Sometime in the 1940s, South African government scientists looked at the veld in the Drakensberg and acknowledged the universal truth: that a lonely grassland must be in want of a tree.

Bad move, says Rhodes University soil scientist Dr Lindokuhle Dlamini, both historically, but also because of some contemporary thinking that planting trees is the only sure-fire way to halt global warming.

Dlamini says it’s better to keep ecosystems intact, and to let them do the heavy lifting, which can fix a range of problems. “Interventions like afforestation … risk degrading rather than enhancing ecosystem services,” he warns. “In South Africa’s strategic water source areas such as the Drakensberg, where Afromontane grasslands naturally support high soil organic carbon (SOC) stocks, preserving these ecosystems in their natural state, with the careful use of fire, is a more scientifically sound and sustainable strategy.”

“’Plant the right trees, in the right location, for the right reasons’,” he says, quoting Professor William Bond, the venerable firebrand from UCT on the subject of grasslands and forests.

Dlamini’s research aims to rethink the early ideas, as well as some modern attitudes which propose that planting trillions of trees is a feasible and desirable “solution” to global warming. “Ambitious tree-planting campaigns must take heed,” he says, “or risk causing more harm than good. In the Drakensberg, fire-managed grasslands store more carbon and offer a stronger climate buffer than planting trees.”

His thinking chimes with recent findings that there is less land available for planting trees for planetary benefit than previously thought: 195 million hectares, or 71–92% less area that can be planted to help the climate with minimal trade-offs. The reassessment factors in risks to wildlife habitat, food production, and water resources, taking a conservative approach to avoid harming other ecosystems.

Dlamini acknowledges that those 1940s scientists were seeking solutions for a water-scarce country. Inspired by the pine-covered slopes of Europe and North America, they wondered whether planting trees in high-altitude grasslands might enhance rainfall through increased evapotranspiration, ultimately feeding streams with more water. This thinking sparked a series of experiments in catchments at Cathedral Peak, designed initially to answer hydrological questions but which would, decades later, become the stage for critical research into fire, afforestation, and carbon dynamics.

Today, Dlamini is at the heart of research into those catchments, work made more critical because the Drakensberg, rich in carbon, is a formidable redoubt in the war on global warming.
Dlamini’s research has revealed the complex, and sometimes counterintuitive, relationships between fire, tree planting, and soil organic carbon storage in these catchment grasslands. In a world eager for carbon solutions, his work sounds a cautionary note.

He will be presenting a paper at the Oppenheimer Research Conference later this year on fire, afforestation and carbon in South Africa’s Afromontane grasslands.

The fire-grassland paradox

Afromontane grasslands, like those in the Drakensberg, coevolved with fire. Lightning strikes trigger natural blazes every two to five years, says Dlamini, maintaining the open grasslands and preventing forest encroachment despite the region’s high rainfall and deep, fertile soils. “If you find a way to exclude fire,” Dlamini explains, “these grasslands can transition into forest-type systems. But naturally, fire keeps them as grasslands.”

In some Cathedral Peak catchments, keeping fire at bay led to woody encroachment and the gradual transformation of grasslands into tree-dominated ecosystems. In others, trees, specifically fast-growing pines, were deliberately planted as part of the original forestry experiments. These long-term experiments provided Dlamini with a rare opportunity: semi-controlled conditions to study how both natural afforestation (through fire exclusion) and intentional tree planting influence carbon storage.

His findings are striking. In areas where fire was excluded, grassland soils still stored more carbon in the topsoil (about 30% more) compared to nearby forested sections. And when examining the deeper subsoil layers, isotopic analysis revealed that more than 40% of the carbon beneath the forested plots originated from grasses, not trees. Despite the trees towering above, much of the soil carbon remained a legacy of the grassland past.

The carbon storage illusion of trees

These results challenge the popular global narrative that planting trees is always beneficial for carbon sequestration, the buzzwords of global warming. Carbon dioxide is the main gas causing global warming, and carbon sequestration is the way in which atmospheric carbon dioxide is caught and stored, which helps efforts to ward off global climate change.

“Most people assume that under trees, because they are large and store a lot of carbon above ground, the soil would store more carbon too,” says Dlamini. “But actually, we found the opposite.”

Not only do grasslands store more soil carbon, but they also release less carbon dioxide back into the atmosphere. In forested plots, soil respiration rates (the amount of CO2 released from soil), driven by microbial activity, were higher and more sensitive to temperature increases. “When you increase temperature by a certain amount, the amount of carbon dioxide released from forest soils is double that of grassland soils,” he explains. As global temperatures rise, this sensitivity could trigger a dangerous positive feedback loop: warming accelerates microbial decomposition, which releases more CO₂, which in turn drives further warming.

A devastating experiment

The planted pine catchments offer a sobering lesson in ecological risk. After about 20 years of growth, a wildfire swept through one of these experimental plots. “Pine trees grow quickly, but they don’t protect the soil well,” says Dlamini, and the fire raced through the flammable pine needles, burning so intensely that it destroyed much of the soil structure. Massive soil erosion followed, stripping away tons of carbon-rich topsoil. “The catchment was literally removed,” says Dlamini, and “tons and tons of soil was lost because they had disturbed the soil when they were planting.” In its place, invasive species like bracken fern took hold, creating a fire-prone landscape that now burns even hotter, “cooking” the soil and further impairing recovery.
Has there been any recovery at all? “It can’t recover,” says Dlamini. “It’s dominated by alien plants now.”

Beyond carbon

For Dlamini, the implications of his research go far beyond carbon credits or simple tree-planting schemes. “There is this global push to plant trees,” he notes. “But managing ecosystems solely for carbon sequestration risks undermining broader ecological goals.”
Instead, he advocates for a “nexus approach” that considers the interconnectedness of carbon storage, biodiversity, water regulation, and overall ecosystem health. In strategic water source areas like the Drakensberg, where grasslands provide essential services, preserving these ecosystems in their natural state, complete with prescribed burns that mimic historical fire regimes, is both scientifically sound and sustainable.

Measuring the invisible

Central to Dlamini’s work is the precise measurement of carbon in and from the soil. Using elemental analysers, he burns finely ground soil samples at temperatures ranging from 800 to 1200 degrees Celsius to measure how much CO₂ is released, thereby calculating the percentage of carbon present in the soil sample. He also collected continuous monthly gas samples of CO2 released from the soil in the field for over three years, combined with automated CO2 measurement using the LI- 8100 soil CO2 flux instrument installed long-term in Drakensberg by South African Environmental Observation Network (SAEON) Grassland’s Node. This meticulous process allowed him to capture carbon dynamics across multiple catchments over three long years of monthly data collection.

A personal journey rooted in the grasslands

Dlamini’s fascination with grasslands and soils traces back to his childhood in rural Melmoth in KwaZulu-Natal. Herding his grandfather’s cattle from the age of five, he observed where animals chose to graze and developed a deep curiosity about the land beneath his feet. “You manage cattle until there’s a younger child who can take over from you,” he quips, recalling his many years of responsibility before handing over the reins to the next generation.

“It’s a rural area there,” says Dlamini, “so when you’re herding, you play with clay and you mould it into cattle, and other things. And I grew up being fascinated by why animals choose to eat here, and not there? Because I would leave them in one place, and they would wander off to another area, and I didn’t understand why they do that”.

“So I grew up with that interest in soils and grasslands. My undergrad degree was environmental science, my Honours degree was in rangeland ecology and savanna dynamics, and then I went to do a proper grassland science Master’s. Even though maybe I didn’t notice it at first, this was linked to how I was raised and the type of activity I used to do when I was growing up because I enjoy being in the grassland. Now I like to understand how these systems function as a whole. Studying soil science in my undergrad, I understood that you can see that a plant is deficient in nitrogen or phosphorus by looking at the colour of the leaves, I realised this was very important, and I grew interest in soil-plant interactions, which is why I ended up having a PhD in soil science. It gave me a holistic understanding of the environment.”

Today, as a scientist, Dlamini still views grasslands as living systems worthy of careful stewardship. His research serves as both a warning and a guide: that in our haste to fight climate change, we must not sacrifice the very ecosystems that quietly store carbon beneath our feet, regulate water, and sustain biodiversity. And in South Africa’s Afromontane grasslands, fire remains not a threat, but a vital ally.

Yves Vanderhaeghen writes for Jive Media Africa, science communication partner of Oppenheimer Generations Research and Conservation.

Dr Lindokuhle Dlamini will be presenting a paper titled “Burning for Carbon: Fire, Afforestation, and Soil Organic Carbon Dynamics in South Africa’s Afromontane Grasslands” at the 14th Oppenheimer Research Conference which takes place in Midrand from 15-17 October 2025.