(4b) Salvage near home (details)

Datasets:

REMVEG (polygon). Remnant forest vegetation of Tasmania, 1 December 1996 - 31 January 1997. Based on 1:25 000 scale forest mapping; boundary positions typically accurate within 25 m. Remnants are polygons 20-200 hectares in area, totally surrounded by cleared land and separated from larger forest patches by at least 100 m. Some additional patches were added based on advice from experts. Source: Forestry Tasmania.

Terrestrial localities (point). Centres of 1 km squares containing locality records for butterflies; carabid, chrysomelid and lucanid beetles; earthworms; geometrid moths; land snails; talitrid amphipod landhoppers; millipedes; and velvet worms. (See below.)

Aquatic localities (point). Centres of 1 km squares containing locality records for caddisflies, dragonflies, parastacid malacostracans and stoneflies. (See below.)

Background:

REMVEG was produced for the 1996 Comprehensive Regional Assessment (CRA) of Tasmania, a project providing background for the 1997 Regional Forest Agreement (RFA) between the Commonwealth and State governments. Under the RFA, large native forest areas were set aside as reserves and others were earmarked for intensive silvicultural management.

The locality records come from another 1996 RFA project, Invertebrate Bioregions in Tasmania, which was my own work. A detailed project report can still be found online by Googling, although the Commonwealth government now stores all RFA reports in a digital archive. The project database contained 13929 well-located records for 792 native, non-marine Tasmanian invertebrates, mainly from the period 1970-1994. All records were generalised to 1 km grid squares, a spatial “blurring” which reduced the database to 10871 1 km square occurrences.

Analysis in ArcView 3.2 GIS (Environmental Systems Research Institute):

The three datasets were clipped to the main island of Tasmania (excluding Bruny, Maria and Schouten Islands, and all Bass Strait islands). The result was 630 remnants, 2856 terrestrial localities (with up to 115 species per 1 km square) and 1560 aquatic localities (up to 45 species per 1 km square).

The closest terrestrial and aquatic localities to each remnant were found using the Closest Feature function in the AlaskaPak Toolkit for ArcView 3.x (US National Park Service). This function also calculates the separating distance, in this case from the nearest point on the remnant polygon boundary to the centre of the 1 km square locality.

I identified the 10 remnants furthest from a terrestrial or aquatic locality. The 10 furthest-from-terrestrial remnants averaged 9.2 km separation (range 8.7 - 10.1 km), while the 10 furthest-from-aquatic remnants averaged 14.0 km separation (13.2 - 15.6 km).