Factors influencing the loss of an endangered ecosystem in an urbanising landscape: a case study of native grasslands from Melbourne, Australia

Over the past two decades, the decline and destruction of native grasslands in Australian cities has intensified. In Melbourne, large remnants of this endangered vegetation type have been subdivided and destroyed by urban development while linear reserves are being degraded by changes to management practices. To analyse fragmentation patterns we developed a temporal dataset spanning the period 1985-2000 that recorded the extent and distribution of native grassland patches in western Melbourne. Of the 7230 ha of native grassland present in 1985, 1670 ha (23%) were destroyed by development and 1469 ha (21%) were degraded to non-native grassland by 2000. There were fewer patches and greater distance between patches in 2000 than in 1985, indicating that fragmentation has intensified. Logistic regression models were used to determine the probabilities that a patch would be destroyed, degraded or remain as native grassland. Patches that were privately or government owned, close to major roads and close to Melbourne were more likely to be destroyed while patches close to streams or on railway land had a lower probability of destruction. Patches with high perimeter to area ratios had a higher probability of being degraded. Biological significance ranking was also an important explanatory variable determining patch fate but areas of higher significance were not necessarily preserved. The preservation and ecological management of grasslands in Australia is a high conservation priority and utilising landscape and societal based predictors of threat can help set priorities for the protection and management of sites.