Can rangelands save the world?

Earlier in the year Allan Savory, a biologist from Zimbabwe, gave a powerful TED (Technology, Entertainment and Design) talk on promoting "holistic grazing" to reverse desertification and combat climate change. Chastened by an early career decision to kill 40,000 elephants which failed to help the African savannah, Savory has relentlessly pursued a career around the idea of using of fast moving managed livestock as a proxy to mimic the grazing herds of nature on grasslands.

In the talk Savory explains that the trampling and excretions of the herd provide cover for the soil and allow grasses to decay before the next growing season. Savory did point out that the method only works where there is seasonal rain. Many before and after photos show degraded areas of bare land flourishing with grasses and shrubby growth after the holistic grazing treatment. Towards the end of the talk, Savory makes the impressive claim that enough carbon can be removed from half the world's grasslands through this process to take us back to pre-industrial levels of carbon dioxide in the atmosphere. The TED talk struck a chord and was wildly popular - around 2 million views.

So can rangelands really save the world? It's a pretty big claim.

I have to say I've been curious about this presentation and keeping an eye for more information. Instinctively it didn't seem like the scenario painted was broadly applicable in Australia, but certainly the idea of cell grazing does have a lot of currency. Had we missed anything?

It didn't take too long for scientists to point out that a comprehensive review of Savory's method in 2002 was not favourable - in fact, there were problems with stressed animals and the survey period had high rainfall, but more importantly, the trials "failed to produce the marked improvement in grass cover claimed". Elsewhere others pointed out problems with Savory's simplified memes about desertification and arid landscapes. It seems the science of these systems is complex!

Happily, the good folk at Real Climate have recently addressed Savory's climate claims. In simple terms, they point out that the land absorbs about one third of annual carbon emissions - about 2.6 gigatonnes of carbon each year. To even address current emissions levels, vegetation would need to triple its uptake. And to take us back to pre-industrial levels, vegetation would need to absorb over 200 gigatonnes of carbon - about half their current total. So for Savory's claim to be true, the world's grasslands alone would have to sequester half of the current carbon in the whole of the Earth's vegetation. Extravagant!

Have a look for yourself. Savory's a good story teller. But does he have a story? I think I'll wait for the rangelands methodology to come out based on peer reviewed science.