Evaluating the spatial distribution of endangered frogs in Northern Queensland and the threats to their continued survival

Evaluating the spatial distribution of endangered frogs in Northern Queensland and the threats to their continued survival

The conservation of threatened species is hampered in the absence of fundamental ecological information, such as species’ abundance and distribution. The aim of this study is to determine the spatial distribution of four species of critically endangered frogs in order to clarify their conservation status and determine potential threats to their distribution. These species are: Litoria lorica, Litoria nyakalensis, Taudactylus acutirostris and Taudactylus rheophilus. These frogs have large knowledge gaps relating to their preferred habitat, factors that affect distribution, current distribution and threats, undermining effective conservation strategies. This study used both climatic and environmental variables, combined with the historical, verified sightings of these frogs to determine potential, suitable habitat. The variables used include land use, land cover, precipitation, temperature variables, elevation and distance to water sources. These were preprocessed using ArcGIS and run through MaxEnt to generate species distribution models. The distribution models were mapped using ArcGIS and the suitability of this habitat was shown as “not suitable”, “low suitability”, “moderate suitability” and “high suitability” with a tabulation of the hectares and variables that influence this distribution. These models show that there are significant areas of high suitability habitat remaining for each species with 164,302 hectares (9.2% of the total area) for Litoria lorica, 93,179 hectares (5.2%) for Litoria nyakalensis, 82,840 hectares (4.7%) for Taudactylus acutirostris and 252,481 (14.2%) hectares for Taudactylus rheophilus. The data was validated using the Area Under the ROC (Receiver Operating Characteristics) Curve (AUC). The average AUC was 0.76 giving a high degree of confidence in the accuracy of the model outputs. The future climate models show that by 2040 the amount of habitat that is suitable, specifically highly suitable, will have decreased to 128,641 hectares for Litoria lorica (2%) in 2040, 91,787 hectares for Litoria nyakalensis (0.1%), 81,492 for Taudactylus acutirostris (0.1%) and increased to 304,153 (2.9%) hectares for Taudactylus rheophilus. This is possibly due to the climatic conditions changing to suit the optimal conditions for Taudactylus rheophilus. In 2080, this trend continues to the point where there is very little suitable habitat within the Wet Tropics for any of these species and therefore it is obvious that significant measures need to be implemented in order to mitigate the effects of climate change to save these species.

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