Climate-change impacts on sagebrush habitat and West Nile virus transmission risk and conservation implications for greater sage-grouse

Abstract

Greater sage-grouse (Centrocercus urophasianus) are threatened by loss of sagebrush habitat and the spread of West Nile virus throughout much of their range in North America; yet, future impacts of climate change on these potential stressors have not been addressed. Here, we aim to quantify the potential impacts of climate change on the distribution of climatically suitable habitat for sagebrush and on transmission risk for West Nile virus in the eastern portion of the species' range. We used Maxent to model the current and future climatically suitable habitat for two dominant sagebrush species in the study area, and we used a degree-day model to predict future West Nile virus transmission risk under likely climatechange scenarios. Our models suggest that areas with the highest future suitability for sagebrush habitat will be found in southwestern Wyoming and north-central Montana. The degree-day model suggests that greater sage-grouse in western portions of the study area, which are generally higher in elevation than where West Nile virus currently occurs, will see increasing risk of transmission in the future. We developed a spatially explicit map of suggested management actions based on our predictions that will aid in conservation of the species into the coming decades.

Application of a degree-day model of West Nile virus transmission risk to the East Coast of the United States of America

“…The total number of WNV-positive birds (including crows) and crows collected, the percent of these that are accounted for by the model, and the number of birds collected before the model-predicted onset of the transmission season are shown. California and Montana/Wyoming data from Konrad et al (2009) and Schrag et al (2011), respectively. Fig.…”

“…In Connecticut, a total of nine bird (all crows) early-season deaths were not predicted (also 0.3% of the total birds collected). For comparison, Table 1 includes data from two previous studies: Santa Clara county, California (Konrad et al, 2009) and northern Wyoming/southern Montana (Schrag et al, 2011). In California, two early-season crow deaths were missed out of 339 collected (0.5%), and in Wyoming/ Montana, no early season deaths failed to be predicted.…”

“…Our approach exploits the position and timing of these collected birds, along with local temperatures leading up to the birds' death, the time it takes for birds to die post-infection, and estimates of both mosquito and bird travel distances. We successfully calibrated the model for WNV transmission in Santa Clara county, California (Konrad et al, 2009) and in the northern Rocky Mountains (Schrag et al, 2011), finding that similar parameters worked in both locations independent of mosquito species. Here, we test the calibrated model in eastern USA, using birds collected in South Carolina and Connecticut.…”

“…Model parameters can be determined with captive mosquitoes or using observational data. Previous research has shown that model calibration can be successfully achieved using WNV-killed birds (Konrad et al, 2009;Schrag et al, 2011). Many regional vector control districts have active or historical surveillance programmes for WNV which involve the collection and testing of dead birds.…”

A geographical information system-based web model of arbovirus transmission risk in the continental United States of America

“…A geographical information system (GIS)-based model which uses degree-day (DD) temperatures to identify regions and times of West Nile virus (WNV) transmission risk has been successfully tested in Wyoming, California, Montana, South Carolina and Connecticut (Zou et al, 2007;Konrad et al, 2009;Schrag et al, 2011;Konrad and Miller, 2012b). Here, we adapt the model to a web-platform allowing Internet users the ability to observe risk both in forecast mode and from the viewpoint of historical transmission.…”