In 1940, when John Steinbeck sailed along the coast of Baja California, collecting marine specimens, he rounded the tip of Baja and discovered Cabo Pulmo—the largest living coral reef in western North America and the jewel of the Gulf of California. Steinbeck described the reef in his book, The Log from the Sea of Cortez:

The complexity of the life pattern on Pulmo Reef was even greater than at Cape San Lucas. Clinging to the coral, growing on it, burrowing into it, was a teeming fauna. Every piece of the soft material broken off skittered and pulsed with life—little crabs and worms and snails. One small piece of coral might conceal 30 or 40 species, and the colors on the reef were electric.

Decades later, the Cabo Pulmo reef still teems with life, filled with bat-like devil rays, singing humpback whales, playful sea lions, giant conches and leatherback sea turtles. It also supports hundreds of fish species in numbers so robust that, for instance, schools of Bigeye trevally have been known to blot out the sun above deep sea divers. Only about 50 miles northeast of Cabo San Lucas, its dirt roads, rustic accommodations and laid-back atmosphere make this beach hideaway feel like it’s on the other side of the sea.

Though now one of the most ecologically-diverse marine environments on the planet, the Cabo Pulmo reef almost collapsed in the 1980’s after years of overfishing. In 1995, the Mexican government intervened and declared the reef a national park and fishing off-limits, following pressure by forward-thinking locals and environmental groups.

“The people realized that the tourism and diving industry were their lifeline, and that if something happened to the reef, they wouldn’t have any more tourists,” explains Sandra Moguel, an attorney with the Interamerican Association for Environmental Defense (AIDA). Her organization partners closely with Earthjustice to protect key ecosystems and human communities severely threatened by environmental degradation.

The ban worked and marine life exploded, with scientists recording a 463 percent increase in biomass in 2009. It wasn’t long before the biodiversity hotspot was designated a UNESCO World Heritage site and named a wetland of international importance under the Ramsar Convention.

However, despite its remarkable rebound, the Cabo Pulmo reef and other coral reefs worldwide face deep peril. The world’s oceans absorb about a quarter of all carbon dioxide emissions. As dissolved CO2 levels rise, these waters turn more acidic. Unlike other ocean stressors such as pollution and overfishing, which threaten the vitality of existing reefs, ocean acidification is a more insidious foe. Turn up the acidity level too high and you threaten a reef’s very existence.

Corals are built by polyps that produce hard skeletons made of calcium carbonate. As oceans absorb carbon dioxide, they become more acidic. When this happens, the amount of available carbonate diminishes. Because carbonates are the building blocks that reefs and other marine species like shellfish and pteropods need to grow and maintain shells and body structures, ocean acidification poses a grave threat to these species. Though often miniscule in size, shell-bearing, bottom feeding creatures like pteropods serve as the base of the food chain for many economically important species such as salmon.

Corals have flourished for millions of years under wide-ranging conditions, but many scientists believe that if we continue emitting carbon dioxide at current levels, all corals will likely be threatened by mid-century. According to the World Resources Institute, seventy-five percent of corals now face high to critical threat levels. These reefs, often called the “rainforests of the sea,” support a quarter of all marine life. If you pull the plug on coral reefs, you’re pulling the plug on the entire ocean ecosystem.

“We are emitting CO2 at rates greater than worst case scenarios in early reports. If fossil fuel extraction and burning continues at current rates, the future for the ocean is very bleak,” says John Guinotte, a coral specialist at the Marine Conservation Institute.

The phenomenon isn’t just limited to the tropical areas that people usually imagine when talking about coral reefs. The Arctic’s frigid waters—which like cold soda holds more carbon or “fizz” than warm soda—are acidifying faster than anywhere else. Scientists tell us that by 2020, 10 percent of the Arctic is likely to reach corrosive levels. By the end of the century, the entire Arctic Ocean will be corrosively acidic.

Unfortunately, even if humans stop emitting all carbon dioxide today, the oceans will continue to acidify because we’ve already loaded so much into the atmosphere and oceans are a major carbon sink. Add to that the bleak prospects of governments making significant reductions in carbon emissions and it’s clear that humans won’t be giving up their carbon-intensive lifestyle anytime soon.

In the absence of a global agreement on reducing carbon emissions, many scientists are advocating for the use of existing laws to reduce environmental stressors and build up the ocean’s resilience.

“A lot of the scientists are telling us that to make oceans more resilient to resist climate change, we need to reduce other stressors like pollution and overfishing,” says Earthjustice’s Oceans Program Director Steve Roady.

For more than a decade, Earthjustice has been spearheading efforts to use the law to increase the health and resilience of the oceans. In New England, Earthjustice is working to end the overfishing of cod, haddock and flounder, and to help restore one of the nation’s oldest fisheries. In the Caribbean, Earthjustice is suing the government for failing to protect parrotfish, which play a key role in promoting the health of coral reefs. And from Washington State’s Puget Sound to Florida’s coastal waterways, Earthjustice attorneys are working to stem the tide of ocean pollution like sewer runoff and agricultural pollution, and marine-based sources like cruise ships.

In the absence of a global agreement on reducing carbon emissions, many scientists are advocating for the use of existing laws to reduce environmental stressors and build up the ocean’s resilience.

Earthjustice is also working with its partners in AIDA on ocean protection in Latin America and with several small island developing states in the Pacific, which are literally on the water’s edge in terms of sea level rise and ocean acidification impacts.

“For many Pacific islands, intact coastal corals serves as the primary first line of defense against storm surges which are getting worse as the oceans warm and sea level rises,” says Earthjustice attorney Erika Rosenthal. “It’s those storm surges that may soon make many low-lying coastal areas uninhabitable.”

In June of 2012, Rosenthal was in the Earthjustice delegation at the Rio+20 Earth Summit on sustainable development to press for international action on ocean resilience.

“We know what to do, but we’re not doing a good enough job,” says Rosenthal. “We need to take the agreements that we have, fill the gaps and implement the projects that will make a difference on the ground.”

That includes continuing to protect healthy reefs like Cabo Pulmo, which is once again under threat from expanding tourism development in Baja California Sur. Although Mexico’s President Calderón recently announced the official cancellation of the proposed resort posing the greatest threat to the reef, other projects remain—all of which reduce reef resilience.

“Although we are pleased with Mexico’s recent move to protect Cabo Pulmo, threats remain,” says Anna Cederstav, staff scientist with Earthjustice’s International office and co-director of AIDA. “Given the threat of ocean acidification and the importance of reefs to fishing economies, protecting reefs should be a national priority everywhere.”

Written by Jessica A. Knoblauch. First published in the Earthjustice Quarterly Magazine, Summer 2012 issue.