SYDNEY, Australia — In a bid to keep the Great Barrier Reef from being reclassified by the United Nations as “in danger,” the Australian government on Monday unveiled a 35-year plan to manage risks to the reef, one of the natural wonders of the world. But conservationists warned that the plan did not go far enough.

“The plan does not deliver bold, concrete actions that scientists have told us we need to turn around the future of the reef,” said Louise Matthiesson, a reef campaigner with the group WWF-Australia. “Over all, it is not business as usual, but it is close enough to it.” WWF-Australia contributed to the report, but Ms. Matthiesson said that only some of the group’s views had been adopted.

The United Nations Educational, Scientific and Cultural Organization listed the reef as a World Heritage site in 1981 but warned that it might put the reef on the List of World Heritage in Danger in 2015. Of Unesco’s 1,007 cultural and natural World Heritage properties, 46 are considered “in danger,” several of them in war-torn countries like Syria.

The Australian government acknowledged in the report that the reef, which stretches along most of the coastline of the state of Queensland and is about the size of Italy or Japan, was under increasing threat from climate change, poor water quality and the impact of coastal development that includes the controversial expansion of a major coal-loading port at Abbot Point. A government report in 2012 found that the reef had lost over half of its coral cover in 27 years.