believes that they would likely not become unstoppable (and thus meet the definition of a tipping point) until global warming of around 4 °C. However, the certainty level is still limited and it is possible that 1.5 °C would be sufficient for either tipping point; on the other hand, the southern die-off may not be inevitable until 5 °C, while the replacement of tundra with taiga may require 7.2°C. Once the "right" level of warming is met, either process would take at least 40–50 years to finish, and is more likely to unfold over a century or more. While the southern die-off would involve the loss of around 52 billion tons of carbon, the net result is cooling of around 0.18°C globally and between 0.5°C to 2°C regionally. Likewise, boreal forest expansion into tundra has a net global warming effect of around 0.14°C globally and 0.5°C to 1°C regionally, even though new forest growth captures around 6 billion tons of carbon. In both cases, this is due to the snow-covered ground having a much greater albedo than the forests. Other threats Human activities Some of the larger cities situated in this biome are Murmansk, Arkhangelsk, Yakutsk, Anchorage, Yellowknife, Tromsø, Luleå, and Oulu. Large areas of Siberia's taiga have been harvested for lumber since the collapse of the Soviet Union. Previously, the forest was protected by the restrictions of the Soviet Forest Ministry, but with the collapse of the Union, the restrictions regarding trade with Western nations have vanished. Trees are easy to harvest and sell well, so loggers have begun harvesting Russian taiga evergreen trees for sale to nations previously forbidden by Soviet law. In Canada, only eight percent of the taiga is protected from development, and the provincial governments allows clearcutting to occur on Crown land, which destroys the forest in large blocks. The blocks are replanted with monocrop seedlings in the following season, but the trees do not grow back for many years, and the forest ecosystem is radically changed for hundreds of years. Products from logged boreal forests include toilet paper, copy paper, newsprint, and lumber. More than 90% of boreal forest products from Canada are exported for consumption and processing in the United States. Most companies that harvest in Canadian forests use some certification by agencies such as the Forest Stewardship Council (FSC), Sustainable Forests Initiative (SFI), or the Canadian Standards Association (CSA), in their marketing.