Soil carbon: pay dirt, or dead duck?

Papers show an official abundance of caution persuaded New Zealand to downplay soil as a carbon sink, instead of bringing it into the ETS, as a carrot for farmers

You know the old cliche, about wood, and trees.

Carbon build-up, in the atmosphere, is worrying; we talk and talk and talk, globally and locally, about how to incentivise tree-planting to offset it. What about the biggest carbon sink of all, in the ground under our feet?

Soil is said to hold more carbon, from dead and decaying things, than the world’s atmosphere and trees combined. If it could be altered for the better by land management, the idea is that it might be a carbon sink, in the same way as planting trees — a no less fruitful option for managing greenhouse gas levels.

Alternatively, managing it badly could be a bit of a problem.

Article 3.4 of the Kyoto Protocol allowed parties to voluntarily account for soil carbon changes from productive land management: cropping, grazing, and so on.

Farming savvy New Zealand did not sign up to this bit of the Protocol.

Nonetheless, it’s an option farmers are reportedly interested in. The Ministry of Agriculture and Forestry (MAF) says there has been interest and speculation by farmers that they may be able to use carbon stored in their soils to offset future emissions trading scheme (ETS) liabilities. Right now, though, this is not in the ETS, which focuses on our Kyoto obligations; and nor, of course, are farmers.

In other words, then, a much-needed carrot for agriculture’s entry to the ETS has been spurned, out of an official abundance of caution.

But for every bean-counting official, there is a soil scientist keen to dig the dirt. A soil carbon conference convenes in Wellington tomorrow. Presumably, like last year’s, it will try to demonstrate that this is real science, worth real money, that could help to solve climate change, and benefit the environment in other ways. To demonstrate, in short, that this is a good option for New Zealand.

I am very excited. I have a media pass.

Officials, a naturally cautious breed, cannot afford another ‘billion dollar Kyoto bungle’. The reasons for their caution are set out in 2009 briefings from MAF to the Minister of Agriculture “on recent science on soil carbon changes on farmland”, and from the official Emissions Trading Group to the Emissions Trading Scheme Review Select Committee. (The ‘billion dollar bungle’ isn’t mentioned.)

The first reason: it was all too hard. “The methodology for accounting for soil carbon is complicated.” “New Zealand does not have data to establish 1990 baseline soil carbon levels.” “There are technical barriers related to measurement and monitoring.”

The second: national self-interest (my emphasis).

There was a high degree of uncertainty as to the cost/benefit implications of accounting for these activities due to incomplete knowledge of what was occurring in soils across New Zealand (for example, in erosion areas). Once a country starts accounting for these categories they are obliged to continue to do so.”

The science was uncertain, and might backfire economically; if it did, we would be unable to wriggle out of our international accounting obligations.

According to these papers, although “soil carbon losses appear to be associated with higher land-use intensity”, all of the factors are not fully understood. But one possible trend is emerging: two independent recent studies showed that land used for intensive dairying, in particular, has lost more carbon than land under other uses.

There are also quite high soil carbon levels in New Zealand, relative to some other countries, perhaps making it hard for us to sequester any more. This seems to be more about luck than management, with possible factors including the relative youth of the country (recent deforestation), and rainfall.

So officials know how much we don’t know, and their conservatism isn’t surprising, even if it seems yet another example of bureaucratic fiddling while Earth burns.

However, hints are that under post-Kyoto protocols, if negotiated, this sort of accounting may be compulsory; therefore, whether we like it or not, this is one to watch.

It’s on the work programme of our hub for the global agricultural research alliance. If I was the government, I’d be pursuing it with stealth, but speed, as a useful way of chivvying farmers into the ETS.

Even though soil scientists may not yet understand all the factors, or may struggle to measure them, the likelihood, or the hope anyway, is that what is good for carbon storing, will also be good for the environment and productivity:

“The focus is on supplying oxygen, water, food and comfort to the most important farm livestock — the underground ones … Active soil humus means more fertile and friable soils, better water utilisation, reduced need for fertilisers and pesticides, and greater nutritional density of the food produced. This translates to better animal health, less erosion, no leachate, greater profit, and more satisfaction for the farmer.”

[Source: BioAgNZ "Biological agriculture examples" (May 2007), given to me by Simon Terry, Sustainability Council.]

If carbon science backs up this emphasis on building soil organic matter, we might, in the end, find that soil carbon farming is really just big organic gardening. How cool is that?