Microclimate regulation

For urban areas to be liveable residential zones the adequate provision of vital ecosystem services which contribute to the regulation of microclimate conditions and water

attenuation is of great importance. Few considered attempts have been made to put together a tool kit to provide accurate accounting of the effects of differing vegetation structures and mosaics on issues such as cooling and heating of the urban microclimate. Similarly studies into reduction in wastewater treatment, through run-off intercepted by green elements in urban micro-scapes, are hitherto underdeveloped.

One such attempt has been the Green Infrastructure Valuation Toolkit created by Green Infrastructure North West (2010) which echoes the ecosystem services framework but which re-categorises such services as an inventory of 11 environmental benefits. Being a valuation toolkit, it is largely based on a monetary assessment of green space developments. Given

145 that OSEI consisted chiefly of small-scale community-managed spaces such an approach did not address the site specific concerns and values which a given community attached to their local spaces. That is to say that OSEI exhibited a variety of management approaches based on local preferences. An appreciation of the dynamics of ecosystem benefit production and subsequent trade-offs, would be better achieved through alternative non-monetary

evaluation methods which did not prize certain goods and services over others. A calculation of the projected value of OSEI for the study area as a whole is dealt with separately in

Chapter 6. Other similar tools have emerged to monitor and place value on natural capital but of those researched most were found to be incomplete, lacking in terms of evidence base, or aimed primarily at landscape-scale ecological processes. As such, most were not adaptable to the scale and detail required for a realistic evaluation of the chosen sites in this case-study.

One tool found to be readily applicable to various scales without reducing the accuracy of the result was a management tool based on the concept of “ecologically effective area”. It has appeared in several versions and is known by various names, depending on the country in which it has been applied and used, but principally the Biotope Area Factor Tool or the

Green Space Factor Tool. This tool has been primarily applied as a rapid assessment urban planning tool with the aim of predicting the overall ecological impact of a given development proposal. The tool was first designed for use in the Berlin and Hamburg metropolitan areas by the German Senate Department for Urban Development and the Environment in the 1990s under the terminology Biotope Area Factor. The authors of the tool described its rationale as follows: “The biotope area factor (BAF) designates the ratio of areas of a site that have a positive effect on the ecosystem or an effect on the development of the biotope of a site in relation to the entire area of the site.” (Becker and Mohren, 1990, p.2). The basic premise of the tool is to create a score ranging from zero to one based on the surface area cover types as well as secondary and (in later versions) tertiary layers (made up of structural elements such as shrubs, trees, green roofs/walls and water harvesting

systems). In this way it gives a three dimensional appraisal of the site in question, taking into account area cover types as well as vertical elements. In essence, the score resulting from the tool, ranging from 0 to 1, represents the proportion of a site which can be considered ecologically effective. However, with the consideration of secondary and tertiary “layers” it is in fact possible to achieve a score higher than 1, though this is unusual in urban areas.

146 Weightings are assigned to each category of surface cover as a reflection of their ecological integrity and this value is multiplied by the total area in square metres of each present at the target site. The overall site score is then calculated as the ratio of the combined total value of all surface types to the total area of the site in question. The weightings of the BAF have been adapted to varying degrees by later version of the tool but those of the original tool were as follows (Table 5.1):

147 Table 5.1 Biotope Area Factor weightings/descriptions.

Surface Type Weighting

Factor Surface Description Examples

Sealed surfaces 0.0 Surface is impermeable to air and water and has no plant growth. No infiltration. No soil function.

Concrete paving, asphalt, slabs with a solid sub-base.

Partially sealed surfaces

0.3 Surface is permeable to water and air; some infiltration; as a rule, no plant growth.

Stone/mosaic paving, slabs with a sand or gravel sub- base.

Semi-open surfaces

0.5 Surface is permeable to water and air; some

infiltration; some plant growth.

Gravel with grass coverage, wood- block paving; honeycomb brick with grass. Vegetation not connected to soil below (<80cm)

0.5 Vegetation with less than 80 cm of soil depth.

Raised beds, roof of underground parking. Vegetation not

connected to soil below (≥80)

0.7 Vegetation with 80cm soil depth or greater.

As above.

Vegetation connected to soil below

1.0 Vegetation connected to soil below, available for

development of flora and fauna. N/A

Rainwater infiltration (per m² of roof area).

0.2 Rainwater infiltration over surfaces with existing vegetation.

Any built structures with roofs draining onto vegetation. Vertical greenery

up to max. 10m height

0.5 Greenery covering walls and outer walls with no windows.

Green facades.

Green roofs 0.7 Extensive and intensive coverage of rooftop with greenery.

N/A

(Adapted from Senate Department for Urban Development and the Environment – Berlin (2013)).

148 Once a survey of a given site has been carried out, a simple calculation is then required to obtain the BAF:

BAF = Ecologically Effective Surface Areas/total courtyard area i.e. (area A x factor A) + (area B x factor B) + (area C x factor C) + (area n x factor n)/total courtyard area

A worked example is presented in Table 5.2: Table 5.2 Worked example of BAF tool.

Total site area (m²) = 500

Surface type GI factor Area (m²)

Ecologically effective area (m²)

Concrete paving 0 300 0 x 300 = 0

Gravel coverage 0.5 175 0.5 x 175 = 30

Raised beds (90cm soil depth) 0.7 15 0.7 x 15 = 10.5

Open soil 1 10 1.0 x 10 = 10

Total ecologically effective area (m²) = 50.5 BAF = ecologically effective area/ total site area = 50.5/500 = 0.1

As can be seen in the above example the tool was well adapted to the urban environment and designed to be applied on small-scale “courtyards” – where built and natural elements intersect and overlap. As such the method had to acknowledge the varied surface types as well as the often complex vertical elements which are to be found in the urban environment. As such it avoids an over-simplified appraisal of land cover as either “built” or “green” in order to capture the ecological characteristics of our city spaces, as specified in the original expert paper on the objectives for development of the tool (Becker and Mohren, 1990). The tool was designed in conjunction with environmental policies with the aim of achieving a minimum requirement of ecologically effective green space and as such target BAF scores were designated for various types of development. The plans of any given development had to demonstrate that any proposed changes would meet the minimum required BAF factor for that type of development. Although initial examples of usage focussed on relatively small urban “courtyards”, the straight-forward scoring method of the tool has allowed it to be adapted to much larger sites and even used to achieve an overall score for whole cities as in the case of Southampton in the UK in 2012 (Phillips and Moore, 2012).

The BAF was developed further by planning authorities in Sweden where it was adapted in 2001 for the Malmö Green Space Factor (GSF). The tool was used following the same principles as in Berlin and Hamburg though weightings were customised and different

149 requirements for sites were applied appropriate to the local environment and planning policies. As well using the GSF score, a checklist of points known as the Green Points System

was created to allow for more robust planning constraints. Developers were given a list of 35 Green Points and were required to choose 10 of them to meet the environmental

requirements. Several versions of the GSF have been created in Malmö since as planning considerations have been updated (Krause, 2011).

More recently (2006), a version of the tool appeared as the Green Factor tool for the first time in the United States in Seattle. Again building on previous versions of the tool, the Seattle Green Factor has been modified only to a minimal degree to fit with the planning priorities and climate of the area; the principle concept of the biotope/area ratio is intact. The Malmö green points systems has been included and further guidelines for developers were added including recommended and prohibited tree and plant listings.

In the UK, the Malmö GSF had been adopted by several partner agencies in the Pan-

European Green and Blue Space Adaptation for Urban Areas and Eco Towns (GRaBS) project, including the London Borough of Sutton, the (now defunct) Northwest Regional

Development Agency (NWDA), Southampton City Council and the Town and Country Planning Association. The Malmö GSF was adopted almost seamlessly in the UK by Sutton and Southampton councils but was modified to some degree by the Northwest Development Agency to support the existing green infrastructure objective which had already been put in place as part of a policy to support a natural economy approach to environmental

management in North West England (Krause, 2011). To this end the NWDA developed the Green Infrastructure Toolkit (Green Infrastructure North West, 2010) which was still aimed at informing and constraining land developments but which took a GI-centric approach and incorporated elements of the BREEAM sustainable development framework. The tool adopted the “very good” score of the latter as its standard for land cover configurations, to be used and understood by developers. The Green Points System was adapted to provide a list of GI Interventions with the aim of fulfilling one or more of the 11 economic benefits of green infrastructure as outlined in the NWDA‘s Sustainability Policy for the Built

Environment (Gill, 2010). The method is again in keeping with the original concept of the BAF with only slight modifications to the weighting of certain surface types.

It is this latter version of this tool that was adopted in the methods of this thesis as it

150 of England, fits in with the context of the study area and will therefore also be comparable with other reports from the North West. One important change was made to the GI toolkit for use with the case-study sites of this thesis – the addition of the “rainwater infiltration per roof area” factor of the original BAF tool. This factor had been removed from later versions of the tool and is absent from the GI Toolkit to no advantage as far as the author of this thesis is concerned. The inclusion of this factor, however, adds an added level of detail to site evaluations, especially given that this element featured significantly in most of the case- studies surveyed.

For the purposes of this research the tool has been applied to give a score for the current status of the ecological character of a site without the need for a “before and after” scenario type of comparison for which it was originally designed. The relatively simple, modular nature of the tool allowed for this modification to be applied without any significant changes necessary to the method.

The GI toolkit has been chosen as one which can provide an indicator of the quality of and/or potential for microclimate regulation services given that the original premise of the tool is to quantify the ecological effectiveness (or, the quality of ecological functions) inherent in the physical characteristics of a given site. The concept of ecological effectiveness as put forward by the authors of the original Biotope Area Factor framework is directly related to the

provision of ecosystem services (Phillips and Moore, 2012). This is reflected in the ecological goals targeted by the original BAF concept, namely: improvement of the microclimate and air hygiene quality, safeguarding soil function and the efficiency of water management, and increased provision of habitat for plants and animals. These goals are achieved by the BAF through protection of ecological functions which underpin those services of greatest salience in the context of the urban environment, namely:

1. high evapotranspiration efficiency, 2. high capacity for binding dust,

3. infiltration ability and storage of rainwater,

4. long term guarantee of the conservation of soil function,

5. availability of habitat for plants and animals. (Becker et al., 1990).

It could, therefore, be said that the promotion of ecologically effective areas as outlined in the original BAF and subsequent versions support the conservation and creation of a range of ecosystem services across regulating, provisioning, supporting and cultural categories. It

151 shall be used in this thesis however, primarily as an indicator of the quality of microclimate regulation (including water attenuation and air temperature regulation) provided by the case-study sites. The reason for this is that the majority of the criteria which achieve the targets of the original BAF tool (stated above) are those ecological functions underpinning such regulating services. That is to say that these services depend directly on the presence, quality and structure of vegetative elements in the landscape and it is similarly these elements upon which the original BAF scoring is based. As such this premise has been adopted in the methods of this research through the application of the GI toolkit as a modified version of the BAF in the context of the policy and urban character of England’s North West. The assessment of effectiveness is derived, generally speaking, from the presence of vegetative structures and further informed by the level of succession involved in such structures and finally, the additional “artificial” functions from man-made elements such as swales or other water-harvesting features.

Data were collected from each site through field measurements during detailed site surveys and attributing the relevant surface type designated within the GI toolkit to that observed on-site. The data were then entered directly into the GI toolkit sheet (see Appendix 2 for details), the results of which are presented in Section 5.3.2. The toolkit is available for download from the GI North West website at: http://www.ginw.co.uk/climatechange Data were collected during site surveys which were carried out between April to September 2013. On each occasion, a single site visit was sufficient to complete the assessment.