Protecting Warrup For The Future

Old-growth forest
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.

Buffer zones
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
to 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 an ecosystem.

Warrup’s 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 its purpose.

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 conservation.

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 Block.

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.
Map of Warrup Block showing old-growth and proposed corridors