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How Termites Built the Delta

In this blog, we celebrate the friendship that built the Okavango Delta: the mighty termites and their farmed-fungus. One of the first things you’ll notice when visiting the Delta are the colossal termite-mound-spires that dot your surroundings. In this otherwise flat landscape, these mounds are coveted lookout points for sharp-eyed residents or convenient burrows for them to protect their young. But the termite mounds are so much more important than that. Indeed, we can thank their tiny architects for the very existence of the 150,000 islands that pepper this vast inland oasis today. In this blog, I delve into the various hidden benefits of termite mounds, from improving habitat diversity, to enriching the soil, and disposing of toxic salts that could quickly overwhelm the Delta. There is a saying in Africa that goes: ‘if you think you’re too small to make a difference, then you’ve never spent a night with a mosquito’. The real saying, however, should read ‘if you think you’re too small to make a difference, then you’ve never heard of termites!’.


The termite mounds are coveted lookout points for the Okavango's sharp-eyed residents, from leopards to lions, dogs to hyenas, and even birds of prey. NHFU/Hannah Gormley/Liz Johnston.


Dating back over 50-million years, termites are one of the most ancient species on our planet. In this time, some have evolved an extraordinary talent: the ability to farm fungus. Macrotermes michaelseni have a very unappetising wood-based diet. So unappetising, in fact, that they don’t even digest it and have evolved an ‘external stomach’ to do it for them. These termites ‘seed’ fungal spores onto complicated, aerated comb structures and when they return to their mounds, bellies full, defecate their ‘psuedo-faeces’ on top. This is the fertiliser for the lucky fungus, who digests the tough material into a delicious, nutrient-rich meal for the colony. In exchange, the fungus not only receives a delicious banquet of food, but also water, shelter, protection, and a colony of constant gardeners to cultivate and look after it. So, forget the rumours you’ve heard, because this symbiosis is truly the oldest evidence of agriculture here on Earth, without which, there could be no Okavango Delta.


Everywhere you look, termite mounds dot the Delta. NHFU/Hannah Gormley.


As the first rains hit the parched Kalahari ground, something quite extraordinary happens. Millions of winged alates (the lucky few termites in a colony that are born to be sexually mature) emerge for an all-or-nothing nuptial flight. A dramatic feeding frenzy of all of the Okavango’s residents (including its humans) ensues and it’s a miracle that any survive. But, in a classic tale of romance, a female from one colony meets a male from another, they chop off their wings and get down to business. If not, they die. She is the queen of her new colony, and the male, her king. Their dynasty gives rise to an army of sterile workers each of which has a highly specified job. Termites have a caste system, including the king, queen, workers, soldiers, and the lucky few who get to move out and reproduce. All toil night and day to provide for the colony. Nestled in a protective capsule in the heart of the mound, the royalty’s sole purpose from then on is to mate. The Queen will lay one egg every three seconds for up to 15-years. Over time, this taxing process causes her to distend, transforming into a white, swollen grub the size of a human index finger. She can live until 60-years old: the most ancient of all grubs.


One of the Okavango's countless termite mounds - this one is actually relatively small! NHFU/Hannah Gormley.


What you see above ground actually functions as one enormous chimney and ventilation system for where the real activity is going on: underground. From the queen’s very first eggs, worker termites emerge, ready to begin collecting the food that will be necessary to support the colony. The period after the rainy season is an important one: the ground is soft and malleable, allowing the termites to gather it up to waterproof their mounds in anticipation of the flood. Not only must they waterproof their nests, but they must collect enough food stocks to last them until the floodwaters recede. Termite mounds are home to a series of intricate channels and mazes that ventilate their residents greenhouses. Deep tunnels tap into the water table, consolidated shafts reach up to the surface, gallery chambers house the all-important royal capsules and fungus gardens, and foraging tunnels taper off to the extremities as entry and exit points for the scouts. And all of this is built from their saliva and poo, with the helpful addition of some soil. The average termite mound contains 15kg of termites who move a fourth of a metric ton of soil (and even more water) each year.


Baboons and other animals use the termite mounds as look-out points and toilets. Their excrement sows seeds that take root in the surrounding soil and grow the mounds further. NHFU/Hannah Gormley.


The termites toil day and night to build their majestic kingdoms and the results are incredible structures that stand for decades, surviving fires, floods, and even elephants using them as ideal rubbing posts. But the other Okavango residents also play a role in their growth. Perched birds use these elevated spots as handy take-off and landing points and, while they’re at it, toilets. Their excrement contains seeds that take root in the mounds nutritious soil. The process continues, as herbivores come to graze on the plants, excrement, and so on. As the mounds grow, they start to impede the flow of the Okavango’s ephemeral waters and sand and soil is deposited on their perimeters. The tall trees trap dust, and so the cycle of growth continues. It is thanks to these collective efforts that the Okavango’s 150,000 islands were formed and new islands still continue to develop today.


A herd of lechwe courses past a termite mound island. NHFU/Hannah Gormley.


These structures also, quite literally, hold back the desert. Without them, the Delta would look akin to its drier counterpart – the Mgkadikadi Pans. The termite's activities allow water to penetrate into the ground, holding on to critical nutrients and retaining water where else it would have disappeared. In combination with all the nutrients being dropped on the islands by passing-poopers, the islands become reservoirs of life, even in the harshest of droughts. Indeed, studies show that the islands have much more diverse vegetation than surrounding areas. As trees grow on their fertile soil, the plants draw up water which is eventually expelled through their leaves by transpiration. But they don’t take the salt. As a result, the islands become hugely saline –so much so that a large part of their mass is thanks to the magnesium calcite and silica this process leaves in its wake. As these chemicals become more and more concentrated, the areas underneath the islands become so concentrated that they are toxic to most life-forms. The salt-infused water is now sufficiently dense that it sinks to the bottom and stratifies. Thus, fresh-water sits above and is constantly replenished by the trees drawing in water, and floodwater rushes in from the surrounding floodplains to replace it. This, of course, is a lifeline for the countless weird and wonderful creatures that call the Okavango home.


The Okavango is home to a tapestry of habitats unlike anywhere else on earth. In the wet season, the termite mounds are the only source of dry land for miles around. NHFU/Hannah Gormley.


In this modern world, it’s easy to feel too small to make a difference. Next time you do, remember the tiny architects who quite literally built the Okavango Delta. If termites can be masters of construction, imagine what you’re capable of!


Blog written by Hannah Gormley.