On his first trip to Colombia's Gulf of Urabá, once occupied by guerrillas, geologist Camilo Montes hunts for clues to when the Americas collided.

Juan Cristobal Cobo

Colombian scientists race to study once-forbidden territory before it is lost to development—or new conflict

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TRIGANÁ, COLOMBIA—The rare travelers intrepid enough to find their way here to northern Colombia come for quiet beaches and coral reefs. Not Camilo Montes. After enduring a choppy motorboat ride across the Gulf of Urabá to this ramshackle village, he and three other geologists head into the jungle, seeking clues to a profound geological event that transformed the Americas.

The team hikes for 3 hours before reaching a spot where a creek spills gently over a mass of smooth, dark rock. They call out GPS coordinates and use rock hammers to chip off flecks, which they examine with magnifying glasses. There's no doubt about it: The rock and its pistachio-colored inclusions were formed as magma welled up and created the mountains of the Panama arc, which forms Panama and northern Colombia. "It's like a photo of when the magma was crystallizing," Montes says, bagging several kilograms of samples to take back to his lab. It's exactly what he came here hoping to find.

Montes, a geologist at the University of the North (Uninorte) in Barranquilla, Colombia, has studied rocks like these his entire career. He investigates the formation of Panama's volcanoes and their collision with South America, which linked the Americas and allowed ecosystems separated for millions of years to mingle. For decades, scientists have thought that the land bridge between the continents formed about 3.5 million years ago. Citing fossil evidence and the ages of volcanic rocks, Montes and others argue that the continents joined before 10 million years ago. If confirmed, the older date would change both how scientists analyze fossils from the two continents and how they calibrate the molecular clocks used to estimate when species diverged. "If the 3.5-million-year date is wrong, it could upend everything," says Susana Caballero, a biologist at the University of the Andes (Uniandes) in Bogotá. Dating the crystalline inclusions, Montes says, may influence that scientific debate.

Before venturing here, Montes had limited his fieldwork in this geological collision zone to Panama, where telltale rocks are also uncovered. For decades, the Urabá region, just across the border in Montes's home country, was occupied by the Revolutionary Armed Forces of Colombia (FARC), a leftist guerrilla group that had waged war on the Colombian state since 1964. "Those who went in never came out," Montes says. That all changed with a stroke of a pen on 26 September 2016, when Colombian President Juan Manuel Santos signed a peace deal with the FARC. Guerrilla fighters shuttered their jungle camps and handed over their weapons.

Now, Montes and other Colombian scientists are rushing in, exploring the geology of their country, its wealth of species, and how its ecosystems are coping with stresses such as deforestation and climate change. Those forays are risky: Vast areas haven't yet been cleared of land mines (see sidebar), and drug traffickers, paramilitary groups, and non-FARC armed insurgents plague the countryside. But the researchers are seduced by the prospect of prying scientific secrets from huge swaths of land that are no longer off-limits. Urabá's geology, Montes says, "is all a blank slate."

A landscape opens up

A 2016 peace treaty signed by Colombia and the Revolutionary Armed Forces of Colombia (FARC) allows scientists to study some of the most biodiverse and geologically significant territory in the world.

Magdalena Medio andBajo Cauca Barranquilla Encenillo BiologicalReserve Triganá Sapzurro La Miel (Panama) Gulf of Urabá Chingaza National Park MacarenaNational Park Pacific Ocean Bogotá COLOMBIA PANAMA FARC presence in 2013 FARC presence in 2002 0 Km 250
CREDIT: (MAP) N. DESAI/SCIENCE; (DATA) INTERNATIONAL CRISIS GROUP; A. LUNA ET AL., TROPICAL CONSERVATION SCIENCE VOL. 9, 788 206

Terrae novae

Much of Colombia's biodiversity is also unexplored. The nation is thought to contain nearly 10% of Earth's known species. It has the most bird species of any country and trails only Brazil, nearly eight times larger, in amphibians. The wellspring of that diversity is a unique geography: In Colombia, the Andes mountain system fractures into three ranges, crucibles of speciation that have spawned hundreds of distinct ecosystems. "Colombia has an enormous responsibility to conserve these species," says Andrés Link, a biologist at Uniandes who studies monkey behavior. But to protect its species, researchers need to inventory them.

Until now, surveys have been difficult, and prospects for long-term studies were even bleaker. As a student in 2002, Link studied monkey populations from a research station in Macarena national park, 200 kilometers south of Bogotá. At the time, Macarena was a FARC stronghold, and hostilities were intensifying. Link was at the station that January when locals, following FARC orders, urged the scientists to leave. Biologist Adriana Sánchez Andrade, another Uniandes student then, also found that critical areas of Colombia were off-limits for her work on plant ecology. She opted to do fieldwork in Ecuador. "It was unbelievable, not to be able to go out and explore my own country," she says.

Now that researchers are more free to explore, they are finding that the long conflict had an ecological upside: suppressing development in guerrilla-held territory. FARC fighters deforested some areas to plant coca, but their camps were well hidden and had a light environmental footprint. The violence also deterred farmers and ranchers from encroaching on the wilderness.

Biologist Juan Manuel Posada and his team are monitoring the Encenillo forest, secondary growth that is thriving on the site of a former limestone mine.

Juan Cristobal Cobo

In the months since peace took hold, the Colombian government has sponsored collecting trips to those ecological terrae novae. The Alexander von Humboldt Biological Resources Research Institute, an environmental nonprofit in Bogotá, has run four such trips since August 2016 and is planning a fifth. "We've found new species on almost all the expeditions," says Javier Barriga Bernal, a Humboldt biologist and expedition coordinator. The team has collected thousands of samples and is putting the data online. "This is the most optimistic moment I've ever experienced in Colombia," says Mailyn Gonzalez Herrera, who spearheads Humboldt's genetic research. "It's a privilege and a dream for us as scientists to be able to discover our own megadiverse country."

But the once-occupied ecosystems won't remain pristine for much longer, Link says. "These areas haven't just opened up for scientists," he says. "They've opened up for the whole machinery of development." Deforestation is picking up nationwide, including in Colombia's Amazon region, as farmers clear forest for pastures and crops. In 2016, the last year for which statistics are available, deforestation in Colombia jumped 44%. "The country is experiencing more environmental deterioration than ever before," Link says.

He is now studying spider monkeys in Magdalena Medio, an area in central Colombia with rampant deforestation over the past several years. Link has seen the monkeys' habitat shrink and fragment, making the fruit they depend on hard to find. He has also spotted several albino spider monkeys—a sign, he says, of inbreeding, which becomes more common as populations shrink.

The environmental destruction is in vivid relief on the geologists' journey in Urabá. On their trek to the smooth, dark rock, the landscape becomes hilly. In one entrancing swath of forest, towering ceiba trees loom and hooting howler monkeys leap from branch to branch in the understory. But over the crest of the next hill, cornstalks wither along the trail, and the valley below is carpeted with grass where the land has been cleared for cattle ranching.

Road to recovery

"Here's the entrance," says Juan Manuel Posada, pointing to an apparently impenetrable thicket. The biologist tucks his tall frame between branches and vines and slips into the forest of the Encenillo Biological Reserve, where he and others are studying the ability of denuded landscapes to regenerate. Until 1992, this area, about a 90-minute drive from Bogotá, was a limestone mine. Depressions—former pits, now filled in—are visible below the overgrowth. The FARC captured La Calera, a town along the road to Encenillo, in 1994, severing access to the reserve.

Now, taking advantage of what he calls "the post-postconflict" that Bogotá has enjoyed since the FARC was driven away in 2003, Posada is chronicling how secondary forests are rebounding in this and 45 other plots around the capital. His team from Del Rosario University in Bogotá is tracking pioneer species, how long reforestation takes, and whether secondary forests in the Andes sequester as much carbon as primary forests. At Encenillo, dashes of red paint mark trees in a 20-square-meter plot that Posada and his colleagues have monitored since 2013. They measure size, growth rate, root mass, rate of photosynthesis, carbon storage, and other indicators of ecosystem health.

The moist, high-altitude terrain of Chingaza national park, once a guerrilla stronghold, supplies 80% of Bogotá's water.

Juan Cristobal Cobo

A mature forest at this latitude and elevation—about 2800 meters—would be so thick with tall trees that little light would reach the forest floor. Here, patches of blue sky are visible through the canopy. But the forest is on the mend, and wildlife is coming back. Spectacled bears, an emblematic but vulnerable and rarely seen Andean species, have even been spotted. "There's a lot of biodiversity even after centuries of human intervention," Posada says. His research, he says, supports safeguarding areas even after they are no longer pristine.

Still, Encenillo and other ecosystems face a reckoning as the climate changes. Posada is tracking that trend in another landscape once occupied by guerrillas: the rainy, high-altitude páramo of Chingaza national park, a treeless ecosystem that supplies 80% of Bogotá's water.

A few years ago, Sánchez Andrade, now Posada's colleague at Del Rosario University, spent 18 months collecting data on temperature, precipitation, cloud cover, and how each variable affected the growth rate and photosynthesis of plants native to the páramo. She and Posada hope to anticipate how the ecosystem may respond to climate change. Its plants should be resilient to rising temperatures, Sánchez Andrade says, because they can withstand the páramo's daily 20°C swings. But if climate change were to curtail the páramo's nearly year-round rainy season, the consequences could be devastating for the ecosystem—and for the millions of Bogotá residents who rely on the aquifer. "Everything is so uncertain right now," Sánchez Andrade says. But at least, she says, she can be here to study it.

Lingering threats

"Bienvenidos a Panama." The hand-painted wooden sign greets Montes and his team of geologists at the border between Sapzurro, Colombia, and La Miel, Panama, a short boat ride from Triganá. To Montes's chagrin, the geology here turns out to be less compelling. It's dominated by sedimentary rocks that built up gradually, rather than volcanic rocks that provide a precise time marker. But that's not the only reason the area might not be ideal for his research.

The sleepy, beach-town feel of Sapzurro and La Miel belies a humanitarian crisis engulfing the border. Elsewhere, Colombia is struggling to absorb more than half a million refugees from Venezuela's deepening calamity. Here, migrants come from as far away as Asia and Africa, hoping to cross into Central America on their way to the United States or Canada. The turmoil attracts human traffickers to Urabá.

Volcanic rock exposed in Colombia, near the Gulf of Urabá, holds clues to when North and South America were united. A team of Colombian geologists including Felipe Lamus Ochoa (lower left) is taking advantage of peace to study them.

Juan Cristobal Cobo

The region also has long been a popular route for drug smugglers. It connects the remote mountains of Antioquia, a state where farmers grow coca for processing into cocaine, to the Caribbean Sea. "The stars look beautiful here," a guide tells the geologists. "But some of them aren't stars—they're drones," which drug cartels use to monitor the gulf. The FARC, like other rebel groups in Colombia, funded its activities through the cocaine trade. Paramilitary groups, cartels, and smaller guerrilla outfits have filled the vacuum. "Now it's pretty anarchic," says Pablo Stevenson, an ecologist at Uniandes who studies primates. In the past couple of years, coca production in Colombia has soared, according to the United Nations Office on Drugs and Crime. That trend could usher in more violence and more land mines—and restrict access again as cartels and paramilitary groups expand production and occupy more territory.

Warning signs are flashing elsewhere. Farther inland, Stevenson wants to reopen Macarena station. He has made three trips to the area since 2015 and has observed healthy populations of monkeys there. But negotiations to turn the station's lights back on haven't been smooth. Despite the support of some villagers hoping for jobs, armed groups in the area haven't agreed to allow the researchers back in. "The optimism I had at the beginning of the year is diminishing," Stevenson says. Barriga Bernal, who coordinates the Humboldt expeditions, also has faced resistance. "Distrust is a generalized feeling in places where the conflict lasted nearly 60 years … and violence is still a daily occurrence," he says. "In these areas, the postconflict era is still far away."

Many scientists also see a looming threat in Colombia's presidential elections next month. A conservative, Iván Duque Márquez, leads in the polls, vowing to modify the peace accord to jail former FARC fighters. Some fear that Duque, if elected, "could blow up the peace process," says Uninorte's Felipe Lamus Ochoa, a geologist working with Montes. In that event, further fieldwork in Urabá would be unlikely. For now, Montes has seized on what may be a fleeting opportunity; earlier this week, he was back in Urabá with dozens of students. "The access has improved," he says. "But who knows how long it will last?"

Reporting for this story was supported by the Pulitzer Center on Crisis Reporting.