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In remote Gabon, warmer nights and less rainfall may be preventing trees from growing the nutritious fruit the animals depend on.

Dusk was falling when we drove into the forested expanse of Lopé National Park in central Gabon, leaving the town of Lopé—the last outpost on the way to the reserve—far behind. 

In the distance, the hills were changing color from blue to gray. On either side of the dirt road, a mosaic of savanna and thick tropical rainforest stretched to the horizon. The landscape looked so primeval that it was possible, in the moment, to think of human civilization as an illusion. Then, just as we were about to enter a dense patch of forest, our driver, Loïc Makaga, who manages the park’s research station, slammed on the brakes.

“Elephants!” he said in a low, excited voice, pointing ahead. He turned off the engine.

A few hundred yards in front of us, a procession of elephants emerged from the forest. In the moonlight I counted six, including a calf nudged along, presumably by its mother. They lumbered across the road at a leisurely pace, gliding into the foliage on the other side with an assuredness that suggested they’d been here many times before. Watching them from so close, I felt like a stranger who had ventured, uninvited, into some family’s ancestral home. Nevertheless, I pulled out my phone to capture the moment, but as I fumbled around with it, hoping to fulfill this trivial, human wish, a huge bull elephant standing less than a hundred feet to our right trumpeted aggressively, its trunk raised in the air.

The rainforests of Gabon are one of the last strongholds for forest elephants, whose numbers in Central Africa have suffered a dramatic decline in recent decades because of poaching. Smaller than African savanna elephants, forest elephants are enigmatic beasts that roam trails they have traversed for generations, feeding on grass and leaves and fruit. They tread softly, moving quietly among the trees, like ghosts in the night. They appear to plan their search for food, much like humans once planned their food gathering around seasons, returning to the same trees when the fruit is most likely to be ripe.

Just as the elephants depend on the forest to survive, many of Lopé’s trees rely on elephants to disperse their seeds through the animals’ dung. Some even produce fruit that cannot be digested by any other animal, suggesting a fragile interdependence with origins deep in evolutionary history.

Despite being remote and relatively untouched by people, Lopé National Park and its elephants appear to be in trouble. Researchers have discovered that Earth’s warming temperatures could be lowering the fruit yield of many species of trees at the park, which in turn seems to be causing forest elephants to go hungry. Some are so undernourished that their bones poke into their thick hides. Because certain tree species depend on the animals to survive, the struggles of the elephant population could jeopardize the long-term sustainability of the forest.

“Even in a place like Lopé National Park, where we have very little human pressure and very low density of population, wildlife cannot escape the impact of human activities—that being climate change,” says Robin Whytock, an environmental scientist at the University of Stirling in Scotland and one of the authors of a 2020 paper describing these findings in Science magazine.

A FOREST’S FEAST

On a sunny, humid morning, I joined Edmond Dimoto, a field researcher with Gabon’s national park agency, on a hike through a lush forest on the slopes of a mountain called Le Chameau, since it’s shaped like a double-humped camel.

Dimoto, a man of muscular build, had swapped his shoes for knee-high rubber boots. Treading carefully on a trail still damp and slippery from the previous night’s rain, he snipped tendrils and vines in his path with a pair of pruning shears. The forest hummed with the sounds of insects and trilled with birdsong.

Stopping by a tree, Dimoto pointed out ants crawling on the trunk. Their bites were horribly painful, he told me: “Your arm will swell up like a balloon for a day.” We decided to move along, stepping over branches and fallen logs as we climbed. He showed me an elephant’s footprints. Still fresh, the markings showed that the animal had slipped in the mud.

Dimoto came to a halt in front of a tree known as an Omphalocarpum procerum, which was dotted with doughnut-shaped fruit sprouting out of its trunk. The fruit has a tough shell that makes it unpalatable for every animal species except elephants. They use their head like a battering ram against the tree to shake off the fruits. Then, with stunning dexterity, they pick one up with the tip of their trunk, cradle it in a crook of the trunk, bring the fruit close to their mouth, and finally pop it in with a deft push from the tip.

Sweat trickling down his neck, Dimoto peered through binoculars at the canopy above. He gazed up and down, doing a quick count of the number of fruits. After a couple of minutes, he took out a notebook and jotted down his observations about the abundance of leaves, flowers, and fruits. He rates each of the trees he surveys on a scale of one (sparse) to four (abundant).

Dimoto’s observations are the continuation of a study that a primatologist named Caroline Tutin began in 1984, when she and her colleagues established a research station that’s still operating inside the park. They wanted to understand how seasonal variations in the amount of fruit affected gorillas and chimpanzees. Tutin’s research ended in the early 2000s, but the monthly monitoring of hundreds of trees marked with metal tags bearing unique numbers went on, making it the longest continuous study of its kind in Africa.

Examining Lopé’s weather data for the previous three decades, Bush and her colleagues found that the average nighttime temperature had gone up by about 1.5 degrees. The amount of rainfall also had decreased significantly. Climate change was making Lopé hotter and drier.

“We think this is the most credible theory as to why fruit has been declining,” Bush says.

After Bush shared her results with Whytock, the two discussed how to figure out whether this was affecting the park’s wildlife. Whytock had just started a project to assess biodiversity in Lopé using hundreds of camera traps. He also had seen recent images of elephants from camera traps that Anabelle Cardoso of Oxford University had set up for her research.

Looking for old images of elephants, Whytock turned to Lee White, a biologist who is Gabon’s minister of water, forests, the sea, and the environment. In the late 1990s, while doing research at Lopé, White had recorded hundreds of videos of elephants on his camcorder. “And he had kept all the tapes—literally hundreds of tapes,” Whytock says. “I was handed this enormous case of tiny digital camera tapes. I had no way to play them.”

Whytock’s mother found a camcorder in her attic. From White’s tapes and other sources, Whytock was able to compile a database of thousands of elephant photos. He found that, on average, the body condition of forest elephants—scored by such criteria as how bony the animals looked—had declined by a pronounced 11 percent from 2008 to 2018. The scarcity of fruit in Lopé was the likeliest explanation. “Fruits and seeds are the highest calorie food in the elephant diet,” Bush says.

One way Lopé’s elephants try to make up for the fruit shortage is by raiding people’s gardens in the middle of the night. Jean-Charles Adigou, whose house was on the edge of the park in a settlement of a few dozen homes, told me he often was woken up by elephants visiting his backyard, where bananas and plantains grew. To scare them away, Adigou and his neighbors would make as much noise as they could. But frequently it was too late, he said. A herd of six elephants can destroy a backyard plantation in minutes. “When I was young, this didn’t happen,” he said. “Elephants stayed far away from the village.”

Another resident in the settlement, a fisherman named Vincent Bossissi, was expecting the worst. I talked to him as he sat on a plastic chair under a mango tree in his backyard, where he also grows corn. When I asked him about elephants, he turned grim and looked away. Mangoes were especially attractive to the animals, he said. He fully expected them to visit one of these nights and strip his mango tree of all its fruit. This explained the row of ripe mangoes on a table beside him. As the conversation went on, I watched him eat one after another, apparently to preempt any losses from a nighttime raid.

Though Bossissi wasn’t enthused about elephants, Brigitte Moussavou, one of his neighbors, told me that many in the community were aware that elephants enable the regeneration of certain tree species, including the greatly valued moabi tree, whose seeds are used for cooking oil.

“We want to protect our crops,” she said, “but we are not against elephants.”

At Lopé National Park, scientists now are investigating whether climate change is altering the elephants’ diet. One morning, I accompanied two field researchers in search of elephant dung. We didn’t have to drive far before coming upon a fresh brownish-green, bucket-size pile beside the road. After slipping on rubber gloves, one of the researchers counted the number of lumps and then determined the circumference of each with a tape measure.

The reason behind collecting such detail, he explained somewhat abashedly, was to document how much dung the elephants were producing—over time, these data would reveal how much they were eating.

After collecting the dung in a plastic bag, we drove to a stream. The researchers emptied the contents onto a rectangular wire mesh and lowered it into the water, letting the finer poo wash away while leaving behind seeds, stems, and branches. From the seeds, Whytock explains, scientists hope to discover which fruits—and how much of them—the elephants are eating and then compare that with the dung studies White and others did three decades earlier. “This is a more direct way to measure if the forest elephant’s diet has been affected,” he says.

On the drive out of Lopé early one morning, not far from where I’d seen the elephants, we saw a buffalo in the road, blocking our path. We stared at it, and it stared at us, standing its ground. A mist hung over the shrubs and trees. In the hushed silence, I found myself wondering about a world being reshaped by warming temperatures. The buffalo finally sauntered away, and we drove on. As the hills and forests receded, I was left with a troubling thought: Could the fraying of the ancient bond between trees and elephants in a place as pristine as Lopé be a forewarning? Was it the case that other seemingly untouched forests, with no Edmond Dimoto to observe their trees, already were being harmed in as yet unnoticed ways?

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