Rules for Prioritization of the Network
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 Table of frictions used)
Table X: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 node, 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)
NO
This has dealt with classification of the nodes (which are either single NHR, grouped adjacent NHR or a group of NHRs that are very close to each other (<2 km).
This decision works
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 wet land will also be included as a Class A Node (and this aligns with the original commitment that all wetlands should be conserved with mobile dune systems (***** do we extend this qualification to include this as well?****** 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 ofr B node and should principally be open areas and ideally will fallen within a class A. or class B. corridors. These nodes are seen as either sanctuaries with the potential for some development or steppingstone along the corridor.
Corridor prioritisation
A class A. corridor needs to have a high degree of permeability, together with potentially greater widths. Aclass A corridor should mostly not require high investment with respect to restoration.
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 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.