MODELLING SPECIES DISTRIBUTION & CLIMATE CHANGE NICHE RESPONSE OF TARICHA GRANULOSA

Abstract

Amphibians are highly valued as bio-indicators of ecosystem health due to their sensitivity to environmental changes, with population and range being a key identifier for North American freshwater biomes. In this study, we use Maxent and several GIS programs to model present day distribution of Taricha granulosa, the rough skin newt, as well as predict habitat niche changes in 2050 and 2070 under climate schemes RCP 4.5 and 8.5 in the Pacific Northwest region. We used more than 11000 volunteer contributed newt observation records as well as several environmental bioclimatic variable layers such as annual mean temperature, minimum and maximum temperature, elevation, and mean precipitation. We found that in our study area, suitable newt habitats (suitability score >0.7) currently occupies only 4.6% of the total area. Under both climate change pathway prediction models, suitable habitat area doubles by the year 2050 to >9% before settling at around 8% in 2070, though overall the degree of suitability somewhat drops. When accounting for land use types and urban human activity, we calculate that instead of a 100% increase in habitat area, the growth in Washington and Oregon will be only 11%, suggesting that conservation activity may be required in the future.