Although many scientists are painting a bleak picture of the Great Barrier Reef coral bleaching, which is said to be the worst bleaching event on record, one Queensland tourism body is claiming that the damage is less than what was previously reported.

Approximately 1,300 kilometers of the reefs from Papua New Guinea south to Townsville have been surveyed by air, and the results don't show much promise.

"Seventy-five per cent of corals north of Cairns are snow white," Terry Hughes, convenor of the National Coral Bleaching Taskforce, said on Monday. "The amount of corals in the northern third (of the reef) used to be substantially higher than further south. That's no longer the case."

Hughes said last week that the damage extended further south than previous estimates, suggesting that approximately 74 reefs between Cairns and Townsville bleached between 25 to 30 percent on average. However, Alex de Wall, chief executive officer at Tourism Tropical North Queensland, said that the areas where boat tours frequent the most - Cairns and Port Douglas - are "looking great."

"Our operators have reported just a few isolated incidents of staghorn coral bleaching in the areas they operate," he said.

No matter the extent of the bleaching, recent research suggests that Australia will not likely meet the water quality targets needed to protect the Great Barrier Reef from coral bleaching.

Researchers from the Association of Marine Park Tourism Operators (AMPTO) and other organizations are currently examining the reef in order to get a better look at the real extent of the bleaching.

"In the last two weeks AMPTO has already conducted more than 100 Reef Health Indicator Surveys (RHIS) on reefs off Cairns that show a bleaching average of less than 5 percent," said Col McKenzie, the AMPTO's executive director.

"Of course, the current bleaching event is very concerning but we need the facts before we react emotionally," he said, adding that the AMPTO should have more data on the event by the end of the week.

Meanwhile, Hughes and his colleagues will fly over a 2,000-kilometer region of the southern part of the reef on Wednesday and Thursday and up the total number of surveyed reefs to more than 750, giving scientists more data to work with.

The team hopes to use its data to create a detailed map of the Great Barrier Reef coral bleaching event and compare it to similar events that took place in 2002 and 1998.

"We already know it's far greater than we thought it was," Hughes said. "The bleaching is very starkly visible from the air."