The City of Cape Town’s biodiversity is globally unique and its conservation is of international importance. The local variability and uniqueness of vegetation types and species diversity together with processes of urbanisation have resulted in 65% of the remaining natural vegetation in the City being classified as critically endangered or endangered. No other City in the world harbours as many threatened plant species per unit area.

In 2003, the City of Cape Town committed to implementing a Biodiversity Strategy. This Strategy requires, amongst others, that a Biodiversity Network be established to enable the conservation of Critical Biodiversity Areas. These areas represent the minimum amount of terrestrial and freshwater habitat that is required to meet the City’s biodiversity conservation targets. An iterative systematic conservation planning process, which started in 2001, has established biodiversity conservation targets and the identification and prioritisation of the Biodiversity Network.

In summary, area-based targets, for representation of vegetation type and species, were set based on the revised City Vegetation Map (habitat type and distribution) and species database (Protea Atlas, CREW and SaS species locality data), the revised remnant layer (remaining natural habitat areas or Natural Habitat Remnants (NHRs)) and an analysis of areas considered to be conserved within the City (existing Protected Areas). A GIS-based analysis was undertaken (using agreed key criteria of Irreplaceability, habitat condition, size of NHR, percentage contribution to meeting target and vegetation type diversity) to select remnants that would best meet conservation targets for each vegetation type. The extent to which this coarse filter selection, based on vegetation targets, catered for the conservation of the species targets, was then assessed. Additional NHRs were then selected in order to ensure that species targets also were met.

The methodology applied in the identification of the City’s Biodiversity Network conforms to accepted systematic conservation planning methodology and used C-Plan as well as other GIS software packages such as Marxan, designed and adapted for conservation planning.

Description of Critical Biodiversity Areas (CBAs)

CBAs (as defined by SANBI in the document “SANBI Guideline for Publishing Bioregional Plans”) are features critical for the conservation of biodiversity and maintenance of ecosystem functioning and should remain in a natural state as far as possible.  CBAs must also include aquatic components, so it is imperative that results from an aquatic Species Conservation Assessment be integrated into the results of this terrestrial analysis.  In the meantime, all natural wetlands are considered part of the Biodiversity Network.  To assist in the development of these CBAs, each planning unit was characterized on the basis of:

1. Reason for or stage of planning unit inclusion during the selection process
2. Location in expert defined corridors
3. Ecosystem status
4. Planning unit condition (high, medium or restorable)

We combined the various groupings from the analysis into the following CBA categories:

CBA Category	CBA name
Protected	Conservation Areas
CBA 1a	Irreplaceable Core Flora sites
CBA 1b	Irreplaceable High & Medium Condition sites
CBA 1c	Minset High & Medium Condition sites
CBA 1d	Irreplaceable Consolidation sites
CBA1e	Connectivity sites
CBA 2	Restorable Irreplaceable sites
CESA 1a *	Transformed sites of Conservation Significance
CESA 1b *	Additional Wetlands, Rivers & Groundwater Recharge areas
Other Natural vegetation	Unselected natural vegetation in high, medium or restorable condition
No Natural Habitat	Unselected Transformed Sites

* Indigenous vegetation remnants in the CESA 1a and CESA 1b categories are in the process of being identified and this information is not yet available.

Excerpts from a report done in February 2007 by Marlene Laros & Associates – Sustainability Matters, working in association with GISCOE (Pty) Ltd, entitled “City of Cape Town: The Identification & Prioritisation of a Biodiversity Network for the City of Cape Town”.