Are we in the midst of the sixth mass extinction? A view from the world of amphibians

Abstract

Many scientists argue that we are either entering or in the midst of the sixth great mass extinction. Intense human pressure, both direct and indirect, is having profound effects on natural environments. The amphibians-frogs, salamanders, and caecilians-may be the only major group currently at risk globally. A detailed worldwide assessment and subsequent updates show that onethird or more of the 6,300 species are threatened with extinction. This trend is likely to accelerate because most amphibians occur in the tropics and have small geographic ranges that make them susceptible to extinction. The increasing pressure from habitat destruction and climate change is likely to have major impacts on narrowly adapted and distributed species. We show that salamanders on tropical mountains are particularly at risk. A new and significant threat to amphibians is a virulent, emerging infectious disease, chytridiomycosis, which appears to be globally distributed, and its effects may be exacerbated by global warming. This disease, which is caused by a fungal pathogen and implicated in serious declines and extinctions of >200 species of amphibians, poses the greatest threat to biodiversity of any known disease. Our data for frogs in the Sierra Nevada of California show that the fungus is having a devastating impact on native species, already weakened by the effects of pollution and introduced predators. A general message from amphibians is that we may have little time to stave off a potential mass extinction.chytridiomycosis ͉ climate change ͉ population declines ͉ Batrachochytrium dendrobatidis ͉ emerging disease

Reconsidering the Loss of Evolutionary History: How Does Non-random Extinction Prune the Tree-of-Life?

“…Taxonomic groups are not, however, equally at risk of extinction. Among terrestrial vertebrates, amphibians have the highest proportion at at-risk species, with at least a third of ~6600 known amphibians threatened with extinction (Wake and Vredenburg 2008 ). It is estimated that 12 % and 20 % of continental birds and mammals, respectively, have already been lost (Wilson 1992 ), but with a higher rate of loss observed on islands (Lohle and Eschenbach 2011 ).…”

Evidence that climate sets the lower elevation range limit in a high‐elevation endemic salamander

“…Both temperature and relative humidity control distribution patterns for salamanders in the genus Plethodon (Bernardo & Spotila, 2006; Kozak & Wiens, 2010), which rely on cutaneous moisture for respiration and whose activity is related to temporal and spatial patterns of cool and moist microhabitats (Feder, 1983). Typical of this family of salamanders, the federally endangered Shenandoah salamander ( Plethodon shenandoah ; Highton & Worthington, 1967) is thought to be restricted to talus habitat on elevations above 900 m along the western slopes of the Blue Ridge Mountains in Shenandoah National Park (Jaeger, 1980); if this lower distribution limit is determined by climate variables, it is likely to be unstable given climate change forecasts (Richardson, Denny, Siccama, & Lee, 2003; Wake & Vredenburg, 2008; Walls, 2009). Unlike more widespread species, the small range of this species may afford little chance for local adaptation as there would be little variation in response to climate across the range (Rehm et al., 2015).…”

The Capricorn Eddy: a prominent driver of the ecology and future of the southern Great Barrier Reef

“…The rapidity with which these environmental changes have occurred appears to have exceeded the ability for biologic systems to keep up through changes in distribution and genetic structure. If current rates of change in atmospheric carbon dioxide are not reduced, many analysts predict widespread species extinction and ecosystem collapse (Myers and Knoll 2001;Veron 2008;Wake and Vredenburg 2008).…”