Taking Nature's Pulse - Biodiversity BC

a primer on biodiversityThese animals clearly influenced the ecological processes, structure and composition of plant communities. Inaddition, a new species – humans – began to depend upon and influence B.C.’s evolving biological diversity.In the freshwater realm, a degree of stability returned as the land was stabilized by vegetation. Familiar ecosystems,such as cattail (Typha spp.) and bulrush (e.g., Scirpus spp.) marshes and shallow-water communities,developed widely. Lime-rich, marl-depositing ecosystems occurred widely on parts of the south coast and inthe southern interior. The marine zone was, however, much less stable because of sediment input from waningvalley glaciers and the invasion of salt water on a glacially depressed landscape. Diverse cold-water molluscfaunas predominated. 92Between 11,000 and 10,000 years ago, a brief, but profound cooling event (called the Younger Dryas in Europe),brought cold, dry conditions for about 500 years and widely disrupted the landscape. 93 Temperatures declinedover a few decades by as much as 5°C and cold-climate processes such as solifluction (the slow, downslopemovement of moist or saturated, seasonally frozen, surficial material and soil) disturbed the landscape as farsouth as Vancouver Island. 94 There was widespread forest loss and return of cold and unstable ecosystems, creatingalder (Alnus spp.) scrub along the coast. 95 Migration and extinction of the ice-age megafauna took placeglobally. As far as scientists know, none of the megafauna survived the dramatic climatic and ecological changesinto the Holocene Epoch and non-glacial climates in B.C., 96 as hunting by humans hastened the disappearanceof these species. 97Skull of the now-extinct giant bison(Bison antiquus) from the SaanichPeninsula on Vancouver Island, about12,000 years ago.photo: andrew niemann,royal british columbia museum.1.4.5 warm dry early holocene epoch: 10,000 to 7,000 years agoAround the world, rapid warming by as much as 5–8°C ushered in the warm, interglacial climates of the modernHolocene Epoch. This period of roughly 10,000 years can be broadly divided into three climatic intervals, duringwhich B.C.’s pre-European disturbance biodiversity arose: warm, relatively dry (from 10,000 to 7,000 years ago);warm, moist (from 7,000 to 4,000 years ago); and moderate, moist (from 4,000 years ago to the present). 98The warm, dry early Holocene was a time of rapid immigration of species and establishment of newecosystems in many regions under climates warmer than today. On the south coast, Douglas-fir (Pseudotsugamenziesii) spread widely and rapidly to dominate forests and woodlands well into the zone of today’scedar-hemlock forests. 99 In the moist climates of western Vancouver Island and the central and north coast,Sitka spruce combined with western hemlock (Tsuga heterophylla) to form an ecosystem that has no modernequivalent in B.C. 100