Seventy-Three Percent Of Marine Protected Areas Are Polluted By Sewage, Says Study

A study by the Wildlife Conservation Society and the University of Queensland (attached) found that nearly three out of four of the world's marine protected areas (MPAs) are polluted by sewage. In the ocean regions most critical for coral reefs and tropical sea life, the problem is even worse: between 87 percent and 92 percent of protected areas are affected, and typical pollution levels inside these zones are ten times higher than in surrounding unprotected waters. Over 16,000 MPAs globally were evaluated in the study.

“Land-based pollution, particularly untreated or poorly treated domestic wastewater, is among the most pervasive and poorly managed threats to coastal ecosystems such as coral reefs, seagrass meadows, and mangrove forests,” states the study.

Wastewater carries nutrients, pathogens, and chemicals that damage important coral reef and seagrass ecosystems and harm coastal wildlife. Previous studies have linked wastewater pollution to coral reef decline around the world, harmful algae blooms, and even Alzheimer's-like brain disease in dolphins. The consequences for people are just as serious: polluted drinking water is estimated to cause up to 1.4 million deaths a year from diseases like cholera and typhoid fever, and as much as $12 billion in economic losses.

The findings are important for the “30 by 30” initiative, wherein world leaders have committed to protecting 30 percent of the ocean by 2030. The study suggests the push to protect more ocean area may be missing the fact that protected areas cannot do their job if pollution keeps flowing in.

"What we found was striking," said David E. Carrasco Rivera, lead author and Ph.D. candidate at the University of Queensland. "Using global pollution data, we mapped wastewater exposure across thousands of protected areas and compared it to unprotected waters nearby. In region after region, the areas set aside for conservation were actually receiving more pollution than the areas with no protection at all."

The researchers analyzed pollution exposure across 16,491 marine protected areas worldwide, focusing closely on 1,855 protected areas within 50 kilometers of the coast in six tropical regions: Australasia and Melanesia, Mesoamerica and the Caribbean, the Coral Triangle, East Africa, the Indian Ocean, and the Middle East and North Africa. They used a geospatial model to measure how much nitrogen from sewage was reaching each protected area, then compared those levels to nearby unprotected waters.

"Even a perfectly managed marine protected area will fail to achieve benefits for conservation and for people if wastewater keeps flowing in from upstream," said Dr. Amelia Wenger, WCS Global Water Pollution Lead. "You cannot put up a barrier inside a protected area to stop pollution from coming in. The solution has to happen on land, upstream, and it has to be part of how governments plan and fund ocean protection. Right now, it’s not.”

The study calls on governments and conservation planners to account for sewage and other land-based pollution when designing marine protected areas and when measuring whether those protections are working.

“Addressing pollution in these contexts requires governance reform, international cooperation, and targeted investments that integrate land-based pollution management into MPA design and coastal conservation strategies,” states the study.

The researchers point to the Global Biodiversity Framework, the international agreement that sets the 30x30 goal across 23 interconnected targets, and warn that Target 3, the area protection goal, cannot succeed without also delivering on other targets for land and sea use planning (Target 1), restoration (Target 2), and pollution reduction (Target 7).