The mineral-rich Baja California peninsula is no stranger to gold fever and its environmental cost. During the 19th century, miners burrowed into its rocky ground to find gold—as well as copper, silver and minerals—leaving behind great mounds of discarded earth and high levels of arsenic that plague residents to this day. Now, a recent court decision annulling government permission for a huge, open-pit gold-mining project inside a nature reserve in the state of Baja California Sur has handed a victory to environmental advocates and civil society groups working to stave off a new mining boom.

The ruling at least temporarily prevents mining in the buffer zone of the United Nations-designated Sierra de la Laguna Biosphere Reserve, whose hills capture water for nearby coastal tourism hubs including La Paz, Los Cabos and Todos Santos. More broadly, the ruling by Mexico’s Federal Court of Administrative Justice bolsters groups throughout the peninsula that are trying to stop a welter of extractive projects, from gold and copper mining to seabed dredging. It also could serve as a precedent for stalling environmentally questionable development planned for protected areas, experts say.

“People have been watching to see whether the judicial system was going to work or not,” says Mark Spalding, president of the U.S.-based The Ocean Foundation, which monitors mining activity in Baja California. “In Mexico, the politics tend to control, so it is very encouraging when someone wins a victory and you feel you can take your case to court.”

The Court of Administrative Justice ruling, issued in March, cancelled a permit approved in 2014 by Mexico’s Secretariat of Environment and Natural Resources (Semarnat) for the Los Cardones mining project. Prompting the decision was a lawsuit filed two years ago by the Citizens’ Front in Defense of Water and Life, a coalition of civil society organizations that promotes sustainable development on the peninsula.

As proposed, the 540-hectare (1,330-acre) Los Cardones mine would produce about 1.2 million ounces of gold—worth US$1.5 billion at current prices—over 10 years. The mine, in the feasibility stage until the court ruling forced its suspension, is owned by Desarrollos Zapal, a subsidiary of Invecture Group, a Mexican company that also owns a copper mine, Cobre de Mayo, in Sonora State. Emails and calls to the company for comment were not returned.

Los Cardones would include two open pits, from which 173 million metric tons of earth would be extracted, according to a 2012 environmental impact assessment. Of that, 135 million tons would be placed in piles of waste rock, while the rest, contaminated processed material, would be deposited in a tailings pond. The project also calls for the construction of a desalination plant on the Pacific Coast of Baja California, which would produce about 7,500 cubic meters of water each day for processing ore.

Local residents fear that mining will deplete and pollute the arid region’s water supplies, cause soil contamination and leave behind mountains of earth that would transform the landscape. They argue that the state stands to benefit far more from preserving its natural assets and boosting tourism than from pursuing mining’s dubitable gains. “It’s about protecting tourism and economic activity, our water and our health,” says Jeanneht Armendáriz, a biologist and member of Environment and Society, an organization based in Baja California Sur that is a member of the Citizens’ Front. Also, says Armendáriz, because Baja California is a peninsula and therefore less connected to other ecosystems, the region’s flora and fauna are more vulnerable. “Many of our species are endemic,” she says. “That’s reason enough in itself.”

The issue at the heart of the court case was the mine’s location—in the buffer zone of the 112,000-hectare (277,000-acre) Sierra de la Lagunas reserve. Sierra de la Lagunas is home to pine and tropical dry forests of rich biodiversity. A 2016 binational survey conducted where the mine would be located identified 877 plant and animal species. The researchers counted nearly 400 plant species, including some rarely found in the peninsula, such as mountain yellowshow (Amoreuxia gonzalezii) and the leguminous shrub Crotalaria pumila.

Among the mammals recorded were the desert shrew (Notiosorex crawfordi) and pocket mouse (Chaetodipus ammophilus), both of which the Mexican government considers threatened. Nearly 80 kinds of bird were spotted, among them a strong population of San Lucas Cassin’s vireos (Vireo cassinii lucasanus), which are endemic, and Hutton’s vireo (Vireo huttoni cognatus)—both of them threatened species. Exequiel Ezcurra, who helped lead the survey, notes that the environmental impact statement approved by Semarnat in 2014 puts the number of species present in the area at 220—a quarter of the number the survey ultimately found. “The [statement] says there is nothing here, that it’s a silly desert with very little,” says Ezcurra, who is director of the University of California’s Institute for Mexico and the United States. “We’re sick and tired of environmental impact statements that say there is nothing there.”

The 2015 Citizens’ Front complaint argued Mexican law only permits economic activity in a nature reserve’s buffer zone if it is “promoted by the communities that live there.” The law states natural resources in a reserve may only be used “to satisfy the basic economic necessities of and consumption by inhabitants” and “without damaging the ecosystem, changing the landscape in a significant way or causing irreversible environmental impact.” Fernando Ochoa, director of Northwest Environmental Defense, a Baja California legal nonprofit, says the very presence of a mine “completely goes against the spirit of a protected area.” Says Ochoa: “Mining is an activity that by its nature destroys the environment. Minerals are non-renewable.” He adds that designating an area of natural importance and then permitting mining there is “a paradox.”

While the legal complaint against Los Cardones centered on the mine’s presence in a nature reserve, scientists and environmental activists allege the project also is riddled with problems that were glossed over by the environmental impact statement. For one, say experts, gold in the earth is bound with arsenic, which would be released when the granite is ground up. Particles could seep into the ground when it rains, compounding the region’s existing problems with elevated concentrations of arsenic in groundwater. That problem, experts say, would emerge in a decade or so, after the mining company has moved on.

Another concern is the water supply. In parched Baja California Sur, it would be impossible to spare the volumes of water needed to process ore, experts say. While the company says it would produce fresh water through desalination, Ezcurra is skeptical. The process would cost a fortune, he says, forecasting that the company would build a plant for show, then seek water elsewhere. Spalding says a desalination plant would produce torrents of “high-salinity brine.” He adds: “Where are you going to dispose of that? Put it back in the ocean? Put it back into near-shore aquifers?”

Ezcurra points in addition to a geological issue—namely, that the Sierra de la Laguna reserve lies on a seismic fault. The risk this poses—that an earthquake might cause the tailings pond to crack—was not addressed in the impact statement, he notes, even though the pond would contain cyanide used in the leaching process.

Mark Chernaik, staff scientist at the Oregon-based Environmental Law Alliance Worldwide, says the project could employ dry tailings disposal, a process in which water is removed from the mining waste and the residue is stacked in a smaller area without need for a pond. But even if the project were substantially modified in an attempt to address environmental risks, Chernaik says, the fact that the mine is in a protected area would remain. “You could improve the project so that it’s not as horrendous,” says Chernaik. “But, given the location, nothing you could do would make it acceptable.”

Mexico’s profile as a mining-investment magnet has grown in recent years. The country now ranks among the world’s top five recipients of mining dollars; it mines more silver than any other country, and is among the top producers of gold. Its terms are attractive: foreign investors may hold up to 100% of a Mexico-based mining corporation and own mining concessions outright. Concessions can be sold, and rents are relatively inexpensive—as little as 41 US cents per hectare per year.

Baja California Sur has far less in the way of mining activity than some other Mexican states, but interest in projects in the state is growing. During 2010-15, the share of land in the state covered by mining concessions grew from 6% to 12%, according to a report by The Ocean Foundation. Many of the new concessions are in Loreto, home to the state’s biggest mining operation, the US$2 billion Boleo copper mine, which has both underground and surface operations and began production in 2015.

Many concerns about Los Cardones extend to other mining projects. Farmers, tourism entrepreneurs and environmental activists fear that mining will deplete and contaminate the region’s already-fragile water supplies. They also worry that the process of extracting gold would pollute groundwater, with contaminants making their way to local ocean waters—an important destination for migrating turtles and whales. Project critics argue that in return for taking on heavy environmental risks posed by the mine, Baja California Sur would gain only a few hundred direct and indirect jobs and little long-term economic benefit. They question the wisdom of pursuing mining in a state that already leads Mexico in many economic and social indices; Baja California Sur enjoys the country’s highest education and life-expectancy rates and lowest poverty rates.

Local businesses worry mining will affect the fast-expanding tourism industry, which accounts for about three quarters of the state’s economic growth. Among those who joined the legal case against Los Cardones are hotel owners from Los Cabos and organic farmers, Environment and Society’s Armendáriz notes. “They know it’s a threat to tourism, to organic farmers,” she says. “They know their economy will be affected.”

Northeast of the proposed Los Cardones site—outside the biosphere reserve and near the mining town of San Antonio—a subsidiary of the U.S. mining company Argonaut is in the exploration phase of an open-pit gold mining project. The subsidiary, Minera Pitalla, says the mine would cover 800 hectares (2,000 acres) and employ 350 people. The Niparajá Natural History Society, a group that promotes sustainable development in Baja California Sur, argues the project would deplete the local aquifers and leave the area with a crater the size of 84 football fields.

Further north, near the border of the state of Baja California, Mexican mining giant Grupo México is seeking permits for open-pit gold and copper mines near the community of El Arco, just outside the Vizcaíno Biosphere Reserve. Environmental experts worry that the projects, which would involve investments of some $1.5 billion, would damage the Vizcaíno aquifer.

Seabed targeted, too

Nor are Baja mining plans restricted to terra firma. The so-called Don Diego mining project in Bahia de Ulloa, an estuary on Baja California Sur’s Pacific coast, calls for dredging phosphate-sand deposits on the seabed. The Bahia de Ulloa is the prime feeding ground for olive ridley (Lepidochelys olivacea) and loggerhead (Carreta carreta) turtles, both of which are on the International Union for Conservation of Nature (IUCN) red list. It is rich in red crabs, blue whales and black marlin and on the migratory route of grey whales that breed in lagoons to the south. It is a vital fishing ground, accounting for about 42% of fishing in Baja California Sur.

The Ocean Foundation’s Spalding says the Don Diego project, led by a subsidiary of Odyssey Marine Exploration, would create a plume of sediment about 2.5 miles (4 kms) long. This, he says, would worsen water quality, limit photosynthesis and thus diminish food supplies for whales, turtles and other marine life.

The battle over Los Cardones is by no means over, local activists caution. The project has already been defeated and revived twice. It first emerged under the name Paredones Amarillos in the late 1990s, but local resistance and problems over land tenure held the mining project up so long that its permit expired. It was later re-launched under the name of Concordia, but the government denied the project a “change of land use” permit. Vista Gold, which had a majority stake in the Concordia project, sold it to Invecture, which revived the project under its current name.

Desarrollos Zapal has appealed the March ruling to a district court in Baja California, according to Arturo Rubio Ruiz, a lawyer and member of the Citizens’ Front. If the appeal succeeds, the Semarnat permits will be reinstated. In the meantime, the project is suspended.

The court decision and the pending appeal mark just one front in the legal battle over the project, however. At least two legal complaints have been brought by academics and hoteliers on grounds that the environmental impact statement is misleading and never should have been approved. Gabriel Patrón, who for years campaigned against Los Cardones with Niparajá Natural History Society, says the fight against the mine is a “game of chess that will go on for years.” Still, he describes the March court decision as “very important.” Says Patrón: “It was a big citizens’ movement. A lot of people were involved. One thing is the legal victory and another is the social triumph.”

Unusual mix of opponents

Certainly, the Los Cardones fight has animated urban stakeholders who, at least in Mexico, have not traditionally weighed in on mining projects. Disputes over mining in mainland Mexico tend to involve opposition from people, often members of indigenous communities, who live near the project sites. Armendáriz points out that Los Cardones, by contrast, has drawn opposition from a “mainly urban” mix of academics, business people, retirees and hoteliers. “The fight has been quite different here,” she says. “We have a different social profile.”

Miguel Angel Mijangos, representative of the Network of Mining-Affected Peoples (Rema) in Mexico City, says that the Baja coalition’s unusual profile may make it harder for them to connect with other anti-mining groups around Mexico. “They have a long struggle ahead,” he says. “They’ll need a network.”

If the district court upholds the annulment of the permit, activists and lawyers hope the government will respect the decision and not try to find a way around it, such as an executive order. “The government has to decide whether it’s going to sacrifice this place for short-term mining,” says Spalding. “I am mildly hopeful that they won’t do that.”