The impact of industrial fluoride fallout on faunal succession following sand mining of dry sclerophyll forest at Tomago, NSW.—I. Lizard recolonisation

Abstract

This study examines the response of lizards recolonising dry sclerophyll forest following sand mining, to the added impact of fluoride fallout from an aluminium smelter. Pitfall trapping was used to survey a chronosequence of sites at three, eight and 20 years post-mining. Three nominal levels of fluoride contamination were selected: background, low and high. Six lizard species were captured: Ctenotus robustus, Ctenotus taeniolatus, Amphibolurus muricatus, Carlia tetradactyla, Lampropholis guichenoti and Lampropholis delicata. There was little evidence of fluoride fallout having a direct toxic effect on lizards. Lizard species appeared to respond to changes in vegetation structure as a function of both fluoride contamination and regeneration age since mining so that their species-specific life history requirements were met. Ctenotus robustus was the first colonising species at three and eight years post-mining and was associated with open habitats at high and background fluoride levels. At low fluoride levels, lizard succession appeared to be accelerated at three and eight years post-mining. This was denoted by an increase in the abundance of Ct. taeniolatus and A. muricatus relative to Ct. robustus and is attributed to “low” levels of fluoride increasing the growth of understorey vegetation. By 20 years regeneration age, trees were well established. Regression analyses showed canopy cover to explain 60% and 55% of the variance in L. delicata abundance and biomass, respectively. At low fluoride levels, a reduction of canopy cover, attributed to fluoride fallout and the absence of L. delicata, suggests that fluoride fallout retards the succession of lizard species. The additional disturbance associated with fluoride fallout appears to alter the trajectory for lizard species succession following sand mining and may in the long term, increase the time taken for the lizard community to resemble the predisturbance state. Fluoride-mediated habitat change appears to be an important factor affecting vertebrate communities near sources of fluoride emissions.