2.1 - Introduction

Analyses of historical fauna records are increasingly being used to inform management and conservation decisions. The koala is an iconic Australian marsupial that has been the focus of one national survey (Phillips 1990), while in NSW three statewide surveys have also occurred (Gall 1978; Reed and Lunney 1990; Lunney et al. 2009). Analyses of the data that results from these surveys are increasingly being used to inform planning outcomes at LGA level (Lunney et al. 1998; Phillips et al. 2007; Phillips et al. 2011).

Extent of Occurrence (EoO) and Area of Occupancy (AoO) are two key range parameters that relate to the spatial distribution of a given species. The EoO is that area encompassed by the outermost limits of the area within which the species occurs and is most typically represented by a Minimum Convex Polygon. In contrast the AoO is the actual area within the EoO over which the species can be found (Gaston 1997) and is typically enumerated using a grid-cell based approach with occupancy estimated by the total number of occupied grid cells; AoO estimates are therefore sensitive to sampling parameters such as study area and grid cell size. Although more useful, changes in AoO over time are harder to quantify for species such as the koala because and amongst other things, there tends to be an increase in available records over the last two to three decades. This creates the potential for an increase in the probability of a record being present in a given area over more recent years. Thus, using historical records to examine change in quantitative range parameters can potentially misrepresent the full extent of change (positive or negative) if the inherent biases cannot be effectively accommodated.

In this section of the report, analysis of historical koala records for the LGA is undertaken with a view to exploring the following issues:

(i) identifying broad changes/trends in the geographic distribution and habitat occupancy rates of koalas over time; and

(ii) determining the extent to which the historical record may be capable of informing decisions relating to koala conservation by way of identifying important source populations and/or other issues that may assist longer-term management objectives.