Jiuzhaigou National Park, known for its clear, colorful lakes, has branded tourists who use underwater cameras “uncivilized,” citing fears that their behavior may disturb the area’s fragile ecosystem.

The UNESCO World Heritage Site in southwestern China’s Sichuan province published a statement on its Weibo microblog on Thursday in which it “strongly condemned” tourists who use their photography equipment underwater. It also reminded visitors of signs in the park that say people are banned from touching the water in any way.

The park later explained in another Weibo post why it is forbidden to step into the lakes and take underwater footage. Man-made objects, the park’s account wrote, bring irreparable harm to the calcium deposits in Jiuzhaigou’s lakes, which are responsible for the water’s turquoise color and only grow 1 millimeter per year. Foreign objects may also cause eutrophication — an excess of nutrients — and disturb the sensitive ecosystem, and if any batteries were to end up in the water, they would cause severe contamination, the post explained.

Earlier in the day, a Weibo user had uploaded two 10-second videos of the underwater world of Jiuzhaigou: schools of fish swimming in the crystal-clear water, with tree trunks and branches scattered across the lake bed. The videos soon elicited angry comments from fellow net users.

“The videos are actually shot by a person who attended my university — he posted the videos on his WeChat Moments [social news feed],” Elsa Wang, the video’s uploader, told Sixth Tone. “I posted the video and tagged the [park’s] official account, hoping they could tell tourists to take pictures without harming the environment.”

Wang said that according to the person who made the videos, no one in Jiuzhaigou stopped him when he made the footage. Both the original videos and Wang’s post have since been deleted.

“This is the first time we’ve encountered tourists taking underwater videos,” an employee surnamed He from the park’s tourism and marketing department told Sixth Tone. “Before, they didn’t have these special cameras.” An online search returned footage taken in 2013 of a man testing a smartphone’s underwater capabilities in one of Jiuzhaigou’s lakes.

The park officially opened to tourists in 1984 and became a UNESCO World Heritage Site in 1992. Some are concerned that the steeply increasing number of visitors will harm the reserve’s environment. More than 5 million people visited the park in 2016, up from fewer than 1 million in 2000 and fewer than 100,000 in the 1980s.

Contributions: Wang Yiwei; editor: Kevin Schoenmakers.

(Header image: A view of a lake at the Jiuzhaigou nature reserve and national park in Sichuan province, July 20, 2007. Wang Zheng/VCG)