Urban Green Network Mapping

1
Urban Green Network Mapping in Brighton and Hove
2
Policy Base

• PPS 9 paragraph 12
• Networks of natural habitats provide a
  valuable resource. They can link sites of
  biodiversity importance and provide routes or
  stepping stones for the migration, dispersal and
  genetic exchange of species in the wider
  environment. Local authorities should aim to
  maintain networks by avoiding or repairing the
  fragmentation and isolation of natural habitats
  through policies in plans. Such networks should
  be protected from development, and, where
  possible, strengthened by or integrated within
  it. This may be done as part of a wider strategy
  for the protection and extension of open space .
  . .

3
Policy Base

• PPG 17 paragraph 3
• Local authorities should also recognise that
  most areas of open space can perform multiple
  functions. . . . These include
• promoting health and well-being providing
  opportunities to people of all ages for informal
  recreation, or to walk, cycle or ride within
  parks and open spaces or along paths . . .
• iv. havens and habitats for flora and fauna
  sites may also have potential to be corridors or
  stepping stones from one habitat to another and
  may contribute towards achieving objectives set
  out in local biodiversity action plans

4
Wider context

• SE Regional Biodiversity Strategy
• Biodiversity
• Opportunity
• Areas
• - rural areas only

5

• Work on the Brighton and Hove network
• began in Spring 2007
• Partnership between
• Sussex Wildlife Trust
• Brighton Hove Council
• Geospec (GIS consultancy based
• at Brighton University)

6

• The study was divided into four tasks
• Define the functions of the network
• B) Define the existing baseline of information
  for the network
• C) Identify the additional
• areas required to
• complete the network
• D) Peer review

7

• The Functions of the Network
• People-orientated function
• - To take account of access to natural green
  space by people.
• 2. Species-orientated function
• - To improve connectivity between habitats
• 3. Ecological services function
• To promote air quality and
• ameliorate the effects of
• Climate Change (reduce
• storm water runoff, urban
• heat island effect, etc.)
• - 3. Could not be progressed

8
Existing Baseline

1. People-orientated function

NE no-one should be further than 300m (in a
straight line) from their nearest natural green
space. Natural green space should be
provided at a ratio of not less than 2 ha per
thousand people.
Ordnance Surveys Address Point dataset was used
to define population density across the city.
Projected changes in population to 2020 (LDF)
were also taken into account.
9
Existing Baseline

1. People-orientated function (cont/d)

- Brighton Hove Open Space Audit 2007
10
Existing Baseline
2. Species-orientated function
Designated Sites - Sites of Special Scientific
Interest, - Local Nature Reserves, - Sites of
Nature Conservation Importance
Brighton Hove Biodiversity Audit 2007
all areas of natural habitat in the urban area
and surrounding downland - 25m2 or greater.
11
Additional areas
1. People-orientated function Assumes land
within 300m of natural green space is the
most appropriate for connecting spaces. Did not
take account of areas of deficiency
12
Additional areas

• Projected OS address point data then used to
  calculate future population pressure.
• 300m buffer areas reduced to meet 2 ha /thousand
  people standard.

13
Additional areas
2. Species-orientated function Assumptions
Expert opinion used to define hypothetical
generic species. Generic reptile maximum
dispersal distance of 1km Generic
butterfly maximum dispersal distance of 3km.
These generic species were designed to move
progressively less easily through increasingly
urbanised habitats and features. The species
were not able to move through private gardens or
over wholly urban features (such as buildings and
roads)
14
Additional areas
Generic butterfly (used a logarithmic series
ranging from 10 to 10,000,000 to assign
permeability values to different urban features)
15

• The final potential network was defined by
  overlaying
• All areas of natural habitat identified
• by the Biodiversity Audit 2008
• (the Accessible Natural Greenspace layer)
• population pressure buffer areas
• areas where the generic species maps
  overlapped with the buffer areas

16
Overlays of NSN population pressure buffer
Generic species networks
17
Final potential network (red light green
areas from previous slide) - overlaid onto a
Brighton Hove Open Spaces base map
Some interpretation required, using aerial
photography and local knowledge, to create hard
line boundaries
18
Interpreted map draft 1 (with thanks to the
SBRC Andrew Motley)
19
Map Detail
Green protected wildlife sites existing
natural habitat (core areas) Purple
potential core areas Brown connection
zones Turquoise other open space where
biodiversity enhancement possible
20
Brown connection zones
21
Purple potential core areas

• Account for an additional 543.22 ha
• Amount of NSN required by PMP study 119 ha
• - 4.5x as much!
• BUT
• Most of the purple is beyond 15 minutes walk time
  from the urban area
• Doesnt address areas of deficiency in NSN
• Hasnt taken account of other potential land uses

22
Does address - Biosphere Reserve aspirations -
BAP habitat creation targets
23
Peer Review Ongoing

• BOA definition in Sussex
• WAG
• SEEBF Regional Biodiversity Strategy
• LDF consultation