Tuesday, April 26, 2011

Charles Rice on Livestock's Contribution to Climate Change

Kansas State's Charles W. Rice, Ph.D. is a soil microbiologist who has served on the UN’s Intergovernmental Panel on Climate Change. Rice’s research has focused on soil dynamics and global climate change, including carbon and nitrogen emissions in agricultural and grassland ecosystems and the potential benefits of carbon sequestration in soil.

Cattlenetwork recently featured a Q&A with Rice about agriculture and livestock in relation to climate change:

Q. But is it fair to say that on a global basis, the contributions of methane (CH4) and nitrous oxide (NO2) are coming disproportionately from agriculture?

Rice. Yes, that’s right. Because CH4 and NO2 are so much more potent, the total GHG contribution of agriculture represents about 13.5% of the overall global emissions of GHGs.

Q. Is all that directly linked with livestock production?

Rice. No. That’s all of agriculture, which includes the release of NO2 from the use of fertilizers and CH4 production from growing rice, for example. Livestock is a smaller part of the total. Some of the media reports that allege that agriculture contributes 30% of all GHG emissions are inaccurate. They’re lumping farming and forestry together, and thus the impact of deforestation skews the data.

Q. So how accurate are the conclusions that appear in the media, that if livestock contribute significantly to global warming, then people need to cut back on eating meat. Is that a valid conclusion?

Rice. Good question. If we look at the short term—that is, the next 20 years—the mitigation potential of changes in livestock production would be pretty small, only about 5%.

Q. Wow. That’s not much.

Rice. Remember, we only examined the mitigation potential of various tactics between now and 2030. Longer term, there are other strategies that would have a larger impact. But overall, about one-third of the total mitigation impact that agriculture could contribute to lessen its impact on GHG emissions are connected with livestock production.

Q. What would those mitigation strategies involve?

Rice. Most of that 30% would come from better rangeland management, such as improving degraded grazing areas and changing the vegetative composition of pasture lands by inter-seeding legumes, balancing soil nutrients and using rotational grazing strategies—things like that. Truthfully, most of the potential for agriculture to positively impact climate change comes from carbon sequestration within the soil.

Q. For those of us who missed that particular lecture in soil science, could you explain what you mean by that?

Rice. Well, for example, here in Kansas, the tall grass prairie areas cause a net reduction in carbon emissions, because the root systems of the plants trap carbon within the soil and it eventually becomes organic matter. As much as 60% of a grassland plant’s density is below ground, so grasses are an efficient way to sequester carbon form the atmosphere into the soil.

Q. But much of that kind of rangeland improvement would be focused in the developing world, not North America, correct?

Rice. Yes, that’s right. U.S. livestock production is actually very efficient, so there are fewer opportunities for mitigation tactics. The greater potential for [agriculture] to impact GHG emissions is in Africa and Latin America and other regions where rangelands and farmlands tend to be degraded by poor management and overgrazing.

Q. So what about recent research, particularly some studies from Australia, that seems to indicate that the carbon footprint of grass-fed beef may actually be larger than that of grain-finished beef?

Rice. Well, in general, it’s true that if livestock production is inefficient, if cattle are consuming large amounts of forage to produce less meat, then grassfed systems could have a more negative impact. If you have lots of animals eating lots of grass, then the GHG potential per animal unit is going to be higher.

Q. Finally, with all the sobering news about the potentially disastrous effect of climate change, is there any good news you can share from your work on this issue?

Rice. Well, I wouldn’t use the term “disaster.” Agriculture certainly has a role to play, but as a matter of fact, the No. 1 area where the IPCC identified potential climate change mitigation is in building efficiency: Better insulation, more efficient heating and cooling systems, and so on. Livestock producers can certainly offset some of the GHG emissions that contribute to the problem, but much of that needs to take place elsewhere in the world. The good news is that what needs to happen in production agriculture relies on technology we already have and on strategies that can be implemented sooner rather than later.