The South African spekboom, a carbon-trapping succulent plant

Only a few scattered bushes dot the brown and dusty earth, while the summit is covered with green shrubs with small, round, fat leaves: the "spekboom" (Portulacaria afra), a succulent endemic to South Africa, renowned for its capacity absorption of carbon dioxide (CO2).

The plant once dominated these semi-arid regions in the Little Karoo region (south), extending very widely towards the east of the country. But decades of “overgrazing and poor land management” have damaged huge areas of vegetation, sighs Andre Britz.

Ten years ago, this 62-year-old farmer with a strong Afrikaans accent founded the organization Jobs4Carbon, dedicated to the rehabilitation of natural scrub by replanting spekboom, to “achieve an impact on climate change”.

A few meters below, around twenty workers plow the stony soil with shovels and picks, placing a spekboom branch in each hole.

A long drought devastated the region, from 2015 to 2020, and since then, many farmers have stopped all livestock activities. The hills are now empty.

“Miracle” plant

On adjacent land, around a small spekboom planted two years ago, shoots emerge from the dry earth. In total, Jobs4Carbon has already replanted nearly 700 hectares. “It brings nature back to life,” smiles team leader Jan Cloete, 49.

Replanted in its natural environment, a semi-arid ecosystem called "subtropical scrub", spekboom "can be considered a miracle plant", explains botanist Alastair Potts, 41.

It recreates “a miniature forest environment” and a “carpet of leaves” that “retain water, dust and nutrients.”

But above all, the succulent is a carbon sink, thanks to its rare ability to oscillate between two types of photosynthesis.

In times of drought or high heat, it stores carbon dioxide at night in the form of malic acid. The plant then closes its pores, called stomata, during the day to minimize water loss and uses this store to carry out photosynthesis.

Its sequestration capacity is thus increased tenfold: a 2006 study carried out on a farm replanted with spekboom showed that one hectare sequestered on average 4 tonnes of CO2 per year, but other estimates go up to more than 15 tonnes annually per hectare.

Carbon credits

“Soil degradation is a major source of carbon,” underlines the scientist. To finance their rehabilitation thanks to the spekboom, all eyes are on the carbon credit market, purchased by companies to offset their greenhouse gas emissions.

Scientists have yet to definitively establish how much CO2 is sequestered by the little succulent.

But, unlike many tree planting projects, criticized in particular for the risks of monoculture in unsuitable ecosystems, spekboom is "ideal", according to Alastair Potts, since it "restores the functioning of the ecosystem thanks to carbon ".

Andre Britz hopes one day to also be able to finance his teams using carbon credits.

The objective for the region has been set at 13.000 hectares but could be much more ambitious across the country, he says, juggling requests for funding from international foundations or private companies.

His organization replants spekboom for free if, in return, the owners agree to leave the land fallow for at least fifteen years.

In the courtyard of his village church, 15.000 small plans are ready to join the arid soil which reminds him of the saying repeated by his grandfather: "Take care of your land and it will take care of you".