NUSA DUA, Indonesia, April 10, Reuter - Tourism, by some counts the world's largest industry, has become a double-edged sword threatening the beauty spots it seeks to promote, environmentalists said on Wednesday.

"If not properly managed (tourism) will lead to the destruction of the very environment visitors have come to enjoy and both conservationists and the travel industry would lose out in the long run," Prince Bernhard of the Netherlands, a president of the World Wide Fund for Nature, told an international travel conference in Bali.

Indonesia's Minister for Population and the Environment, Emil Salim, told the annual conference of the Pacific Asia Travel Association the industry would have to invest in protecting the environment if it was to keep attracting customers.

"It is essential the basic capital (of environmental and cultural wealth) be sustained and it would be foolish and even disastrous should we ruin or diminish that basic capital," he said.

Salim warned delegates that the tendency to tailor culture to tourism was self-destructive. "The result is tourist art and a cheapening and vulgarization of indigenous art and culture," he said.

Souvenir sellers in Bali, the holiday island that is the vortex of Indonesia's exploding tourist industry, provided the travel agents, hoteliers and others gathered for the conference with plenty of examples of tourist kitsch.

With careful management, the travel trade and conservationists could become comrades-in-arms, Prince Bernhard said.

"From your point of view it will mean sectoral growth, jobs, income, profits," he told the conference, adding that nature tourism -- "ecotourism" in the jargon of the day -- also gave conservationists a chance to make money and educate people.

Environmental pressure groups in Indonesia agree in principle, but accuse the Indonesian government of failing to enforce laws designed to protect the country's vast rainforests and wildlife from the ravages of tourism.

"The laws governing national parks are there, but then you find ex-ministers building guest houses in the wilderness zones and ex-generals cutting down trees in core (research-only) zones," said an activist from a leading environmental group.

Salim acknowledged the difficulty of enforcing environmental laws in Indonesia. "We are a developing country -- there are shortcomings. But at least the direction must be clear," he told Reuters.

Environmentalists suggest charging high prices to allow small numbers of people to visit Indonesia's nature reserves, which are home to rare species such as orang-utans, rhinoceros and Komodo dragons.

"We need to go for value rather than volume. If you go for volume, how can you possibly sell yourself as an exotic destination?" an Indonesian environmentalist asked.