Using Circuitscape to analyse landscape connectivity and guide restoration activities in SE Australia.

Habitat loss and fragmentation have resulted in the decline of biodiversity worldwide, where remaining wildlife populations are threatened by isolation, and the modifying effects of human land-use. It is widely recognized that species ranges will need to shift with future shifts in climate zones, and this requires landscapes that are ‘connected’ allowing movements to occur. As a result, continental scale connectivity conservation initiatives have commenced worldwide as a key management response, focusing on maintaining and restoring key linkages in landscapes (Crooks & Sanjayan 2006).
The 'Slopes to Summit’ (S2S) Initiative, which is part of the “Great Eastern Range’s” Australian continental-scale connectivity program, aims to carry out restoration actions to strengthen landscape connectivity in the Holbrook region, south-eastern Australia (GER 2017). Much of the region is heavily cleared and fragmented, where isolated patches of remnant Eucalypt woodlands primarily exist along roadsides, water-courses, and farms. As part of a major project aimed at enhancing landscape connectivity in the region, connectivity analyses were performed using Circuitscape. The objectives of this analysis were to identify major corridors in the landscape (with a focus on the threatened Squirrel glider; Petaurus norfolcensis), help prioritise and validate on-ground actions, and assist with evaluating the success of the project.
Circuitscape uses circuit theory to identify multiple pathways from multiple points, by running current through a resistance layer to provide an accurate, quantitative assessment of landscape connectivity. Unlike other least-cost models, the output shows dispersal patterns in multiple directions and of varying strengths due to the influence of the resistance layer (McRae et al. 2008). As a result, proponents suggest that the output more accurately reflects the dispersal patterns of an organism.
To conduct analyses, a binary map of native woodland vegetation was first created using ADS40 Imagery, which provided 50cm spatial resolution (NSW SS 2017). A resistance map was then created, where variables and resistance values were assigned using a combination of published information and following previous studies. The region was analysed in two directions to produce an omni-directional connectivity map (Pelletier et al. 2014). High current areas were then used to identify major corridors in the region. Proposed restoration sites were prioritised using maximum current values for each site polygon, in conjunction with other planning criteria (risk, opportunity and site measures).
Using this approach, the application of circuit theory allows land managers and researchers to better quantify habitat connectivity in a wide variety of environments. One of the key benefits of this approach is in providing a decision support tool for land managers to run investment scenarios to achieve maximum connectivity gains.