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Calling it the most extensive review of how coral on Australia's Great Barrier Reef is faring, scientists on Monday reported some alarming news: The amount of coral covering reefs there has been cut in half since 1985 and will likely continue to decline unless steps are taken to at least attack the easiest of several factors.

"We show a major decline in coral cover from 28 percent to 13.8 percent" of the entire system, the experts wrote after reviewing 2,258 surveys of 214 reefs within the marine sanctuary. 

"Two-thirds of that decline has occurred since 1998," they added.

John Bruno, a coral expert who was not part of the study, called the findings "really grim" and reflecting loss even higher than deforestation in the tropics, a topic that generally gets much more attention.

"In 2007, we first sounded the alarm that the Great Barrier Reef, and Pacific reefs in general, were not as pristine and resilient as a lot of people wanted to believe," Bruno, a marine biology professor at the University of North Carolina Chapel Hill, told NBC News. "But still, this is really shocking to me."

"This is a really high rate of loss for an entire region," he added. "This is just nuts and it appears to have been sustained over the last five to 10 years. Just mind blowing. I really didn't expect this."

The researchers estimated that tropical storms, coral predation by crown-of-thorns starfish and coral bleaching accounted for 48 percent, 42 percent and 10 percent of the respective estimated loss in coral cover.

Coral bleaching, whereby coral expels the tiny single-celled algae inside that provide color, is triggered by stress such as warm seas or pollution.

The experts didn't have much faith in quick actions to counter warming seas, storms and bleaching, but they believe it might be possible to reduce starfish populations.

They based their hope on evidence that starfish are linked to poor water quality, and the fact that the northern Great Barrier Reef, which has little starfish predation, showed no overall decline. 

Nutrient-rich waters stimulate plankton, which starfish larvae thrive on, the experts noted, and if fertilizer and other nutrient-rich pollution in the water is cleaned up, starfish populations would decline and coral cover could increase by nearly a percentage point a year, they estimated. 

"Survival of the plankton-feeding larvae ... is high in nutrient-enriched flood waters, whereas few larvae complete their development in seawater with low phytoplankton concentrations," the experts wrote.

Bruno, for his part, said the impact of starfish on the reef is "striking," with the carnivores actually eating away at coral. "They are huge and scary beasts," he said, citing outbreaks in which the starfish "move in massive waves down the Great Barrier Reef like a plague."

Related: 360-degree tours of Great Barrier Reef

The study's authors predicted that without intervention the coral cover on the reef will probably decline up to 10 percent in the next 10 years.

They also noted that reducing starfish is a short-term step that can "only be successful if climatic conditions are stabilized, as losses due to bleaching and cyclones will otherwise increase."

The study by experts at the Australian Institute of Marine Science and the University of Wollongong was published in the peer-reviewed Proceedings of the National Academy of Sciences.

Bruno called the study "a sea change in the attitude" of the institute, a branch of the Australian government, because it had been "resistant to the idea that the Great Barrier Reef was degrading" — even challenging the 2007 study he and a colleague published.

"Ten years ago nearly everyone assumed, and argued, that due to its isolation, size and huge biodiversity, the Great Barrier Reef had resisted the decay that the rest of the world's reefs had experienced," Bruno added.

The study follows a report earlier this month estimating coral cover in the Caribbean and Florida Keys has fallen from 50 percent of reef surface area in the 1970s to just 8 percent today.  

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Reefs in the Caribbean and Florida Keys have lost most of the colorful corals that feed a rich ecosystem and made the region a diving and snorkeling mecca, a major conservation group reported Friday. On average, reefs have live coral on just 8 percent of their surface area, down from more than 50 percent in the 1970s.

Impacts including warming seas and human sewage have contributed to a steady decline that shows "no signs of slowing," the International Union for Conservation of Nature (IUCN) said in releasing its report, which was based on new data compiled by 36 experts earlier this year.

The decline was not uniform, the IUCN noted, and those areas with less human impact fared better. "Corals declined precipitously on the Jamaican north coast in the 1980s ... but not at Curacao and Bonaire where coral has more gently declined to about 25-30% today," the IUCN said in the report.

In contrast, total coral cover in the Florida Keys, the U.S. Virgin Islands and Puerto Rico "has progressively declined from 25 to 35% in the 1970s to less than 15% today."

Many of those severely deteriorated reefs instead are covered with large algae, which make it harder for coral to get established, "and virtually no fish larger than" a few inches, the report stated.

The report cited a number of factors causing the decline: disease, pollution, overfishing, hurricanes and "coral bleaching" — a process triggered by stress such as warm seas or pollution whereby the coral expels the tiny single-celled algae inside it that provide its color.

The IUCN did not try to weigh the importance of each factor, but some experts voiced their belief that global warming is paramount.

John Bruno, a University of North Carolina marine biologist who contributed to the new data, told NBC News that a study published last July shows the key driver in the decline is a warming ocean.

"Our preliminary analysis suggests that the state of Caribbean reefs continues to worsen, primarily due to ocean warming," he said. "To reverse this dire trend, job one is to halt the increase of greenhouse gas emissions."

Related: Study ties coral crisis to climate change
Related: Slideshow on threats to coral

The IUCN released the report at its annual convention and urged nations to step up efforts to reduce fossil fuel reliance, thereby reducing greenhouse gases. It also called on nations with coral reefs in their waters to take several actions:

• Limit fishing through catch quotas;
• Create or extend marine protected areas, which provide havens for coral and fish populations to recover;
• Halt runoff from land of sewage and fertilizers, among other pollutants.

The impacts on coral must be "immediately and drastically" reduced, said Carl Gustaf Lundin, director of IUCN’s Global Marine and Polar Program, "if coral reefs and the vitally important fisheries that depend on them are to survive in the decades to come."

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Tanya Brown

Peter Ross, seen here holding a harbor seal off southern Vancouver Island, is one of 75 staff losing their jobs with the closure of Canada's marine pollution program.

Canada has been sending letters to government scientists notifying them that their jobs will be eliminated or affected by the closure of the country's marine pollution program -- but at least one isn't going without making some noise.

"It's perplexing that we face the loss of this program, given the 25,000 chemicals on the market and the ever-increasing threats posed by shipping and oil and gas exploration and development in temperate and Arctic waters," Peter Ross told msnbc.com. Ross is perhaps Canada's best known marine scientist for his work on identifying killer whales as the most contaminated marine mammals on the planet. 

"As can be expected when one is told their position is being terminated, one is shocked and saddened," he added. "However, when told that the entire pollution research and monitoring program for Canada's oceans is being eliminated, I was speechless."

The program, which employs 75 staff, is set to be shut down by April 1, 2013, the Victoria Times Colonist reported. 

"I cannot think of another industrialized nation that has completely excised marine pollution from its radar," Ross said.

The program is under the Department of Fisheries, which is shedding a total of 400 jobs. More than 600 others will be "affected." Of the some 1,000 jobs impacted, three quarters are with the Canadian Coast Guard.

A Department of Fisheries spokesperson told the Colonist that the cuts would produce $79 million in savings and that an advisory group from academia and the private sector would instead provide advice.

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Ross countered that those groups wouldn't be as accountable as government agencies are. "I can't think of any scientist or agency outside of government that is held to account on issues related to public health, the health of marine fish or mammals, or the identification of emerging pollution concerns in the coastal environment," he said.

Ross also published an opinion piece, titled "Silent Summer," on environmentalhealthnews.org. He concludes:

"It is with apprehension that I ponder a Canada without any research or monitoring capacity for pollution in our three oceans, or any ability to manage its impacts on commercial fish stocks, traditional foods for over 300,000 aboriginal people and marine wildlife. 

"Canada's silence on these issues will be deafening this summer and beyond."

So what's the plan for Ross? "My personal and professional hope," he said, "is to transfer somehow to a university where I will be able to continue to work on ocean pollution priorities."

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University Of Miami / AFP - Getty Images, file

A diver notes marine species in the Dry Tortugas National Park in Florida. A new study recommends that the United Nations appoints a High Commissioner for Oceans to coordinate research and action and that there should be more preparation for a 1-2 meter (up to 6.5 feet) sea level rise by the end of the century.

The cost of damage to the world's oceans from climate change could reach $2 trillion a year by 2100 if measures to cut greenhouse gas emissions are not stepped up, a study by marine experts said Wednesday.

The study found that without action to limit rising greenhouse gas emissions, the global average temperature could rise by 4 degrees Celsius (about 7 degrees Fahrenheit) by the end of the century causing ocean acidification, sea level rise, marine pollution, species migration and more intense tropical cyclones. It would also threaten coral reefs, disrupt fisheries and deplete fish stocks.

In the study, "Valuing the Ocean,” marine experts led by the Stockholm Environment Institute analyzed the most severe threats facing the world's marine environment and estimated the cost of damage from global warming.

The hunt is on for world's strongest corals

The SEI found nitrogen-rich fertilizers and waste would strip more ocean areas of oxygen, causing what is known as hypoxic dead zones, which are already found in more than 500 locations.

The institute said that under a business-as-usual scenario, without radical cuts to emissions, the annual cost would hit $1.98 trillion, or 0.37 percent of global gross domestic product, by 2100.

However, in a statement, the SEI added that "a rapid emission reduction pathway that limited temperatures increases to 2.2 degrees Celsius would 'save' (i.e. avoid) almost $1.4 trillion of those damages."

"These figures are just part of the story, but they provide an indication of the price of the avoidable portion of future environmental damage on the ocean -- in effect the distance between our hopes and our fears,” Frank Ackerman, director of the Climate Economics Group at SEI-US, said in the statement.

“The cost of inaction increases greatly with time, a factor which must be fully recognized in climate change accounting,” he added.

As sea levels rise, Kiribati eyes Fiji as new home for thousands

The loss of tourism would incur the highest cost at $639 billion per year. The loss of the ocean carbon sink -- the seas' ability to soak up carbon dioxide (CO2) -- would cost almost $458 billion, the study showed. Warmer water holds less carbon dioxide.

Ackerman told Reuters that radical cuts to emissions would require the widespread use of radical carbon removal technologies like sucking carbon dioxide out of the atmosphere.

"The faster we stop emissions rising, the lower the damage will be. But on current technology, I wouldn't be surprised if we end up on a 4 degree C pathway," he said.

Oceans' acidic shift may be fastest in 300 million years

The study did not put a monetary value on the loss of some species which inhabit the world's oceans, critical processes like nutrient cycling or the loss of coastal communities' traditional ways of life.

"The challenge is to figure out what parts of the ocean environment have a value you can put a meaningful price on. There are very important areas which we still can't incorporate into a market," Ackerman said.

Pollution, other threats
The SEI statement said that while climate change was “an enormous threat,” there were others.

"A key point of Valuing the Ocean is that the convergence of multiple stressors -- acidification, ocean warming, hypoxia, sea-level rise, pollution, and overuse of marine resources -- could lead to damages far greater than just from individual threats," it added.

Warming oceans could melt ice faster than expected

The study recommended that the United Nations appoints a High Commissioner for Oceans to coordinate research and action and that there should be more preparation for a 1-2 meter (up to 6.5 feet) sea level rise by the end of the century.

“We must develop an integrated view of how our actions impact the ocean, and threaten the vital services it provides, from food to tourism to storm protection,” Kevin Noone, director of the Swedish Secretariat for Environmental Earth System Sciences at the Royal Swedish Academy of Sciences, said in the statement.

Noone, a co-editor of the report, added that the global ocean was “a major contributor to national economies … yet is chronically neglected in existing economic and climate change strategies at national and global levels.”

Reuters contributed to this report.