Ecosystem Guidelines for Environmental Assessment

MAINLAND THICKET
What are the critical things to maintain in terms of managing these
systems for biodiversity, and ensuring its persistence
Maintain all remaining intact fragments across the range of Mainland Thicket to help buffer against
climate change.
Corridors are especially effective for thicket because of bird-dispersed seed and herbivore migration.
Rehabilitation of connecting corridors between isolated patches is critical.
The minimum viable size and isolation of thicket patches, or the structure and maintenance of the
mosaic pattern, all require detailed, on-site assessments. Only fine-scaled, detailed analysis of present
and past thicket distribution patterns will determine mosaic patterns and minimum viable patch sizes.
There must be integrated management of disturbances such as fire, grazing and drought.
Certain patches of thicket, especially solid, non-mosaic units, require total protection from fire. Fire
and alien plant invasions must therefore be managed in the adjacent, non-thicket, ecosystem. Never
allow adjacent "fire biomes" to remain unburnt for longer than 30 years, or to become invaded. Degraded
solid thicket should be prioritised for restoration.
Maintain the appropriate fire regime in terms of fire frequency and seasonality in fire-prone thicket
types. Farms should be organised into Fire Protection Associations to avoid unnecessary clearance of
fire breaks.
Keep patches and surrounds free of alien vegetation.
What, if any, reliable indicators could be used in monitoring ecosystem
health, as related to key vulnerabilities
Most of the Arid and Valley Thicket types should have a relatively high cover percentage of spekboom.
The absence of spekboom often indicates a transformed state.
If adult thicket trees die during drought periods, remove all stock and game and implement rehabilitation.
If fire remains absent in mosaic types for longer than the prescribed period then targeted burning is
required.
If summer rainfall is below average, reduce stock density.
If thicket clumps coalesce and displace plants of the adjacent biome, ensure that this only happens
in prescribed areas where solid thicket once occurred and not in areas where mosaic types are found.
How reversible are impacts over a 5 – 10-year period
Where rainfall is higher - closer to the coast or topographically induced - impacts may be reversible,
but restoration of thicket is a very slow and costly process. Almost no information is available on
thicket restoration techniques or recovery rates.
In more arid types, impacts such as over-grazing or cultivation are probably irreversible at this time scale.
What are acceptable trade-offs, compensation or off-sets
for biodiversity loss
Restoration of degraded thicket areas should be a mandatory condition of authorisation for
development activity in this threatened ecosystem.
Trade-offs involving spatial planning and development authorisations should require detailed maps
on biodiversity pattern and transformation so that proposals can be carefully assessed in accordance
with current conservation targets for thicket.
JAN VLOK
66 : MAINLAND THICKET ECOSYSTEMS