If the Mesoamerican Reef were a patient and Melanie McField a doctor, she would be administering CPR. “The reef is sick,” says McField, and the illness “life-threatening.”

The recently released 2010 Reef Report Card, authored by McField, a marine scientist and the director of the Healthy Reefs Initiative (HRI), is a bill of health for the Mesoamerican Reef, which runs from Mexico’s Yucatán Peninsula south through Belize, Guatemala and Honduras. In all, 130 sites in the four countries were examined, and the results compared with those of the previous reef survey, which was based on studies from 2006. The prognosis, though not quite terminal, is poor and getting worse.

The report card rates reef health with a user-friendly, color-coded system: sites are ranked according to coral coverage and other factors, from critical (red) to excellent (green) condition. Overall, the reef experienced a 20% decline in health from 2006 to 2009. But most alarming in this second report card, McField says, is the sharp drop in reefs considered to be in “fair” condition, from 41% of the total in 2006 to just 21% in 2009.

“Those were your average citizens, the ones that could easily have gotten healthier, but instead got worse,” says McField, whose group, an international collaborative, focuses on the Mesoamerican Reef system. “Now we’ve got far more of these problem patients. We need to bring them back from the brink.”

The problem is comparable to that of deforestation in the Amazon rainforest, she argues. There, land clearing brings the forest to a tipping point, small patches of healthy woodlands become isolated, and the chances of large-scale recovery and reforestation ever more remote. “Seventy percent of the reef is in poor or critical health—and we’re passing that tipping point,” McField says. As more of the reef dies and fish populations plummet, she explains, the corals needed to reseed the banks diminish in number, and the fish habitat becomes poorer and more dispersed. Asks McField: “Where are all the baby corals going to come from?”

The root problem, she says, isn’t a single ailment, but, rather, mounting stress from “a thousand cuts” that have left the reef more vulnerable than ever before.

The report card identifies four major factors that have conspired against reef health: coastal development and marine dredging; inland land-clearing and agriculture; overfishing; and climate change. It also examines two new threats: the growing prospects for offshore oil drilling in the region, and the sudden population boom of the exotic lionfish, a ravenous, fish-eating predator from the South Pacific that has quickly colonized the Caribbean.

Nadia Bood, a reef scientist for the World Wildlife Fund, considers climate change the most insidious problem. Like secondhand smoke, she argues, it originates elsewhere but deeply affects the health of the reef. “We’re a small, third-world country,” Bood says. “We don’t produce much carbon. But in a global environment, we’re forced to suffer the consequences anyway.”

Growing concentrations of global carbon emissions warm the atmosphere, which in turn heats the shallow coastal waters where corals thrive. When sea temperatures crest 30 degrees Celsius, corals expel the symbiotic algae that give them their color—in essence, regurgitating the very food they need to survive.

They “bleach,” becoming malnourished and more susceptible to disease and pathogens, which, unlike corals, thrive in warm, shallow waters. “What climate change has done is reduce the reef’s immune system,” Bood says. “It’s a ripple effect that suddenly makes it more vulnerable to a host of other problems.”

That includes hurricanes, which climatologists believe will grow increasingly destructive as ocean temperatures warm.

Marine scientists say that if carbon-dioxide concentrations in the atmosphere exceed 350 parts per million (ppm), a level many climatologists consider to be a safe upper limit, some individual corals could survive. But in such conditions, they say, the complex, three-dimensional structures that result from a diversity of healthy corals—in effect, the reef itself—would cease to exist.

McField worries that as the United Nations Climate Change Conference in Cancún approaches (Nov. 29-Dec.10), some groups seem ready to settle for a more politically expedient 450 ppm. She adds: “But that’s missing the boat for reefs.”

Instead of giving up hope, however, she believes countries along the reef must focus on minimizing the threats they can control—namely, coastal development, overfishing and land-clearing. Sometimes it’s easier, she says, to point fingers than to come to terms with one’s own bad habits.

Development along the coast fronting the Mesoamerican Reef has increased 12% since 2006, according to the report, even amid a world economic crisis that stifled construction in neighboring Central American countries. Much of the region has no coastal zoning or coordinated land-use planning to ensure sustainability, so development is haphazard and loosely controlled, says McField. Mangrove fish nurseries are cut and filled, the ocean floor is dredged, sediment and runoff cloud the water, and sewage and runoff from development smother the reef.

McField says that like smoking, such reckless tourism development “feels good,” but is having profound effects on the region’s main attraction.

Vincent Gillett, chief executive officer of Belize’s Coastal Zone Management Authority and Institute (CZMAI), believes the implementation of a coastal zoning plan would be the “single most important component to the long-term survival of the reef.” But producing such a plan, which would dictate where development should and should not occur while imposing strict restrictions to ensure sustainability, has proved easier said than done. A coastal zoning effort, Gillett says, would touch virtually every constituency and individual in his tiny beachfront country. It’s a juggling act, he says, of politics, science, conservation and economics.

Gillett has been wrangling with the complexities of a coastal zoning plan for almost a decade. During that time, he says, funding has come and gone, as has political will. “If we were a country with a government that had a lot of money, the process would have been faster,” he says. “But the reality has been different.”

Still, Gillett helped revive efforts to draft a costal zoning plan two years ago, and hopes the blueprint will be ready within 12 to 15 months. “We know the reef is at the center of our economy, in terms of tourism, coastal development and fisheries, and all that is dependent on the reef remaining a viable product,” he says.

The reef’s importance is hard to overstate in a region known for economic underdevelopment.

According to a study by the World Resources Institute, the reef was estimated to generate US$395 to $559 million in goods and services for Belize’s economy each year. Its contributions aren’t just to tourism and fisheries; the reef also protects the mainland communities from increasingly destructive storms—a benefit that often goes unnoticed, says McField.

“Reefs are the heart of the ocean” and the “life blood” of the regional economies, she says. Losing them, she adds, “would be devastating to people and marine biodiversity.”

Many scientists liken the loss of the reef in a hurricane-prone area like Belize or Mexico to the destruction of coastal wetlands and barrier islands around New Orleans. Much of the destruction from Hurricane Katrina was attributed to long-term degradation of such natural buffers.

Scientists and conservationists like McField and Bood have long prescribed a straightforward cure for the reef’s ailments: fully protected, ‘no-take’ marine reserves. In these areas, fish could grow unhindered, reproduce and then spread to surrounding areas. This, in turn, would help ensure the long-term health of commercial fish species, the corals they need to survive and the human populations that depend on both. Still, it has been a hard sell among cash-strapped fishermen pressed by declining resources and disappearing habitat. They are far more apt to be thinking about feeding their families in the short-term rather than pondering long-term reef health.

Thus far, efforts to protect ocean territory have been scattered and largely insignificant. Belize leads the region with a paltry 2% of its marine territory in fully protected zones. Mexico and Honduras are second, with less than 1%, and Guatemala has none. That, says McField, isn’t nearly enough territory to realize the advantages of protected areas and ensure long-term sustainability.

Scientists believe 20-40% of the region’s marine area must be covered to maximize ecological and economic benefits. Without such protection, the effect on fish populations is predictable, says McField. Less than 1% of the fish surveyed in the Mesoamerican Reef region in 2009 were over 20 cm (7.8 inches) long, and sharks, apex predators that keep ecosystems in balance, were largely absent. Reef grazers, as important to reef health as a toothbrush to dental care, are also in sharp decline. Without reef grazers, macroalgae overgrow and smother corals, rendering them vulnerable to disease.

For Eloy Cuevas, a fisherman from Monkey River, along Belize’s remote southern coast, it has been like seeing an old friend fade away. “In the 1970s, there were big black grouper around every reef, conch in every grass patch, and lobster antennae sticking out from every hole,” he says wistfully. “Now they’re all gone.”

Cuevas, once a commercial conch and lobster fisherman, now guides sport fishermen who catch and release their prey but pay big money to do so. Protected areas, he says, are what all fishermen—commercial and sport—need to ensure a future for themselves and their children and grandchildren. But hardheaded politics, disputes between nations in the region and corruption often get in the way.

Over the years, Cuevas, whose home is near the Guatemalan border, has seen more and more foreign fishermen and vessels in Belizean waters. Sometimes legally, sometimes illegally, they seek to profit from the Mesoamerican Reef’s renowned abundance. High-seas technology, the enticement of hungry global markets and backing from multinational corporations have increased pressure in the very few places left with healthy reef and fisheries resources, like Belize.

“We see more and more fishermen coming into Belize and competing for our resources. If everyone fishes here, there won’t be anything left,” says Cuevas. “We need to get past our bickering before it’s too late.”

There have been some advances. In 2009, Belize fully protected key reef grazers, like parrotfish, and the “big three” sport fish: tarpon, bonefish and permit, which drive a multimillion dollar tourism industry. This year, Honduras declared a permanent moratorium on all shark fishing, a major step forward, says McField. And in the few places where no-take marine reserves exist, the reef and fisheries have recovered spectacularly, with fish populations rebounding, then spilling into surrounding areas.

The report highlights a small reef outside Laughing Bird Caye National Park, one of the largest fully protected marine areas in Belize, as proof that solutions are within reach. Despite its location almost one nautical mile outside the park boundaries, the reef jumped from ‘critical’ to ‘good’ condition in just three years, thanks largely to skyrocketing fish biomass that resulted from its proximity to the park’s no-take zone. Commercial fishermen from neighboring Placencia reaped the benefits.

“The reef will recover if we give it a chance,” says McField.

The next report card will be issued in 2012. To keep it from reading like an obituary, McField believes countries like Belize, Mexico, Guatemala and Honduras must collaborate to control threats to the reef from land and sea.

What’s ultimately needed, she says, is a concerted global conservation effort, including the establishment of international limits on carbon dioxide emissions.

“We’re taking our vitamins,” says McField. “We’re doing a little bit of exercise. But we haven’t quit smoking. We need to act now.”