Eastern forests are currently undergoing dramatic shifts in composition, structure, and function as a result of the invasive insect, the hemlock woolly adelgid (Adelges tsugae, HWA). This invasive pest is causing widespread mortality in eastern hemlock (Tsuga canadensis (L.) Carrière). Without any resistance, eastern hemlock is experiencing widespread mortality throughout its range, which extends from the southern Appalachians to the northeast. This disturbance is a particular concern because eastern hemlock has been identified as a foundation species, which defines the ecosystem properties and microclimate of its community, providing habitat for a unique suite of species. As mortality expands, vast areas, including vital riparian forests adjacent to headwater streams, are experiencing large-scale transitions with implications for ecosystem dynamics at fine and landscape scales. These transitions will vary across regions. In particular, current understanding indicates HWA impacts are exacerbated in warmer southern regions with accelerated rates of spread and mortality. In northern areas of New England, the Lake States, and Canada, HWA is thought to be constrained by winter temperatures. However, future climate models indicate that only the northern most areas of hemlock’s US range will experience mimimum winter cold below HWA’s critical threshold. There is also concern that HWA is developing greater cold tolerance at the northern edge of its range. Thus, combining data from forests that across the range and invasion chronosequence will allow development of macro-scale understanding prior to further advancement of the northern front. Our proposed session brings together researchers from across the range of eastern hemlock, from the northeast to the central and southern Appalachians. At the same time, our speaker list combines researchers with years of hemlock data and expertise with investigators who have more recently incorporated HWA-related questions in their research. We have also targeted presentations on scales from tree physiology to remote sensing. The session should serve as a platform for speakers and ESA members to engage in discussion and synthesis of the widespread forest change resulting from HWA. Greater understanding will contribute to improved reality in modeling and contribute to forest management, conservation, and restoration planning. Hemlock mortality is both a regional concern throughout the east, as well as a local concern for Pittsburgh and western Pennsylvania.