Friday, November 05, 2010

Tropical Agriculture Food Production is NOT Efficient

A recent report indicates the poor efficiency of crop production in the tropics. The conclusion seems to be why bother with food production in this region.

An alternate conclusion may be that the region has not received the same inputs into research and development for food production that has occurred in temperate regions. Another alternate view may also be that inhabitants of the tropics may have been able to obtain a far greater percent of requirements from existing vegetation through more "hunter / gatherer" activities.

If you have lived in some curent societies in rural aras of the tropics that is still very common, with local sourced food very important over and above any crop production.

Yet, modern rice production in some regions of the tropics does have very high grain yields. And it is true the grain yield/ stover ratio in some other tropical crops eg sorghum, millet, tef etc is lower than the temperate zones. Again, is this inherent or just an outcome of less R and D?

Biogeographical studies also tend to conclude that high rainfall tropical regions should concentrate on efficient biomass production [think sugarcane, tree crop horticulture, cocoa,trees for wood] with tropical crop production [annual crop production is inferred] moved to the medium rainfall regions. Those regions also tend to have greater seasonal variability too! Their definition of the tropics is too broad.

The issue of grains for meat production is also not especially relevant for beef and goat production in the tropics, as most is grown on grass........or food residuals, and rarely is grain used for finishing, let alone growing animals!

Read this article linked below............draw your own conclusions.

Tropical agriculture "double-whammy": high emissions, low yields

Food produced in the tropics comes with high carbon emissions and low crop yields, according to a new study in the Proceedings of the National Academy of Sciences (PNAS).

In the most comprehensive and detailed study to date looking at carbon emissions versus crop yields, researchers found that food produced in the tropics releases almost double the amount of carbon while producing half the yield as food produced in temperate regions. In other words, temperate food production is three times more efficient in terms of yield and carbon emissions.

"Tropical forests store a tremendous amount of carbon, and when a forest is cleared, not only do you lose more carbon, but crop yields are not nearly as high as they are in temperate areas," explains lead author Paul C. West, a graduate student at the University of Wisconsin-Madison, in a press release. The researchers found that one ton of food emitted approximately over 75 tons of carbon in the tropics, whereas a ton of food grown in temperate regions released just less than 27 tons of carbon.

The tradeoffs between the release of carbon to the atmosphere and agricultural production are markedly different between the world's temperate and tropical regions. In this representation, for each hectare of land cleared for agriculture, each rail car is equivalent to 68 tons of carbon released to the atmosphere and each bushel represents 3.9 tons of maize produced. "This creates a kind of 'double whammy' for a lot of tropical agriculture: we have to clear carbon-rich ecosystems to create tropical croplands, and unfortunately they often have lower yields than temperate systems," says co-author Jonathan Foley, director of the University of Minnesota's Institute on the Environment. "In terms of balancing the needs of food production and slowing carbon dioxide emissions, this is a tough tradeoff."

Rising human population, increasing consumption of meat (which requires more grain per area), the demand for biofuels, high commodity prices, and economic development plans have pushed many tropical nations to pursue large-scale agriculture over forest protection. However, the authors say the realities of carbon loss in the tropics makes a strong argument for intensifying agriculture on already cleared land, rather than more deforestation. "Our results corroborate recommendations to concentrate reforestation and avoid deforestation in the tropics to have the greatest worldwide impact," the authors write.

But, West admits, "the realty is there will be some of both [agriculture intensification and deforestation]." The authors explain in the paper that "despite the clear benefits of concentrating reforestation and forest conservation efforts in the tropics, several local and regional factors influence implementation. […] Choices are made locally and are influenced by local and regional food security, transportation costs, labor, poverty, and technology rather than global atmospheric carbon. Thus, local and global outcomes must be coupled to manage ecosystem services and assess their tradeoffs."

The study also highlight that agriculture comes with additional tradeoffs on top of carbon including impacting ecosystem services such as "soil and groundwater recharge, runoff, and nutrient regulation as well as ecosystems, species, and genome diversity of landscapes." The broad study looked at 175 different crops worldwide using government data and satellite imagery. "We have a very fine resolution of both what the carbon stocks and the yields are globally," says West. "Spatially, it is much more explicit than anything that has been produced before."

Approximately 20% of the temperate region is used for crops, as opposed to 10.5% of the tropics. In all, deforestation contributes more greenhouse gases to the atmosphere than global transportation: 12-20% of the total greenhouse gas emissions are due to the loss of forests. Scientists say that such emissions are driving global climate change.

CITATION: Paul C. West, Holly K. Gibbs, Chad Monfreda, John Wagner, Carol C. Barford, Stephen R. Carpenter, and Jonathan A. Foley. Trading carbon for food: Global comparison of carbon stocks vs. crop yields on agricultural land. PNAS. DOI: 10.1073/pnas.1011078107.

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