When an unmanned camera captured movement inside the demilitarised zone (DMZ) that separates North and South Korea, it wasn’t a sign of troops on the march. Instead, photographs released this week show a rare black bear clambering on rocks next to a peaceful stream.

The animal has been identified as an Asiatic black bear, a species that is native to parts of Asia including the Korean peninsula and is classified as “vulnerable” on the Red List of Threatened Species compiled by the International Union for Conservation of Nature.

Experts say the discovery underlines the ecological importance of a region that is largely cut off from human observation because of landmines and long-running tensions between the two Koreas.

In South Korea, the Asiatic black bear was nearly eradicated before the government launched a recovery programme 15 years ago. The number of these bears in South Korea has increased from five in 2001 to 61 now, according to figures cited by the Yonhap news agency.

Information about the status of threatened species within the DMZ, however, is harder to collect.

“The ecological value of the Korean DMZ has been documented for several decades as many scientists in Korea and from around the world have researched the region,” explains Seung-ho Lee, the president of the DMZ Forum, a group that campaigns to protect the area’s ecosystem.

“But it has been mostly speculation based on the research in the CCZ [civilian control zone] because of an estimated 2m landmines in the DMZ.” The CCZ is an extra buffer zone on the South Korean side of the DMZ, largely off limits to civilians.

In an email interview with the Guardian, Lee describes the bear images as “very significant” as they are “evidence of the unique ecological value of the DMZ that has been cut from human contact for nearly 66 years since the Korean war armistice in 1953”.

About five years ago, South Korea’s National Institute of Ecology installed more than 90 cameras throughout the DMZ, which is about 250km (155 miles) long and 4km wide and dominated by forests and grasslands. The devices automatically take photos when a heat sensor detects the movement of a potential animal. One of these captured the image of the Asiatic black bear in the eastern section of the DMZ in October last year, leading to the release of the image by the South Korean environment ministry this week.

Ministry officials estimated the bear was about eight or nine months old and weighed 25-35kg (55-77lb) when the photograph was taken, Yonhap reported. It said officials believed the bear was “a descendant of the Asiatic black bears who had inhabited the DMZ region for quite a long time” and that the DMZ was home to at least three of the creatures including the two parents.

The lack of human activity and development has provided a unique environment for wildlife, according to the environment ministry, which has previously said the DMZ is inhabited by 5,097 species, including about 106 protected species.

Rare residents include the red-crowned crane and black-faced spoonbill.

Lee says the DMZ is also home to lynx, leopards, a type of sheep known as the Amur goral, and 18 endemic fish species, while there have been reports of tigers in the region.

The DMZ Forum, based in New York, has long called for Unesco to designate the eastern part of the DMZ, between Mount Kumgang in North Korea and Mount Seorak in South Korea, as a World Heritage Site. The two Koreas would need to work together to seek the listing, which Lee believes would help preserve the area’s biodiversity and lead to sustainable ecotourism.

But regional tensions have flared over the past week as North Korea conducted a series of weapons tests, including the launch of two projectiles on Thursday that the South Korean military assessed to be short-range missiles.

Asked about threats to endangered species in the DMZ, Lee highlights how increased military tension and deeper economic cooperation between Pyongyang and Seoul would each present challenges.

“Of course, the major threat is another war between the two Koreas; but ironically a major threat also comes from peace between the two Koreas that are willing to sacrifice the nature for development of their economy by linking rail and roads through the DMZ,” he says.

“We need to plan very carefully not to disrupt this ecological bonanza.”