Vegetated Dunes: Sleeping Giants of the Namib Dune Sea

Backdrop of Sleeping Giants - the vegetated dunes of the southern Namib

Although dunes are often seen flying impressive sand-plume pennants (image below), the sand-sea of the western Namib has dunes stable enough for grass to take hold.  While the dune sea does not have the soil chemistry to support the large variety of grass species which occur inland, one species does stand out:  Stipagrostis; particularly subulicola - although Stipagrostis saelae and Stipagrostis ciliate also occur.

(Image above of the massive star dunes of the southern Namib - Wild Horses Safari)  Star dunes (see blog on Namibia’s Sea of Sand) are the real giant of the Sand Sea, although by no means the highest in the world they are impressively over 300 metres in places.  China has dunes over 500 metres high.

Image of sand plumes flying off a dune crest

Where wind direction is variable, and blasting south-Atlantic gales do not reach far enough inland, we find these sleeping giants - the massive star dunes of the central Namib.  Stable enough to be colonised by Stipagrostis and other woody vegetation such as Trianthema hereroensis.  These plants give shelter to desert-adapted creatures which in turn bring in small predators and so the circle of life flourishes even in these extremely arid environments (see blog on Aridity).

Image below of Namib's - Namibia's wild horses - grazing on Stipagrostis

Grass requires a good shower of rain to stimulate growth from the existing seed-bank, which is surprisingly resilient to drought.  Stipagrostis is able to be sustained by fog alone (see blog on Namibia’s Fog Desert).  Image above shows the condition of the grasses after drying - yet still able to supply nutritional value to the wild horses (see blog on the Namib’s, Namibia’s wild horses).  Grazing animals seldom venture into the dune sea so the grasses remain for decades.

Grassy hummocks pockmark the giant southern dunes

Using their shallow roots, rather than their leaves and stems, to take up fog-water, the root systems extend some twenty metres from the plant, taking up water from fog-dampened sand.  These grasses don’t occur beyond the coastal fog belt which extends some 60 - 100 km inland, occurring over 100 days a year.

On our Wild Horses Safari, we cross some 27 km of vegetated dues - no mean feat on horseback!  Here we can see why Stipagrostis is often referred to as the ‘mound building’ species - image shows the hummocky nature of this part of the dune sea.

Anything capable of ‘holding’ fog - and grass heads are good at that - but also horses’ fur - image right of a foggy nose.

To see these remote Sleeping Giants one does need to know where to find them.  Hidden in a remote part of the dune sea  we get a close up look on our Wild Horses Safari which crosses their southern extremity.

for more information on our adventurous riding safaris have a look at Our Safaris page for details on each safari.