exposed to climate change. The number of trees we can specify is dramatically dwindling. Acer pseudoplatanus (Sycamore) has been declared invasive. Yet it is the only alternative to Fraxinus excelsior (Ash). While we mourn the loss of this native, as Ash Dieback spreads across the country, it is not unrealistic for other species to be dealt a similar blow from other Phytophora. If Xylella makes it to Ireland, it will wipe out our native Oak.

The guide recognises the importance of native species, but it accepts that it would be fool hardy to think that climate change can be reversed. We must adapt to ensure we have sustainable landscapes.

The guide also deals with the built elements of the landscape. It details how we want development design teams to adapt the design of public and green infrastructure to ensure that it accommodates wildlife. The wonderful biproduct of including wildlife in our schemes will be the engagement opportunities for residents. This type of considerate design can offer sensory stimulation, facilitate learning and offer opportunities for community science and activities.

Living with nature is far more rewarding than living in a housing development where bird song has fallen silent. “The Landscaping and Biodiversity Guide” will hopefully provide a set of pragmatic and realistic design measures to ensure new housing developments harmonise with the landscape. It is a document that intends to provide tangible positive change in our built environment.