Australia has fallen short in its efforts to protect the Great Barrier Reef from the damaging effects of port developments, a report commissioned by an environmental group has found, leaving the nation at risk of having one of its top tourist attractions placed on the United Nations’ list of endangered heritage sites this year.

The Great Barrier Reef is a network of about 3000 reefs and 900 coral islands along Australia’s northeast coast that attracts about 2 million visitors each year, and sustains tens of thousands of jobs....