In a densely built-up borough like Tower Hamlets, greening our built environment is an important component of biodiversity conservation. This can include green roofs and walls, providing places for nesting birds and roosting bats in or on buildings, using sustainable urban drainage systems to provide wetland habitats, and a variety of other design and landscape features. The London Biodiversity Partnership has published guidance on Design for Biodiversity.
The best landscaping for biodiversity usually involves creating natural-type habitats, such as meadows, woodlands and ponds, using locally native species. However, there are many places where this is not appropriate, and something more formal is required. Formal landscapes can still benefit wildlife if they include plants that provide nectar or fruit, or places to shelter and nest. Local bee expert Mark Patterson of Api:Cultural has produced a list of the best garden plants for bees, and a matrix showing the flowering times and colours of good plants for pollinators. Further lists of good nectar plants for pollinators are available on the Royal Horticultural Society and London Beekeepers’ Association websites. The Royal Horticultural Society also has a list of night-scented plants which will attract moths and other nocturnal insects, and hence provide food for bats. The Wild About Gardens website provides information on which plants will benefit wildlife in any situation from a meadow to a herbaceous border, and is endorsed by the Wildlife Trusts and the Royal Horticultural Society.
Invasive species in landscaping
Invasive non-native species are a significant threat to biodiversity, as well as causing economic damage and, in some cases, threatening public health. While high-profile invasive species such as Japanese Knotweed, Giant Hogweed and Himalayan Balsam are widely known to be a problem and are highly unlikely to feature in landscaping, some potentially invasive species are still widely used in horticulture. This includes several species on Schedule 9 of the Wildlife & Countryside Act 1981 (as amended). Under the Act, it is an offence to cause species on Schedule 9 to grow in the wild. These include popular landscape plants such as Virginia Creeper (Parthenocissus quinquefolia) and its close relative P. inserta, Montbretia (Crocosmia x crocosmiiflora), several species of Cotoneaster, Japanese Rose (Rosa rugosa) and False Acacia (Robinia pseudacacia). Further plant species have been identified as potential threats in London by the London Invasive Species Initiative (LISI). These include the widely-planted Cherry Laurel (Prunus laurocerasus), Tree-of-heaven (Ailanthus altissima) and Buddleia (Buddleja davidii). Policy D.ES3 of the Tower Hamlets Local Plan states that potentially invasive non-native species (those on Schedule 9 and/or identified as threats by LISI) should not be included in the landscaping of developments. The current list of species covered by this policy can be found here. This is up to date as of April 2021, but those planning developments or other landscape projects are recommended to consult the sites linked above for the latest lists.
Right Place, Right Tree
The Forestry Commission and Mayor of London have published advice on which trees to plant to provide a variety of benefits, taking account of climate change predictions. The Right Trees for a Changing Climate database is available to anyone who registers (registration is free).
Planning policies in the London Plan (policy 5.11) and Tower Hamlets Council’s Core Strategy (policy SP04) and Managing Development Document (policy DM11) promote green roofs in new developments. The Mayor of London has published a technical report on the benefits of various types of green roofs in support of the London Plan policy. This technical report can be downloaded here (PDF 2.6MB). The Green Roof Organisation, representing the green roof industry, has published a Code of Practice, the Green Roof Code, which provides a lot of useful information and best practice guidance.
Some types of green roof are better for biodiversity than others. The commonest type of green roof in new developments in Tower Hamlets is a sedum mat, like the one at Canary Wharf in the photo above. While these roofs provide some habitat for wildlife, there are far more biodiverse approaches to green roofs. Buglife has published best practice guidance on creating green roofs for invertebrates (PDF 6MB). This is widely regarded as the best current guide to creating biodiverse green roofs.
Nesting and roosting features for birds and bats
Boxes and bricks for nesting birds and roosting bats are widely available from a number of suppliers.
The London Biodiversity Partnership has published guidance on providing bat roosts and peregrine nest sites in new development. The Swift Conservation website contains a wealth of information about providing homes for swifts in new development, and contains links to suppliers of swift boxes and bricks. This leaflet provides more information on boxes and bricks for swifts, and here is a design for an easy-to-build swift box.