Global finance is flowing into mass planting of the indigenous succulent, but ecologists disagree over how, and how soon, to judge whether the wider ecosystem will recover.
Those in the know simply call it Cambria. Passers-by might notice the scruffy plot overgrown with the indigenous succulent, spekboom (Portulacaria afra). It sits on the shoulder of a dirt road that winds between farmland and wild Albany thicket, near the citrus hub of Patensie and towards the craggy foothills of South Africa’s Baviaanskloof UNESCO World Heritage Site.
Few outside the thicket ecology community will have heard of Cambria, or know that it is contested territory. Orphaned by the government department that set up the research plot two decades ago, its fences are gone and the plants feral.
Yet, it remains an important data point in a question that ecologists have been working on since Cambria’s infancy: how to draw on carbon markets to pay for thicket repair at scale.
About 90% of Albany thicket is partly or severely degraded after generations of livestock pressure, mostly from mohair-producing goats. Where dense, hedge-like bush once stood, many farms have been reduced to hard-baked ground. Some are so exhausted that little can grow, except spekboom.
A bird’s eye view hints at why this site has many in the thicket community at odds. From above, Cambria looks like a recovering hair transplant. The plugs of growth remain in their ordered grid, even as a few plants strain into the heat-rinsed ochre between them.
Is this Albany thicket on the way to recovery? Or is it a spekboom monoculture, caught in stasis before the rest of the plant community can return? The answer matters to an emerging restoration sector whose business model depends on delivering both carbon drawdown and ecosystem repair.
The “problem child” research plot
Mike Powell might feel about the Cambria plot how a parent would for a problem child.
Today, he’s director of the Rhodes Restoration Research Group at Rhodes University in Makhanda in the Eastern Cape. Although back in 2004, Powell was leading a team for the then Department of Water Affairs and Forestry and charged with planting the Cambria plot, one of 330 others like it, to see if mass spekboom planting could start a process of thicket recovery.
Since then, ecologists have been building a business case for financing thicket restoration through the carbon markets: borrow money to restore degraded land now; repay it from future carbon-credit revenue. To make a convincing case, they had to determine whether spekboom establishes itself after mass planting, how soon other species return, and how much atmospheric carbon the plant community draws down as it regrows.
This model is specific to Albany thicket, a biome covering only about 2.4% of South Africa and which accounts for roughly 4% of the country’s land-based organic carbon. Yet, it has attracted considerable international interest recently. Earlier this year, the World Bank listed a US$120-million outcome-based bond available specifically for thicket repair initiatives. Since this work starts with spekboom planting, the bond is named after the tough succulent. Tech giant Amazon agreed to buy some of the carbon credits generated by the first developer to draw on the World Bank purse, helping to reduce lenders’ risk.
Spekboom is one of several endemic canopy-forming woody thicket trees. But being a succulent, it can establish in badly degraded ground where other tree types struggle.
It is easy to propagate from cuttings and plant at scale. As its canopy spreads, including a skirt of low-growing branches and leaves that cover the ground quickly, the trees shelter their surrounds from rain which can pound the surface to an impermeable crust or strip topsoil. The canopy also softens the sun’s heat which, in summer, can bake the ground at temperatures approaching 60°C.
Botanist Alastair Potts, associate professor at Nelson Mandela University in Gqeberha, explains how this growth creates a nursery environment that restores water filtration, returns soil nutrients as leaf litter builds, and allows other species to return.
“Instead of a hard cap of dense, impenetrable soil, you have fluffy soils that can absorb moisture,” he says. The skirt, and its leaf litter layer, allows other organisms to move in, such as insects, centipedes, millipedes, earthworms, and frogs.
The tension within the thicket community is about how to measure the return of life to the system, and over what period of time.
“This is my fault,” Powell says of Cambria, with the benefit of hindsight “I was naive. It was my first day at work.”
The instruction was to plant spekboom cuttings in an orchard-like grid, two metres apart, and fence the plots to test where the plants would grow and how they performed without livestock or game. The government-led experiment was abandoned, though, and post-Covid budget cuts mean there is no money to revive it. Cambria’s fences are long since gone, animals can wonder through and feed as they like. Although while the cuttings in this plot are growing unattended, they still have lessons for the ecology community.
“They all grew,” Powell says of the original cuttings. “And now they’re a closed canopy.”
Spekboom still accounts for almost all of that canopy. In intact valley thicket nearby, Powell says, it would typically only make up only about 40% to 60%.
The Cambria plot embodies the question that most frustrates thicket recovery studies. Plants grow extremely slowly in an ecosystem this dry. It may take decades, centuries even, before scientists can say with certainty if the thicket community is returning, along with the natural functions that create a healthy ecosystem.
“These processes are going to kick in, and yes, (it) will be slow,” says Potts. “But it will be happening, just not at a time scale that humans appreciate.”
What counts as recovery
Seventy-five kilometres east of Cambria, the Krompoort research plot offers a longer view. A farmer planted its first spekboom in 1976 to stabilise a goat-stripped slope where mud kept flooding his barn. Half a century later, the oldest plants stand above head height, their water-laden leaves forming a dense hedge.
“These are the old ones,” says Nick Hamp-Adams, general manager at Return to Thicket. Krompoort is one of two exhausted mohair goat farms now owned by Return to Thicket and which are receiving the spekboom treatment.
“Over time, [the plot has] been added to and expanded,” Hamp-Adams explains. “Researchers have experimented with different methods of planting spekboom.”
Research from Krompoort, often referred to as the holy grail of restoration research, is the capstone for the sector’s carbon case.
A 2006 study found that the site had accumulated an average of 0.42 kilograms of organic carbon per square metre each year over 27 years. Converted to carbon dioxide equivalent, that is about 15.4 tonnes per hectare per year. While this drew wide attention at the time — the number suggested a more significant carbon capture potential than might be expected from such a dry ecosystem — many ecologists cautioned that this number shouldn’t be generalised across the biome. Project developers have, for the most part, used more conservative estimates to build their business case in recent years.
Krompoort shows why restoration research depends on the metric used to measure ecosystem repair. Judged by canopy composition, the plot could still be described as spekboom-dominated: the original planting lines are still visible and the succulent makes up most of the canopy. Judged by the number of plant species surrounding the spekboom boles, though, a different picture emerges.
Dr Anthony Mills, director of Return to Thicket and an author of the 2006 Krompoort study1, says one survey of the plot from 2013 suggests that it is repairing.
“Plant diversity in this restored patch is equivalent to intact thicket,” he says. “So I think it can be deemed successful restoration.”
The study he references found that a number of canopy-producing plant species had established naturally, and that this suggested that the botanical composition resembled that of an intact thicket.
Which to measure: canopy cover and the suite of ecosystem functions that it restores, or the species diversity returning because of repaired ecosystem function? This is the crux of the restoration argument.
Richard Lechmere-Oertel, an ecologist who helped draft a 2023 guide to restoration in arid and valley thicket — the thicket types most suited for this kind of restoration work — expands on the issue that has ecologists at odds. Biodiversity is an expansive term, covering species, ecological processes and ecosystem services. It’s not realistic to expect all of these to recover fully. A useful assessment, he says, is to distinguish functional recovery, such as canopy cover rebuilding soil and moisture processes, from taxonomic recovery, measured by which species are present.
“If you’re rebuilding the foundations of an ecosystem,” he says, “it is going to be around soil integrity, plant diversity and structural diversity within the plant community.”
Carbon money raises the stakes
Until recently, thicket restoration projects have been comparatively small, with ambitions of planting across about 5,500 hectares or less. That scale changed when Singapore-based developer Imperative entered the sector in 2024, and quickly planted its first 10,000 hectares.
The company made international news earlier this year when it announced that it had secured US$91 million in loans – US$25 million from the World Bank bond and US$66 million from other investors – to kick off its second development phase of 50,000 hectares. Should it raise additional funding, Imperative aims to plant spekboom across 100,000 hectares in all within four to five years, according to chief operations and projects officer Mark Welch.
If thicket restoration through spekboom planting were classified as a mono crop plantation, and only offering climate stabilising services, the credits generated from the work would be a bargain-basement $14, by 2025 prices, according to a World Bank report of the sector. But because they have the added value of ecosystem repair, they trade at a premium.
Amazon has agreed to buy 1.95 million credits from Imperative’s second phase development. Imperative and Amazon describe these as high-value credits which will be bought at a fixed price over an open-ended time of “more than a decade”. But they would not disclosed the amount. MSCI Carbon Markets, an industry analytics firm with Imperative as a signed-up client, told Nature Africa that credits from this kind of project could trade at about US$45 each, while a local industry source says many spekboom projects are working in a price range of US$20 to US$25.
This range puts the value of Amazon’s purchase at between US$39 million and US$87.75 million.
Imperative estimates that the first 60,000 hectares will bring US$500 million into the region’s struggling agricultural economy over the next four decades through wages, land rental, farmers’ share of carbon revenue, taxes and small business development.
This projection depends on how much carbon the recovering landscape eventually stores, though, along with future carbon prices, and the revenue share terms agreed to by the landowners.
The profit motive is what has ecologists like Powell anxious — that the economic incentives may encourage the planting of spekboom at densities higher than is appropriate or where the succulent doesn’t occur naturally.
Thickets that merge with neighbouring biomes, such as fynbos or grasslands, are particularly at risk. These mosaic thickets are botanically rich and diverse, and typically don’t have much, if any, naturally-occurring spekboom.
“That’s the danger,” says Powell. “A policy vacuum from government, and no oversight or regulation, means anyone can plant whatever they want. The precautionary principle should apply.”
The thicket community is in agreement on one thing, though: this restoration work must be done. But it must be done correctly. Ecologists warn that projects shouldn’t be surprised if carbon yields don’t measure up to today’s model projections. Investors must anticipate that the returns may be lower than hoped for, and must not abandon the work as a result.
There needs to be patience, too: it will take centuries for the ecosystem to finish what these initiatives are starting. It the work fails in the short term — if investors lose confidence, if there’s capital flight, or financiers withdraw — it could mean that farmers here won’t even be able to grow this one new agriculture crop, carbon. This could be the death knell for a rural economy that’s already on its knees.
This article also appeared in Nature Africa. It is from the mobile journalism project Story Ark – tales from southern Africa’s climate tipping points, by science journalist Leonie Joubert, in an award-winning collaboration with the Stellenbosch University School for Climate Studies and the Henry Nxumalo Foundation. Read parts one, two, three, four and five.
References
- Mills, A. & Cowling, R. Restor. Ecol. 14, 38–49 (2006).
https://doi.org/10.1111/j.1526-100X.2006.00103.x
- Van der Vyver, M., Cowling, R., Mills, A. et al. Restor. Ecol. 21, 736–744 (2013).
https://doi.org/10.1111/rec.12000