Will boosting Australian coal exports threaten the Great Barrier Reef?

The Great Barrier Reef is under threat, according to a United Nations agency overseeing its conservation, and the issue is the Australian government's plan to boost coal exports.

Just beneath the waves near Whitsunday Islands is a shimmering kaleidoscope, a menagerie of life so significant that the Great Barrier Reef has been deemed a U.N. world heritage site, an equivalent of a national park, reports CBS News' Lee Cowan.

Like a park, it's to be protected. However, on Wednesday the U.N. agency expressed concern over a decline in the reef's overall health, citing threats both natural and man-made.

Near the reef are a number of commercial shipping ports, one serving Australia's valuable coal reserves. The Australian government wants to double the port's capacity to nearly 130 million tons of coal every year.

"We're talking about building the world's largest coal port in the most fragile and iconic place on earth," said Cherry Muddle who is with the Australian Marine Conservation Society.

She said the reef is already under assault by a variety of natural causes.

"We know that cyclones, climate change, storms -- they all have a great impact on the reef. So why then are we adding another threat?" Muddle said.

At issue is just how the planned expansion of the port would work.

To make room for more ships, at least 1 million cubic feet of sand and mud would have to be dredged from the seabed below the pier. It's enough to fill about 150,000 dump trucks.

The "spoil," as it's called, would be dumped in the Great Barrier Reef Marine Park. Environmentalists liken that to discarding millions of tons of waste in the middle of the Grand Canyon.

"I'm all for having a fair fight, but at the moment, this isn't a fair fight," Queensland's environment minister Andrew Powell said.

He said the government is being unfairly tagged as the bad guy.

"We care about the environment, we care about the Great Barrier Reef, we care about the reef's reputation," Powell said. "I've got five kids, I want them to inherit a better reef than the one I did."

Any potential damage he said is being purposely distorted by what he calls alarmist propaganda.

In an animated Greenpeace Australia ad, a carnival game crane clamps down on the reef and uproots organisms. A ferris wheel spinning ships of mud knock down dolphins and whales.

"Turtles, dugongs and humpbacks better watch where they're going. It's going to get noisy down there!" a carnival announcer said on the ad.

"What the extreme environmental groups will have you believe through their hysteria and their lies is that this is being disposed right on our pristine reef," Powell said.

He said the dredged sediment won't be dumped on top of the reef but would instead be carefully let loose over a deep natural channel. The sediment would be left to sink to the bottom made of sand and clay.

Marine scientist Paul Doyle, environment manager of Queensland ports, insisted that any impact would be negligible and that the natural channel would be a good choice for the dredged sediment.

"I guess it's in deeper water, so it doesn't re-suspend and travel as far as it would if it was disposed in shore," Doyle said.

Critics, however, question that theory and fear the sediment could float all the way to the reef itself and smother sensitive corals and sea grass.

"Imagine getting a bucket of mud or sand and dumping it in your swimming pool. Now it doesn't just sit still and stay in one place, it spreads," Muddle said.

The distance from the proposed dump site to the outer portions of the Great Barrier Reef is about 25 miles, but in between there are thousands of fringe reefs as well.

"It may not directly impact the coral because, as the government says, they're not dumping directly on the coral, but the coral is part of the system. So if you impact any part of the system, it will eventually impact the coral itself," said Tony Fontes, Cowen's diving guide. He is a California dive instructor who came on vacation to the Great Barrier Reef over 34 years ago and never left.

The U.N. is encouraged by some environmental progress by the government but warns that unless more is done, it may consider putting the Great Barrier Reef on its list of sites that are in danger. In the meantime, the reef and its silent inhabitants are left to battle the threats they're used to battling while the world above argues loudly around them.