Ecosystem Guidelines for Environmental Assessment

TABLE 4: EXAMPLES OF SPATIAL COMPONENTS OF ECOLOGICAL PROCESSES AND THEIR LOCATION
TYPE
OBJECTIVES & CHARACTERISTICS
SCALE AT WHICH SPATIAL COMPONENTS
OF ECOLOGICAL PROCESSES FUNCTION
- To maintain migration and exchange between inland and coastal
biotas (and also between lowland and upland biotas) by protecting
riverine habitats that function as ecological corridors
- Riverine corridors in many lowland areas retain some of the last
remaining semi-continuous patches of natural vegetation and
thus have special significance in terms of providing ecological
connectivity between areas
- Migration of plant species along riverine corridors has resulted
in species diversification
- Riverine corridors may also serve as fire refugia. The lower
frequency of fire results in a different plant and animal community
- Riverine corridors also serve as refugia from drought and have
provided refugia for mesic species during major climatic events
in the past
- Ecological processes can function at a very wide scale in the
case of riverine systems that breach the Cape Fold Belt and link
the Karoo basin with the coastal forelands
- The scale is reduced with single drainage basins – and even more
so with individual tributaries – on the coastal plain
EXAMPLES
VEGETATION BOUNDARIES
ECOLOGICAL CORRIDORS
UPLAND-LOWLAND
INTERFACES AND
BIOME BOUNDARIES
(THICKET-FYNBOS)
SOIL INTERFACES
SAND MOVEMENT
CORRIDORS
RIVER CORRIDORS
- The inland movement of marine sands represents a dynamic
process that drives ecosystem functioning and determines
biodiversity patterns.
- Sand deposits create a complex sequence of sediments of various
ages and chemistries associated with unique, soil-specific plant
assemblages and diversification of species.
- Sediment corridors can also be important links for coastal thicket
- Sediment corridors can be important links in the seasonal
replenishment of sand for bathing beaches
- The entire system, i.e. from source (input) to core and sink
(outgoing) areas and adjacent habitat. These systems are often
in the form of headland bypass dunes (i.e. cross a peninsula or
headland that cuts across the prevailing wind direction)
- Certain dune plumes may be as small as 10 ha, but many cover
hundreds or even thousands of hectares
- In the STEP planning domain, sand movement corridors were
considered functional if less than 50% of each section had been
transformed by agriculture and urbanisation. Dense alien stands
can ‘choke off’ the movement of sediments between source and
sink areas
- Maintain ecological diversification of plant and animal lineages
in response to fine-scale gradients
- For the CAPE conservation planning programme, fine-scale
edaphic gradients entailed ca.1 000 ha areas of juxtaposed and
strongly contrasting edaphic habitats
- These interfaces may be visible on the ground over a few metres,
often as a staggered mosaic rather than as a purely linear divide,
and are often marked by a change in topography, such as a break
of slope
- To maintain ecological diversification of plant and animal lineages.
- To support faunal seasonal migration.
- Areas spanning upland-lowland gradients.
- In STEP planning domain, identified as a 500 m wide buffer of
untransformed habitat along interfaces between solid thicket
and vegetation of the adjacent biome
- These boundaries can also correspond with ecotones such as
between sandstone fynbos-renosterveld-succulent karoo, or
shale renosterveld-granite renosterveld-granite fynbos
The Gouritz River corridor (widescale; links Nama Karoo-Succulent
Karoo to the Indian Ocean coast)
Coastal plain section of the Gouritz River (Riversdale Plain)
Olifants-Doring (links Tankwa Karoo with Sand Fynbos of West
Coast forelands)
Goukou River (links Langeberg mountains to the Indian Ocean
coastline)
Breede River (links Fynbos and Succulent Karoo biomes with coast)
All rivers that are not irreversibly degraded should be included in
biodiversity networks to assist in conserving ecological processes
across landscapes
West Coast: Atlantis, south of Langebaan, north of Eland’s Bay,
extensive areas north of Lambert’s Bay
Cape Peninsula: Hout Bay-Sandy Bay (now largely destroyed),
Witsand, Buffels Bay, Strandfontein coastline
South Coast: Betty’s Bay-Hanglip, Walker Bay, Quoin Point,
Agulhas, Waenhuiskrans–De Hoop, Gouriqua, Kanon-Vleesbaai,
Goukamma, Robberg Peninsula.
There are numerous examples, e.g.:
West Coast: Saldanha Strandveld (limestone or granite) abutting
Atlantis, Cape Flats and Leipoldtville Sand Fynbos (acid sands);
also between various Renosterveld types (alkaline shales,
occasionally granites) and Sand Fynbos and Sandstone Fynbos
types (acid sands)
De Hoop: De Hoop Limestone Fynbos (limestone) and Potberg
Sandstone Fynbos (acidic sands) and Rûens Shale Renosterveld
(clay)
Riversdale Plain: Canca Limestone Fynbos (limestone and calcrete),
Mossel Bay Shale Renosterveld (clay), and Swellendam Silcrete
Fynbos (silcrete) and Albertinia Sands Fynbos (acid sands)
Upland-lowland vegetation boundaries, e.g.:
Coastal plain/coastal mountain range (e.g. Riversdale Plain-
Langeberg)
Coastal range/interior basins (e.g. Langeberg-Little Karoo)
Inland range/interior basins (e.g. Klein Swartberg-
Moordenaarskaroo
Inland range/Karoo basin (e.g. Roggeveld-Great Karoo)
Biome boundaries: Interface of solid thicket and fynbos, grassland,
succulent karoo or Nama karoo biomes.
SCEPS
84 : SPATIAL COMPONENTS OF ECOLOGICAL PROCESSES