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Identifying corridors in KZN, creating linkages in a fragmented landscape

Citation

Ezemvelo KZN Wildlife (2010) KZN Landscape Ecological Corridors, Version 3.1. Unpublished GIS Coverage [ kzncor05v3_1_10_wll .zip], Biodiversity Conservation Planning Division, Ezemvelo KZN Wildlife, P. O. Box 13053, Cascades, Pietermaritzburg, 3202.

A series of altitudinal and biogeographic corridors were created in KZN to facilitate evolutionary, ecological and climate change processes and to create a linked landscape for the conservation of species in a fragmented landscape. A coarse filter approach focusing on terrestrial matrix species was adopted.

Using the latest land cover map (KZN Land Cover Map, 2005, Version 2) a friction surface for the province was developed. Friction values were associated with different land cover categories and refer to the level of ease or difficulty with which species would be able to move through or live in that land cover category. Friction values ranged between 100 (low friction) and 1000 (high friction).

Discount layers were developed for Protected Areas, Stewardship sites and commercial game ranches. Protected areas received a 100% discount, current stewardship sites a 70% discount, proposed stewardship sites a 50% discount and commercial game ranches a 30% discount. The discount layer was only applied to natural vegetation. This layer was multiplied with the baseline friction layer. Hence natural vegetation within protected areas effectively had a friction value of 1.

The rural dwelling category of the land cover map was buffered based on research done by Scott-Shaw (2008) which showed that grassland vegetation close to the dwellings was very depauperate. Sweetveld areas received a 200m buffer whereas sourveld areas received a 600m buffer. Each 100m interval received a different friction value. This layer was added to the modified friction layer.

A 10 class land form classification was developed using Topographic Position Index software. Based on their topographic position within the landscape, each land class was weighted to select against drainage areas and to select for spurs, ridges and mountain tops. The topographic position index layer was added to the modified friction layer.

The corridors were developed in ARC Map 9.2 using the modified friction layer and the cost distance and corridor functions. The software selects the least cost range of values between two points based on the friction layer. Each corridor that was created was cleaned, edge-matched and where possible expanded using the next lowest corridor cost , to be at least 1km wide (this was not possible in all cases). The Admiralty reserve was used as a coastal corridor as the landscape was too transformed to create a conventional corridor. Once all the individual corridors (17) were created they were combined into a single coverage.

On the ecological corridor coverage (KZNCor0905_wll) two new corridors were created: The

Tugela North Corridor was created to supplement the Tugela Corridor which passes through highly transformed landscapes and frequently could not meet the minimum width criteria. The Opathe Imfolosi link corridor was created to link the Opathe and Imfolosi protected areas.

Update:

Update by Boyd Escott

The dune corridor was extracted from the TSCP Planning domain and represents all the planning units identified (through manual observation) as being east facing dune surfaces. These were added to the Macro-ecological coverage to form [Kzncor05v310_wll.shp]. In cases where the dune polygons overlap with existing corridor network, the dune polygons were merged into that network. Please Note. No transformed surfaces were extracted from the Dune networks prior to their incorporation into the original corridor coverage.

Logical consistency report

Consistent with various datasets

- KZN Land Cover Map (2005, Version 2)

- Ezemvelo Protected areas (2010)

- Stewardship Sites (2010)

- Commercial Game Ranches (2009)

- Topographical Positional Index

- Admiralty Reserve (2008)

Notes:

As explained in the native dataset the dune corridor was created by adding in the east facing dunes from the Terrestrial Planning Units file. These were merge with the admiralty reserve, the areas were they overlapped, these needed to remain separate. The admiralty reserve boundary was a legislative boundary and could not be edited or changed by Ezemvelo and therefore the extent of the boundary needed to be maintained.

The Admiralty and Dune corridors were removed from the corridor dataset [ kzncor05v310_wll] and replaced using the following procedure:

1. The Dune Corridor

- Polygons in the Terrestrial Planning Units dataset were extracted as explained in the native dataset.

- The KZN boundary 2008 was used to clip the planning units to the vegetation line boundary

- This was merged into the corridor file [kzncor05v210_wll ](but with the admiralty reserve corridor removed). The union toll was used.

- In areas where the dune corridor overlapped with an existing corridor (as developed using the criteria explained in the native dataset) the dune polygon was merged into the existing corridor and named as the existing corridor. In areas were the dune corridor overlapped with the existing corridor and filled the doughnut areas of the existing corridor, these areas were deleted. The reason for that was that the doughnut or holes existed because those areas did not meet that criteria set for corridors and should therefore not be selected. If the dune corridor extended on the outside boundaries of the existing corridor it was kept and named dune corridor.

2. Admiralty Reserve Corridor

- The Admiralty reserve area could not be dissolved or extended for reasons explained above. The admiralty dataset was merged (using union tool) with the dataset that had

the edited dune corridors and the existing corridors.

- Areas where the admiralty reserve corridor overlapped with another corridor, the area covered by the admiralty reserve was remained. This area was named with existing corridor name and admiralty reserve eg if the admiralty reserve cut through the dune corridor, this area was named Dune_Admiralty Res Corridor.

To align with National terminology, the file name macro ecological corridor was changed to landscape corridor.

SANS 1878

FGDC-STD-001-1998