Rising heat puts the Kalahari’s ecosystem on the edge of survival

Twin silhouettes are motionless in the night. Above, a silver-veiled moon hints of a sky. Below, Earth is a darkened disk.

Sound gives the night depth: Common barking geckos rattle like castanets in receding waves into the shadows. The two women have been seated on a shallow dune for hours in hushed anticipation. One unfolds her legs, stretches, crosses them at the ankles. The other rocks, as if uttering a prayer mantra, limbering her muscles. Their radio-tracking gear drew them at sunset to this spot in the southern part of the Kalahari, which has long been called a desert but has characteristics of a dry savanna ecosystem.

Somewhere below them in a warren of burrows is a ground pangolin they’ve been monitoring for two months. She’s late to rouse—it’s 10 p.m.—which might have something to do with the day’s withering heat.

For the purpose of recordkeeping, she’s called Hopewell 3, after the place where local trackers first found her and doctoral researchers Wendy Panaino, 28, and Valery Phakoago, 30, tracked her by following her spoor in the sand. Now they follow her by reading the bleep-bleep-bleep of radio waves sent by a device fixed to a scale on her rump.

Tonight the researchers are on a quest for pangolin dung—“Kalahari gold,” they call it—the source of a trove of information about how this shy, ant- and termite-eating animal’s life is interwoven with grasses and the tiny insects that reap their seeds and eat them. It’s another important thread in scientists’ understanding of the interconnectedness of living things in the dry African savanna, all of which starts with the summer rains, usually from November to March.

Their research, through the University of the Witwatersrand’s Wildlife Conservation Physiology lab in Johannesburg, is part of a bigger study called the Kalahari Endangered Ecosystem Project (KEEP) that aims to understand how climate disruptions will tug on the delicate fabric of life here.

This part of the Kalahari is already red-flagged as a climate hot spot. Modeling by climate scientists at the University of Cape Town suggests that within a decade, when the global temperature could exceed the rise of 1.5 degrees Celsius (2.7 degrees Fahrenheit) that the UN’s Paris Agreement seeks to avoid, average temperatures in Botswana—just north of Hopewell 3’s foraging grounds—will already have warmed by nearly four degrees F. Beyond 5.4 degrees F in average warming globally, which would mean 7.6 degrees F here, the science points to system collapse for the Kalahari.

A recent study of the pangolin’s termite-eating dune neighbor, the aardvark, during a drought in the summer of 2012-13, gives distressing clues as to what climate change could mean for life here: If the rains fail, a cascade of disasters may unfold, starting with the withering of the grasses, a crash in numbers of ants and termites that feed on them, and hunger—or starvation—for anything that depends on those insects for nourishment. If the failure of the annual greening means disaster for these two insect-eaters during a drought spell, what would a longer-term system collapse driven by searing temperatures and crippling droughts mean for the many different threads of life that are entangled in a food chain that draws vitality from the grasses?

The Kalahari is the world’s largest expanse of unbroken sand, a rolling ocean of windblown dunes across Botswana, Namibia, South Africa, and beyond that are topped with savanna, a mostly grassy landscape dotted with occasional trees. Here on the region’s southern edge, air currents have swept up a series of north-south–running dunes lapping against the flanks of bare, quartzite hills that rise like whalebacks from the deep.

Decades of farming have thrown the region into disarray, and now it seems that the freight-train effects of planetary heating are bearing down too. What Panaino and Phakoago learn about the secretive lives of creatures out here on the dunes will give conservation managers emergency signals to help them better protect this vestige of the Kalahari.

(Surviving the extremes of the Kalahari)

Hopewell 3 is the third pangolin found for the study on what was formerly Hopewell Farm, one of 50 reclaimed cattle ranches that have been absorbed into Tswalu Kalahari Reserve, established nearly 30 years ago. At 294,000 acres, Tswalu is South Africa’s largest private game reserve, a remnant of the once wild Kalahari that has been carved up by farms, roads, and iron ore and manganese mines.

Aside from its luxury private lodgings for game-watchers, the reserve hosts the KEEP research hub, managed by the Tswalu Foundation, which connects the work of scientists interested in semiarid ecologies. Their efforts focus on a central question: How will this hot, dry place respond to rising temperatures and more frequent and intense droughts if, as predicted, atmospheric carbon dioxide pollution keeps heating the planet?

Answering that question will be key to how the reserve’s managers balance the abundance of the grasses with the appetites of the creatures that depend on them, from grazing insects and their pangolin predators to the roaming antelope herds and the carnivores that chase them down.

When Hopewell 3 surfaces, she’ll announce herself with sound. Eventually, they hear it—even over the clicking of geckos—the scritch-scratch of bony grass rasping against the pangolin’s scales. Panaino and Phakoago glide to their feet, their headlamps casting a stage light into which Hopewell 3 sways, floating over the dune like a hunched clockwork toy in a suit of armor. Her shield of articulated plates starts with a widow’s peak over the bridge of her nose and flares out across her shoulders. It flows down her domed back and tapers across a broad plank of tail. The hem has a jagged edge.

If startled, she’ll snap into a ball so tight that even a lion would struggle to pry her open. But Hopewell 3 is unfazed. She totters across the dune on stout hind legs, her feet pressing blunt marks in the sand. Her forelegs are tucked demurely into her chest, like a mantis in prayer, touching the ground only when she tips off kilter.

A button eye glints above a conical snout that nods this way and that, reading the ground. Olfactory wizardry leads her to tonight’s first course: cocktail ants, as they’re commonly called. She claws at the bole of a runty gray camel thorn, pulling the cap from a nest hidden in the bark, releasing a rivulet of ants flowing up the trunk.

She plunges headfirst into the stream, face hidden as her sticky ribbon-tongue laps up dinner. It’s impossible to know how many ants she eats with each mouthful, but after five years of sifting through the digested remains of meals like this, Panaino knows that less than a third of what the pangolin takes in tonight will be insects. The rest will be dune sand. Panaino also knows that Hopewell 3’s preferred foods are cocktail ants, pugnacious ants, and snouted harvester termites.

Panaino has calculated that on average the pangolin will eat about 15,000 of the rice-grain-size insects each night, supplying most of the nutrition and water she needs to survive in this parched dunescape.

Satisfied with her first feeding, Hopewell 3 toddles off in search of her next course. The humans follow behind, hoping for gold.

October in the southern Kalahari is anguished and liminal, poised for rains to break the fast. The dry winter of 2020 has drawn to a close, and the grasses that anchor the dunes are as brittle as fine fossils. Winter has taken its usual toll. The dunes are also threadbare after intermittent droughts and decades of gleaning by cattle and, more recently, game such as antelope, zebras, wildebeests, and buffalo.

Forecasts hint that this summer’s rains may be good. A La Niña has been brewing half a planet away in the Pacific Ocean. This cyclical ocean-atmosphere dance usually conjures rain for parts of southern Africa. It’s the yin to the El Niño’s parching yang, and Tswalu is gasping for it.

On an artist’s swatch, the color of the sand might show as pumpkin or carrot, tinting into apricot when the sun’s low on the horizon. But life here doesn’t have the effortless fecundity of an orchard. Rust doesn’t describe its particular hue either, even though it’s mixed from a palette of ground-down quartzites stained by oxidized iron.

Grass is the golden thread that makes life possible in this nutrient-scant ocean of sand. It tethers the dunes against the winds’ pull. It soaks fickle moisture from the soil and dams it in its cells, to quench the thirst of ants and termites; their subterranean homes are larders for pangolins and aardvarks but also insect-eating bat-eared foxes and aardwolves.

Grass is the wattle and daub for the Kalahari’s aerial architects—the sociable weaverbirds, whose decades-old nesting chambers are stitched from grass blades. These high-rise tenements give shelter to generations of weavers and also draw in African pygmy falcons as tenants. Their avian residents entice hungry Cape cobras and boomslange whose lithe forms loop among the chambers like strings in a chandelier. Grass is fodder for the grazing ungulates that themselves are food for lions, cheetahs, leopards, wild dogs, and other predators of the African savanna.

Rebirth in Tswalu starts with the rain-fed flush of grass. Thundershowers deliver an average of about 13 inches a year, and they’re notoriously capricious. In some years, rain gauges might register fewer than seven inches; in others, nearly double the average. In times past, game animals responded to the boom-and-bust greening by traveling across great distances, often tracking the rain clouds, knowing that they would lead them to grazing bonanzas. But decades of cattle ranching slung fence lines across migratory paths, corralling the remaining wild herds into reserves like this one.

Conditions are changing further still. During the past half century, temperatures in parts of southern Africa have risen at twice the rate of the global average.

According to the South African Weather Service, 2015, 2016, and 2019 were the hottest years on record since at least 1950. In January 2016, thermometers at Augrabies Falls, about 150 miles southwest of Tswalu, registered more than 119°F. That’s “amongst the highest temperatures ever recorded so high above sea level in the Southern Hemisphere,” says Stefaan Conradie, a doctoral researcher with the Climate System Analysis Group at the University of Cape Town, and “the second highest reliably measured temperature in southern Africa.” Without climate change, the 2015-16 heat wave would have been about a 1-in-10,000-year event, he says, citing recent analysis.

How temperature increases will disrupt rainfall is difficult to predict, but in this part of the continent, the summer rainy season is likely to start later and be shorter. When rainstorms occur, they may be more intense, dropping greater volumes of water over shorter periods, which could result in surface flooding. There could be longer dry spells between storms.

What could this mean for the tenuous web of animals and plants in the southern Kalahari? What would happen if the summer rains failed repeatedly, if drought conditions were more frequent, if the summertime greening didn’t come on time? What would it mean for the ants and termites that fill up their underground larders with seeds and grasses each summer?

And if the numbers of those insects fell drastically, what would happen to the pangolins, already threatened with poaching in many parts of southern Africa, and the other ant-eating mammals?

The aardvark looks as if it has trotted right out of a nonsense verse: the snout of a pig, the ears of an ass, an improbably long face in between. It has the skin of a balding man and whiskers like the eyelashes of a drag artist, but only on the lower lids.

Aardvark means “earth pig” in Afrikaans, and they’re earthmoving machines. Shovel-shaped claws on taloned feet allow an aardvark to jackhammer through baked soil crust, opening up the ground for burrow-building or to break into rooms stuffed with bugs.

A host of other animals—jackals, Cape cobras, puff adders, pythons, ground squirrels, mice, wild cats, warthogs, swallows, chats—use the underground dwellings that aardvarks hollow out in a sort of time-share arrangement to endure the Kalahari’s extremes.

Nora Weyer, also with the Witwatersrand physiology lab at the time, tracked aardvarks in Tswalu from the winter of 2012 to the spring of 2015 for her doctoral work. She used small traps sunk into the ground to collect ants and looked for telltale conical soil heaps left by termites in the area to measure their abundance. She collected their scat to find out what insects they ate, and how many, and found that harvester termites account for about 90 percent of an aardvark’s water and energy needs. She also monitored temperature-logging implants in the aardvarks to determine if the animals were getting enough energy to keep warm through the chilly Kalahari nights, when daily minimum temperatures can dip to about 65°F in summer and even nudge below freezing in winter.

In typical years, when the summer rains arrive with their usual sound-and-light show, the dunes burst to life, with ants and termites thriving and aardvarks feasting on them. But in the first summer of Weyer’s study, 2012 into 2013, no rain fell during the hottest months. The overall season was well below average, and Tswalu limped into the next winter with poorly stocked pantries.

While following her study aardvarks and decrypting their scat, Weyer noted a dramatic reduction in grasses, which she knew would lead to a decline in harvester termites. By summer’s end, the aardvarks were wasting away, their spines and hip bones straining against drum-tight hides. These normally nocturnal animals started leaving their burrows during the day, sometimes even before noon, in search of food to make up for their hungry nights.

The implants indicated that the animals’ body temperature swung wildly in 24-hour periods, compared with more stable body temperatures when their food supply was reliable and their energy levels good. This suggested that they weren’t getting enough energy to stay warm at night, and they seemed to compensate by using the daylight hours to bask and warm up.

But this immediate emergency adaptation didn’t see many of Weyer’s aardvarks through to the next rainy season. Of the six animals equipped with trackers in the study in 2012, five died in 2013. Weyer saw the bodies of many other dead aardvarks in the veld, and survivors looked listless, dazed, and gaunt. The message from this drought year was clear: If the rains fail, even for a single summer, the fabric that keeps grasses, ants, termites, and insect-eating animals woven together for survival may start to unravel.

After Hopewell 3 has supped on her first helping of cocktail ants, she follows a meandering loop to her regular haunts, moving with an endearing swank and swagger. Panaino’s sneakered feet tread lightly behind her, while Phakoago slips away to scan for signs of buried dung.

About an hour later, the pangolin pauses, and scoops a slim hollow into the sand. Panaino shimmers with excitement, flashing her light to alert Phakoago.

Poised over the depression, Hopewell 3 delivers a mound of glistening black scat. Panaino usually avoids interfering with study animals, but if the pangolin drags her tail as she waddles off, this Kalahari gold will melt into the sand. Using one finger, Panaino raises the pangolin’s tail a fraction as she moves, keeping the treasure intact.

For the scientists, it’s hard enough to find an animal as secretive as this, let alone the dung that might otherwise be lost in the sand. The two women are on their knees, scooping it up with bare fingers and dropping it into a sample bag. Once they’ve recovered every last fragment, they erupt into a synchronized jig, stage-whispering an improvised ditty about “pango poo.”

A few days later, Phakoago is back at the research site, with little more than a bucket, jug, tea strainer, and a take-out food container as her lab equipment.

She weighs dried scat collected two months earlier. Then she drops it into the bucket, sloshes a cup or two of water onto the sample to separate the good stuff from the sand, and swirls the container like a frontier woman panning for gold.

The dung dissolves into a coffee-colored brew with a foam of body parts—mostly ant and termite heads and a million pinprick legs—collecting on the surface. She sieves the liquid, gathering a heap of what looks like coffee grounds. Later she’ll put a small sample of this under a microscope and count every insect head, identifying and tabulating each species.

The researchers use this laborious technique to understand the nuances of pangolins’ and aardvarks’ diets. This knowledge ultimately will yield a better appreciation for the complexity of relationships that weave back to the veld and how it should be managed.

The drought that gripped Tswalu during Weyer’s aardvark study gave her baseline data for comparing aardvarks’ diet in good and bad foraging years and noting their resulting behavior changes.

Panaino’s study shows what pangolins eat, and how much. Phakoago’s contribution is to examine the dung of both pangolins and aardvarks, collected in the same seasons and under the same conditions, and give an apples-to-apples comparison between the two animals’ feed-ing patterns.

Based on Panaino’s findings—that a pangolin eats an average of 15,000 ants and termites a night—she calculates that it eats 5.5 million a year. Add to that the number of ants and termites eaten by one aardvark and one aardwolf in a year, and Panaino estimates the total for all three is about 100 million insects. The number would be far higher if it included the many other animals that also feed on ants and termites, even in part. Sociable weavers, for example, eat mostly plants, but about a tenth of their diet is termites, and the ant-eating chat is as its name suggests.

Late one evening, while Panaino and Phakoago scan the radio waves for signs of Hopewell 3 and other nearby study animals, the change comes.

It starts with iridescent orbs exploding voicelessly on the western horizon. But in less than an hour, strobes of lightning play closer on the surrounding dunes, followed by the sound of a drum mallet drawn across a corrugated tin roof. The sky begins to shatter. Luminous cracks tear through the clouds, skewering nearby hills with retina-searing blasts. The percussion is a clatter of cymbals and a roll of shuddering bass drums.

A timpani of droplets smacks the ground, ephemeral islands of moisture in an ocean of desiccated sand, filling the air with iron-scented mist. The researchers decide to retire for the night—it’s too dangerous to be out on the exposed dunes, and with the elements this voluble, the pangolins are very likely staying inside.

The crescendo is brief. The space between the veins of light and their accompanying drumbeats soon draws further apart and farther away as the storm hurries off to the east. It is over for now, but this is how the rains should come. This is how the greening should begin. The grasses will send up lush spears, seeds will swell like dewdrops on their tips, and the life that depends on their abundance will feast once more.

The geckos once again take up their chorus, clicking into the night.