Evidence type: Policy
Author(s): URBED, Oxford, M., English Nature & Green, C.
Supporting a richness of biodiversity is one route to building more sustainable neighbourhoods. The TCPA, in this the first of its 'By Design' Guides, therefore, sets out practical, design led solutions which can be implemented now. UK case studies have been paired with international examples, to provide useful lessons.
The guide takes the user through the design process, presenting a toolkit of best practice that can be tailored according to the scale of the development opportunity.
Carbon sink - Trees have a significant capacity to absorb carbon dioxide. 1 hectare of woodland can absorb emissions equivalent to 100 family cars.
Pollution control - Vegetation has a significant capacity to attenuate noise and filter air pollution from motor vehicles. Street trees can remove sulphur dioxide and reduce particulates by up to 75%. Wetland ecosystems are also effective in filtering polluted run-off and sewage.
Air conditioning - In urban areas the heat island effect can increase temperatures relative to open countryside by up to 5 degrees C. Vegetation provides natural air conditioning. A single large tree can be equivalent to five room air conditioners and will supply enough oxygen for ten people.
Microclimate control - Vegetation can improve local microclimate conditions by providing shade in summer. It can also reduce wind effects created by streets and wind loads on buildings, potentially reducing heating requirements by up to 25%.
Flood prevention - Vegetation can reduce excessive run-off and increase rainfall capture. This reduces the risk of flooding in low lying areas and can also recharge soil moisture and groundwater.
Case Study 1: Berlin's 'biotope' strategy.
The strategy has been closely related to work on urban climate zones and ecological services. Introduced in 1994, the 'Biotope Area Factor' strategy aims to retain densities whilst developing the city's green infrastructure. Plans of existing habitat networks have been prepared covering the whole city, and dividing it into character areas which include:
Central city (intense use and densely populated) - maintain densities whilst retaining or increasing areas available to nature.
Transition areas (mixed uses including residential, industry and infrastructure) - provide habitats that can serve a wider area. Linkages are prioritised.
Landscape elements (periphery of the urban area) - ensure larger habitats with 'fingers' penetrate into the urban area. These are valuable species reservoirs.
Case Study 2: Eastern Quarry, Kent.
The structure and extent of vegetation in urban areas can have a major impact on temperature, humidity and run-off. The 'biotope' strategy therefore seeks to develop a green infrastructure that delivers air conditioning, microclimate control and flood attenuation. The different climate zones within the city have been mapped, illustrating variations in air temperature, humidity and soil moisture. The city has been colour coded into five broad zones, clearly identifies the moderating effects of greenspaces.
A good example can be found at Kirchsteigfeld in Berlin. SUDS are common in new German housing schemes for flood alleviation, but they also create buffer strips for habitat creation. Tree planting may be required for bank protection and sediment may require periodic removal.
English Nature, The Hyde Group & The RSPB