The Warrup 06 compartment is one of only two significant areas
of old-growth forest in the Greater Kingston area, the other being
in Warrup 04 and 05 which are within the National Park.
The old-growth in Warrup 06 was identified following a nomination
of this area to the Conservation Commission (CCWA), responsible
for overall preservation of the forest.
CCWA found that 259 ha of the total 573 ha in Coupe 6 is old-growth,
and cannot be logged. However, as can be seen from the plan below,
the area of the old-growth is quite irregular, with a very high
ratio of perimeter to area, and large intrusions.
Areas of old-growth have been seen by BGFF in Warrup 08 but because
this area was logged later than 06, are likely to be smaller and
separated rather than in large groups as in Warrup 06 or in the
National Park. BGFF will inspect this forest again before winter
and submit an old-growth nomination if suitable areas exceeding
2 ha (the minimum pixel size recognised by the DEC
database) are identified.
Industrial-style logging using the Bradshaw prescription (a logging
system of near-clearfelling) creates a catastrophic disturbance
to the logged compartments. In turn these impacts affect the old-growth
remnants and some of those effects are carried, potentially some
hundreds of metres, into adjacent undisturbed forest. These edge
effects include weeds, feral animals, temperature variation, stronger
winds, reduced humidity and greater evapotranspiration.
The old-growth areas in Warrup are protected by the HCV forest
surrounding them. The FMP does not require any edge protection
for old-growth and Forest Products Commission (FPC) may log right
up to the boundaries of the old-growth. BGFF claims that buffers
of 125 to 250 metres should be retained around old-growth, which
would preclude logging in almost all of Warrup 06.
In an environment where rainfall is contracting to the south west,
corridors must be left for the migration of wildlife and flora
ahead of drying conditions. Although corridor design in relation
biological function is a somewhat imprecise science, Dr Denis
Saunders, head of CSIRO wildlife division, proposes that corridors
should be tens of metres wide for a single flora species, hundreds
of metres for a community-scale corridor and kilometres wide for
Warrups key location and important conservation values,
and the precautionary principle, suggest that a width well in
excess of 200 metres would be far more appropriate. The retention
of a wide corridor of intact and mature vegetation will result
in a resilient and generous corridor that can be expected to serve
A corridor system should link the two old-growth areas in Warrup
06 to each other and to old growth areas in the National Park
and the Kingston fauna habitat zone.
Buffer zones connecting catchments
Another aspect of corridor design, connecting catchments across
ridgelines, is now recognised as an important feature of landscape-scale
Ridgeline connections are significant for the movement of amphibians
and other partly aquatic species, probably some frog species and
possibly fresh water crustaceans, that may have to move from catchment
to catchment, not only along creeklines, but also across ridge
lines between smaller catchments. The western edge of Warrup 06
roughly defines the catchment boundaries of the Yerraminnup and
Wilgarup Rivers. Along this catchment ridgeline, the headwaters
of Yeardup Creek & Dudijup Creek, tributaries of the Wilgarup
River, lie within 600 metres to 1 kilometre from headwaters of
tributaries of the Yerraminnup River. This area of ridgeline corridors
extends out from Warrup 06 into the adjacent State Forest of Yardup
These ridges lines should be protected from logging in order to
leave viable connections between the river systems. We have not
proposed a specific width for these connections, but material
presented above suggests that 200 metres would be minimal.