and is known to prefer the cool, shaded streams of hemlock forests during spawning events. Vulnerable animal populations are expected to diminish as a result of loss of hemlock habitat to the invasive hemlock woolly adelgid. One factor giving hope is that the adelgid does not seem able to survive prolonged or bitter cold. Following the winter of 1999-2000, a considerable dieback of adelgids and subsequent regrowth of infested trees was observed across Connecticut. The same phenomenon was repeated after the prolonged winter of 2013-2014, in time to save numerous nearly succumbed forests. A 2009 study conducted by scientists with the U.S. Forest Service Southern Research Station suggests the hemlock woolly adelgid is killing hemlock trees faster than expected in the southern Appalachians, and rapidly altering the carbon cycle of these forests. According to Science Daily, the pest could kill most of the region's hemlock trees within the next decade. According to the study, researchers found "hemlock woolly adelgid infestation is rapidly impacting the carbon cycle in [hemlock] tree stands", and "adelgid-infested hemlock trees in the South are declining much faster than the reported 9-year decline of some infested hemlock trees in the Northeast." In fact, as of 2007, the rate of HWA expansion was recorded as 15.6 km/year south of Pennsylvania and 8.13 km/year (or less) in the northern section of the HWA's range. References External links University of Vermont entomology website Species Profile- Hemlock Woolly Adelgid (Adelges tsugae), National Invasive Species Information Center, United States National Agricultural Library. Lists general information and resources for Hemlock Woolly Adelgid. US Department of Agriculture HWA Tree-Savers, Biological Control for HWA How Was HWA Introduced?: The Gilded Age Garden Hypothesis, How When & Where was HWA introduced to Eastern US? New York State Hemlock Initiative Adelgidae Parasitic bugs Insect pests of temperate forests Conifer pathogens and diseases Insects described in 1928 Insects of Japan