By Roelof Bezuidenhout

Amid the hype around sustainability, regenerative farming and carbon credits, several schemes – backed by huge amounts of international money – have popped up, enticing livestock farmers to sign contracts promising future carbon credit earnings. Now, several South African researchers have cautioned farmers to tread carefully before committing to agreements that could legally bind them for decades in an unpredictable carbon market.

One problem is that much of South Africa’s grazing land is too hot and dry to effectively capture and store carbon from the atmosphere. Any gains made in good years are likely to vanish during droughts. One researcher warns against what he calls “the carbon credit bandwagon”, arguing that carbon sequestration is unrealistic in semi-deserts and most grasslands – although the Eastern Cape’s spekboom thicket veld is a potential exception, despite ongoing uncertainty about optimal planting densities for restoration projects.

He says the best possible improvement in soil carbon is around 3%, far too low to support a viable carbon credit business.

Another expert says even 3% is overly optimistic, warning that many schemes being pitched to farmers are based on unrealistic projections rather than sound science.

That said, early measurements from high-density grazing farms in the eastern Free State and wetter central regions of the province suggest some improvements in soil carbon, root growth and soil properties. However, in healthy veld that is already in balance, the potential for increasing soil carbon by any significant degree remains minimal. The situation may be different on cultivated lands – so much so that in Australia some land is already being advertised for its carbon value.

The so-called natural approach

In South Africa, at least one scheme has linked carbon sequestration with a grazing system that is supposed to mimic the natural grazing patterns of wild animals. The idea is that this “natural” approach is more sustainable and regenerative – although the term “regenerative” is often loosely defined and can be ambiguous.

High-density grazing in semi-arid grasslands may increase organic matter in the upper soil layers but can also lead to soil compaction and reduced moisture content, according to Prof Linus Franke of the University of the Free State’s Department of Soil, Crop and Climate Sciences. “Higher livestock densities and more unselective grazing generally come at the expense of animal condition and productivity, but significantly higher stocking rates may nevertheless result in higher productivity and revenue per unit area,” he says. However, the impact of grazing on soil organic carbon levels is site-specific and affected by factors such as rainfall, temperature and soil texture. To study the relationship between grazing systems and climate change mitigation, he says, the additional methane and nitrous oxide emissions arising from higher livestock densities should also be taken into account.

Principles of high-density grazing are inspired by natural rangeland ecosystems, where large herds of migratory game once played a key role. Historically, large hoofed animals were an integral part of Africa’s ecology, with between eight and thirteen species of large herbivores known to have migratory populations.

The migratory behaviour of grazers is primarily driven by the availability of food and water, with predation playing only a minor role. Wildebeest, for example, are selective grazers that prefer short, early-growth grass, and their migrations help them access this ideal forage. However, many large grazing and browsing species do not migrate at all.

Prof Franke concludes that livestock farmers have not only replaced the ecological roles of diverse indigenous grazers with one or two livestock species but are also working with animals that may be better suited to high-density systems. For cattle, this typically means medium- to small-frame animals with relatively large rumen capacity and lower nutritional requirements.

It’s clearly difficult to base recommendations for livestock densities and resting periods on “natural” grazing patterns, as little is known about veld conditions before human intervention. So the question remains, do we really have enough knowledge to design effective grazing management systems?