Photo by Yayan Indriatmoko/CIFOR

DURBAN, South Africa (9 December, 2011)_A bearded scientist bloke addresses the microphone. “Human activity,” he tells us, “releases 9 petagrams of carbon dioxide into the atmosphere each year.”

At which point, while some of us struggle to dredge up long-forgotten SI prefixes, the rest of the audience has zoned out. But then the bearded bloke amazed me. “I tell my mother that a petagram is a equivalent to a cube one kilometre by one kilometre by one kilometre of solid carbon.”

It could be graphite. Here in South Africa, it should be diamond. Either way, it is a lot of carbon. And not just one 200-trillion carat diamond, but nine of them.

The scientist is Bob Scholes, systems ecologist and leader of the Ecosystem Processes and Dynamics research group at the Council for Scientific and Industrial Research in South Africa. And unlike all the other speakers at Forest Day 5, he has been permitted a single slide. Well, several, really, if you consider separately each animation as he leads us through what happens to those kilometre-cubed diamonds.

Reminding us that “carbon is just a symbol for all the greenhouse gases,” Scholes goes through the flows, the carbon sinks and sources, and the traps for the unwary. Traps like the forest swamps, which sequester carbon dioxide right enough, but which also release methane, a much more potent greenhouse gas.

Or the climate-smart improved agriculture, which because it is profitable and land-use policy is in disarray, results in more tree-covered land being converted to crops. Anyone paying attention can see that just working out where the carbon comes from and goes to is a really, really complex problem, despite Scholes’ best efforts to simplify it. But he also has a relatively simple message.

“The transformation now is happening in the dry forests of Africa. We love that landscape, from the comfort of our armchairs, watching National Geographic,” Scholes said, “but it’s really hard to live there.”

Degradation of dry forests follows a fairly typical pattern. First, all the high-value timber is removed for export, like the now very rare African blackwood (Dalbergia melanoxylon), converted into petasquillions of oboes, clarinets and the like and, now, luxury cases for mobile phones.

Then the charcoal burners move in to turn trees into cooking fuel. And finally, low-input low-output agriculture, yielding around half a tonne of maize per hectare for a few years before the land is degraded and just about worthless. With investment and time, such land can become productive again, but the costs are high.

“We can’t expect Africa to stop to make us a national park for the world,” Scholes, a South African, said. “But we can help leapfrog the degraded stage.”

Part of that, he said, would require the use of known, tried and tested agricultural techniques that can boost maize yields with no ill effects on the environment.

“We can easily get five tonnes per hectare, so we spare 10 more hectares from being cut down.”

Such intensification of agricultural yield is part of climate-smart agriculture strategy which some have pushed to be included in the UNFCCC negotiations as part of a landscape approach to looking at ecosystem services. Negotiators have agreed to a broad agenda-setting discussion on agriculture at next year’s COP in Qatar.

“It’s one of the key things that we need to do,” said Scholes. “There’s no choice for us but to transform some of these landscapes into agriculture but we need to do this in a climate-smart way.”

Jeremy Cherfas is a biologist and senior science writer at Bioversity International. He is Bioversity’s focal point for communications in the Forests, Trees and Agroforestry CRP.

Bob Scholes’ keynote address is available as both a video and as a downloadable PDF.