To find out if marine protected areas achieve their environmental and socioeconomic goals, we read 42 scientific studies and talked to seven experts.Overall, marine protected areas do appear to help marine animals recover within their boundaries. But a lot more rigorous research is needed.The effects of marine protected areas on socioeconomic outcomes and fisheries are less clear.This is part of a special Mongabay series on “Conservation Effectiveness.” In 1962, at the First World Conference of National Parks in Seattle, U.S., Carleton Ray, a marine biologist at the University of Virginia, pleaded the cause of setting aside “unmolested” areas in the sea. “Man is using the sea at a great rate, polluting it, developing its borders,” he said in one of the conference sessions. “If we conservationists and biologists do not think of the planet as one — earth and water — then I ask, who will? If we do not press for marine as well as terrestrial sanctuaries and for regulations over our marine activities, then I ask again, who will?” This plea to begin establishing marine protected areas gained momentum over decades. At the 1992 Rio Earth Summit, for instance, countries agreed to maintain marine biodiversity by establishing networks of marine protected areas. Many scientists also began presenting evidence that fishing was causing the world’s fish stocks to collapse: Overfishing was pushing many marine species toward extinction and destroying or altering marine habitats. Creating marine protecting areas, they stressed, was the best approach to addressing this degradation of the marine environment. In 2004, the world’s governments adopted their first tangible international target under the U.N. Convention on Biological Diversity (CBD): They committed to conserving at least 10 percent of coastal and marine areas by 2012. But when the coverage remained below 2 percent in 2010, the CBD extended the deadline to 2020. Where there were only about 430 marine protected areas as of 1985, today there are more than 15,600 covering more than 25 million square kilometers (9.7 million square miles), or nearly 7 percent of the Earth’s oceans, according to the latest figures from the U.N.’s Protected Planet data repository at the time of writing this story. Grey reef shark numbers have declined within Australia’s Great Barrier Reef Marine Park largely due to illegal fishing. Photo by Albert Kok/Wikimedia Commons. Charting the course for marine protection Protecting marine life and conserving biodiversity remains the main driver behind the creation of marine protected areas. “A marine protected area is the one tool with which you can effectively conserve all levels of marine biodiversity from genes to species to the ecosystem,” said Graham Edgar, a marine ecologist at the University of Tasmania, Australia. “And there are no other tools for achieving that outcome as effectively.” But this goal has evolved. Marine protected areas are now widely seen as a tool to rebuild fish stocks and ensure sustainability of fisheries outside their boundaries. In fact, the U.N.’s Food and Agriculture Organization (FAO) defines a marine protected area as “any marine geographical area that is afforded greater protection than the surrounding waters for biodiversity conservation or fisheries management purposes.” Intuitively, closing off areas to fishing to help the long-term recovery of fish stocks sounds simple enough. But not everyone is convinced. Some critics counter that marine protected areas only really extend “protection” against one threat to oceans — legal fishing — from a long list: think global warming, acidification, oil spills, plastic pollution, agricultural waste, illegal fishing. Take Australia’s iconic Great Barrier Reef National Park, for example: Despite being considered one of the best-protected and most successful marine parks in the world, its coral reefs just suffered two years of severe bleaching and death due to warming waters. Marine protected areas also don’t reduce fishing pressure, but simply move it to a different area, argued Ray Hilborn, a marine biologist and fisheries scientist at the University of Washington, U.S. “Sure things get better inside the marine protected area, but you are fishing harder outside,” he told Mongabay, adding that legal fishing can be regulated more effectively by other means. Many scientists have also expressed concern over what marine protected areas mean to people who depend on fisheries for their living. As with terrestrial protected areas, conservationists and governments are now trying to understand how marine protected areas affect local people and find ways to either improve their lives or at least avoid harm. Countries are now frenziedly creating more marine protected areas, increasingly very large ones, either out of genuine concern for marine life or to meet international targets. In the midst of it all, the efficacy of this conservation tool remains heavily debated. Is establishing marine parks better for species and habitats than leaving areas unprotected? Do marine parks improve fisheries and the well-being of fisheries-dependent communities? We read through some of the scientific literature and talked to experts to find out more.