Australia's Great Barrier Reef, one of the seven natural wonders of the world, is already threatened by climate change, coral bleaching, pesticides, overfishing, oil spills and invasive species. Now we can add four unexploded bombs to the list.

U.S. Navy pilots dropped the four bombs on the Great Barrier Reef this week during Talisman Saber, a joint exercise between the Australian and United States militaries. More than 28,000 soldiers and other military personnel converge on northern Australia every two years as an exercise to improve combat readiness and ensure that the two military forces work well together.

As part of the exercise, two U.S. Navy Harrier fighter jets planned to drop four bombs — two inert bombs filled with concrete and two unarmed bombs that carried explosives — on Townshend Island. When they approached the island, however, they found civilian boats near the target. The aircraft apparently circled the area until their fuel ran low. According to the Navy, the Harrier jets are incapable of landing while still carrying the bombs. "Due to low fuel and inability to land with the amount of ordnance they were carrying, the on-scene commander determined it was necessary to designate an emergency jettison area for the ordnance," U.S. Navy Commander William Marks told

Marks characterized the dropped bombs as "safe" and the Australian Defense Force said the devices posed "minimal risk or threat to the public, the marine environment or civilian shipping transiting the reef area."

A Navy spokesperson told the media that the bombs are about 200 feet below the surface of the water and said that the surrounding reef and any ships that might pass through the area are not in danger. Vice Admiral Scott Swift said the decision to retrieve the bombs lies with the Australian government and that in similar cases bombs have often been left on the ocean floor.  

Environmentalists, who have previously criticized the scope of Talisman Saber, were quick to judge the Navy for dropping the bombs. Australian Green Party senator Larissa Waters told the media: "Have we gone completely mad? Is this how we look after our World Heritage area now? Letting a foreign power drop bombs on it?"

Waters also spoke to The Guardian, explaining that the military training area is exempt from the environmental protections normally in place for the Great Barrier Reef. "It's simply not an appropriate place for war games," she said while criticizing the fact that the civilian boats had not been cleared from the area. "It's outrageous there wasn't better safety with the boats involved, especially given that this area is a tourist Mecca."

Related on MNN:

U.S. Navy drops 4 bombs on Great Barrier Reef
The potential damage to the famous site is not yet known, but thankfully, none of the bombs were armed.