Modeling the impact of hemlock woolly adelgid under several climate change scenarios

Abstract

The hemlock woolly adelgid (Adelges tsugae), or HWA, is a species of insect invasive to eastern North America that has caused significant mortality amongst its hemlock (Tsuga spp.) hosts. Survivorship and subsequent population expansion of the HWA is theorized to be limited primarily by minimum winter temperatures. As climate change reduces the severity and cold periods of winter, the potential for a northward expansion of the HWA is introduced. This study utilized maximum entropy modeling (MaxEnt) in conjunction with an iNaturalist citizen-science occurrence dataset via the Global Biodiversity Information Facility (GBIF) and WorldClim (HadGEM3) downscaled climate projection data to model habitat suitability for the HWA throughout eastern hemlock’s (Tsuga canadensis) range. In addition to a historic conditions baseline, species distribution models were generated using SSP 126, SSP 245, and SSP 585 emissions scenarios for mid-century (2041-2060) and late-century (2081-2100) climate change scenarios. The results showed that under a low emissions SSP 126 scenario, the HWA will be capable of inhabiting almost the entirety of the eastern hemlock’s current range by the end of the century. More extreme SSP 245 and SSP 585 warming scenarios resulted in a more rapid northwards shift in suitable habitat, encompassing the entire range of eastern hemlock by the middle of the century. The consequences for eastern hemlock are significant, with HWA infestations likely to become more widespread and severe due to climate change.