Outdoors enthusiasts have expressed concern that alpine sports venues might be built inside a nature reserve in suburban Beijing after the city was named host of the 2022 Winter Olympics. Construction of the sites and future snow-making, they say, could damage an important "ecological barrier" that helps Beijing - a victim of chronic air pollution - ward off sandstorms. While the celebration of Beijing's victory in bidding for the Winter Games was still underway on the weekend, hikers in Beijing waved goodbye in online forums to one of their favourite sites: the Haituo mountain range that straddles the city's border with Hebei province. The range comprises two peaks - Da (Big) Haituo and Xiao (Little) Haituo. Those concerned about the project found in official bidding documents that the 2,198-metre high Xiao Haituo, in Beijing's Yanqing county, was the preferred site for downhill skiing events for the Games. Trails for sledding events will be built lower down, at about the 1,000 metre mark. An assessment by the International Olympic Committee last year said the venues and the Olympic Village at Yanqing would be "adjacent to the 4,600 hectare Songshan National Nature Reserve" and is part of the same mountain ecosystem with nearby ranges. "This would impose a number of environmental requirements that would have to be taken into consideration during the detailed planning phase," the assessment, which includes two photos, reads. But the hikers were quick to discover some of the sites would be built inside the Songshan nature reserve, one of Beijing's two national nature reserves, after comparing IOC photos, satellite images and official geological positions of the reserve. Their online posts with detailed information were relayed over the weekend on major social media sites. Many internet users questioned why the Olympic venues had to be built inside a nature reserve. But the posts were later deleted by censors. Songshan nature reserve had "the best-preserved ecological system" in Beijing's northwest, and played an important role in conserving water resources, warding off wind and sand, and purifying the air, according to the reserve's official website. A frequent hiker surnamed Guo said the mountains offered unique views at different altitudes because of the area's rich biodiversity. "But we may not be able to see the same Haituo if winter sports venues are built there," he said. Building ski trails will involve removing trees and grading the land into suitable runs, while intensive snow-making - the area receives an average snow depth of only 5cm - will cause damage to soil and vegetation, according to previous studies. While the Beijing Olympic Committee could not be reached for comment, a Songshan reserve employee said by phone that it would be closed to all visitors from October 15 "in preparation for the Winter Olympics", but refused to say whether venues would be built within the reserve. A Xinhua video report in February 2014 said the Songshan reserve would host the skiing and sledding events if Beijing's bid for the Games was successful. Annie Zhu, a Beijing-based environmental consultant and frequent hiker, said "the authorities need to know that the world is watching the country's green promises for such iconic events".