Current status and future prospects of reptiles and frogs in Sydney's urban-impacted bushland reserves

Abstract

Five large (greater than 35 ha) urban bushland reserves in Greater Sydney were selected where herpetofaunal assemblages could be deduced and there were recent herpetofauna surveys. Four reserves (Rockdale Wetlands Corridor, Wolli Creek Valley, Burnt Bridge Creek Corridor and Middle Harbour Bushland Reserves) had been surrounded by residential development for more than 50 years. The fifth (University of Western Sydney, Richmond campus) was surrounded by agricultural and peri-urban development. Records from the scientific literature, local natural history groups, amateur herpetologists and council archives were used to gather historic information on the frogs and reptiles. Interviews were also conducted with researchers and neighbours of the reserves. Eight extant species were common to all reserves while another, predicted to be in all reserves, was universally absent. Despite the relatively large size of these bushland remnants, in all reserves the number of reptile and frog species had declined since urbanisation. The largest losses occurred in the four urban reserves. Seven species predicted to have occurred historically were now only present in the peri-urban site. Some herpetofaunal groups were more vulnerable than others. Goannas were locally extinct in urban reserves. Tree frogs and geckos were depleted while ground frogs and skinks were reduced to approximately half their original species numbers. This is in contrast to the peri-urban site where there had been no loss of tree frogs or goannas and generally more than half of the species in each group were extant. Urban impacts that appeared to relate to herpetofauna decline were direct human intervention that resulted in death or removal of individuals (e.g. goannas, large snakes), interference with habitat such as bush rock removal (e.g. smaller snakes, geckoes, skinks), fire (e.g. non-burrowing small residents), interference with the water cycle including infilling and pollution (e.g. frogs) and exotic predators (e.g. dragons, turtles, skinks). In general, herpetofauna with the least future prospects were those most susceptible to decline. These included the large, conspicuous fauna that required a substantial home range, attracted the attention of humans because of 'pet appeal' or due to their perceived danger; were vulnerable at some stage of the lifecycle to predation by feral species; and had specific habitat requirements for reproduction such as quality water or open sandy banks for egg incubation. Those that are small, generalist and unappealing to humans are most likely to survive. There is, therefore, little doubt that diversity in reserves will continue to dwindle unless strategies are devised to overcome the present trend. Current conservation strategies that generally target single species need to be expanded to ecosystem level to monitor threats and management implemented for their removal.

The potential for golf courses to support restoration of biodiversity for BioBanking offsets

“…Tadarida australis golf course was in stark contrast to the 64% of predicted biodiversity reported for remnants in north-western Sydney (White and Burgin 2004), where most of the species not observed were either nocturnal or otherwise cryptic and therefore have been present but not targeted in the collation of data from the area (Burgin 2008b). Some species with potential source populations nearby, for example, the agamid Pogona barbata and the gecko Underwoodisaurus millii, were not present.…”

“…2). White and Burgin (2004) reported on herpetofauna of four urban reserves across Sydney's eastern suburbs that had been bounded by urbanisation for over 50 years. They deduced that between 25 and 41.2% of the frog species predicted to be historically present were extant.…”

“…The diversity of frogs on the golf course when the survey began was close to the upper limit of this range (38.9%) and within 1 year of survey the numbers had reached a plateau of 55.6% of the predicted historical fauna, substantially above that found in the remnants of Eastern Sydney suburbs. However, in intact remnants of the Cumberland Plain Woodland within a peri-urban matrix, approximately 80% of the predicted diversity was present (White and Burgin 2004), and at least one of the missing species, Heleioporus australiacus the giant burrowing frog, may be missed in the ad hoc collection of data because of its burrowing habit (Burgin 2008b).…”

‘Mitigation banks’ for wetland conservation: a major success or an unmitigated disaster?

“…In determining the fate of dams, either existing or proposed, there is no consideration of their benefit as habitat for native species. Despite this lack of concern for such wetland areas, research undertaken on the farmlands of the University of Western Sydney has demonstrated that farm dams can create important habitat for native frogs, freshwater turtles (White and Burgin 2004) and eels (Dalem 1998).…”

Comparison of sympatric freshwater turtle populations from an urbanized Sydney catchment

“…Lane Cove River } Rosser, 1997; wetlands within the major eastern-suburbs bushland } White and Burgin, 2004; wide range of impoundments } Burgin and Dalem, 1996;Wong and Burgin, 1997;Burgin et al, 1999;White and Burgin, 2004;Burgin, 2006). In contrast, E. m. dharuk (or related taxa) are apparently restricted to rivers or adjacent backwaters (Lane Cove River } Rosser, 1997; Hacking River } Griffiths 1997; Georges River } Burgin, 2006) and, where details were given, they were relatively less abundant than C. longicollis (Cann, 1998;Burgin, 2006).…”