Image above: Coastal fog drifting in from the Atlantic
One of the unique features of our westward oriented horse riding safaris, is that we traverse one of the most unique fog desert in the world - the Namib. Home to more endemic species than any other desert, the Namib has many delightful surprises to those who have the eyes to see the extraordinary.
Situated in the sub-tropics, Namibia’s generally warm conditions disperses all moisture from the air resulting in hyper-arid conditions, particularly along the coast. The Namib would however be much more arid if it were not for fog precipitation which has resulted in some extraordinary desert adaptations.
The unique adaptations of life in this desert depends on the frequency of this life-giving fog. Occurring 60 to 120 days a year, producing five times more precipitation than rain - and it is much more predictable than rain which is rare on the coast.
What is fog and how is it formed?
Fog is formed when moisture laden air is rapidly cooled resulting in condensation into fog or low-level clouds. The cold upwelling Benguela Current that runs in a northerly direction along Namibia’s coast is responsible for the cooling.
It is the nutrient rich Benguela Current which produces the huge biomass of plankton and fish that in turn lead to a large variety of coastal desert fauna - seals, birds, jackal, hyena and even lion.
Fog occurs either are advective or intercepted. Advective fog is less than 200 m high and extends no more than 15 km inland, depositing moisture on any surface it touches - plants, the bodies of ‘fog-basking’ creatures such as the Darkling beetles and even our horses.
Image of fog-laden horse right
The iconic Welwitschia, which we encounter on our Namib Desert, Damara Elephant and Skeleton Damara Safaris, are also able to harvest all their moisture needs from fog and provide moisture, good and shelter to many desert creatures.
Intercepted fog or low stratus cloud can extend inland as far as the escarpment. Where the fog intercepts the land gradient - generally 60 km from the coast - precipitation on any object in its path can be over 1 litre per fog event.
Nets designed to harvest fog are able to extract up to 15 litres of water per square metre during one fog event. Anyone who as experienced a night out in foggy conditions - as sometimes happens on our safaris - knows how incredibly wet everything gets despite the aridity of the desert. And then how quickly it disappears again in the dry air when the sun burns through the fog.
Image of Darkling beetle (left) harvesting fog by doing a headstand on a dune crest, allowing water to roll down to its mouth.
Fog is partially responsible for the more than 1000 shipwrecks which litter the notorious Skeleton Coast - a veritable graveyard of wrecks. Many an incredible tale relate the extraordinary feat of survivors who have walked hundreds of kilometres in search of help. No doubt the life-giving fog aided them in making these challenging journey’s.
Rodents, reptiles and smaller creatures suck or lick moisture from the plants or the wet sand on foggy mornings. Here (image right) a Palmetto Gecko which licks the condensed fog from its eyes.
Plants (like the Welwitschia Mirabilis above) are uniquely able to utilise fog for water or (image left) of Tamarix whose needle-like leaves trap copious amounts of moisture which drops onto its shallow root system. Dune grasses have a similar method of ‘watering’ themselves during a fog event.
Deserts may seem harsh and unforgiving to our momentary glimpse, yet there is so much life able to utilise the small miracles of nature we hardly notice.