Holocene

These "megafauna" lived in an austere landscape of shrub-steppe grassland and boreal forests of spruce and pine around the edges of the retreating glaciers. The Holocene is generally considered to be the last 10,000 years, but the transition from the Pleistocene was gradual, lasting many thousands of years. Pielou (1991) described this period in her book, After the Ice Age: Return of life to North America. Huge lakes filled valleys dammed by glacial moraines, or by giant chunks of ice. Their ancient shorelines, perched on slopes high above current valley bottoms, can be seen today in places like Castlegar, and many parts of the Rocky Mountain Trench. Later the soft earth or ice dams eroded, spilling the lakes - often catastrophically.

This was the environment that the first humans of the regions found. People were in South America by at least 20,000 years ago, and must have come from Siberia through Alaska. The first positive anthropological sites in North America occurred about 12,500 years ago, when humans were hunting mammoths, mastodons, caribou and giant bison around the Strait of Georgia as the glaciers from the last Ice Age retreated from the rest of the province (Pielou, 1991; Ludvigsen, 1996). People in the southern Interior shared with other peoples throughout North America a culture characterized by a "Clovis point," a crude stone spear tip suitable for killing the abundant woolly mammoth and other large, slow-moving herbivores (Carlson, 1989). When the megafauna went extinct, not long after people arrived, they adopted a more refined, fluted arrow tip designed for hunting bison and other smaller, swifter game. Temperate forests of Douglas-fir advanced from the south and thrived, while shrub-heather ecosystems followed the glaciers north and to the tops of mountains. From 7,000 to 4,000 years ago, grassland and sagebrush plant communities shrank. Lakes expanded, and the landscape took on an appearance much as it is today. By that time, the main First Nations cultures were well established and quite diverse.

Several millennia later and some degrees cooler, fir forests diversified with cedar and hemlock in moist interior mountains and, later still, ponderosa pines in the drier parts of the Columbia Basin. Although fossil salmon are known from 18,000 years ago in the Thompson River system , which was linked at that time to the Columbia system through the Okanagan Valley, the flowering of interior salmon-based cultures, along with population expansion and development of permanent villages, did not occur until about 3,500 years ago. With the establishment of permanent villages, the region entered a period of cultural as well as ecological stability. River people extended technology and traditions linked to the annual cycle of salmon. The Kootenai grew tobacco for trade and, with horses descended from those of Spanish conquistadors, led military and hunting expeditions across the Rockies to the Great Plains. These First Nations were consequently well-positioned to welcome, guide and protect the next wave of immigrants, mainly from Europe and Asia, during the last two centuries. These newcomers, however, brought more ecological changes: exotic species, livestock grazing, commercial forestry, and river impoundments. The ecosystems in British Columbia today are a result of these geological, climatic, evolutionary and social events, and they are still changing.