CITY OF CAPE TOWN BIODIVERSITY NETWORK PRIORITISATION PROJECT

Concept Document: Nodes, corridors and criteria for categorisation and prioritisation of the Biodiversity Network

presented by

Marlene Laros & Associates – Sustainability Matters

in association with

Biodiversity & Conservation Biology Department University of the Western Cape

Settlement Planning Services

GISCOE

and

The Freshwater Consulting Group

June 2004 CCT Biodiversity Network Prioritisation Project – Draft Concept Document: Nodes, Corridor & Criteria

CONTENTS

1. Introduction...... 2 1.1. Purpose of the Discussion Document...... 2 1.2 An overview of the document...... Error! Bookmark not defined. 2. Building on city-wide biodiversity conservation and metropolitan open space initiatives...... 2 2.1 The City of Cape Town’s Biodiversity Strategy...... 2 2.2 The identification of the Biodiversity Network...... 4 2.3 Conservation Management Models for the City of Cape Town...... 5 2.4 Cape Metropolitan Open Space System Synthesis Project...... 6 2.5 Assessment of Rivers and Vleis in the City of Cape Town...... 6 2.6 Catchment, Stormwater and River Management Strategy...... 6 2.7 Coastal Zone Management Strategy and proposed Marine Protected Area...... 6 2.8 Other related initiatives of the City of Cape Town...... 7 3. Nodes and corridors: key concepts for the biodiversity network...... 7 3.1 Introduction...... 7 3.2 Nodes - definition and function within the CCT’s Biodiversity Network...... 8 3.3 Corridors – definition and function within the CCT’s Biodiversity Network...... 9 3.4 Freshwater systems and nodes and corridors...... 11 4. Prioritisation and categorisation of the Biodiversity Network...... 12 References and sources...... 17 Appendix One: Background research on best practice: Nodes, corridors and prioritisation...... 17 Appendix Two: City of Cape Town Biodiversity Network Prioritisation Project: Report on Stakeholder Workshop One. 17

General comment: the grammar and sentence construction in parts of this report are not great. I have made some changes where the errors were obvious, but there were many others. Generally, I foresee no major problems from the GIS analytical perspective, however some of the criteria/decision rules will need to be expanded upon and fleshed out with more specific values (e.g. with what inter-patch distance would we consider patches to be in close proximity – a distance of 2km is mentioned, but the reason for it being chosen is not clear).

MLA – Sustainability Matters, BCBD UWC, Setplan, GISCOE and FWCG, June 2004 1 CCT Biodiversity Network Prioritisation Project – Draft Concept Document: Nodes, Corridor & Criteria

1. Introduction

1.1. The City of Cape Town Biodiversity Prioritisation Project

The Biodiversity Prioritisation Project ….include ToR and products, the team etc…

1.2 Purpose of the Concept Document

The purpose of this document is to present draft concepts and prioritisation criteria to be used in the prioritisation and categorisation of the City of Cape Town Biodiversity Network. The concepts and criteria have built on the best practice research and background information presented in a discussion document (see Appendix 1) that informed Workshop One within the project process. Inputs received during and after this workshop (Appendices 2 and 3) have informed the further development of the concepts and criteria.

The key purpose of this document is to present the concepts and criteria for peer review prior to the implementation of a GIS prioritisation analysis. This analysis will assist in the prioritisation of the Network into three categories for which management land use management guidelines will be developed

Key aspects of current open space and biodiversity initiatives within the City are Cape Town are presented as the local context, most importantly, the previous steps undertaken in establishing the Biodiversity Network. Thereafter the concepts of Biodiversity Nodes and Biodiversity Corridors are presented as two key conceptual elements defining the Biodiversity Network and its functions.

2. Building on city-wide biodiversity conservation and metropolitan open space initiatives 2.1 The City of Cape Town’s Biodiversity Strategy

The City of Cape Town Integrated Metropolitan Environmental Policy (IMEP) and implementation strategy, the Integrated Metropolitan Environmental Management Strategy (IMEMS) provide the super-ordinate framework for the sectoral strategies approved by Council to date: Biodiversity Strategy; the Coastal Zone Strategy; and the Environmental Education and Training Strategy. The City of Cape Town formally adopted the Biodiversity Strategy in on the 29th October 2003. The Biodiversity Strategy provides some specific guidance on the proposed definitions and functions and prioritisation of the components of the Biodiversity Network. Furthermore the Biodiversity Strategy acknowledges the need to

The Strategic Objectives of the Biodiversity Strategy are:  Primary Biodiversity (conservation and biodiversity nodes)  Secondary Biodiversity (conservation through corridors, links and mixed use areas)  Conservation of biodiversity in freshwater aquatic systems  Invasive alien species management  Biodiversity legislation and enforcement  Biodiversity information and monitoring system, and  Biodiversity education and awareness

The first three of these strategic objectives provide the strategic spatial concepts that must inform the Biodiversity Network Prioritisation Project. The following are summarised extracts from the Biodiversity Strategy, providing a description of the strategy and the goal and principles for these first three objectives:

Primary Biodiversity Conservation (Conservation Areas and Biodiversity Nodes) This Strategic Objective (Primary Biodiversity Conservation) refers to the establishment and effective management of a network of biodiversity areas and biodiversity nodes that are actively managed with the primary function of conserving Cape Town ’s biodiversity. These areas include all local government nature reserves, possible public-

MLA – Sustainability Matters, BCBD UWC, Setplan, GISCOE and FWCG, June 2004 2 CCT Biodiversity Network Prioritisation Project – Draft Concept Document: Nodes, Corridor & Criteria private partnerships and any other area that is managed for the specific purpose of conserving and protecting biodiversity. This Biodiversity Network must align itself within a regional context and integration with the WCNCB and CPNP is therefore essential. Further, this Strategic Objective refers to the effective and efficient management of the indigenous fauna and flora of Cape Town.

Goal The goal of the Primary Biodiversity Strategic Objective is to, using existing protected areas and initiatives, and by identifying appropriate new areas, establish and secure the key biodiversity areas and biodiversity nodes component of the Biodiversity Network. This Biodiversity Network must effectively conserve and protect an adequately representative sample of all the unique biodiversity in Cape Town for the benefit of current and future generations. This Biodiversity Network must conserve at a minimum, sufficient area and habitat to ensure the long-term sustainability of all of Cape Town ’s biodiversity. Further, the goal of this strategic objective is to ensure, that appropriate, effective and efficient management plans and policies are developed and implemented at each of the Primary Biodiversity Conservation Areas.

Principles Use the biological principles within the theory of:  Island Biogeography  Biodiversity pattern (representation)  Ecological process (persistence)  Complementarity and efficiency  Conservation of habitat diversity  Recognise the importance of all freshwater aquatic systems in biodiversity conservation  Maximise the habitat diversity conserved  Optimise the social and economic potential of each of the areas under conservation, and  Open, transparent, effective, accountable, measurable, reportable management of the conserved areas.

Secondary Biodiversity Conservation (Corridors, links and mixed areas) The CCT recognises the urban context within which the conservation of biodiversity will take place. As such the importance and role of open space, that although serving other primary functions, may play in the conservation of biodiversity is recognised. This type of open space includes amongst others rivers, ecological buffer zones along rivers, areas forming part of the Stormwater Management System, linear parkways, parks, scenic drives, road verges, servitudes and transport routes. These areas can facilitate the movement of species from one area to the next by acting as corridors and links. The Secondary Biodiversity Strategic Objective refers to all areas that are not actively and specifically managed with a primary function as biodiversity conservation areas but which connect the Primary Biodiversity Areas and Biodiversity Nodes into a complete and functional Biodiversity Network. Secondary Biodiversity includes all areas that act as mixed-use areas, corridors, links and stepping-stones.

Goal The goal of the Secondary Biodiversity Strategic Objective is to promote, establish and manage open space as a critical component in the success and functioning of the Biodiversity Network. This includes the role of mixed-use areas, corridors and links, which complete and connect the Biodiversity Network. In addition the goal is to initiate a process whereby appropriate local indigenous vegetation is used for horticultural purposes thereby creating biological opportunity within an urban context.

Principles  Biological opportunity and biological corridors  Promotion of indigenous fauna, flora, habitats and landscapes  Pride in the unique flora of the CCT, and  A green urban environment.

Conservation of Biodiversity in Freshwater Aquatic Systems

MLA – Sustainability Matters, BCBD UWC, Setplan, GISCOE and FWCG, June 2004 3 CCT Biodiversity Network Prioritisation Project – Draft Concept Document: Nodes, Corridor & Criteria

Cape Town ’s unique rivers, wetlands, vleis, dams and estuaries, form important ‘green corridors ’between the mountains and the coastline as well as providing habitats for a rich diversity of terrestrial and aquatic life. These freshwater systems are essential components of the Biodiversity Network. Further, they moderate floods, purify water and generate and renew soil fertility. In addition to these natural ecosystem services, they form a vital component of the city ’s stormwater management system, are key recreational nodes and are also utilised for the conveyance and disposal of wastewater effluents. Over the past few decades, many rivers were canalised and wetlands in-filled and drained to allow for urban development, dramatically altering runoff patterns. In retrospect, this approach has inadvertently also precipitated a decline in water quality with concomitant adverse effects for human health and welfare as well as the ecological integrity of the city ’s rivers and vleis. In addition, potential community interaction and enjoyment thereof has been seriously compromised. This strategic objective refers to effective management of these freshwater aquatic systems in a manner that maintains or enhances biodiversity whilst ensuring effective functioning for stormwater management and other purposes.

Goal To ensure the conservation and protection of freshwater aquatic systems, and their associated biodiversity as well as to optimise the role that rivers and wetlands play as effective ecosystem corridors.

Principles  Acknowledge the vital role played by rivers and wetlands in the provision of stormwater management services as well as the conveyance and disposal of effluents.  Recognise rivers, freshwater aquatic systems as highly significant biodiversity refuges and corridors.  Protect and enhance the social, ecological and amenity value of freshwater aquatic systems.  Where at all possible avoid any further canalising or hard engineering solutions.

2.2 The identification of the Biodiversity Network

During 2001/2002 a project aimed at identifying a representative conservation network was initiated by the Environmental Management Department of the City Cape Town. The project used the Systematic Conservation Planning approach to identify remnants of land within the City of Cape Town that would need to be conserved to ensure the protection of a representative sample of the areas biodiversity. This same approach was also used during the C.A.P.E. project, and has also subsequently been applied in the Succulent Karoo (SKEP) and Subtropical Thicket (STEP).

The identification of these areas was based on a set of conservation targets aimed at setting benchmarks for the conservation of vegetation types, floral species and a selected set of ecological processes. The setting of the conservation targets was done through a consultative process, which engaged key stakeholders involved in conservation within the City of Cape Town. The vegetation map developed by Barrie Low (Low, 2000) was used as the primary biodiversity layer (surrogate for habitat) for this study, with floral species distributional data from the Protea Atlas and the Species and Sites database used to supplement this.

This study identified a set of 261 remnants (32 262ha) from an initial set of 886. These selected remnants are in addition to the existing protected areas representing about 54 293ha. A set of corridors were then identified, which linked the following significant areas; Zandvlei, Macassar, Gordons Bay, Cape Point, Noordhoek Wetlands, West Coast, Mamre and Paardeberg. These corridors were identified to ensure that ecological gradients are conserved, and to account for the predicted impacts of global climate change. Effectively, these corridors optimise routes containing natural vegetation. Nineteen corridors were identified, along with 18 nodes. The nodes are originally seen as areas where the corridors intersect, and potentially represent critical “biodiversity intersections”. However, the nodes were not necessarily represented by large contiguous remnant areas. Stakeholders have subsequently understood the concept of nodes to be a term that best describes large remnants or groups of remnants (“biodiversity hubs”) meeting a significant proportion of conservation targets and providing a range of conservation-related uses. It is this concept that the CCT wishes to explore further with stakeholders.

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An initial prioritisation of the selected remnants was based on remnant size and the conservation of three critical vegetation types, and secondarily on whether the remnants were located in nodes or corridors. These three types (sand plain fynbos on inland older non-marine derived acid sands, west coast renosterveld on shale and west coast renosterveld on granite) were listed as critical because the extant area was smaller than the area required for representative protection as described by the conservation targets.  Level 1 sites (71 sites identified) were those larger than 10ha area conserving any of the three critical vegetation types (plus the existing protected areas, Core Botanical Sites, wetlands and estuaries).  Level 2 sites (97 sites identified) were those conserving at least one of the three critical vegetation types, but irrespective of size.  Level 3 sites (69 sites identified) were those remaining remnants greater than 10ha.  Level 4 sites (25 sites identified) were the remaining remnants from the selected set of 261 not falling into the previous three levels. The remaining unselected remnants (474) were grouped into level 5.

Levels 1 to 4 should be considered the minimum viable network needed to adequately conserve the biodiversity of the City of Cape Town and should be protected from incompatible land uses. Levels 1 and 3 focus on relatively large units of habitat for species and processes and levels 2 and 4 concentrate on conserving the rare and threatened habitats of species with restricted distributions. The most important levels are 1 and 2, as these represent the areas on which any of the three vegetation types for which there does not currently exist sufficient land to meet their targets are found. These should thus assume the highest priority.

The document that described in detail the methodologies used and the results obtained, “Identification of a biodiversity network for the City of Cape Town”, is available from the City of Cape Town’s Environmental Management Department. 2.3 to 2.7 into appendix?? Seem more relevant than the others – tell me what you think? I think that this section can be left as is, it provides a nice synthesis of the conservation initiatives and projects which have set the scene for the current project. It would be difficult to read this as a complete set if some sub-sections were moved to an Appendix.

2.3 Conservation Management Models for the City of Cape Town

During 2002, the CCT commissioned Envirocentric and Common Ground Consulting to undertake research on the legislative status, management implications and resource requirements for an identified set of conservation models. This work was focused on learning from a range of international, national and international case studies. The final report recommended four complementary strategies to guide biodiversity conservation strategies together with a set of tools described within a ”toolkit”: i) Designation of private and public key conservation areas with formal protected area status together with detailed assessment of the management planning considerations and funding arrangements. ii) Establishment of a suite of complementary “off-reserve” mechanisms for private and public land zoned agricultural or rural in the zoning scheme. These include formal and informal land management agreements, statutory land covenants, financial or technical assistance, advice and financial incentives. iii) Negotiated planning solutions for private and public land zoned other than agricultural or rural or land earmarked for development through approved planning processes. This proposes the use of structure plans, guided development schemes, subdivision and development controls and density trade-offs. iv) Negotiated management solutions for public land including designated for public infrastructure (e.g. road reserves), service requirements (e.g. water catchments) or other broader community needs (e.g. Parks) and/or under different public agency management (e.g. public works).

Even though this report was finalised prior to the final publication of the Protected Areas Act, the research, recommendations and associated toolkits will be helpful in the implementation of the Biodiversity Network.

MLA – Sustainability Matters, BCBD UWC, Setplan, GISCOE and FWCG, June 2004 5 CCT Biodiversity Network Prioritisation Project – Draft Concept Document: Nodes, Corridor & Criteria

2.4 Cape Metropolitan Open Space System Synthesis Project

The Cape Town Metropolitan Open Space System (CMOSS) Synthesis Project has developed a vision and criteria for the identification of open space in the City of Cape Town. A pilot study was undertaken in the Metro South East to test the identification and mapping methodology. After the successful conclusion of the pilot project the remainder of the metropolitan area was mapped. As part of this study a Framework for Management Guidelines for CMOSS was developed. The CMOSS Mapping Project has used an open space typologies or categories that were originally developed for the CMOSS Value Study, a further initiative of the CCT that undertook research based on resource economics methodologies to establish the value of open space in two pilot areas. These definition and typologies of CMOSS are presented in section 4. The full report is available from the City of Cape Town’s Spatial Planning Department.

2.5 Assessment of Rivers and Vleis in the City of Cape Town

In 2001 the Catchment, Stormwater and River Management Branch (the then Catchment Management Department) commissioned a study that assessed all rivers in the CCT. (River & Vlei Assessment and Monitoring in the CMA: assessment of rivers and wetlands). This study has provided a firm basis for the further strategic prioritisation of rivers with specific reference to criteria of habitat integrity, rehabilitation potential and ecological importance and sensitivity.

2.6 Catchment, Stormwater and River Management Strategy

Developed in 2002 and effective until review in 2007, the proposed outcomes of this strategy that are directly relevant to guiding role and function and prioritisation of rivers and wetlands as part of the Biodiversity Network and include:  Effective stormwater drainage  Improved water quality of surface, ground and coastal waters  Ecologically healthy rivers, vleis, dams and wetlands  Multi-functional, sustainable use of river corridors, and  Active support of the CCT Indigenous Fauna and Flora Policy.

2.7 Coastal Zone Management Strategy and proposed Marine Protected Area

One of the three approved IMEMS Strategies, the Coastal Zone Management Strategy, identifies the following strategic objectives:  Development and implementation of Sustainable Coastal Management Plans for each area of the coast  The establishment of Blue Flag Beaches  The implementation of a Coastal Recreation Plan  Effective estuary management  Monitoring of coastal water quality  Coastal legislation  Coastal education and awareness  The conservation of natural coastal areas  The management of developments within the coastal zone, and  Coastal engineering. Many of these objectives are linked to the Biodiversity Strategy implementation, specifically “effective estuary management” and “the conservation of natural coastal areas”. A critical challenge in the future will be the integration of natural coastal areas, including estuaries, into the Biodiversity Network.

The Table Mountain National Park (TMNP) is planning to establish a Marine Protected Area along its coastline. The zoning definitions of this MPA will assist in the conservation of natural coastal areas and estuaries contiguous with

MLA – Sustainability Matters, BCBD UWC, Setplan, GISCOE and FWCG, June 2004 6 CCT Biodiversity Network Prioritisation Project – Draft Concept Document: Nodes, Corridor & Criteria the TMNP. The CCT’s attention will therefore need to be focused on the areas along the False Bay Coast and coastal areas on the west coast to the north of the currently proposed MPA.

2.8 Other related initiatives of the City of Cape Town

Related initiatives of the City of Cape Town

Title Description Shortened Title Identification of Key The selection of a minimum set of nature areas within Cape Town that, together Key Nature Conservation Nature Conservation Areas with existing protected areas, if managed and protected, would ensure the long Areas in the City of Cape Town term protection and enhancement of Cape Town’s biodiversity

Cape Flats Flora Core 38 sites, which, if managed and protected will together, conserve 97 % of the Core Flora Sites Conservation Sites flora species on the Cape Flats.

Mainstreaming To design and implement sustainable management and funding systems for Mainstreaming Biodiversity on the Cape conservation management in important biodiversity areas on the Cape Flats with Biodiversity on the Cape Flats emphasis on community involvement. Flats

Environmental Mapping of environmentally significant sites (according to certain criteria) in ESM Significance Mapping terms of aquatic, marine, terrestrial, social, geophysical, heritage, social and visual information.

Towards a Conservation Initial stage of a project aimed at establishing a conservation and development Towards a False Bay CDF and Development framework along the north-eastern portion of False Bay from Strandfontein to Framework for the False Kooelbaai. Bay Coast Status Quo Assessment of A study to assess and gather all relevant information on each of the Core Flora Status Quo Assessment of the Core Flora Sites Sites the Core Flora Sites Natural Interface Study The development of guidelines for more effective management of the interface Natural Interface Study between urban and natural areas, with specific reference to fire and stormwater management. Urban Edge for the City of The definition of the urban edge demarcating the outer limits of urban expansion Urban Edge Study Cape Town and the development of management guidelines associated with management zones on either side of the demarcated line.

3. Nodes and corridors: key concepts for the biodiversity network

3.1 Introduction

Landscape level necessitates the concept of a network.

Urban landscapes as transformed as they are need to focus on maintaining processes and what levels of transformation will still enable such patterns and processes to exist. Perhaps the question is what type of urban development will allow Capetonians and Biodiversity to co-exist. How much is needed, where (accommodating climate change, and providing enough space, levels of connectivity and naturalness (ecosystem function) to pervade or be sustained over the long term). Ultimately, the need is to create value in the open space system, the backbone of which must be the biodiversity network. The greatest value areas are areas that are seen as having a use. Values of functioning ecosystems….Bill Harding. There are no exact answers but what we do know is that the areas – use best or state of the art planning principles and science and apply this to the best set of information, involve the right people.

Special ecosystem status in terms of the legislation.

Some initial considerations and definitions

Biodiversity: this reflects the diversity of genetic composition of organisms, diversity of species including maintenance of subpopulations, maintenance of species assemblages including the diversity of co-existing communities and the maintenance of ecosystem services at the landscape level.

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From the review of urban conservation at global and national levels it is evident that the City of Cape Town is unique with respect to the amount of biodiversity and the high turnover of biodiversity within short geographical distances. A secondary process that effectively renders the City as being unique is that Cape Town has a long history of human impact (colonization) but within a developing country's economic circumstances (very rapid urban growth especially in the informal housing sectors). An off-the-shelf solution for conserving biodiversity in any urban context does not exist in this regard the city of Cape Town is no different to any other city. However, clear trends in the approach to urban biodiversity planning are evident, with Northern European cities having a focus on maintaining environmental services (since their biodiversity has largely been irreversibly altered through centuries of urbanisation), whereas the North American cities have a focus on planning and maintenance of biodiversity by using the Greenways planning framework.

Since no other major city has a combination of high biodiversity levels and high turnover species over such short distances (called beta diversity) together with a developing country economic circumstances it makes the planning of biodiversity management especially difficult since the development needs of the City must inevitably lead to increasing fragmentation of the landscape and the conservation of biodiversity being compromised. In this regard South American cities would have been the most analogous situation to that of Cape Town, however, none of them have progressed as far in implementing a biodiversity strategy within their urban development frameworks.

We propose that the biodiversity network for City of Cape Town will lean towards the Greenway's concept for planning which is explicit and structural rather than the North European planning frameworks which are more inferred and conceptual in nature . The Greenway concept embraces planning for a sustainable physical environment that is less altered but also ensures maintenance and even increasing economic activities within urban areas (in contrast to the North European situation which largely which generally has lower human population growth and maintenance of current economic activities rather than planning for expansion of these. As a consequence of this decision, essential spatial components need to be identified that correspond to the Greenways planning framework which uses nodes and corridors. In essence a node is an area of concentration or an area of attraction for the maintenance of processes and a corridor maintains flows or fluxes between these areas of concentration/attraction.

In using the Greenways concept we will refine its specific use for the maintenance of the biodiversity within the city of Cape Town rather for an overall spatial planning objective. Consequently, the concept of a node and a corridor are further refined into a "biodiversity node” and a "biodiversity corridor".

In this study we will use the existing natural habitat remnants that were previously identified using an iterative reserve selection algorithm for their initial prioritisation (Identification of a biodiversity network for the city of Cape Town, 2002) as the spatial planning units and is represented by 261 land parcels.

3.2 Nodes - definition and function within the CCT’s Biodiversity Network

Definition of Biodiversity Nodes Nodes are discrete and circumscribed spatial objects usually identified by cadastral parcels of land, which will be referred to as "Natural Habitat Remnants" (NHRs) within this description. Essentially these NHRs should have relatively high area to edge ratio so that they can maintain ecological processes. Within urban development, nodes are seen as areas of opportunity for economic growth. By adding the qualifier of "biodiversity" to a node concept we wish to imply that biodiversity nodes are essentially areas to attract and maintain biodiversity. They are the key areas that "anchor" the maintenance and flows of biodiversity at a landscape level. These nodes are analogous to refugia (areas where species can either remain protected from the effects of the environmental stress or can migrate to such areas) and we see the development of urbanisation promoting fragmentation and environmental stress and the nodes function to mitigate these effects.

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An essential component of the node is that it does not have to be a single NHR but can be a cluster of NHRs that are in close proximity to each other . This is also analogous to the development of urban growth where twin cities such as Johannesburg/Pretoria develop. A cluster of adjacent nodes creates a hub of opportunity, which in our case reflects the opportunity for the maintenance of biodiversity. The biodiversity node concept strongly parallels concepts developed from island biogeography and shares many processes and states. For example small islands have fewer species (less biodiversity) and with increasing area more species may coexist and thereby increase species numbers/biodiversity. Similarly small islands that are close to a mainland may have more species (higher biodiversity) than the same size island that is situated further from the mainland. This outcome reflects that an island closer to a source of new species is more easily colonised than an island further away. A cluster of islands in close vicinity tends to support more species (higher biodiversity) than islands that are more distantly dispersed. Consequently clear functional analogies exist between the concepts of island biogeography the spatial planning processes required to define a suitable biodiversity node. This definition of a biodiversity node directly addresses the maintenance of biodiversity at the site specific-level (alpha-diversity), as well as the spatial turnover of biodiversity (beta diversity). Consequently we further define a biodiversity node either as a discrete, larger, contiguous NHR, a collection of discrete adjacent NHRs (that can be smaller), or a collection of discrete NHRs in close proximity to each other (that can be smaller sized) . Insert a rule set to less than 40% fragmentation. Furthermore, the NHRs that constitute a biodiversity node may have different levels of prioritisation within the network (see section 4 below). An additional qualification to the definition would be a smaller discrete NHR that has exceptional value with respect to biodiversity or maintenance of ecosystem services (e.g. wetland or site important for the recharge of underground aquifers).

3.3 Corridors – definition and function within the CCT’s Biodiversity Network background from friction analysis – still to be edited and debated – Grant and Rich – is it possible to get a brief description of “friction analysis”that Joe and Josephine Public would understand? Just an overview para.. Richard did the friction analysis in the previous project and will be better able to describe it. However, friction analysis is aimed at identifying “paths of least resistance” among selected points within a study area. The entire study area is categorized on the basis of the level of resistance that it may present to the movement of individual animals or propagules (this can also be considered as the potentially negative impacts that an area would have on biodiversity. By way of example, an area which is essentially undisturbed would have a low resistance, while a densely urbanized area would have a very high resistance.

My Attempt below…..

Corridors were defined based on the idea that different landuses had the potential to support different amounts of biodiversity within a concept we defined as biodiversity compatibility. So highly impact areas such as informal settlement had relatively little potential to support biodiversity whereas a natural remnant had a large potential to support biodiversity. In order to define the ideal corridor we created a surface that integrated all of these land uses as a biodiversity compatibility layer by applying a score from 1 (highest biodiversity ) to 256 (lowest biodiversity compatibility). We used 256 classes to keep the processed raster images within limits of an 8-bit image to save processing time and disk space. This biodiversity layer represents a cost surface (also known as a friction surface) and biodiversity corridor can developed from any point that has shortest route but connects the areas with the highest biodiversity compatibility. We optimized the process by dividing the perimeter of the unicity into perimeter segments with mid points and these were each calculated to each other every mid point of an arc was routed to every other arc in the perimeter of the unicity to ensure that corridors in every direction were evaluated. Since many route overlapped on one another it products a network that has optimized efficiency in all directions.

Below is a quote on corridor functionality from the Fragstats documentation see comment above

“Corridors may also be defined on the basis of their function in the landscape. At least four major corridor functions have been recognized, as follows:

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1. Habitat Corridor.--Linear landscape element that provides for survivorship, natality, and movement (i.e., habitat), and may provide either temporary or permanent habitat. Habitat corridors passively increase landscape connectivity for the focal organism(s).

2. Facilitated Movement Corridor.–Linear landscape element that provides for survivorship and movement, but not necessarily natality, between other habitat patches. Facilitated movement corridors actively increase landscape connectivity for the focal organism(s).

3. Barrier or Filter Corridor.–Linear landscape element that prohibits (i.e., barrier) or differentially impedes (i.e., filter) the flow of energy, mineral nutrients, and/or species across (i.e., flows perpendicular to the length of the corridor). Barrier or filter corridors actively decrease matrix connectivity for the focal process.

4. Source of Abiotic and Biotic Effects on the Surrounding Matrix.–Linear landscape element that modifies the inputs of energy, mineral nutrients, and/or species to the surrounding matrix and thereby effects the functioning of the surrounding matrix.”

Once the results of C-Plan have been obtained there will need to be further selection. C-Plan is not a spatially explicit method and therefore does not address processes. Using the principle of minimum sets that is central to C-Plan a friction model can be developed of all conserved areas, core sites and selected areas from C-Plan in relation to other features such as rivers which were to be conserved and all other land use patterns (roads, built up areas, agricultural activities etc). A friction is a value greater than 1 by which you multiply the base cost of movement (Protected Areas and Core Sites) in order to arrive at the actual cost of movement (habitats suitable for maintaining diversity). From the friction surface a cost surface is generated from one known point and distances away from this are measured according to the minimum amount of friction that must be accumulated to move from that cell to the nearest source target. Movements are in 8 directions from any cell, with horizontal and vertical movements producing a cost of 1 times and diagonal movements producing a cost of 1.41 times the friction value. From the cost surface, pathways are defined from the start point to target areas, which are demarcated by a line. By examining all pathways along known gradients such as altitude or examining pathways to connect critical ecosystems (mountains to mountains or coasts to coasts) a network of flows is generated which will describe areas most compatible for conserving biodiversity. Where pathways cross they form nodes, which are effectivity the biodiversity crossroads. By using buffers around the corridors and nodes a planning framework is established for identifying and prioritising the final selection of remnants areas for conservation.

The development of these spatial modelling approaches ensures that ecological gradients and possible effects of global changes are managed within corridors. Such corridors linked the following significant areas, Zandvlei, Macassar, Gordons Bay, Cape Point, Noordhoek Wetlands, West Coast, Mamre, and Paardeberg) Effectively these corridors optimise routes containing natural vegetation and all major vegetation types. The advantages of this procedure is that it looks at the viability of patches in relation to where neighbouring viable patches are located and is therefore fully spatially explicit. Without the development of this specific protocol the final selection of remnants could not be further prioritised.

Definition of a biodiversity corridor

A biodiversity corridor in structural terms is non-discrete and has an essential function that reflects linearity and connection so as to ensure that flows/fluxes are maintained within larger spatial process. Within an urban development context corridors are seen as physical movement such as transportation, or conceptual movement such as flows of economic investment between development nodes. By redefining this concept of a corridor to the identification of the biodiversity network for the city of Cape Town as a "biodiversity corridor" it is evident that it is not as easily and physically defined as a biodiversity node and is analogous to structural planning and spatial development frameworks within the urban economic development context. Corridors are most usefully defined using models such as transport networks and are often mathematically generated through processes of optimisation. Consequently a biodiversity corridor should provide for movement of species and organisms, thus ensuring the maintenance of critical processes for maintaining biodiversity at the landscape level. It is now evident that the biodiversity node is essentially a planning unit, whereas the biodiversity corridor is essentially a management tool

MLA – Sustainability Matters, BCBD UWC, Setplan, GISCOE and FWCG, June 2004 10 CCT Biodiversity Network Prioritisation Project – Draft Concept Document: Nodes, Corridor & Criteria and consequently the ecological sustainability of a biodiversity node is complemented by the appropriate planning and regulation of activities occurring within the biodiversity corridor.

Natural ecosystems provide many physical corridors which promote and maintain levels of biodiversity and include rivers, coastlines and skylines. Generally such landscape features are not as transformed by economic activities as other areas and therefore provide ideal conduits for the movement of species and organisms that are essential for the maintenance of biodiversity. In the case of the city of Cape Town mobile sand dunes represent a further potential biodiversity corridor. Consequently biodiversity corridors should be seen as the natural routes that species/organisms would have used in the past when migrating towards "refugia" during periods of adverse environmental change. Migration to refugia is not the only function of corridors, could also be for seasonal migrations, for movement between foraging grounds, dispersal of propagules or immature individuals (thus mixing of genomic material) etc Need to add in the perspective of corridors being tracts of land or river that with varying degrees of transformation. What does this mean in the context of the CFR and in the context of the City connecting with the CAPE BHUs? Rich/Grant A graphic needs to be added here that illustrates the corridor concept – maybe one from your presentation Rich/Grant

3.4 Freshwater systems and nodes and corridors Kate this probably needs revision in light of above – better still if it is integrated into the overall concepts, These feel more like principles governing river/wetland prioritisation within the system – is there a way of knitting these principles with the data we have/will have? - Southern Waters

Freshwater biodiversity nodes

In a paper reporting on the outcomes of an IUCN workshop held in Switzerland in June 2002, which aimed to develop a draft methodology for the prioritisation of sites for the conservation of freshwater biodiversity, Darwall & Vié (2003) suggest a number of species-based criteria for the identification of important sites. It is recommended that some of these be used as the initial “filter” for the identification of a biodiversity node within the Biodiversity Network. Thus, a node is a site (river reach or wetland) that satisfies any of the following four criteria (explanatory notes are in italics): . A site is known or thought to hold a significant number (which is taxon specific) of one or more globally threatened species (as determined by the IUCN Red List Categories and Criteria, IUCN 2001) or other species of conservation concern (this would include species of regional or national concern). . A site is known or thought to hold non-trivial numbers (taxon specific) of one or more species of restricted range (taxon specific). . A site is known or thought to hold a significant component of the group of species that are confined to an appropriate biogeographic unit or units. The biogeographic unit that is appropriate here could be the Cape Floristic Kingdom, but could also be a smaller unit such as the Cape Peninsula or even river catchments. . A site is known or thought to be critical for any life history stage of a species.

A suggested second “filter” is to ensure full representation of all the types of river and wetland. For instance, conservation of at least 10% of all types of rivers was suggested as a “first step” in conserving the biotic and habitat diversity within that river type class. With regards to wetlands, it is suggested that all of the large wetland areas within the CMA be considered biodiversity nodes. Although in many instances it is not known whether these systems support a high number of aquatic species, or whether they support species that fall into the IUCN criteria listed above, these wetlands provide important habitat to both aquatic and terrestrial species.

Freshwater ecological corridors

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Rivers, by their longitudinal nature, are corridors. This would apply even to canalised systems. However, the effectiveness of rivers as corridors varies according to the location of the river, its river type, condition etc. The importance of connectivity i.t.o. the ecological importance of rivers and wetlands: . Ecological priority of one river “unit” affects the ecological priority of the unit upstream, as this unit supplies the one downstream. . Wetland management class delineation is affected by the proximity of a wetland to other systems of importance / sensitivity. It is important to realise that the conservation importance of a particular freshwater ecosystem within the boundaries of the CMA may be elevated due to the influence of that ecosystem on or influence by others outside of the boundaries. For instance, maintenance of habitat integrity within the upper reaches of a river affects the integrity of the lower reaches. I am still a bit unclear on what this means for the GIS analysis.

4. Prioritisation and categorisation of the Biodiversity Network

4.1.1 Introduction A key output of this project is the prioritisation of the network’s biodiversity areas into categories A, B and C, where:  Category A areas will be those areas that must be protected as biodiversity areas and will include amongst others existing nature reserves, biodiversity nodes and other areas that meet the established criteria.  Category B areas will be those areas that are managed for biodiversity but which will also support other appropriate activities and landuse types.  Category C areas will be those areas that will fulfill a primary function of supporting an activity or landuse that is mutually inclusive of biodiversity but not managed primarily as a biodiversity area.

The challenge is to develop a prioritisation and categorisation system that is appropriate in the context of the CCT’s Biodiversity Strategy strategic objectives and which can be effectively integrated with the Metropolitan Open Space System and Spatial Development Framework, while applying conservation models and land use management guidelines that assist in protecting biodiversity while accommodating appropriate uses and promoting opportunities for social and economic benefit.

4.1.2 Summary of feedback received from Workshop One Still to be summarised from record of workshop

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4.1.3 Criteria for prioritisation of the network (including freshwater components)

Essentially terrestrial, freshwater and coastal components had been integrated through the biodiversity compatibility mapping exercises which together with the least-cost surface analyses produced the final corridor solution (original of frictions used – see Table 1).

Table 1: Friction values ascribed to various features and landscapes for the development of the corridors for conservation management. The base value of 1 is all areas that are either protected or been selected for protection. As friction values increases the area becomes increasingly unattractive for biodiversity. The corridors ensure the viability of existing biodiversity is optimised through a network of areas most compatible for supporting it.

Base Friction = 1 Existing Nature Reserves, Core Floral Sites, Selected remnants (all), Wetlands, Estuaries, Vleis Friction = 3 Rivers with natural banks, non-selected remnants Friction = 5 Dams, waste water treatment works’ water bodies Friction = 10 Major powerlines, reservoirs, detention ponds, retention Friction = 15 Irrigation ponds, canals, composite canal, open channels, weirs Friction = 30 Major Roads and Freeways, Urban Open Spaces Friction = 60 Low intensity agriculture*, wheat fields*, built up areas Fiction = 120 High intensity Agriculture, Vegetable growing, Commercial areas Friction = 240 Industrial areas, Settlements *Originally run with frictions of 120 but no difference was observed in the network

The final integration of the plan

This will involve a scoring of A, B and C for each NHR, and each corridor and for each river system. It is imperative that the nodes representing the conservation core sites are effectively integrated into the corridor systems. In order to achieve this a rules set for connecting nodes with corridors needs to be formulated. The following is a proposal based on what was presented at the workshop and feedback from the work shop (Dr B. McKenzie)

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Proposed decision tree for prioritisation of NHRs into A, B and C

RULE 1. Is the NHR a protected area or a core area? YES A

area. Thsite should be classified as category A.

NO

RULE 2. Does the NHR have 1 of the 3 critical vegetation YES A types? (list these?)

NO

RULE 3. Is the NHR ≥ 10ha in area? A YES

NO

A RULE 4. Does the NHR have an irreplaceability of ≥ 0.9? YES

NO

RULE 5. Is the NHR a significant wetland? YES A

NO A

RULE 6. Does the NHR have a irreplaceability of between ≥ 0.75 and ≤ 0.9 and is either a wetland, or is ≥ 10 ha in area or has a known rare and endangered population or is critical to YES create a hub or is within an “A” corridor?

Rule 7. Does the NHR have an irreplacebility of between ≥ 0.75 B and ≤ 0.9? NO

YES

NO

Rule 8. Does the NHR have an irreplaceability of ≤ 0.75 and is also a wetland or is > 5ha in area, or ha known rare and YES B has a rare or endangered population or is within a corridor or connected to a river corridor?

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NO C What happens with this decision tree if a NHR is made up of a set of remnants in close proximity to one another? This will influence the irreplaceability values, as at this stage we have these values for individual remnants and not for groups. This will require a re-analysis of irreplaceability after grouping remnants into NHRs on the basis of a minimum inter-patch distance. The alternative would be to assign the highest irreplaceability value from a set of remnants to the composite NHR. Rule 6 – how will a hub be defined I don’t remember it being mentioned earlier in the document, but I may have missed it. This has dealt with classification of the NHR/nodes (which are either single NHR, grouped adjacent NHR or a group of NHRs that are very close to each other (<2 km) (is this the proximity distance that is being proposed – on what is it based. We will definitely be called to defend this distance).

This decision tree works as follows:

Class A. nodes should principally be defined by its current protection status, its criticalness with respect to conserving the three vegetation types that could not reach target and therefore all available representation of them needs to be included in the network irrespective of any other consideration, the size of NHR and its irreplaceability as defined by the original study. Any NHR that was identified as a candidate and is a wetland will also be included as a Class A Node (and this aligns with the original commitment that all wetlands and should be conserved with mobile dune systems (***** do we extend this qualification to include this as well?****** Yes) and final whether it will contribute to creating a local hub of nodes and its connection to a class A corridor.

Class B. nodes should principally be critical nodes that might fall out of the corridor network but include a high degree of irreplaceable and biodiversity value. A connection to a river system is also considered an important issue in elevating anode from C to B.

Class C. these are generally represent the NHR not include within an A or B node and should principally be open space areas and ideally would have fallen within a class A. or class B. corridors. These nodes are seen as either sanctuaries with the potential for some development or steppingstones along the corridor.

Corridor prioritisation

A class A. corridor needs to have a high degree of permeability, together with potentially greater widths. A class A corridor should mostly not require high investment with respect to restoration. Ideal ranges for widths need to be defined. A class B. corridor is characterised by less permeability or having less widths. A class B. node should have the potential to partly fulfil the role of a class A. corridor in the event of a class A. corridor becoming compromised to development (failure to implement legal protection) or through a natural disaster. A. B. class corridor should be considered for considerable restoration, especially in the event of it having to take over the role of a class A. corridor. Essentially class B. corridors are seen as functional rather than spatial buffers in the biodiversity network.

A class C. corridor is usually defined as a narrow linear connection, such as a river or a road reserve, or a servitude. A class C. corridor should have the potential to be used for certain recreational activities such as a walking, horseriding or bicycle trail. Class C. corridors are therefore seem to provide widespread but relatively weak connectivity.

River prioritisation

The river network should be added over the existing corridor/node network. An A category should be considered to include extreme or high ecological priority, a B category should have more modest ecological priority where a C

MLA – Sustainability Matters, BCBD UWC, Setplan, GISCOE and FWCG, June 2004 15 CCT Biodiversity Network Prioritisation Project – Draft Concept Document: Nodes, Corridor & Criteria category need only have a low ecological priority and could be used for either limited development or for restoration where a strong need for connectivity is required. There is a basic issue here that needs to be addressed. Are the rivers be prioritised as biodiversity elements in themselves or are they only being accommodated within the process of corridor selection? Rich, Grant, Kate – It would be more correct to prioritise them based on biodiversity considerations (is this not what was done by the freshwater study?), and then further assign them on the basis of their position relative to the corridors. In other words, use the same process as that executed for the terrestrial remnants.

5. The way forward – next steps in the project

Next steps….

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References and sources

Appendix One: Background research on best practice: Nodes, corridors and prioritisation

Appendix Two: City of Cape Town Biodiversity Network Prioritisation Project: Report on Stakeholder Workshop One.

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