Amphibians in the climate vise: loss and restoration of resilience of montane wetland ecosystems in the western US

Abstract

Wetlands in the remote mountains of the western US have undergone two massive ecological “experiments” spanning the 20th century. Beginning in the late 1800s and expanding after World War II, fish and wildlife managers intentionally introduced millions of predatory trout (primarily Oncorhynchus spp) into fishless mountain ponds and lakes across the western states. These new top predators, which now occupy 95% of large mountain lakes, have limited the habitat distributions of native frogs, salamanders, and wetland invertebrates to smaller, more ephemeral ponds where trout do not survive. Now a second “experiment” – anthropogenic climate change – threatens to eliminate many of these ephemeral habitats and shorten wetland hydroperiods. Caught between climate‐induced habitat loss and predation from introduced fish, native mountain lake fauna of the western US – especially amphibians – are at risk of extirpation. Targeted fish removals, guided by models of how wetlands will change under future climate scenarios, provide innovative strategies for restoring resilience of wetland ecosystems to climate change.

Fish reduce anuran abundance and decrease herpetofaunal species richness in wetlands

“…This assumption was supported by concurrent dip‐netting efforts and surveys of anuran calls, which found similar trends in species composition (J. D. Holbrook, A. P. Berman, and D. Filipiak, unpublished). Although this was an observational study, the evidence for predatory impacts of fish on aquatic amphibians is supported by experiments (Smith et al ., ; Baber & Babbitt, ), observations of fish introductions (Segev et al ., ) and other observational studies (Skelly, ; Babbitt & Tanner, ; Ryan et al ., ). The community‐level differences observed in our wetlands suggested that all anurans were sensitive to fish to some extent.…”

Do geographically isolated wetlands influence landscape functions?

“…Frequent dry conditions and the absence of persistent surface connectivity can preclude fish population establishment or recruitment after extirpation (35,125). Fish preclusion has implications for survival of juvenile amphibian, crustacean, and insect fauna (32,(126)(127)(128), many of which disperse as adults to upland habitats or downstream water bodies. Indeed, models predict that loss of GIW habitats would impact a wide array of fauna, not just permanent residents, and most prominently, turtles, amphibians, birds, and small mammals (36), many of which are imperiled (38).…”

Is green infrastructure an effective climate adaptation strategy for conserving biodiversity? A case study with the great crested newt

“…zero recruitment (Arntzen and Teunis 1993;Griffiths andWilliams 2000, 2001;Ryan et al 2014). Pond desiccation may also be beneficial to amphibians as it can periodically eliminate predators (Adams 2000;Ryan et al 2014). However, irrespective of predation pressure, desiccation before the juveniles are ready to leave the pond is detrimental for recruitment.…”

“…However, irrespective of predation pressure, desiccation before the juveniles are ready to leave the pond is detrimental for recruitment. It is this effect of early desiccation on recruitment, which can be enhanced by climate change as shown by Ryan et al (2014), that is relevant to consider here. The probability of pond desiccation was assumed to depend on a combination of the accumulated water deficit, and the ground water level at the pond's location.…”