Drought, fire, and rainforest endemics: A case study of two threatened frogs impacted by Australia's “Black Summer”

Abstract

Deepening droughts and unprecedented wildfires are at the leading edge of climate change. Such events pose an emerging threat to species maladapted to these perturbations, with the potential for steeper declines than may be inferred from the gradual erosion of their climatic niche. This study focused on two species of amphibians—Philoria kundagungan and Philoria richmondensis (Limnodynastidae)—from the Gondwanan rainforests of eastern Australia that were extensively affected by the “Black Summer” megafires of 2019/2020 and the severe drought associated with them. We sought to assess the impact of these perturbations by quantifying the extent of habitat affected by fire, assessing patterns of occurrence and abundance of calling males post‐fire, and comparing post‐fire occurrence and abundance with that observed pre‐fire. Some 30% of potentially suitable habitat for P. kundagungan was fire affected, and 12% for P. richmondensis. Field surveys revealed persistence in some burnt rainforest; however, both species were detected at a higher proportion of unburnt sites. There was a clear negative effect of fire on the probability of site occupancy, abundance and the probability of persistence for P. kundagungan. For P. richmondensis, effects of fire were less evident due to the limited penetration of fire into core habitat; however, occupancy rates and abundance of calling males were depressed during the severe drought that prevailed just prior to the fires, with the reappearance of calling males linked to the degree of rehydration of breeding habitat post‐fire. Our results highlight the possibility that severe negative impacts of climate change for montane rainforest endemics may be felt much sooner than commonly anticipated under a scenario of gradual (decadal‐scale) changes in mean climatic conditions. Instead, the increased rate of severe stochastic events places these narrow range species at a heightened risk of extinction in the near‐term.

Severe wildfires promoted by climate change negatively impact forest amphibian metacommunities

“…watsoni , P. pughi and P. sphagnicola . While wildfire has previously been considered as a threat to all these species in conservation assessments, this has not been previously quantified (except see Heard et al, 2021). We recommend that wildfire and climate change impacts are prioritized in future conservation assessments of these threatened species, especially since they often occur in isolated populations where there may be limited opportunities for postfire recolonization without human assistance (Klop‐Toker et al, 2022; Mahony et al, 2021; Stock et al, 2022).…”

“…Focus has been placed on understanding and predicting the impacts of fire on threatened species (Penman et al, 2015), while little attention has been paid to species that are thought to be common. However, unprecedented weather anomalies driven by climate change may cause sudden and severe contractions in amphibian abundance, recruitment and distribution (Heard et al, 2021; Hossack et al, 2006; Rochester et al, 2010), even for those species buffered by their large population sizes and/or ranges (Beranek et al, 2022). Our analysis shows that amphibian species not currently of conservation concern were negatively impacted by the 2019–2020 fires, including Limnodynastes dumerilii , Lit .…”

Genomic footprints of (pre) colonialism: Population declines in urban and forest túngara frogs coincident with historical human activity

“…These activities had widespread ecological impacts on vegetation and species abundances that persist to this day (Bush et al, 1994;McMichael et al, 2022). Past anthropogenic disturbances may have contributed to the decline of túngara frogs through various direct and indirect ecological impacts such as habitat fragmentation (Andersen et al, 2004;Becker et al, 2010), altered microclimatic conditions (Hoffmann et al, 2021;Kapos, 1989), reduced breeding sites and food availability (Heard et al, 2023) and increased exposure to predators (Denoël et al, 2005). Notably, the observed plateau in the population declines (c. 400-800 ya) corresponds to a period of apparent reduced human activity in this area following a period of intense and recurrent fires linked with agriculture c. 700-1000 ya (McMichael et al, 2022).…”

Bioacoustic Monitoring Reveals the Calling Activity of an Endangered Mountaintop Frog (Philoria kundagungan) in Response to Environmental Conditions

“…For example, extreme droughts have been associated with population declines due to desiccating conditions experienced by amphibians and their egg masses [9], and increasing temperatures have been found to cause physiological stress [10], alter range boundaries [11] and shift the timing of seasonal breeding cycles by up to 76 days [8]. Furthermore, extreme fire events have increased dramatically [12,13] and have started to affect ecosystems where fire has rarely been documented [14][15][16].…”