No abstract

We report reptile and arboreal marsupial responses to vegetation planting and remnant native vegetation in agricultural landscapes in southeastern Australia. We used a hierarchical survey to select 23 landscapes that varied in the amounts of remnant native vegetation and planted native vegetation. We selected two farms within each landscape. In landscapes with plantings, we selected one farm with and one farm without plantings. We surveyed arboreal marsupials and reptiles on four sites on each farm that encompassed four vegetation types (plantings 7-20 years old, old-growth woodland, naturally occurring seedling regrowth woodland, and coppice [i.e., multistemmed] regrowth woodland). Reptiles and arboreal marsupials were less likely to occur on farms and in landscapes with comparatively large areas of plantings. Such farms and landscapes had less native vegetation, fewer paddock trees, and less woody debris within those areas of natural vegetation. The relatively large area of planting on these farms was insufficient to overcome the lack of these key structural attributes. Old-growth woodland, coppice regrowth, seedling regrowth, and planted areas had different habitat values for different reptiles and arboreal marsupials. We conclude that, although plantings may improve habitat conditions for some taxa, they may not effectively offset the negative effects of native vegetation clearing for all species, especially those reliant on old-growth woodland. Restoring suitable habitat for such species may take decades to centuries.

Biodiversity offsetting is widely applied but its effectiveness is rarely assessed. We evaluated the effectiveness of a nest box program intended to offset clearing of hollow-bearing trees associated with a freeway the upgrade in southern Australia. The offset targeted three threatened vertebrates: squirrel glider (Petaurus norfolcensis), brown treecreeper (Climacteris picumnus) and superb parrot (Polytelis swainsonii). Clearing led to the loss of 587 tree hollows and the offset was the placement of an equivalent number of nest boxes in nearby woodland (1:1 ratio). Of these, we monitored 324 nest boxes in six sample periods between 2010 and 2013, yielding 2485 individual checks of nest boxes. For the three target species, we found: (1) no records of nest box use by the superb parrot, (2) two records of the Brown Treecreeper (0-0.76% of accessible nest boxes used per survey period), and (3) seven records of use of nest boxes by the Squirrel Glider (0-2.1% of accessible nest boxes used per survey period). Rates of nest box use by the Superb Parrot and Squirrel Glider were markedly lower than rates of use of hollow-bearing trees observed in other investigations. Low levels of use by target species coupled with the extent of nest box attrition suggest the offset program was unlikely to have counterbalanced the loss of the hollow-bearing trees. We make suggestions for improving future offset programs including a greater emphasis on: (1) avoiding impacts on hollow-bearing trees; (2) offset effectiveness as a measure of compliance; and (3) using realistic offset ratios.

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Natural disturbances are key processes in the vast majority of ecosystems and a range of ecological theories have been developed in an attempt to predict biotic responses to them. However, empirical support for these theories has been inconsistent and considerable additional work remains to be done to better understand the response of biodiversity to natural disturbance. We tested predictions from the intermediate disturbance hypothesis and the habitat accommodation model of succession for reptile responses to fire history and a single major fire event. We focused our work on a broad range of vegetation types spanning sedgeland to temperate rainforest located within a national park in south-eastern Australia. We found no significant relationships between reptile species richness and the number of fires over the past 35 years, the time since the last fire, or the severity of a major fire in 2003. Thus, we found no strong evidence to support the intermediate disturbance hypothesis. A correspondence analysis of reptile assemblages revealed a gradient in species responses to fire history. However, we found limited evidence for an ordered succession of reptiles. Nor could the responses of individual species be readily predicted from life history attributes. Thus, our findings were generally not consistent with predictions from the habitat accommodation model of succession. A possible explanation for the absence of a predictable sequence of recovery following disturbance might be the rapidity of post-fire recovery of many components of native vegetation cover that were found to be important for reptiles (e.g. the extent of grass cover). This would have limited the time for early successional conditions to prevail and limited opportunities for species associated with such conditions. We found that most reptile species responses were much more strongly linked to vegetation type than fire variables, emphasizing a need to understand relationships with vegetation before being able to understand possible fire effects (if and where they exist). We found the disturbance concepts we examined were limited in their ability to accurately predict reptile responses to past fire history or the impacts of a single major fire in 2003. Practical management might be best guided not by disturbance theory, but by carefully setting objectives to meet conservation goals for particular individual species of reptiles.