Taking Nature's Pulse - Biodiversity BC

a primer on biodiversityVegetation zones were displaced southward and to lower elevations (by 400–500 m). In the northwestern UnitedStates, mixed conifer forest alternated in time and space with open ecosystems, dominated by sagebrush(Artemisia spp.) and pines (Pinus spp.) in the interior. 69In B.C., extensive subalpine spruce (Picea spp.) and mountain hemlock (Tsuga mertensiana) forests andparkland prevailed between about 48,000 and 30,000 years ago. 70,71 Wetlands seem to have occurred widely andrivers and lakes may have had relatively high sediment loads.Cold, dry glacial conditions developed across North America, from the north to the mid continent, about30,000 years ago and intensified to about 20,000 years ago. Steppe ecosystems, including elements of the widespreadmegafauna, such as woolly mammoths (Mammuthus primigenius), seem to have prevailed. 72,73 Currenthigh-elevation alpine species, such as Sitka valerian (Valeriana sitchensis) and American bistort (Polygonumbistortoides), 74 grew at sea level. 75 Large glaciers occupied major valleys and fed unstable stream and river systemsthat transported masses of sediment at their leading edges. A brief respite from these glacial conditionsoccurred 17,000 to 18,000 years ago when subalpine-like forest returned (at least in southwestern B.C.), beforethe next intense glaciation began about 15,000 year ago. 76 During that short interval, salmonids were found inunglaciated areas such as the Thompson Valley. 771.4.3 the glacial maximum: 17,000 to 14,000 years agoThe traditional view is that almost all of B.C. was ice-covered during this last glaciation and that B.C.’s terrestrialbiodiversity originated with the subsequent migration of species from the south, east and north. From thisperspective, B.C.’s biodiversity is a regional variation on evolutionary themes largely developed elsewhere. Toa considerable extent this is true. However, recent research, especially DNA studies, suggest that unglaciatedzones, or refugia, in B.C. were larger than previously thought and that elements of the province’s biodiversityhave a long pre-glacial history. 78The most widely recognized B.C. refugia are high-elevation sites and some adjacent slopes on Haida Gwaii/Queen Charlotte Islands and the Brooks Peninsula on Vancouver Island. 79,80 In these areas, alpine and probablyhigh-elevation, cool oceanic ecosystems persisted, resulting in a unique set of plant species and subspecificlineages endemic to the region.DNA studies of mountain sorrel (Oxyria digyna), a globally widespread alpine plant, also suggest therewere ice-free zones for alpine species in northern B.C., possibly with connections to Beringia. 81 These studiesalso confirm the presence of refugia on the north coast. Although it is not known to what extent low-elevationWoolly mammoths (Mammuthusprimigenius) roamed widely in B.C.and adjacent regions in the latePleistocene Epoch, but went extinctwith the warming climate about 10,000years ago.photo: andrew niemann,royal british columbia museum.