The International Union for the Conservation of Nature (IUCN) has proposed a standard global assessment protocol for the evaluation of conservation risks to ecosystems. The assessment criteria mirror the IUCN protocol for the assessment of species, however there are relatively few case studies available to demonstrate their utility across a broad range of ecosystems. We applied the IUCN protocol to assess the conservation status of the Cumberland Plain Woodland (CPW) located in the western suburbs of Sydney, Australia. The ecosystem has been the focus of extensive survey and research and has been determined to be critically endangered under NSW and Australian Government legislation, primarily as a consequence of its history of extensive clearing. The outcome of the risk assessment for CPW using the IUCN protocol was identical to those under the NSW and Australian legislation. Data for risk assessment fell into two categories, each with different limitations. Phytosocialogical data and distribution models provided a strong basis for quantifying past and future changes in the distribution of CPW, but offered only indirect measures of functional symptoms of decline. Conversely, local case studies documenting declines in ecosystem function due to weed invasion, soil disturbance and alteration of fire regimes could not easily be extrapolated in order to evaluate the assessment criteria. The critically endangered rating was based solely on the historic reduction in geographic distribution (92-94%), however clearing poses an ongoing threat to the ecosystem. The contemporary clearing rate of CPW is approximately half the historical average but there is evidence that the rate will double in the next decade as a consequence of ongoing urbanisation and Government policy of biodiversity offsets. A systematic approach to documenting the extent of environmental degradation and disruption to biotic processes would assist the assessment of CPW and other ecosystems against the IUCN criteria.