Geology topics

Hector Gadsden

Publications and source records attributed to Hector Gadsden.

2 recordsLinked to original sources

USGS2024

Climate change and collapsing thermal niches of desert reptiles and amphibians: Assisted migration and acclimation rescue from extirpation

Recent climate change should result in expansion of species to northern or high elevation range margins, and contraction at southern and low elevation margins in the northern hemisphere, because of local extirpations or range shifts or both. We combined museum occurrence records from both the continental U.S. and Mexico with a new eco-physiological model of extinction developed for lizard families of the world to predict the distributions of 30 desert-endemic reptile and amphibian species under climate change scenarios. The model predicts that 38 % of local populations will go extinct in the next 50 years, across all 30 species. However, extinctions may be attenuated in forested sites and by the presence of montane environments in contemporary ranges. Of the 30 species, three were at very high risk of extinction as a result of their thermal limits being exceeded, which illustrates the predictive value of ecophysiological modeling approaches for conservation studies. In tandem with global strategies of limiting CO2 emissions, we propose urgent regional management strategies for existing and new reserves that are targeted at three species: Barred Tiger Salamander (Ambystomatidae: Ambystoma mavortium stebbinsi), Desert Short-horned Lizard (Phrynosomatidae: Phrynosoma ornatissimum), and Morafka's Desert Tortoise (Testudinidae: Gopherus morafkai), which face a high risk of extinction by 2070. These strategies focus on assisted migration and preservation within climatic refugia, such as high-elevation and forested habitats. We forecast where new reserves should be established by merging our model of extinction risk with gap analysis. We also highlight that acclimation (i.e., phenotypic plasticity) could ameliorate risk of extinction but is rarely included in ecophysiological models. We use Ambystoma salamanders to show how acclimation can be incorporated into such models of extinction risk.

Science of the Total Environment↗

USGS2017

Climate change and collapsing thermal niches of Mexican endemic reptiles

Recent climate change should result in expansion of species to northern or high elevation range margins, and contraction at southern and low elevation margins due to extinction. Climate models predict dramatic extinctions and distributional shifts in the next century, but there are few ground-truths of these dire forecasts leading to uncertainty in predicting extinctions due to climate change. Previously, we reported on recent extinctions of Mexican Sceloporus lizards by comparing recent surveys to historical distributional records for 48 species at 200 sites. We also ground-truthed extinctions on five continents across 8 lizard families by comparing observed and predicted extinctions from an eco-physiological species distribution model and obtained a high R 2 of 0.72 (1, 2). Here, we derive more detailed predictions for 15 terrestrial reptile families and 142 species for the Mexican and California Biogeographic provinces using all known museum occurrence records, and detailed measures on eco-physiology. We adopt the eco-physiological model of extinction developed earlier but use a species-specific model. We predict massive and rapid extinctions of 22% of the reptile populations in Mexico within the next 50 years. We also predict that 3 of 15 reptile families, all three endemic to the Mexican and Californian biogeographic provinces, will go extinct by 2070, the hallmark of the beginnings of a mass extinction event. However, extinctions may be attenuated by forest cover and by presence of montane environments in contemporary ranges. We describe impacts of altitude on three species (Gopherus morafkai, G. evgoodei, and Gambelia sila) to illustrate regional management strategies (AZ-Mexico, Sinoloa, CA) for reserves in tandem with global strategies of CO2 limits that might limit climate impacts. By carefully selecting new montane preserves adjacent to desert and tropical forest habitats, and by implementing global controls on atmospheric CO2 emissions, extinctions may be reduced to less than 11% of species and only a single reptile family.

Report↗