Arctic Circle level, although in mountainous regions there is often no direct view of the true horizon. Only four million people live north of the Arctic Circle due to the severe climate; nonetheless, some areas have been settled for thousands of years by indigenous peoples, who today make up 10% of the region's population. Tens of thousands of years ago, waves of people migrated from eastern Siberia across the Bering Strait into North America to settle. The largest communities north of the Arctic Circle are situated in Russia, Norway and Sweden: Murmansk (population 307,257), Norilsk (175,365), Tromsø (71,295), Vorkuta (59,231) and Kiruna
Arctic policy of Russia north of the Arctic Circle. Overall, about 10% of the world's petroleum resources are estimated to be in the Arctic. The dominant portion of offshore Arctic hydrocarbon (oil and gas), as reflected in the USGS studies, is located within the current uncontested Exclusive Economic Zones of the five nations bordering the Arctic. In September 2013, Gazprom's oil drilling activities in the Arctic have drawn protests from environmental groups particularly Greenpeace. Greenpeace has opposed oil drilling in the Arctic on the grounds that oil drilling would cause damage to the Arctic ecosystem and that there are no safety plans in place