Our Burning Planet

Karoo Dust Bowl (Part I) — here come the dunes, a death knell for plant species and farmers’ livelihoods

The Grasvlakte — the “grassy plains” — between Steinkopf, Port Nolloth and Eksteenfontein, has become a focal point for study. This sometimes abundant grazing area is swallowing one farmhouse and surrounding buildings. Some say the dune is the result of the recent drought. Other farmers say it’s caused by poor land management. Researchers now want to see if the damage is reversible. (Photo: Leonie Joubert)

By Leonie Joubert

28 Jan 2025

The recent years-long drought may have tipped parts of the Northern Cape towards an irreversible dust bowl, following decades of heavy grazing and mining. As Earth’s average temperature slips beyond 1.5°C of average warming and threatens to lurch the climate outside of its safe zone, a visit to the Richtersveld shows what happens locally when a region crosses a tipping point, threatening conservation and livelihoods.

This is the first of a three-part Karoo Dust Bowl series which considers recent desertification trends in the Northern Cape, the causes and the likely consequences to conservation and livelihoods.

If Timm Hoffman’s sunhat were his CV, its sweat-cured rim and fading colour would be a record of the many hours the plant ecologist has spent scanning the arid Karoo over 40 years, looking for signs of change.

In November 2024 the emeritus professor revisited one of the holy grails of the Richtersveld and found “shocking” changes.

“Desertification is a real thing,” he says after a three-day survey of a study site on the edge of the Ai-|Ais Richtersveld Transfrontier Park. “I’ve never seen this anywhere. This is something quite unique, quite remarkable. It’s happening now.”

Hoffman, who recently retired as the head of the University of Cape Town’s (UCT) Plant Conservation Unit, is commenting on the reddish eddies of dune sand over Cornell’s Kop, a rocky hill a few clicks south of the Orange River which snakes along the South African and Namibian border.

The koppie’s drawcard: one of the most well-known forests of the giant quiver tree (Aloidendron pillansii), a critically endangered tree aloe that grows in a tiny home range in southern Namibia and the Northern Cape.

Hoffman has been studying this particular community for two decades, doing head counts of adult trees and seedlings, and comparing historic photographs with ones taken more recently, to find trends in the population’s general wellbeing: how fast the trees are growing; how many seedlings are surviving; what the death rate is across the population.

These sand dunes, which on this trip were lapping up against the quiver trees’ boles and catching in rippled swells against rocky outcrops, are reminiscent of the picturesque orange-hued dunes of the Kalahari.

Some of the drifts are only ankle-deep; others go down as much as 2m. But they’re not supposed to be here.

Professor emeritus Timm Hoffman on the well-known Cornell’s Kop hill on the edge of the |Ai-|Ais Richtersveld Transfrontier Park in the Northern Cape in November 2024. (Photo: Leonie Joubert)

Karoo Dust Bowl Timm Hoffman revisited Cornell’s Kop in November 2024 to do a head count of the critically endangered giant tree aloe forest. (Photo: Leonie Joubert)

They’re new since Hoffman last visited the site in 2013, and can’t be seen in the historic photographs taken of the site as far back as the early 1940s. Until now, it was just rocks and hard-packed, stable gravelly ground with the odd succulent shrub here and there amid the bigger tree aloes.

The November 2024 head count shows the aloes’ numbers continue to decline here, in keeping with the longer-term trend. Researchers already noted in 2005 that this population was collapsing.

But it’s the wider landscape-level changes that have Hoffman and other arid systems experts nervous.

Dr Johanna von Holdt first noted something was amiss in 2020, deep into the drought that would ultimately grip the region from 2015 to 2021. The environmental scientist from UCT’s Department of Environmental and Geographical Science who specialises in air quality, was studying satellite images taken over the Northern Cape, and noted a dramatic increase in sand plumes. From high altitude, these look like smoke rising from a chimney stack, although the plumes lie on the ground, starting as if from a single ignition point, fanning out over the landscape and heading west, out to sea.

The trend is clear. What’s causing it is what keeps the experts up at night, along with questions about whether it can be reversed.

Ignition point

The stone is just big enough for one person to stand on, and only someone with an intimate knowledge of the Annisvlakte will be able to find it or know why it’s important. This is the precise lookout point that Hoffman and his team use for the kind of repeat-photography method they use to track decades-long changes in a landscape.

Three scientists cluster around it now, and the late-afternoon sun throws shadows that are longer than they are tall.

Their backs are to Cornell’s Kop, about 15 minutes’ drive away, following a gruelling day of counting and measuring the koppie’s aloes. This lookout spot is about halfway between the tree aloe forest and the Nama town of Kuboes, hidden in the foothills ahead of them. It’s also slap in the middle of a plain that diamond prospector Fred Cornell famously photographed more than a century ago. In the grainy black-and-white landscape image dated around 1910, his wagon trains cut a line through an expanse of succulent-darkened ground.

A recent head count of the giant quiver tree population at Cornell’s Kop on the edge of the Richtersveld National Park shows that its numbers are declining rapidly. Of the 35 seedlings that were counted herein 2013, 25 have died, amounting to a 71% mortality rate in the past decade. Nearly a third of the adults have died in the past quarter-century, but nearly half of those deaths occurred in the past four years. What’s new is the eddies of dune sand washing up against rocks and in deep leeward drifts. (Photo: Leonie Joubert)

Hidden away in the Succulent Karoo’s rocky nooks and crannies are families of plants that have evolved sophisticated survival techniques, and which have made this one of the richest succulent communities on the planet. A quarter of all its plants are unique to this part of the world. (Photo: Leonie Joubert)

Today, this part of the Annisvlakte is mostly exposed sand, with the odd hummock of brittle grass and soutslaai (“salt salad bush”, or Mesembryanthemum barklyi) succulents, an annual shrub that gives a misleading account of overall ecosystem health. This spartan ground cover is the only thing left that can tame the wind.

A semi-desert like this part of Namaqualand – the Nama and Succulent Karoo, in particular – is not a dead landscape, but it is a brittle one, and historically it can only support grazing animals if they are constantly on the move, explains Dr Igshaan Samuels from the Agricultural Research Council. The Annisvlakte shows what happens when heavy use exceeds the ecosystem’s ability to close a wound left by overgrazing.

Even though herd numbers in Namaqualand have dropped by about 60% in nearly a century – there were 11 million sheep grazing across the area in the 1930s, and by 2007 numbers were down to four million – the damage has already been done, as seen in places like the Annisvlakte.

It starts with a small nick in the ground, one that breaks the cap that binds the land in place. A few too many hungry sheep shear the succulent shrubs whose plump leaves act as water reservoirs in this otherwise parched landscape. Cloven hooves trampling the ground around a dwindling number of watering holes. A miner’s front-end-loader scooping out another industrial-sized load of gravel and sand to sift for diamonds. A dump truck’s tyres cutting out a path as it carts more tailings to a growing mound of mining waste.

The sand loses its moorings, and is picked up by winds that can reach speeds of 40km/h.

“You really can’t do much to prevent sand grains (once they’re mobile), which act like sandpaper on plants,” Hoffmann explains.

These sand storms may be short-lived, but lethal, even to desert-adapted plants that have evolved many ways to survive sandblasting. Too much exposure to the razor-edged particles carried in the high-velocity air will destroy plants’ leaves and stems, or smother them, leaving them unable to breathe.

“It abrades not only the seedlings, because of the way in which sand particles move over the surface, but it also kills the adult plants. It covers all the leaves so they can’t transpire. They can’t open their stomata.”

By combining data from Nasa’s satellite imagery taken in July 2020 with on-the-ground observations, earth scientists found a dramatic increase in dust source points in Namaqualand, indicated by the black dots. (Source: Nasa; and Dr Johanna von Holdt, Department of Environmental and Geographical Science, University of Cape Town)

From space, these nicks look like ignition points that fan into a wildfire. Downwind, another frontline of sand-blasted vegetation dies, exposing more ground to the wind, and the sand plume spreads. By Hoffman’s estimation, this is a “runaway train” that may be irreversible in parts of the Richtersveld.

In 2022, Von Holdt led a team of arid systems ecologists and others on a trip to the region. Not only did they confirm what the high-altitude photographs are saying about the intensity of the offshore sand plumes, they also found evidence that onshore winds from the coast are sending sand into the interior.

In many places the ground had lost the physical mechanisms that bind this sensitive landscape in place – succulent plants and the crusty layers that form a natural cap on the ground – leaving many areas vulnerable to winds that strip away any nutrient-rich organic material and the lighter sand and dust. In places, they found wind erosion down to the dorbank, a cement-like dry-pan layer.

This is how the place becomes a dust bowl, with sand dunes that move like slow-motion ocean swells.

Drowning in dune

There’s a farmhouse on the Grasvlakte near Eksteenfontein that’s become something of a media personality. As the crow flies, it’s about 90km south of the Annisvlakte lookout point, and the house and surrounding buildings are disappearing dramatically under a rising tide of dune sand. The two windmills that spin studiously nearby in the restless air are up to their waists in it. A fence is being swallowed whole.

The dune’s origin is contested, though. This is private farmland bordering the communal grazing area that’s allocated for the community living in Eksteenfontein, and the part of the Richtersveld that’s been declared a Unesco World Heritage Site because of its cultural and botanical heritage.

The privately owned land is in an area known as the Grasvlakte – the grassy plains – for good reason. In years of plenty the grazing is abundant. Some locals claim that the recent drought brought on the dune sand. Others say the dune has been here a lot longer and is simply a land management issue: that the number of sheep is exceeding the carrying capacity given that conditions recently have been so hot and dry.

This place has always ebbed and flowed between ample grass and exposed sand, depending on conditions, say some farmers who have lived in the area all their lives.

Picturesque as these reddish dune eddies are on the edge of the |Ai-|Ais Richtersveld Transfrontier Park in the Northern Cape, they shouldn’t be here. Arid ecosystem researchers noticed a dramatic increase in mobile sand in Namaqualand from 2020. (Photo: Leonie Joubert)

Whatever local lore says about the dune’s nature, it has become a focal point for scientists like Von Holdt who want to understand the forces that caused it, and whether a site like this can be rehabilitated.

Since that 2020 red-flag event in the satellite data, and the site visit which confirmed the escalating dust-bowl conditions, researchers have a better idea of what’s happening. This is typical of the death-by-a-thousand-cuts that have been inflicted on the area over the past decades through heavy grazing and aggressive mining where sites haven’t been rehabilitated.

The years-long drought is likely to have escalated the processes that had been ticking over for decades, nudging many areas over an irreversible tipping point. Changing climatic conditions, such as higher temperatures and drought, are likely to accelerate those processes, says Von Holdt.

It’s also a bit more complicated than this: at a wider landscape level, all these forces come into play to a greater or lesser degree. Zooming in on localised dust bowl sites, though, and it might be more of one factor and less of another.

The Annisvlakte lookout point. (Photo: Supplied)

Annisvlakte. (Photo: Leonie Joubert)

Annisvlakte. (Photo: Supplied)

A conservation triage for threatened desert species

While Hoffman and his team were up to their shins in dune sand on Cornell’s Kop, another professor was weathering ferocious sand storms a bit further north in the Sperrgebiet, the heavily access-controlled diamond fields just across the border in southern Namibia.

Professor Norbert Jürgens from the Department of Biology at Hamburg University in Germany, is Hoffman’s contemporary, and has been monitoring a number of small study sites across the region for 45 years, counting species diversity and health in order to track long-term condition of the plant community. Following his November 2024 visit he and his colleagues are busy with the most comprehensive analysis to date of the multiple and long-term factors driving the desertification trend here.

Dust source points in Namaqualand, indicated by the black dots. (Source: Nasa; and Dr Johanna von Holdt, Department of Environmental and Geographical Science, University of Cape Town)

The findings are under wraps until the scientific review process is complete, but until then he’s happy to give one overarching observation: the changes he’s seeing now, which confirm those of the South Africa-based researchers, are extremely alarming. The urgency of the message is out of step with the slower and more cautionary approach of peer-reviewed science.

Namaqualand might look like a dead landscape, he says, but it’s not. Hidden away in the desert’s rocky nooks and crannies are families of plants that have evolved sophisticated survival techniques, and which have made this one of the richest succulent communities on the planet.

The plants of the Succulent Karoo have evolved to thrive in an extreme environment, one of the reasons it was so desirable to the first herders moving through here at least 2,000 years ago, and to today’s commercial farmers and communal shepherds.

Its endemic plant richness is now also what has drawn the attention of well-funded and highly organised poaching syndicates, who are looting the Succulent Karoo at a pace that local conservation and policing authorities can’t match.

Earth scientists found a dramatic increase in dust source points in Namaqualand, indicated by the black dots. (Source: Nasa; and Dr Johanna von Holdt, Department of Environmental and Geographical Science, University of Cape Town)

It has also been the spill-out point for aeons of erosion that have washed Kimberly’s diamonds into the river beds here, bringing in the diamond prospectors. More recently, a mining rush for rare earth minerals is turning this area into a new resource frontier.

“Mining within the Richtersveld area, on the South Africa side, has started booming for the last about five years,” says Elsabe Swart, senior manager with the Northern Cape Department of Agriculture, Environmental Affairs, Rural Development and Land Reform, which processes the environmental impact assessments on mining licence applications.

Swart is also one of the plant specialists who knows the giant quiver tree best. She runs the most comprehensive survey of the entire population in Namibia and South Africa, which started in 2000.

“In (the past) five years, dune movement was way faster than it was,” she says, “specifically when compared with the Cornell’s Kop area.”

If conservationists are going to consider an ecological triage to protect a species as vulnerable as the giant quiver tree, Swart says it will be necessary to grow specimens outside of their wild environment.

The Grasvlakte – the ‘grassy plains’ – between Steinkopf, Port Nolloth and Eksteenfontein, has become a focal point for study. This sometimes abundant grazing area is swallowing one farmhouse and surrounding buildings. Some say the dune is the result of the recent drought. Other farmers say it’s caused by poor land management. Researchers now want to see if the damage is reversible. (Photo: Leonie Joubert)

The Grasvlakte. (Photo: Leonie Joubert)

“A key thing is to look at ex situ conservation, like having people cultivating a plant, having it in gardens, and having some of the seeds in the Millennium Seed Bank.”

But trying to re-establish populations in the wild is probably not feasible, she argues.

“Relocation back into the wild (isn’t) an option because of all the pressures we observe: sandblasting, dune movements and the increased (animal) stocking rates.”

The same applies to keeping alive specimens of the endemic succulents that are now extinct in the wild following years of heavy poaching, says Swart, such as the succulent botanical garden run by the now celebrated Richtersveld-based SANParks conservationist Pieter van Wyk.

The Namaqualand’s remoteness and sparse population means that the heavy toll it’s taking is largely happening outside of public awareness, but is a warning sign as the climate becomes rapidly more unstable everywhere. The spreading dust bowl is a sign that even this desert-adapted plant community has reached a breaking point from which it may not recover, a trend whose toll will first be counted in lost plant species, followed by the livelihoods of the people who have lived here longest, today’s beleaguered farmers. DM

Read part two: Karoo Dust Bowl (Part II): Northern Cape farmers ‘don’t want to inherit dust’ left by mines tomorrow

This article was produced with the support of the Henry Nxumalo Foundation, and is part of a research collaboration with the Stellenbosch University School for Climate Studies: Story Ark – tales from southern Africa’s climate tipping points.

https://www.youtube.com/watch?v=REeWvTRUpMk

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Our Burning Planet

Ignition point

Drowning in dune

A conservation triage for threatened desert species