The Blue Mountains water skink (Eulamprus leuraensis; Scincidae) is restricted to less than 40 fragmented swamp sites, all within the Blue Mountains and Newnes Plateau areas of New South Wales, Australia. Climate change is expected to increase fire frequency in the area, potentially degrading habitat quality for this endangered reptile. We quantified lizard abundances in 12 swamps using standardized surveys, and constructed a Global Information System (GIS) database to determine fire-histories for each swamp since 1967. The abundance of Blue Mountains water skinks was negatively correlated with fire frequency, but not with time since fire. Indirect impacts of fire (mediated via shifts in vegetation density, moisture levels, prey availability and post-fire predation) may be more important than direct effects in these cool, moist habitats. Although lizards were less common in swamps close to urban areas, and less common in frequently burnt areas, viable populations of this endangered reptile still persist even in anthropogenically disturbed swamps and in swamps that have experienced up to four fires in 20 years. Future research could usefully extend these analyses to other swamps in the locality, and explore the broader impacts of fire regimes on the distinctive flora and fauna of this threatened ecological community.

Article impact statement: Early diagnosis of ecosystem collapse can inform risk-reduction strategies to maintain resilience.

Insights into declines in ecosystem resilience, their causes and effects, can inform pre-emptive action to avoid ecosystem collapse and loss of biodiversity, ecosystem services and human well-being. Empirical studies of ecosystem collapse are rare and hampered by ecosystem complexity, non-linear and lagged responses, and interactions across scales. We investigated how an anthropogenic stressor could diminish ecosystem resilience to a recurring perturbation by altering a critical ecosystem driver. We studied groundwater-dependent, peat-accumulating, fire-prone wetlands in southeastern Australia. We hypothesised that underground mining (stressor) reduced resilience of these wetlands to landscape fires (perturbation) by diminishing groundwater, a key ecosystem driver. We monitored soil moisture as an indicator of ecosystem resilience during and after underground mining and, after a landscape fire, we compared the responses of multiple state variables representing ecosystem structure, composition and function in wetlands within the mining footprint to unmined reference wetlands. Soil moisture showed very strong evidence of decline without recovery in mined swamps, but was maintained in reference swamps through eight years. Relative to burnt reference swamps, burnt and mined swamps showed greater loss of peat via substrate combustion, reduced cover, height and biomass of regenerating vegetation, reduced post-fire plant species richness and abundance, altered plant species composition, increased mortality rates of woody plants, reduced post-fire seedling recruitment, and local extinction of a hydrophilc fauna species. Mined swamps therefore showed strong symptoms of post-fire ecosystem collapse, while reference swamps regenerated vigorously. We conclude that an anthropogenic stressor may diminish the resilience of an ecosystem to recurring perturbations, predisposing it to collapse. Avoidance of ecosystem collapse hinges on early diagnosis of mechanisms and preventative risk reduction. It may be possible to delay or ameliorate symptoms of collapse or to restore resilience, but the latter appears unlikely in our study system due to fundamental alteration of a critical ecosystem driver.

The Blue Mountains water skink Eulamprus leuraensis is an Endangered swamp specialist known from ,  sites and restricted to the rare, threatened and fragmented habitat of Temperate Highland Peat Swamps on Sandstone. Understanding the species' ecology, notably its vulnerability to threatening processes such as hydrological disturbance, is essential if we are to retain viable populations of this Endangered reptile. We examined the impact of anthropogenic disturbance (longwall mining practices, development (industrial, urban, infrastructural) and damage by recreational vehicles) on this species, other herpetofauna and the swamp by surveying six paired undisturbed and disturbed sites in south-eastern Australia. The abundance of E. leuraensis was severely affected by disturbance. The species was absent from disturbed swamps, where it was replaced by its congener E. heatwolei and other woodland reptile species. Disturbance was associated with a halving of soil moisture content and a loss of surface water; the dense, live understorey was replaced by a sparser, drier habitat with dead vegetation, logs, rocks and bare ground. In effect, disturbance eliminated the distinctive features of the swamp habitat, transforming it into an area that resembled the surrounding habitat in terms of fauna, flora and physical characteristics. Our surveys suggest that hydrological disturbance (groundwater loss or alterations in surface water chemistry) extirpates E. leuraensis. This species' dependence on groundwater renders it sensitive to habitat degradation through hydrological disturbance. The conservation message for management authorities is clear: to protect the skink, protect the habitat.

The Gospers Mountain Fire was the largest wildfire on record in New South Wales. All of the swamps on the Newnes Plateau were burnt, with some areas experiencing fire of very high severity. Despite this severity, the vegetation in all unmined reference swamps recovered relatively quickly, with substantial vegetation cover and biomass returning within 10 weeks. These swamps retained most of their peat and plant species, and both their surveyed endangered fauna species (Blue Mountains Water Skink Eulamprus leuraensis; Giant Dragonfly Petalura gigantea). This demonstrated the resilience of reference Newnes Plateau Shrub Swamps and their endangered species populations to significant bushfire events. In stark contrast, after the wildfire there was evidence of extensive combustion and oxidization of peat soils in swamps located above the footprint of prior longwall coal mining operations. Populations of endangered species, which were already in significant decline (due to longwall mining impacts on swamp hydrology), are now vulnerable to localised extinctions in these undermined swamps. Mining is ongoing in these areas and failure to protect the remaining Newnes Plateau Shrub Swamps from the hydrological impacts of longwall mining will likely lead to further ecosystem collapse in undermined swamps, and further localised extinctions of endangered species populations in these swamps.