As the world's policymakers and business elites look to curb greenhouse gas emissions, one economic sector due for a closer look is agriculture. What many people presently view as a 'green' agriculture choice is, upon closer examination, deeply environmentally suspect.
Most people do not realize that agriculture is a major contributor to atmospheric CO2. Further, different types of agriculture have very different CO2 emission profiles. The widespread adoption of modern agricultural biotechnology products have allowed farmers to maintain yields while reducing CO2 emissions.
Like all animals, soil micro-organisms "breathe out" CO2. In fact soil respiration contributes approximately 20 percent of all land-based CO2 emissions.
The United Nations estimates a 2-5 degree C increase in global temperature in the next hundred years. Couple this with research that showed a 5 degree C increase doubles CO2 emission from soil and it becomes clear agriculture must be included in future CO2 reduction strategies.
Soil management by farmers is important. Tillage practices can have a major effect on the levels of soil CO2 emissions.
Organic agriculture controls weeds primarily by ploughing. The microbial respiration rate is increased every time a plough churns up the soil. When compared to no-tillage, mould-board ploughing doubles CO2 emissions from the soil.
Along with microbial production of CO2, tractors burn huge amounts of diesel fuel pulling metal ploughs through the soil. Research has shown that a conversion to no-tillage practices can save up to 32 litres/hectare. With no-tillage farming practiced over millions of hectares, there is a huge reduction in the amount of CO2 produced by tractors.
The UN estimates that the conversion from conventional ploughing to no-tillage agriculture would store carbon in the soil at 300 kg/hectare/year. The US and Canada are world leaders in no-tillage agriculture. The advent of genetically modified (GM) herbicide tolerant (HT) crops has allowed farmers to use highly effective, low environmental impact herbicides instead of the plough for weed control.
Over the past ten years US farmers have eagerly adopted GM crops with 84 percent of corn, 90 percent of soy and 85 percent of cotton now planted with GM varieties. In Canada, farmers have increased no-tillage canola from 0.8 million hectares to 2.6 million hectares. Ninety five percent of this acreage is planted with GM herbicide tolerant canola.
Like tillage practices, the type of fertilizer used can have a large effect on CO2 emissions. Conventional agriculture relies on synthetic fertilizers while organic farms primarily use manure. Synthetic nitrogenous fertilizers depress soil respiration rates. Conversely, research has shown that the use of manure fertilizer increases soil respiration rates and therefore CO2 emissions by 2-3 fold.
Some have suggested a complete conversion to organic agriculture. But, on average, organic agriculture produces 30 percent less per hectare than conventional farms. If we were to convert entirely to organic agriculture, we would need at least 30 percent more farmland. Significant amounts of the remaining wilderness would have to be ploughed under to maintain current food production levels.
The conversion to organic farming would also require a tremendous increase in animals to generate manure fertilizer. Anyone who has ever been near the back end of a cow knows this would significantly increase a different greenhouse gas.
The organic food industry proudly states double digit increases in sales each of the last few years. However the world is not black and white and research has demonstrated there are significant environmental consequences of this success.
Organic farming practices generate significantly greater CO2 emissions while producing less than conventional agriculture. On the other hand, growing genetically modified crops allow the farmer to reduce CO2 emissions while maintaining yields.
Research has demonstrated soil and water conservation benefits of genetically modified HT crops. It is now clear that these products of modern biotechnology can also help farmers reduce agriculture based CO2 emissions.
The public is calling for "greener" options in every industry. But when it comes to agricultural CO2 emissions, the "greener" option may not be what people think.
